In plain terms

The claim being assessed: Sporadic Parkinson disease commonly begins with enteric alpha-synuclein pathology that ascends through vagal connections to the CNS and drives nigrostriatal neurodegeneration.

Where the evidence stands: Γ — Plausible mechanism. There is a believable biological story and partial support, but the causal step has not been demonstrated.

What this mechanism does: This makes the process worse or keeps it going, but something else starts it.

Strongest evidence for it: Γ for the registered common sporadic enteric-vagal initiation claim. Scope-matched aggregation uses SC3; primary-subclaim and weakest-link sensitivities also return Γ. The assembled evidence exceeds association alone through timing, animal pathway tests and human natural experiments, but does not cross the full-scope initiation dependency threshold. Conditional transport capability is established in particular engineered models, and human body-first phenotypes are separately supported; neither is silently substituted for common natural gut initiation.

What decisive evidence would look like

In plain terms, researchers would change the proposed cause, confirm it changed as intended, and measure a meaningful health outcome while checking other explanations. The result should be able to support or count against the claim.

Relative explanatory fit: Alternative ranked ahead

What this review means for Gut-origin Parkinson's (Braak Hypothesis)

Claim being assessed: Sporadic Parkinson disease commonly begins with enteric alpha-synuclein pathology that ascends through vagal connections to the CNS and drives nigrostriatal neurodegeneration.. This review asks whether the proposed factor causes the health outcome—not just whether the two appear together. For the wording assessed here, the evidence is rated Plausible mechanism (HSEF Γ; Moderate confidence). There is a believable biological story and partial support, but the causal step has not been demonstrated. That rating applies to this claim and scope; it does not mean the biological process is irrelevant in every setting.

Implications for health and treatment: This is an assessment of a causal explanation, not proof that a particular supplement, diet, test, or treatment improves health. A treatment claim needs studies that test the intervention in people and measure meaningful benefits and harms. These findings can help frame research and informed clinical questions, but they do not identify what is right for one person.

Limits for individual care: Evidence from cells, animals, associations, or a plausible mechanism may not predict what happens in people. The grade is limited to the exact claim, outcomes, and sources reviewed, and it is not a diagnosis or an individual forecast. Do not start, stop, or change care based on this page; discuss personal decisions with a qualified clinician.

Medical information notice: This review provides general health information, not medical advice. It cannot diagnose a condition or replace an individual discussion with a qualified clinician.

This assessment rests on 69 sources and 73 individually checked claims. 73 of those claims were verified against the original paper.

A low grade is not an accusation. It means the causal work has not been done yet, which is the ordinary state of most actively studied mechanisms in biology.

At a glance

Sub-claims assessed separately

ID	Sub-claim	Type	Level	Pivotal card
SC1	Enteric pathology precedes CNS pathology.	existence	Γ	Card ↗
SC2	Endogenous pathological alpha-synuclein transfers from gut through vagal connections to CNS.	mechanism	Γ	—
SC3	Gut-origin accounts for a meaningful common fraction of sporadic PD.	primacy	Γ	Card ↗

Visual Evidence Cards · Pivotal Subclaims

Pivotal subclaim illustrations

Dark-theme simulated-micrograph renders and concise causal evidence summaries for the pivotal subclaims that govern this review's grade. Click any card to inspect the master 2400×2400 render.

Master 2400×2400 render ↗

Master 2400×2400 render ↗

Figures

Explanatory figures summarizing this review. They carry no evidential weight of their own; where a figure and the review differ, the review governs.

Full assessment

From here the review is written for a technical reader: caps and thresholds, competing models, the independence basis, and the citation ledger.

Sources: 69 primary reports; claims: 73; verified: 73; unverified: 0. Verification is bounded attribution. Access: 6 partial-body and 63 complete abstract/status examinations. Literature cutoff: 2026-10-05; source examination UTC date: 2026-10-06. No complete-paper audit or blinded calibration claimed. Adversarial review: Generated by Sol 6.1; adversarially reviewed by Claude Opus 5.5 (Anthropic) on 2026-10-06. 0 corrections applied (see ADVERSARIAL REVIEW AND APPROVAL). Status: Approved as revised.

AT A GLANCE

Gut-to-brain transfer is experimentally possible; a common enteric-vagal origin of sporadic Parkinson disease remains unestablished.

Deciding experiment: Enroll representative prodromal participants before RBD/motor diagnosis, pair serial compartment-specific gut and CSF seeding with autonomic/dopamine imaging, and quantify predefined origin classes. In native disease-relevant models, selectively block enteric pathological-alpha-synuclein transfer while preserving vagal physiology and metabolite/immune signals, with matched restoration and independent replication.

Belief versus evidence: Γ for the registered common sporadic enteric-vagal initiation claim. Scope-matched aggregation uses SC3; primary-subclaim and weakest-link sensitivities also return Γ. The assembled evidence exceeds association alone through timing, animal pathway tests and human natural experiments, but does not cross the full-scope initiation dependency threshold. Conditional transport capability is established in particular engineered models, and human body-first phenotypes are separately supported; neither is silently substituted for common natural gut initiation.

Best-supported rival: Heterogeneous body-first and brain-first trajectories. Longitudinal gut/CSF seed assays and autonomic/dopamine imaging starting before RBD, followed by a selective mediator perturbation, distinguish true enteric ascent from a peripheral phenotype accompanying early central disease. RBD alone cannot define the initiating tissue.

COMPETING MECHANISTIC MODELS

Rank 1: Heterogeneous body-first and brain-first trajectories (Γ). Different individuals have peripheral-predominant or brain-predominant early dysfunction. Multimodal imaging, longitudinal clinical comparisons and early autopsy patterns fit heterogeneity (PMID32830221, PMID40204988, PMID40082617). RBD proxies and a population-based contrary classification study limit a strict binary causal-origin taxonomy (PMID38860478).

Rank 2: Brain-first descending dissemination (Γ). Central pathology can precede peripheral involvement and spread outward. Vagus/stomach autopsies and noncanonical DMV-negative cases, with primate bidirectionality, support this possibility (PMID34151862, PMID18053026, PMID32380543). Late autopsy sampling cannot exclude earlier transient peripheral seeds; other autopsies show isolated sympathetic disease.

Rank 3: Indirect microbial and immune risk modification (Ε). Gut perturbations can affect nigral vulnerability through metabolites, barrier and immune pathways. Native colitis/CD8 and microbial UrdA-ImP perturbations provide bounded causal contributions with neuronal/functional outcomes (PMID34412704, PMID40913049). Conditioned animals and postdiagnostic human associations do not establish common human initiation or a specific vagal mediator.

Rank 4: Common enteric-vagal origin (Γ). Enteric seeds usually initiate sporadic PD and ascend to cause nigral degeneration. Premotor biopsy, suggestive truncal-vagotomy associations and conditional gut-seeding/epithelial models supply the strongest case. No common origin fraction, paired pre-CNS sequence or human route dependency is demonstrated; negative spread and alternative anatomical trajectories remain.

Rank 5: Parallel multi-organ vulnerability (Γ). A shared systemic/genetic insult affects gut and brain without obligatory seed transfer. Global c-rel and inflammatory/genotype models plus multiple non-vagal mechanisms are compatible (PMID41207395, PMID38750146). Specific source-to-recipient transfer and vagotomy blockade in engineered models cannot be explained by parallel injury alone.

The tournament does not alter the nominal level. Compatible pathways and flexible alternatives are not automatically proved by explaining observations.

FULL REVIEW

Registered claim and scope

Sporadic Parkinson disease commonly begins with enteric alpha-synuclein pathology that ascends through vagal connections to the CNS and drives nigrostriatal neurodegeneration.

The SC3 gate tests common gut-origin attribution across sporadic PD. Body-first subtype evidence, vagal transport and origin are distinct; RBD and measured baseline autonomic states may define prospective subgroups, but responders or post-outcome exceptions may not.

Selection: public-interest rank 17 from the editorial ranking compiled 2026-09-23; categorical prior verdicts were visible. Private fresh review; earlier documents are preserved.

Evidence and causal interpretation

Enteric Lewy pathology is well established in diagnosed PD, and selected archived biopsies detect pathological staining years before motor diagnosis. Yet diagnosis is a clinical threshold, not the onset of CNS pathology. Staining protocols can also label healthy colon, while adequate full-thickness tissue and trained readers improve discrimination. Presence, measurement accuracy and origin are separate questions (PMID1972853, PMID27015771, PMID25589666, PMID27044604, PMID27589538).

