Parkinson's

Across my dataset of 101,518 condition records drawn from 49,876 Board decisions, strong-nexus records grant at an average of 89.5 percent. COPD strong-nexus grants at 92.5 percent. Sinusitis at 62.4 percent. PTSD strong-nexus runs in the 90s. The strong-nexus win rate for Parkinson's disease in my dataset is 98.3 percent, the highest single strong-nexus grant rate I've measured for any condition cornerstone.

Read that again. When the Board codes the nexus opinion in a Parkinson's case as strong, the case grants 98 percent of the time. The remaining 1.7 percent (3 of 179 strong-nexus cases) is the only place at the entire intersection of "well-documented Parkinson's" and "strong medical opinion linking it to service" where the Board doesn't grant. That's not a high-grant-rate condition. That's a near-certainty when the file is built right. The rest of this post is about what makes the file build right, why the Agent Orange presumption under 38 CFR § 3.309(e) is the structural lever that drives this, how DC 8004 sets a minimum 30 percent floor before additive ratings for separate manifestations, and how the FY2021 NDAA added the broader parkinsonism category to 38 USC § 1116.

TL;DR

• 892 Parkinson's cases at the BVA. Granted 38.2% (341), denied 30.8% (275), remanded 30.9% (276).
• Strong nexus grants at 98.3%, the highest strong-nexus rate in the entire dataset across all condition cornerstones I've analyzed.
• Agent Orange / herbicide exposure is the presumptive lever. 332 cases invoke herbicide, 81 invoke Agent Orange specifically. Parkinson's was added to the § 3.309(e) presumptive list in 2010.
• Presumptive connection grants at 44.7%, direct at 43.7%, secondary at 40.3%. The three lanes are at structural parity, unusual for any condition.
• DC 8004 (paralysis agitans) sets a minimum 30% rating for diagnosed Parkinson's. Additional ratings stack for separately compensable manifestations (tremor, rigidity, postural instability, speech, swallowing, autonomic dysfunction).
• The FY2021 NDAA added "parkinsonism" (broader than Parkinson's disease itself) to the statutory herbicide list in 38 USC § 1116. The 2022 PACT Act later expanded herbicide-covered locations but did not add parkinsonism.
• The modal granted rating is 30% (54 cases), which is the schedular floor. The combined ratings with separately compensable manifestations are where the higher numbers come from.

892 Cases. The Vietnam-Era Cluster

Parkinson's at the BVA is largely a Vietnam-era story. The condition's primary path to service connection runs through the Agent Orange presumption, which makes it overwhelmingly a Vietnam-veteran appeal type, with a smaller Camp Lejeune cohort and other veterans pursuing direct exposure theories.

The total dataset is 892 cases. The outcome split:

• Granted: 341 (38.2%)
• Denied: 275 (30.8%)
• Remanded: 276 (30.9%)

The 38.2 percent grant rate is solidly above the BVA-wide average of 30.6 percent. The three-way split is unusually balanced, not heavily denial-leaning like fibromyalgia or chronic fatigue, not heavily remand-leaning like COPD. The cases are getting decided on their merits, and the merits tilt toward grants more often than not.

The Vietnam tilt is unmistakable in the data. Across the broader BVA dataset, Vietnam-era veterans grant at 32.5 percent. Among Parkinson's cases specifically, the Vietnam-era subset grants at a rate that pulls above the era average, because the herbicide presumption catches most Vietnam-veteran Parkinson's claims that have documented covered service.

What makes Parkinson's structurally different from most condition cornerstones is the convergence of three things in the same condition:

• A specific neurodegenerative diagnosis with established clinical criteria (UK Parkinson's Disease Society Brain Bank criteria, MDS clinical diagnostic criteria, neurological examination findings