Braak staging has value as a topographical model but cannot itself prove movement. Noncanonical PD brains and autopsies without isolated gastric/vagal pathology provide counterevidence to an obligatory sequence. The 2025 BBAR/Newcastle analysis supports both central and peripheral patterns, including isolated sympathetic pathology; its 51/27/22 percent SuStaIn assignments are modelled archive subtypes, not observed transmission or population gut-origin prevalence (PMID12498954, PMID18053026, PMID34151862, PMID40082617).

Human multimodal imaging and prospective clinical follow-up support phenotypic heterogeneity. RBD-associated autonomic dysfunction may precede marked dopamine-storage loss, but RBD itself has central circuitry involvement. Population-based definitions do not always reproduce a binary split. The Huashan longitudinal study uses an independent 137-patient local cohort; PPMI analyses share source participants and must not be counted as separate replication populations (PMID32830221, PMID29866443, PMID38860478, PMID38834646, PMID40542411).

Truncal vagotomy associations are biologically informative candidates for causal inference. Swedish results were null overall but protective beyond five years for truncal procedures; longer-lag estimates were imprecise. Danish estimates and reanalysis described in Liu Discussion differ with follow-up. Procedure anatomy, indication, smoking proxies and changing surgical eras matter. Appendix removal adds positive and contrary populations but also changes immunity and microbial niches, so it is not a pure seed-reservoir instrument (PMID26031848, PMID28446653, PMID30381408, PMID27621223, PMID30218460, PMID38696328, PMID32595591).

Injected gut fibrils can produce ordered central pathology and nigral loss, prevented by vagotomy or absence of host alpha-synuclein. Other preparations produce only transient brainstem involvement or no sustained primate CNS pathology. Challis original Results are particularly bounded: aged mice had lower striatal dopamine and significant brainstem pathology, but unchanged TH-positive counts and a nonsignificant midbrain pathology increase. Bidirectional primate lesions and sympathetic spread complicate an exclusive vagal model (PMID31255487, PMID29751824, PMID29341898, PMID32066981, PMID32380543).

The epithelial-transfer study is more informative about source than injected seeds: gut-restricted human wild-type/mutant expression generated templating activity in situ, and pre-induction vagotomy blocked distal activity. Original sections show modest expression, isoform mixing, approximately 15 percent postoperative weight loss and donor-to-null-neuron uptake without requiring recipient protein for uptake. It establishes conditional transfer, without a nigral-loss endpoint or the common natural human route (PMID38063197).

Gut processes can influence degeneration through mechanisms other than vagal seeds. Native trophic loss, colitis/CD8 effects and donor microbiota establish bounded dependencies. ImP work includes matched UrdA bacterial colonization, measured brain exposure, neuronal counts and rapamycin protection without lowering metabolite exposure. Its human samples averaged 9.5 years of PD, so they do not locate initiation. These experiments strengthen a gut contribution while also supplying genuine rival mediators (PMID32911010, PMID34412704, PMID39449004, PMID40913049).

Consensus sharpened the separation between common gut origin and body-first phenotype and returned indexed body checks for Liu, Kim and Chandra. Original Liu/Chandra sections were independently examined; Kim remains abstract/status plus a recorded provider body-summary check because original open-body retrieval failed. A Consensus-supplied 2026 autopsy preprint was excluded from the peer-reviewed count and grade. Four linked corrections were examined at the stated depth; no corrected image or raw-data audit is claimed.

HYPOTHESIS STATE EVALUATION FRAMEWORK (HSEF v5.3)

Subclaim matrix and aggregation

Preregistered aggregation: scope-matched. Γ for the registered common sporadic enteric-vagal initiation claim. Scope-matched aggregation uses SC3; primary-subclaim and weakest-link sensitivities also return Γ. The assembled evidence exceeds association alone through timing, animal pathway tests and human natural experiments, but does not cross the full-scope initiation dependency threshold. Conditional transport capability is established in particular engineered models, and human body-first phenotypes are separately supported; neither is silently substituted for common natural gut initiation. Sensitivities: weakest-link Γ; primary-subclaim Γ; scope-matched Γ.

Decisive-perturbation inventory and causal tally

[15] Human stellate-ganglion Lewy-body extracts injected intracerebrally did not reproduce the long-term nigral degeneration previously seen with nigral extracts. Imposed intracerebral inoculation and sympathetic rather than enteric tissue do not test natural gut initiation; they show that peripheral seed source and conformation can affect pathogenicity.

[17] Danish registry comparisons associated truncal vagotomy over 20 years before follow-up with lower PD risk than the general population; selective vagotomy was not protective. Overall and direct truncal-versus-selective estimates were imprecise and crossed unity; surgical indication, smoking and long-survival selection remain alternative explanations, without direct alpha-synuclein mediator measurement.

[18] Swedish matched registries found no overall vagotomy association but lower PD hazard for truncal procedures at least five years before diagnosis, without a selective-vagotomy effect. The truncal overall estimate crossed unity; procedure era, ulcer indication, proxy adjustment and nonrandom exposure constrain route-specific causation and cannot quantify the gut-origin fraction.

[19] Swedish and PPMI analyses associated earlier appendectomy with lower risk or delayed onset, while normal appendix lysates contained aggregation-associated alpha-synuclein forms. Appendectomy changes immunity and microbial niches as well as a possible seed reservoir; effects varied by geography and genetic status and do not directly measure ascending vagal transfer.

[33] Duodenal and pyloric preformed-fibril injection produced ordered brain pathology, dopamine-neuron loss and behavioural deficits; truncal vagotomy and Snca deficiency prevented these outcomes. Exogenous seed injection supplies the proposed initiating event; route necessity within this model does not prove spontaneous human gut initiation or its prevalence.

[34] Intestinal-wall injection of patient brain lysate or recombinant alpha-synuclein produced time-dependent vagal transport to the rat dorsal motor nucleus; cell imaging supported axonal transport. Forced inoculation and detectable transport are not native initiation, templated amplification at every relay or demonstrated human nigrostriatal disease.

[35] Gastric fibril inoculation induced vagotomy-dependent brainstem aggregates, which declined without further rostral spread through 12 months. Supports a conduit but contradicts route sufficiency under these conditions; imposed seed dose and species may differ from natural PD, and linked correction is retained.

[36] Enteric PFF or A53T-overexpression experiments produced gut dysfunction but only transient rodent brainstem pathology and no sustained primate CNS pathology at 12 months. Artificial triggers and tested preparations limit extrapolation; the negative result shows context dependence rather than universal impossibility of gut-to-brain disease.

[37] Even BAC A53T sensitization increased early brainstem aggregates after gut fibrils without sustained caudo-rostral spread to nigra through eight months. Overexpression and imposed fibrils do not model endogenous origin; shares preparation and failure mode with the earlier gastric-inoculation programme.

[38] Gut PFFs caused transient deficits in young mice and persistent deficits with reduced striatal dopamine in aged mice; aged brainstem pathology increased, but midbrain pathology increase was not significant and TH-positive counts were unchanged. Imposed seeds and age-dependent susceptibility establish conditional capability, not the usual human initiating compartment or a universally sufficient vagal route.

[39] Gut fibrils produced sympathetic and parasympathetic pathology and possible bidirectional dissemination in BAC rats, while wild-type rats lacked detectable propagation. Transgenic susceptibility and artificial seeds constrain native causation; sympathetic and anterograde routes undermine an exclusive unidirectional vagal account.

[40] Baboon enteric or striatal patient-extract injection produced both nigrostriatal and enteric lesions, without detectable vagal lesions in the tested setting. Imposed extracts and small primate experiments do not establish a spontaneous route; circulating transfer is a proposed explanation rather than directly traced mediation, and linked correction is retained. A 2025 publisher correction reports duplicated/misassigned representative panels; corrected images and raw data were not audited, so this is qualified rather than singular decisive evidence. A 2025 publisher correction reports duplicated/misassigned representative panels; corrected images and raw data were not audited, so this is qualified rather than singular decisive evidence.

[41] Gut-injected aggregates spread more extensively through autonomic pathways in aged wild-type rats, with cardiac and gastric dysfunction and more mature aggregates. Age improves physiological relevance but initiation remains imposed; bidirectionality and sympathetic routes do not establish a solely vagal natural human origin.

[42] Organoid coculture and epithelial-restricted human-alpha-synuclein mice supported mucosal-to-neural transfer; vagotomy prevented hindbrain templating activity after epithelial induction. Original Methods/Results identify mixed wild-type/A30P/A53T transgenes restricted to gut mucosa and pre-induction vagotomy with about 15 percent weight loss. Modest expression and in-situ seed formation are stronger than injected fibrils, but neuronal uptake need not involve recipient templating; no nigral-loss endpoint or common human origin is established.

[44] Seeded enteroendocrine-to-neuronal cell propagation required physical contact and Rab35, with enhanced lysosomal clearance after inhibition. Cell lines and added fibrils test a transfer mechanism rather than endogenous whole-animal or human gut initiation and degeneration.

[45] Intracerebral transmission of human stomach or brain homogenate produced localized aggregation in sensitized mice, unlike blood or muscle, without overt motor disease. Imposed intracerebral delivery bypasses vagal transport; subtle aggregation after long incubation is not PD neurodegeneration or a native enteric origin, and linked erratum is retained. The correction changes stomach-homogenate pathology denominators including 7/7 to 7/14; no uncorrected rate is used. The correction changes stomach-homogenate pathology denominators including 7/7 to 7/14; no uncorrected rate is used.

[47] Rotenone and fragment-fibril experiments implicated AEP-dependent alpha-synuclein and tau cleavage in enteric and nigral pathology. Systemic neurotoxin effects and forced fragment seeds do not isolate a natural enteric starting site; dependence on AEP does not alone establish vagal mediation in sporadic humans.

[48] Gut conditional loss of trophic factors produced constipation, dopaminergic loss and motor abnormalities, while human tissue correlations and rotenone models implicated C/EBPbeta. A targeted endogenous trophic perturbation supports gut influence on degeneration; it does not by itself identify alpha-synuclein transfer as the necessary mediator or quantify spontaneous human gut initiation.

[49] C/EBPbeta or AEP deletion reduced age- and rotenone-associated pathology and motor deficits in human-SNCA transgenic mice with apparent gut-to-brain progression. Human-protein transgenesis, global pathway effects and toxin exposure complicate origin-specific mediation; related reports share pathway and laboratory components.

[50] Mild chronic DSS gut inflammation accelerated motor dysfunction and nigral marker loss in alpha-synuclein-mutant mice with increased enteric and brain pathology. Genetic sensitization and inflammatory perturbation do not isolate vagal alpha-synuclein transfer from immune or systemic influences; acceleration is not proof of initial human cause.

[51] Microbiota depletion, recolonization, metabolites and patient-donor transfer modulated motor deficits and neuroinflammation in alpha-synuclein-overexpressing mice. Overexpression and microbiome manipulation support a gut modifier; they do not establish enteric seeds ascending the vagus, and germ-free developmental and donor effects limit transfer.

[52] PD-donor microbiota transferred into wild-type mice produced TH-positive cell loss, motor impairment and gut-immune-brain changes. Donor medications, recipient conditioning and systemic immune or barrier routes require separation from vagal transfer; TH-positive counts need corroboration of neuron survival before equating them to complete neuronal death.

[54] Antibiotics reduced progression in a gut-originated model; bacterial and metabolite experiments implicated BCAA-related impaired microglial alpha-synuclein clearance. The abstract does not specify how the initiating mouse model was generated; route dependence and primary origin cannot be assumed, and antibiotic effects extend beyond the identified metabolite.

[55] Gut PFF injection in wild-type mice produced temporally mapped central spread and motor and sleep phenotypes, with central dopamine experiments linking REM abnormalities to nigral dysfunction. Exogenous seeds impose the initiating lesion; RBD-like animal behaviours do not establish a human gut-first subtype, and the final report replaces its preprint.

[56] Microbial UrdA and imidazole propionate manipulations increased brain metabolite exposure and PD-like neuronal and behavioural outcomes, with mTORC1 implicated. Original Results include Nissl/TH stereology, matched bacterial colonization and rapamycin protection without lowering ImP exposure. Germ-free or antibiotic conditioning and administered metabolites constrain transfer; the human plasma comparison follows a mean 9.5 years of PD and cannot establish initiation.

[57] Intestinal inflammation accelerated nigral aggregation and dopaminergic loss in male human-LRRK2-G2019S mice, with sex-chromosome manipulations retaining male susceptibility. A familial-risk genotype and induced colitis support conditional gut influence; myeloid transport, inflammatory signalling and direct vagal transfer remain distinct possibilities.

[58] Human colon inflammation was accompanied by rotenone-model protection after TLR4 knockout despite persistent dysbiosis. Global receptor deletion and neurotoxin exposure do not isolate gut-to-vagus seeds; human cross-sectional inflammation could follow disease, transit or medication changes.

[59] Colitis induced sustained TH-marker reduction and neuroinflammation in male mice; CD8 depletion prevented the TH change, and colitis increased later MPTP vulnerability. Dopamine itself was not reduced after colitis; immune effects and neurotoxin susceptibility are not proven neuron death or alpha-synuclein vagal transfer, providing an alternative gut-brain mediator.

[62] A randomized double-blind supplementation report described motor and medication changes over six months alongside immune and barrier outcomes. The abstract does not establish an inactive comparator or enteric-seed/vagal mediator; retrospective registration, concurrent PD therapy and symptom change cannot prove disease modification or primary origin.

[64] A large Danish matched registry study found a small increased rather than decreased PD hazard at least ten years after appendectomy, persisting after longer follow-up. Nonrandom surgery and inflammation-related indications remain confounders; contradicts a simple universal appendix-reservoir protection prediction without excluding a subset effect.

[65] Prospective Nurses' Health and Health Professionals cohorts found no overall reduced PD hazard after self-reported appendectomy, with higher risk for appendicitis-related surgery in women. Exposure recall and operative indication affect inference; results oppose simple reservoir-removal protection but do not test vagal transfer directly.

[66] Appendectomy after age 35 did not reduce later PD risk relative to cholecystectomy, and the early increase relative to no surgery disappeared with longer follow-up. Midlife surgery may miss an earlier initiation window; comparator procedures and indication confounding leave subtype-specific effects unresolved.

[67] A Korean national cohort found no statistically resolved appendectomy-PD association, with adjusted hazard confidence limits spanning protection and increased risk. Imprecision and nonrandom surgery preclude interpreting a null test as equivalence or excluding an earlier subtype-specific reservoir.

[68] A Swedish nested case-control study associated prior appendectomy with lower PD odds, including long lags, with a less precise tonsillectomy association. Overlaps national register source populations with earlier Swedish studies; surgical indications, smoking proxies and hospital-use ascertainment do not isolate alpha-synuclein reservoir removal.

Tally: 34 discriminating contrasts. Null and negative contrasts are discriminators, not positive threshold crossings. Reports and replications are not independent causal lines. A surgery contrast may discriminate reservoir models without satisfying a rigorous origin instrument. Route blockade after engineered trigger is not prevention of naturally initiated human disease. Corrections and shared specimens limit independent replication; all correction notices were checked at the stated depth.

Cap audit, precedence and Β/Γ/Δ boundary

The neurodegeneration rubric admits vagotomy-type natural experiments only with rigorous confounder control and disease-initiation relevance. These cohorts are considered as field-valid candidates, not rejected because they are nonrandomized; residual indication/smoking/era and mediator uncertainty prevent the registered initiation inference. PFF blockade and engineered gut-expression tests establish restricted route capability. Native trophic and immune perturbations carry real causal weight for alternative gut influences. No literal Gamma cap is claimed over the convergent whole; all three registered gates stop on unmet positive scope burdens.

Gamma hard-rule audit: Injected PFFs and mutant/human-protein transgenes cannot alone carry natural human initiation. Premotor diagnosis and body-first dysfunction do not establish pre-CNS enteric seeds. Native gut trophic, immune and microbial interventions are credited, but may act through non-vagal routes. Convergent classes are assessed together; no absence-of-RCT cap is imposed.

SC1 field-valid definition: “ - Endogenous genetic deletion, suppression, or degron depletion of the proposed mediator in vivo - Selective pathway inhibition that changes onset/progression while preserving broader viability - Vagotomy-type natural experiment, only if confounding is rigorously controlled AND effect is disease-initiation relevant rather than merely associated” Positive full-scope result: no. Premotor enteric pathology and autonomic dysfunction are reproducible in selected groups, but motor diagnosis is not the onset of CNS pathology. Serial paired gut and central seed measurements establishing enteric-before-CNS order are absent from the examined causal case; sampled autopsies provide contrary patterns.

SC2 field-valid definition: “ - Endogenous genetic deletion, suppression, or degron depletion of the proposed mediator in vivo - Selective pathway inhibition that changes onset/progression while preserving broader viability - Vagotomy-type natural experiment, only if confounding is rigorously controlled AND effect is disease-initiation relevant rather than merely associated” Positive full-scope result: no. Vagal continuity is causally relevant in imposed-seed and engineered gut-mucosal systems. The latter generates seeds in situ and is credited beyond injected fibrils, yet uses human transgenes and does not establish nigral loss. Registry vagotomy is suggestive but not a rigorously isolated natural-origin instrument; the native human disease route remains plausible without a demonstrated dependency.

SC3 field-valid definition: “ - Endogenous genetic deletion, suppression, or degron depletion of the proposed mediator in vivo - Selective pathway inhibition that changes onset/progression while preserving broader viability - Vagotomy-type natural experiment, only if confounding is rigorously controlled AND effect is disease-initiation relevant rather than merely associated” Positive full-scope result: no. No examined study prospectively attributes a meaningful common fraction of sporadic human PD to enteric seeds before CNS disease. Body-first phenotype, sympathetic-first pathology and inferred cross-sectional stage assignments are not synonymous with gut-first vagal initiation. Stronger model results do not supply this registered scope gate.

Upward threshold ladder

SC1 Δ: “Requires at least one genuine causal perturbation in a disease-relevant in vivo system, or equivalent human natural experiment that materially supports the mechanism.” Satisfied: no. Prospective paired enteric and CNS seed/activity measures with validated sensitivity show gut abnormality preceding any detectable central involvement, alongside subsequent central conversion.

SC2 Δ: “Requires at least one genuine causal perturbation in a disease-relevant in vivo system, or equivalent human natural experiment that materially supports the mechanism.” Satisfied: no. Selective interruption of native enteric pathological species transfer, preserving autonomic function and systemic immune/metabolite effects, changes onset/progression with matched restoration or a rigorously controlled human natural experiment.

SC3 Δ: “Requires at least one genuine causal perturbation in a disease-relevant in vivo system, or equivalent human natural experiment that materially supports the mechanism.” Satisfied: no. A representative prospective prodromal cohort estimates the prespecified gut-origin fraction using validated temporal and mediator attribution, with independent replication and brain-/sympathetic-first alternatives tested.

Upper ladder: Human vagotomy and appendectomy natural experiments, a randomized supplement intervention and orthogonal native animal pathways were examined. Surgery associations have unresolved instrument/mediator limits; symptomatic supplementation does not measure trajectory or the vagal seed mediator. No qualifying human genetic instrument on enteric-vagal initiation or convergent upstream human dependency carries the registered claim to Ζ/Η. Upper levels remain reachable without an unethical mechanism RCT.

Independence: 69 reports are not 69 independent causal lines. PPMI, Danish imaging comparators, Swedish population registers, shared tissue archives and related seed/pathway programmes are identified. Different failure classes strengthen plausibility but do not jointly measure the missing common human origin fraction.

Human exposure interruption [17, 18]: Tests future clinical PD after anatomical interruption; distinct from staining, but both share ulcer/smoking confounding.

Species and seed perturbations [33, 36, 40]: Tests route capability and limits across species rather than deriving order from autopsy.

Native alternative gut mediators [59, 56]: Tests immune/metabolite influence without requiring enteric seeds to traverse the vagus.

Falsification and pitfalls

Peripheral pathology without sustained CNS propagation. PMID29751824, PMID29341898 and PMID31783082 reject unconditional gut-seed sufficiency in tested systems. Additional downgrade: False.

Noncanonical or sympathetic-first topology. PMID18053026 and PMID40082617 oppose an obligatory exclusive DMV/vagal sequence. Additional downgrade: False.

Inconsistent reservoir-removal effects. Positive Swedish appendix studies coexist with null/increased-risk Danish, prospective Western and Korean analyses. Additional downgrade: False.

Premotor treated as pre-CNS. Biopsy and autonomic imaging before clinical motor diagnosis.

Body-first equated with gut-first. RBD, cardiac denervation and sympathetic autopsy trajectories.

Forced seed origin naturalized. PFF and patient-extract gut inoculation.

TH signal equated with cell death. Challis aged mice and colitis marker changes.

Modelled sequence presented as observed transfer. SuStaIn and extrapolated imaging duration.

Adversarial steelman: above, then below

Δ is attractive because truncal vagotomy changes later PD risk in selected comparisons and epithelial-restricted expression gives a source-specific transfer test. For the registered common human origin gate it would require rigorous confounder/mediator attribution or equivalent native dependency; those positive model results do not measure that gate.

Β would undercredit temporally informative premotor specimens, clinical exposure interruption and direct conditional source-to-recipient transfer. The current mechanism is more than pathology colocalization even though common natural initiation remains unproven.

Reject Β as too narrow an account of the mechanistic evidence and reject global Δ because it substitutes conditional transport for common human origin. Γ reflects a plausible but unresolved registered initiating mechanism, with model causality stated separately.

Final score, causal direction and M/S/D

Γ for the registered common sporadic enteric-vagal initiation claim. Scope-matched aggregation uses SC3; primary-subclaim and weakest-link sensitivities also return Γ. The assembled evidence exceeds association alone through timing, animal pathway tests and human natural experiments, but does not cross the full-scope initiation dependency threshold. Conditional transport capability is established in particular engineered models, and human body-first phenotypes are separately supported; neither is silently substituted for common natural gut initiation.

Step1: gut changes may follow PD, but perturbation experiments show feedback on pathology, so the assembled gut mechanism is not solely downstream. Step2: conditional route and native immune/metabolite effects exclude mere co-occurrence. Step3: common initiating, removable and rate-limiting enteric-vagal origin is not shown. Step4: a universal permissive requirement is contradicted by alternate trajectories. Step5 applies to the defensible broad contribution: gut processes can reinforce degeneration, with stronger route dependencies only in defined experimental settings.

Momentum: Mechanistic only. Published epithelial-transfer, endogenous c-rel, ImP and longitudinal subtype programmes address specific boundaries; no verified ongoing trial testing common native enteric-vagal initiation is asserted.

Stability: Stable. No named pending scope-matched origin-attribution result is verified. The 2026 seed-injection and imaging studies are already included, and an autopsy preprint supplied by Consensus is not treated as an imminent validated crossing.

Divergence: Contested; no single implied-level arithmetic. These dimensions do not change level or confidence.

PROPOSED DECISIVE EXPERIMENTS

Enroll representative prodromal participants before RBD/motor diagnosis, pair serial compartment-specific gut and CSF seeding with autonomic/dopamine imaging, and quantify predefined origin classes. In native disease-relevant models, selectively block enteric pathological-alpha-synuclein transfer while preserving vagal physiology and metabolite/immune signals, with matched restoration and independent replication.

Readout: Compartment-specific first positivity, validated detection limits, later nigral neuronal survival and clinical progression, plus a population-attributable gut-origin fraction. Controls: Brain-/sympathetic-first comparators; blinded repeated assays; transit/medication/diet adjustment; normal-alpha-synuclein controls; vagal-function preservation; immune/metabolite controls; matched species-specific restoration. Supporting: Enteric seeds precede central involvement in a substantial prespecified fraction; selective mediator interruption prevents subsequent central spread and degeneration with restoration restoring the sequence. Falsifying: Central seeds precede gut signals, most peripheral-first cases arise elsewhere, or verified enteric-transfer blockade leaves degeneration unchanged while altering only gut function.

RESEARCH TIMELINE

KNOWLEDGE GAPS

Paired temporal attribution: premotor tissue is not pre-CNS tissue; serial peripheral and central assays must start before central prodromal signs (PMID27015771, PMID29866443, PMID37059509).

Gut versus other peripheral origins: validate enteric, sympathetic and central classes prospectively instead of using RBD as a unique gut surrogate (PMID40082617, PMID38860478, PMID40204988).

Natural seed generation and selective transfer: separate mutant/human expression, injected seeds and spontaneous pathological conformations with non-disruptive route blockade (PMID38063197, PMID31255487, PMID41207395).

Vagotomy instrument validity: distinguish surgical era, smoking, indication, survival and physiological effects from removal of a seed conduit; reconcile lags and independent populations (PMID26031848, PMID28446653).

Degeneration versus dysfunction: corroborate TH/DAT/dopamine changes with neuronal survival and durable clinical trajectories, rather than equating them automatically (PMID32066981, PMID34412704, PMID40913049).

Specific human mediation: test whether gut interventions change native seed movement, systemic metabolites or immune signals and whether this predicts disease progression beyond symptomatic response (PMID41350593, PMID40913049, PMID39218360).

METHODS AND CONSENSUS CONTRIBUTION

Consensus was used through the signed-in browser for discovery, counterevidence, research-gap and timeline suggestions, and attempted checks of specific indexed full-text passages. Returned Methods/Results passages were reconciled with original-paper passages where available; failed retrievals, source substitutions and unverified aspects are recorded in the case reconciliation. Successful passage checks are distinguished from provider summaries. Provider screening counts, citation counts and meters were not used as primary counts or HSEF scores. This source log records access depth; it does not claim complete-paper or supplement review. The monthly API allowance was conserved: zero Consensus API calls in this batch.

REVIEWER NOTES

69 primary reports examined, six selected original body examinations, four linked correction checks outside the primary count. Cutoff remains 5 October 2026; examinations continued 6 October. Exact v5.3 structural validation does not establish scientific correctness or independent blinded review. Consensus browser queries two, API calls zero; provider summaries and counts do not determine grades.

Search leads, reviews, protocols and correction notices do not pad the primary count. Downloaded XML does not earn examination credit. Linked notices remain attached; unexamined correction details limit inference. This is a coordinator source/claim consistency assessment, not independent blinded calibration.

ADVERSARIAL REVIEW AND APPROVAL

Authoring model: Sol 6.1. Adversarial reviewer: Claude Opus 5.5 (Anthropic). Date: 2026-10-06.

Scope of checks. All 69 reference PMIDs re-resolved against PubMed (69/69 correct for first author, title, journal and DOI; no retraction or expression of concern; four linked errata already recorded in the ledger's status_flags). Eleven load-bearing claims spot-checked against primary abstracts or the stored body passages: the Danish truncal-vagotomy hazard ratios, the Swedish register result (null overall, truncal at least five years before diagnosis HR 0.59, 95% CI 0.37–0.93), Kim 2019 vagotomy and α-synuclein-deficiency blockade, Manfredsson 2018 transient rat and primate pathology, Challis 2020 reduced striatal dopamine in aged but not young mice, Chandra 2023 epithelial transfer and pre-induction vagotomy, Park 2025 UrdA–imidazole propionate, the Andersen 2025 SuStaIn subtype proportions (51 per cent brain-first, 27 per cent parasympathetic body-first, 22 per cent sympathetic body-first, confirmed in the stored full text), and the Huashan cohort size of 137 patients (confirmed in the stored full text). Scoring logic re-derived independently before the existing letter was read.

Findings.

Rejected findings (checked, no change).

1. SC2 should cross Δ because truncal vagotomy and α-synuclein deficiency prevented gut-to-brain spread and neurodegeneration in a mouse model. Rejected: that result is produced in an injected preformed-fibril paradigm, and universal cap 5 reads "Seeding or forced-transfer paradigms cap at Γ for endogenous propagation claims. Forced spread is not observed spread." The epithelial-transfer model that generates seeds in situ relies on human transgene expression, which cap 3 ("Overexpression in model systems caps at Γ") governs for the endogenous claim. Γ for SC2 is forced by the framework, not chosen.
2. Scope-matched aggregation. Checked against SKILL.md Step 3. SC3 is the subclaim whose scope matches the registered claim (common sporadic human initiation) and it is Γ; primary-subclaim and weakest-link also return Γ, so the letter is rule-independent.
3. Use of the Andersen subtype percentages. The review states explicitly that they are modelled archive subtypes rather than observed transmission or population gut-origin prevalence; this matches the source.
4. Citation-year differences of ±1 between printed issue year and PubMed e-pub year (references 6, 8, 32, 37, 47, 48, 58, 69). Publication-convention difference, not an error.

Residual limitations. Verification depth is bounded by access: 6 partial-body examinations and 63 abstract/status examinations. One source (Kim 2019) could not be opened in full text here either, consistent with the review's own record; its claims were checked against the abstract only.

Approval: Following adversarial review and the corrections listed above, the revised document is approved. — Claude Opus 5.5 (Anthropic), 2026-10-06.

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Source-specific evidence cards

[1] Parkinson's disease: an immunohistochemical study of Lewy body-containing neurons in the enteric nervous system.

Shows: Autopsies identified Lewy bodies in selected enteric neuronal phenotypes, establishing peripheral involvement in diagnosed PD.

Does not show: Three end-stage observations do not establish temporal origin, gut-to-brain movement or common-fraction causation.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[2] Staging of brain pathology related to sporadic Parkinson's disease.

Shows: Cross-sectional incidental and symptomatic brain pathology supported a caudo-rostral staging scheme beginning in selected brainstem/olfactory sites.

Does not show: A topographical stage reconstruction is not longitudinal transport and does not demonstrate enteric initiation before CNS pathology.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[3] Multi-organ distribution of phosphorylated alpha-synuclein histopathology in subjects with Lewy body disorders.

Shows: Systematic multi-organ autopsy staining mapped widespread Lewy pathology with a decreasing upper-to-lower gastrointestinal gradient.

Does not show: Anatomical distribution at death cannot determine direction or initiating organ; peripheral involvement is compatible with descending or parallel disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[4] Staging of sporadic Parkinson disease-related alpha-synuclein pathology: inter- and intra-rater reliability.

Shows: Observers across institutions reproducibly assigned brain alpha-synuclein stages using a defined section protocol.

Does not show: Reliability of a classification validates measurement consistency, not temporal order, vagal transmission or etiologic necessity.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[5] Applicability of current staging/categorization of alpha-synuclein pathology and their clinical relevance.

Shows: An unselected alpha-synuclein-positive autopsy series contained deviations from the proposed caudo-rostral pattern and substantial pathology without corresponding clinical syndromes.

Does not show: Deviation undermines universal staging but does not exclude a gut-origin subtype; cross-sectional pathology cannot reconstruct an individual's initiating sequence.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[6] Alpha-synuclein in colonic submucosa in early untreated Parkinson's disease.

Shows: Early untreated PD sigmoid biopsies showed a nerve-fibre staining pattern absent from the tested healthy and inflammatory controls.

Does not show: Patients already had motor PD; staining specificity is assay-dependent and does not locate the disease origin before CNS pathology.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[7] Is alpha-synuclein in the colon a biomarker for premotor Parkinson's disease? Evidence from 3 cases.

Shows: Archived colon biopsies from three future PD patients contained alpha-synuclein staining before their first motor symptom.

Does not show: Premotor is not pre-CNS; retrospective cases, small numbers and healthy control selection do not determine population prevalence or causal route.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[8] Accumulation of α-synuclein in the bowel of patients in the pre-clinical phase of Parkinson's disease.

Shows: Blinded archived gastrointestinal biopsy analysis detected phosphorylated nerve pathology in some patients years before motor onset, including serial samples.

Does not show: Sparse sensitivity and retrospectively ascertained diagnoses limit generalization; no contemporaneous CNS measurements exclude earlier brain disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[9] Pathological α-synuclein in gastrointestinal tissues from prodromal Parkinson disease patients.

Shows: Archived gastrointestinal phosphorylated alpha-synuclein staining was detected in 22 of 39 prodromal subjects, sampled on average seven years before diagnosis.

Does not show: Premotor detection does not establish pre-CNS origin; aggregated-alpha-synuclein staining did not differ from controls, and retrospective tissue ascertainment and assay choice constrain prevalence.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[10] Evaluation of alpha-synuclein immunohistochemical methods for the detection of Lewy-type synucleinopathy in gastrointestinal biopsies.

Shows: A multicentre assessment found frequent positive control-biopsy staining and no tested method or pattern with both sensitivity and specificity above 80 percent.

Does not show: Small shared biopsy sets and heterogeneous ratings test assay reliability rather than excluding enteric disease or its causal route.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[11] Multicenter Assessment of Immunohistochemical Methods for Pathological Alpha-Synuclein in Sigmoid Colon of Autopsied Parkinson's Disease and Control Subjects.

Shows: Full-thickness autopsy-colon assessment achieved better discrimination with selected protocols and trained raters, including a perfect result for one method in the tested set.

Does not show: Selected small specimens, sufficient submucosa and reader training limit generalization; shares assay-development components with the earlier biopsy assessment, not independent origin evidence.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[12] Colonic mucosal a-synuclein lacks specificity as a biomarker for Parkinson disease.

Shows: PET-blot and routine immunohistochemistry detected mucosal alpha-synuclein aggregates in many healthy controls as well as PD, including all 11 PET-blot controls.

Does not show: Assay non-specificity undermines biopsy biomarker interpretation; mucosal staining does not exclude pathogenic conformations in other enteric compartments.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[13] Similar α-Synuclein staining in the colon mucosa in patients with Parkinson's disease and controls.

Shows: Blinded right and left colon assessment found similar alpha-synuclein and phosphorylated staining in 19 PD patients and eight controls.

Does not show: Small cross-sectional samples and antibody patterns cannot determine initiating site, transport direction or the absence of a gut-origin subgroup.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[14] Vagus Nerve and Stomach Synucleinopathy in Parkinson's Disease, Incidental Lewy Body Disease, and Normal Elderly Subjects: Evidence Against the "Body-First" Hypothesis.

Shows: Autopsies spanning normal elderly, incidental Lewy pathology and PD found no vagal or gastric phosphorylated-synuclein positivity without brain pathology.

Does not show: Cross-sectional age-related ascertainment, sampled gut regions and detection sensitivity leave transient or unsampled peripheral initiation possible; this is positive counterevidence to a common obligatory sequence, not universal proof of brain-first disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[15] Lack of pathogenic potential of peripheral α-synuclein aggregates from Parkinson's disease patients.

Shows: Human stellate-ganglion Lewy-body extracts injected intracerebrally did not reproduce the long-term nigral degeneration previously seen with nigral extracts.

Does not show: Imposed intracerebral inoculation and sympathetic rather than enteric tissue do not test natural gut initiation; they show that peripheral seed source and conformation can affect pathogenicity.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[16] In vivo distribution of α-synuclein in multiple tissues and biofluids in Parkinson disease.

Shows: The six-site S4 study compared multiple fluid and tissue alpha-synuclein measures in 59 PD patients and 21 controls and reported limited sensitivity for skin and submandibular staining.

Does not show: Cross-sectional diagnosed disease does not identify origin; the abstract does not report a colon result, and measurements across compartments were not correlated.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[17] Vagotomy and subsequent risk of Parkinson's disease.

Shows: Danish registry comparisons associated truncal vagotomy over 20 years before follow-up with lower PD risk than the general population; selective vagotomy was not protective.

Does not show: Overall and direct truncal-versus-selective estimates were imprecise and crossed unity; surgical indication, smoking and long-survival selection remain alternative explanations, without direct alpha-synuclein mediator measurement.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[18] Vagotomy and Parkinson disease: A Swedish register-based matched-cohort study.

Shows: Swedish matched registries found no overall vagotomy association but lower PD hazard for truncal procedures at least five years before diagnosis, without a selective-vagotomy effect.

Does not show: The truncal overall estimate crossed unity; procedure era, ulcer indication, proxy adjustment and nonrandom exposure constrain route-specific causation and cannot quantify the gut-origin fraction.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:RESULTS, 2:DISCUSSION. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[19] The vermiform appendix impacts the risk of developing Parkinson's disease.

Shows: Swedish and PPMI analyses associated earlier appendectomy with lower risk or delayed onset, while normal appendix lysates contained aggregation-associated alpha-synuclein forms.

Does not show: Appendectomy changes immunity and microbial niches as well as a possible seed reservoir; effects varied by geography and genetic status and do not directly measure ascending vagal transfer.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC2, SC3.

[20] Brain-first versus body-first Parkinson's disease: a multimodal imaging case-control study.

Shows: Multimodal imaging separated RBD-associated autonomic dysfunction with relatively preserved dopamine storage from diagnosed PD without RBD dominated by nigrostriatal dysfunction.

Does not show: Cross-sectional trajectory inference, overlapping iRBD comparator participants and functional imaging rather than direct seed tracking do not identify a uniquely enteric initiating site.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[21] In-vivo staging of pathology in REM sleep behaviour disorder: a multimodality imaging case-control study.

Shows: Twenty-two iRBD patients had extensive autonomic and locus-coeruleus abnormalities while most retained normal-range putaminal dopamine storage.

Does not show: RBD already involves CNS circuitry; normative comparator data and functional dysfunction gradients do not demonstrate a gut-before-CNS sequence; iRBD participants overlap the later subtype study.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[22] Assessment of heterogeneity among participants in the Parkinson's Progression Markers Initiative cohort using α-synuclein seed amplification: a cross-sectional study.

Shows: PPMI cerebrospinal-fluid seed amplification classified diagnosed and many prodromal patients and showed substantial olfactory and genetic subgroup heterogeneity.

Does not show: Diagnostic performance and prodromal positivity do not locate the seed origin; repeated PPMI analyses are not independent patient cohorts and some normal-olfaction cases were seed-negative.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[23] Disease progression in proposed brain-first and body-first Parkinson's disease subtypes.

Shows: Possible premotor-RBD grouping predicted more rapid longitudinal motor-score progression than PD without possible RBD.

Does not show: Original Methods identify a Huashan Hospital cohort of 137 patients, not PPMI. Questionnaire-based RBD, retrospective premotor recall, sex differences and treatment-adjusted observational follow-up do not verify enteric origin.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:Results, 2:Discussion, 3:Methods. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[24] Clinical progression and genetic pathways in body-first and brain-first Parkinson's disease.

Shows: Longitudinal PPMI symptom, imaging and genetic analyses supported stable body-first and brain-first phenotype distinctions and different progression patterns.

Does not show: Shares PPMI data with other reports; proxy-defined subtypes do not identify first tissue or transmission direction; linked erratum is retained and requires attention before detailed quantitative reuse.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. ErratumIn: PMID40830880. Subclaims: SC1, SC3.

[25] Sympathetic and parasympathetic subtypes of body-first Lewy body disease observed in postmortem tissue from prediagnostic individuals.

Shows: Two postmortem datasets supported early brain-predominant and peripheral-predominant Lewy patterns; modelled body-first patterns split between vagal and sympathetic predominance.

Does not show: SuStaIn orders cross-sectional scores, not observed transfer; brain-first 51 percent, parasympathetic 27 percent and sympathetic 22 percent are modelled autopsy assignments, not population gut-origin prevalence. Isolated sympathetic cases support peripheral heterogeneity; incomplete Newcastle CNS staging was crossvalidated by inference.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:Results:paragraph3, 1:Results:paragraph17, 1:Results:paragraph18, 1:Results:paragraph19, 1:Results:paragraph20, 1:Results:paragraph21, 1:Results:paragraph22. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[26] The natural history of body-first versus brain-first Parkinson's disease subtypes.

Shows: A prospectively followed Italian PD cohort showed greater premotor symptom burden and faster motor-stage progression in probable-premotor-RBD patients.

Does not show: Retrospective symptom recall and RBD-based subtype assignment do not verify source tissue or vagal transfer; 81 of 400 proxy-positive cases do not estimate all natural gut initiation.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[27] Asymmetric Dopaminergic Dysfunction in Brain-First versus Body-First Parkinson's Disease Subtypes.

Shows: FDOPA and PPMI DaT imaging associated RBD-linked disease with more symmetric dopaminergic dysfunction.

Does not show: Shares imaging and PPMI cohort components with related reports; asymmetry is compatible with route models but does not trace enteric seeds or exclude intrinsic bilateral vulnerability.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[28] A Population-Based Approach to the Argument on Brain-First and Body-First Pathogenesis of Lewy Body Disease.

Shows: A population-based Rochester cohort did not support a stable binary body-first versus brain-first classification across alternative symptom definitions.

Does not show: Definition-sensitive clinical groupings challenge simple subtype proxies rather than proving absence of peripheral initiation; PD and DLB diagnostic composition also varied.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[29] Cardiac sympathetic degeneration informs the duration of the prodromal stage of body-first Lewy body disease.

Shows: Longitudinal cardiac and dopamine imaging across two cohorts yielded modelled sympathetic decline preceding nigrostriatal decline in putative body-first disease.

Does not show: Estimated trajectories and extrapolated prodromal duration are not observed seed transfer or initial enteric pathology; autonomic denervation is a different endpoint from the proposed gut origin.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[30] Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study.

Shows: A 24-centre prospective iRBD cohort documented frequent later parkinsonism or dementia and identified constipation and autonomic markers among predictors.

Does not show: RBD already reflects central dysfunction; predictive symptoms do not identify gut origin, and conversion included several synucleinopathies rather than solely sporadic PD.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[31] Braak's Unfinished Hypothesis: A Clinicopathological Case Report of α-Synuclein Peripheral Neuropathy Preceding Parkinsonism by 20 Years.

Shows: A clinicopathological case documented peripheral sensory neuropathy and archived sural alpha-synuclein staining before overt parkinsonism and DLB.

Does not show: One retrospective non-enteric case without preclinical CNS testing cannot establish common PD initiation or transport direction.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[32] Cardiac sympathetic denervation predicts PD in at-risk individuals.

Shows: In a small at-risk prospective cohort, all four subjects diagnosed with PD over three years had antecedent cardiac sympathetic denervation.

Does not show: Small enriched risk sample and cardiac functional rather than enteric seed measurement cannot locate initiation or exclude earlier CNS disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[33] Transneuronal Propagation of Pathologic α-Synuclein from the Gut to the Brain Models Parkinson's Disease.

Shows: Duodenal and pyloric preformed-fibril injection produced ordered brain pathology, dopamine-neuron loss and behavioural deficits; truncal vagotomy and Snca deficiency prevented these outcomes.

Does not show: Exogenous seed injection supplies the proposed initiating event; route necessity within this model does not prove spontaneous human gut initiation or its prevalence.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[34] Direct evidence of Parkinson pathology spread from the gastrointestinal tract to the brain in rats.

Shows: Intestinal-wall injection of patient brain lysate or recombinant alpha-synuclein produced time-dependent vagal transport to the rat dorsal motor nucleus; cell imaging supported axonal transport.

Does not show: Forced inoculation and detectable transport are not native initiation, templated amplification at every relay or demonstrated human nigrostriatal disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[35] Inoculation of α-synuclein preformed fibrils into the mouse gastrointestinal tract induces Lewy body-like aggregates in the brainstem via the vagus nerve.

Shows: Gastric fibril inoculation induced vagotomy-dependent brainstem aggregates, which declined without further rostral spread through 12 months.

Does not show: Supports a conduit but contradicts route sufficiency under these conditions; imposed seed dose and species may differ from natural PD, and linked correction is retained.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. ErratumIn: PMID31349849. Subclaims: SC2.

[36] Induction of alpha-synuclein pathology in the enteric nervous system of the rat and non-human primate results in gastrointestinal dysmotility and transient CNS pathology.

Shows: Enteric PFF or A53T-overexpression experiments produced gut dysfunction but only transient rodent brainstem pathology and no sustained primate CNS pathology at 12 months.

Does not show: Artificial triggers and tested preparations limit extrapolation; the negative result shows context dependence rather than universal impossibility of gut-to-brain disease.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[37] Limited spread of pathology within the brainstem of α-synuclein BAC transgenic mice inoculated with preformed fibrils into the gastrointestinal tract.

Shows: Even BAC A53T sensitization increased early brainstem aggregates after gut fibrils without sustained caudo-rostral spread to nigra through eight months.

Does not show: Overexpression and imposed fibrils do not model endogenous origin; shares preparation and failure mode with the earlier gastric-inoculation programme.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[38] Gut-seeded α-synuclein fibrils promote gut dysfunction and brain pathology specifically in aged mice.

Shows: Gut PFFs caused transient deficits in young mice and persistent deficits with reduced striatal dopamine in aged mice; aged brainstem pathology increased, but midbrain pathology increase was not significant and TH-positive counts were unchanged.

Does not show: Imposed seeds and age-dependent susceptibility establish conditional capability, not the usual human initiating compartment or a universally sufficient vagal route.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:RESULTS:paragraph7, 1:RESULTS:paragraph8, 1:RESULTS:paragraph9. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[39] Evidence for bidirectional and trans-synaptic parasympathetic and sympathetic propagation of alpha-synuclein in rats.

Shows: Gut fibrils produced sympathetic and parasympathetic pathology and possible bidirectional dissemination in BAC rats, while wild-type rats lacked detectable propagation.

Does not show: Transgenic susceptibility and artificial seeds constrain native causation; sympathetic and anterograde routes undermine an exclusive unidirectional vagal account.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[40] Bidirectional gut-to-brain and brain-to-gut propagation of synucleinopathy in non-human primates.

Shows: Baboon enteric or striatal patient-extract injection produced both nigrostriatal and enteric lesions, without detectable vagal lesions in the tested setting.

Does not show: Imposed extracts and small primate experiments do not establish a spontaneous route; circulating transfer is a proposed explanation rather than directly traced mediation, and linked correction is retained. A 2025 publisher correction reports duplicated/misassigned representative panels; corrected images and raw data were not audited, so this is qualified rather than singular decisive evidence. A 2025 publisher correction reports duplicated/misassigned representative panels; corrected images and raw data were not audited, so this is qualified rather than singular decisive evidence.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. ErratumIn: PMID39873693. Subclaims: SC2.

[41] Ageing promotes pathological alpha-synuclein propagation and autonomic dysfunction in wild-type rats.

Shows: Gut-injected aggregates spread more extensively through autonomic pathways in aged wild-type rats, with cardiac and gastric dysfunction and more mature aggregates.

Does not show: Age improves physiological relevance but initiation remains imposed; bidirectionality and sympathetic routes do not establish a solely vagal natural human origin.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[42] Gut mucosal cells transfer α-synuclein to the vagus nerve.

Shows: Organoid coculture and epithelial-restricted human-alpha-synuclein mice supported mucosal-to-neural transfer; vagotomy prevented hindbrain templating activity after epithelial induction.

Does not show: Original Methods/Results identify mixed wild-type/A30P/A53T transgenes restricted to gut mucosa and pre-induction vagotomy with about 15 percent weight loss. Modest expression and in-situ seed formation are stronger than injected fibrils, but neuronal uptake need not involve recipient templating; no nigral-loss endpoint or common human origin is established.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:Results:paragraph1, 1:Results:paragraph3, 1:Results:paragraph4, 2:Discussion, 3:Methods. No complete-paper or supplement audit claimed. UpdateOf: PMID37645945. Subclaims: SC2.

[43] α-Synuclein in gut endocrine cells and its implications for Parkinson's disease.

Shows: Human and mouse enteroendocrine cells expressed alpha-synuclein and connected to alpha-synuclein-containing nerves, identifying a possible mucosal source compartment.

Does not show: Expression and anatomical contact are not pathological misfolding, transfer or causal PD; the paper's premise that enteric pathology precedes brain pathology is not demonstrated by this experiment.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC2.

[44] Transcellular propagation of fibrillar α-synuclein from enteroendocrine to neuronal cells requires cell-to-cell contact and is Rab35-dependent.

Shows: Seeded enteroendocrine-to-neuronal cell propagation required physical contact and Rab35, with enhanced lysosomal clearance after inhibition.

Does not show: Cell lines and added fibrils test a transfer mechanism rather than endogenous whole-animal or human gut initiation and degeneration.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[45] Transmissible α-synuclein seeding activity in brain and stomach of patients with Parkinson's disease.

Shows: Intracerebral transmission of human stomach or brain homogenate produced localized aggregation in sensitized mice, unlike blood or muscle, without overt motor disease.

Does not show: Imposed intracerebral delivery bypasses vagal transport; subtle aggregation after long incubation is not PD neurodegeneration or a native enteric origin, and linked erratum is retained. The correction changes stomach-homogenate pathology denominators including 7/7 to 7/14; no uncorrected rate is used. The correction changes stomach-homogenate pathology denominators including 7/7 to 7/14; no uncorrected rate is used.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. ErratumIn: PMID33956225. Subclaims: SC2.

[46] Seeding Propensity and Characteristics of Pathogenic αSyn Assemblies in Formalin-Fixed Human Tissue from the Enteric Nervous System, Olfactory Bulb, and Brainstem in Cases Staged for Parkinson's Disease.

Shows: Amplification assays detected seeding from fixed gastric and brain tissues and regionally different assemblies, without a consistent region-specific seeding gradient.

Does not show: Formalin and in-vitro amplification can alter detectable seed properties; postmortem tissue and strain differences cannot determine temporal or transport direction.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC2.

[47] Initiation of Parkinson's disease from gut to brain by δ-secretase.

Shows: Rotenone and fragment-fibril experiments implicated AEP-dependent alpha-synuclein and tau cleavage in enteric and nigral pathology.

Does not show: Systemic neurotoxin effects and forced fragment seeds do not isolate a natural enteric starting site; dependence on AEP does not alone establish vagal mediation in sporadic humans.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[48] BDNF and Netrin-1 repression by C/EBPβ in the gut triggers Parkinson's disease pathologies, associated with constipation and motor dysfunctions.

Shows: Gut conditional loss of trophic factors produced constipation, dopaminergic loss and motor abnormalities, while human tissue correlations and rotenone models implicated C/EBPbeta.

Does not show: A targeted endogenous trophic perturbation supports gut influence on degeneration; it does not by itself identify alpha-synuclein transfer as the necessary mediator or quantify spontaneous human gut initiation.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[49] C/EBPβ/AEP is age-dependently activated in Parkinson's disease and mediates α-synuclein in the gut and brain.

Shows: C/EBPbeta or AEP deletion reduced age- and rotenone-associated pathology and motor deficits in human-SNCA transgenic mice with apparent gut-to-brain progression.

Does not show: Human-protein transgenesis, global pathway effects and toxin exposure complicate origin-specific mediation; related reports share pathway and laboratory components.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[50] Chronic Mild Gut Inflammation Accelerates Brain Neuropathology and Motor Dysfunction in α-Synuclein Mutant Mice.

Shows: Mild chronic DSS gut inflammation accelerated motor dysfunction and nigral marker loss in alpha-synuclein-mutant mice with increased enteric and brain pathology.

Does not show: Genetic sensitization and inflammatory perturbation do not isolate vagal alpha-synuclein transfer from immune or systemic influences; acceleration is not proof of initial human cause.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[51] Gut Microbiota Regulate Motor Deficits and Neuroinflammation in a Model of Parkinson's Disease.

Shows: Microbiota depletion, recolonization, metabolites and patient-donor transfer modulated motor deficits and neuroinflammation in alpha-synuclein-overexpressing mice.

Does not show: Overexpression and microbiome manipulation support a gut modifier; they do not establish enteric seeds ascending the vagus, and germ-free developmental and donor effects limit transfer.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[52] Gut-first Parkinson's disease is encoded by gut dysbiome.

Shows: PD-donor microbiota transferred into wild-type mice produced TH-positive cell loss, motor impairment and gut-immune-brain changes.

Does not show: Donor medications, recipient conditioning and systemic immune or barrier routes require separation from vagal transfer; TH-positive counts need corroboration of neuron survival before equating them to complete neuronal death.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[53] Early alpha-synuclein accumulation, oxidative stress and inflammation in the proximal colon of c-rel-/- mouse model of Parkinson's disease.

Shows: Endogenous global c-rel knockout mice showed early proximal-colon alpha-synuclein accumulation with later oxidative stress, inflammation and enteric TH-positive loss.

Does not show: Global genotype can affect gut and brain in parallel; the reported colon time course does not prove transfer necessity or exclude an independently initiating CNS defect.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC2.

[54] Gut microbiota promote the propagation of pathologic α-syn from gut to brain in a gut-originated mouse model of Parkinson's disease.

Shows: Antibiotics reduced progression in a gut-originated model; bacterial and metabolite experiments implicated BCAA-related impaired microglial alpha-synuclein clearance.

Does not show: The abstract does not specify how the initiating mouse model was generated; route dependence and primary origin cannot be assumed, and antibiotic effects extend beyond the identified metabolite.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[55] Gut-initiated alpha synuclein fibrils drive parkinsonism phenotypes: temporal mapping of REM sleep behavior disorder-like and other non-motor symptoms.

Shows: Gut PFF injection in wild-type mice produced temporally mapped central spread and motor and sleep phenotypes, with central dopamine experiments linking REM abnormalities to nigral dysfunction.

Does not show: Exogenous seeds impose the initiating lesion; RBD-like animal behaviours do not establish a human gut-first subtype, and the final report replaces its preprint.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. UpdateOf: PMID38712208. Subclaims: SC2.

[56] Gut microbial production of imidazole propionate drives Parkinson's pathologies.

Shows: Microbial UrdA and imidazole propionate manipulations increased brain metabolite exposure and PD-like neuronal and behavioural outcomes, with mTORC1 implicated.

Does not show: Original Results include Nissl/TH stereology, matched bacterial colonization and rapamycin protection without lowering ImP exposure. Germ-free or antibiotic conditioning and administered metabolites constrain transfer; the human plasma comparison follows a mean 9.5 years of PD and cannot establish initiation.

Access/status: Complete primary abstract and linked-status metadata examined. Selected body sections: 1:Results:paragraph3, 1:Results:paragraph5, 1:Results:paragraph9, 1:Results:paragraph13, 1:Results:paragraph14, 1:Results:paragraph16, 1:Results:paragraph17. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[57] Sex-dependent interactions between prodromal intestinal inflammation and LRRK2 G2019S in mice promote endophenotypes of Parkinson's disease.

Shows: Intestinal inflammation accelerated nigral aggregation and dopaminergic loss in male human-LRRK2-G2019S mice, with sex-chromosome manipulations retaining male susceptibility.

Does not show: A familial-risk genotype and induced colitis support conditional gut influence; myeloid transport, inflammatory signalling and direct vagal transfer remain distinct possibilities.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[58] Role of TLR4 in the gut-brain axis in Parkinson's disease: a translational study from men to mice.

Shows: Human colon inflammation was accompanied by rotenone-model protection after TLR4 knockout despite persistent dysbiosis.

Does not show: Global receptor deletion and neurotoxin exposure do not isolate gut-to-vagus seeds; human cross-sectional inflammation could follow disease, transit or medication changes.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[59] Experimental colitis promotes sustained, sex-dependent, T-cell-associated neuroinflammation and parkinsonian neuropathology.

Shows: Colitis induced sustained TH-marker reduction and neuroinflammation in male mice; CD8 depletion prevented the TH change, and colitis increased later MPTP vulnerability.

Does not show: Dopamine itself was not reduced after colitis; immune effects and neurotoxin susceptibility are not proven neuron death or alpha-synuclein vagal transfer, providing an alternative gut-brain mediator.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2.

[60] Gut microbiome dysbiosis across early Parkinson's disease, REM sleep behavior disorder and their first-degree relatives.

Shows: Cross-sectional early-PD, RBD and relatives showed dysbiosis including depleted butyrate-producing bacteria after adjustment for several transit and medication variables.

Does not show: RBD and family-enriched associations do not establish direction, first seed tissue or transmission; residual diet and shared-environment confounding remain.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[61] Difference in gut microbial dysbiotic patterns between body-first and brain-first Parkinson's disease.

Shows: A small subtype-classified metagenomic study found different microbial and curli-related gene profiles in body-first proxy groups.

Does not show: Cross-sectional 15-versus-nine subgroup comparisons, transit and treatment can explain microbiome patterns; inferred microbial functions are not measured human seed transfer.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[62] Supplementation with short-chain fatty acids and a prebiotic improves clinical outcome in Parkinson's disease: a randomized double-blind prospective study.

Shows: A randomized double-blind supplementation report described motor and medication changes over six months alongside immune and barrier outcomes.

Does not show: The abstract does not establish an inactive comparator or enteric-seed/vagal mediator; retrospective registration, concurrent PD therapy and symptom change cannot prove disease modification or primary origin.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[63] Parkinson's disease is not associated with gastrointestinal myenteric ganglion neuron loss.

Shows: Quantitative gastrointestinal autopsy comparison found preserved myenteric neuron density despite enteric Lewy pathology, whose distribution followed parasympathetic input.

Does not show: End-stage density and staining do not exclude prior functional injury or origin; the result challenges attributing gut dysfunction directly to enteric neuron loss.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

[64] Appendectomy and risk of Parkinson's disease: A nationwide cohort study with more than 10 years of follow-up.

Shows: A large Danish matched registry study found a small increased rather than decreased PD hazard at least ten years after appendectomy, persisting after longer follow-up.

Does not show: Nonrandom surgery and inflammation-related indications remain confounders; contradicts a simple universal appendix-reservoir protection prediction without excluding a subset effect.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[65] Appendectomy and risk of Parkinson's disease in two large prospective cohorts of men and women.

Shows: Prospective Nurses' Health and Health Professionals cohorts found no overall reduced PD hazard after self-reported appendectomy, with higher risk for appendicitis-related surgery in women.

Does not show: Exposure recall and operative indication affect inference; results oppose simple reservoir-removal protection but do not test vagal transfer directly.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[66] Appendectomy in mid and later life and risk of Parkinson's disease: A population-based study.

Shows: Appendectomy after age 35 did not reduce later PD risk relative to cholecystectomy, and the early increase relative to no surgery disappeared with longer follow-up.

Does not show: Midlife surgery may miss an earlier initiation window; comparator procedures and indication confounding leave subtype-specific effects unresolved.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[67] Appendectomy and the Risk of Parkinson's Disease: A Korean Nationwide Study.

Shows: A Korean national cohort found no statistically resolved appendectomy-PD association, with adjusted hazard confidence limits spanning protection and increased risk.

Does not show: Imprecision and nonrandom surgery preclude interpreting a null test as equivalence or excluding an earlier subtype-specific reservoir.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[68] Appendectomy, Tonsillectomy and Parkinson's Disease Risk: A Swedish Register-Based Study.

Shows: A Swedish nested case-control study associated prior appendectomy with lower PD odds, including long lags, with a less precise tonsillectomy association.

Does not show: Overlaps national register source populations with earlier Swedish studies; surgical indications, smoking proxies and hospital-use ascertainment do not isolate alpha-synuclein reservoir removal.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC2, SC3.

[69] The dorsal motor nucleus of the vagus is not an obligatory trigger site of Parkinson's disease: a critical analysis of alpha-synuclein staging.

Shows: Seventy-one PD brains included widespread noncanonical staging and cases without DMV involvement despite nigral or cortical pathology.

Does not show: Autopsy sampling and lesion clearance limit temporal inference; shows the DMV is not universally obligatory, without quantifying how often gut-vagal origin occurs.

Access/status: Complete primary abstract and linked-status metadata examined. No complete-paper or supplement audit claimed. none_found. Subclaims: SC1, SC3.

Documentary record

Every grade on this site is reproducible from its record. The files below are the posted edition exactly as assessed.

• SHA256.txt
• codex-correction-provenance.json
• consensus-addendum.md
• consensus-validation.json
• edition-approval-audit.json
• gut-origin-parkinsons.review.md
• gut-origin-parkinsons.scorecard.json
• validation-report.json
• validation-round2-2026-10-14.json
• validation.txt

Sources: 69 · load-bearing claims: 73 · verified: 73 · unverified: 0 · contradicted: 0 · schema 5.3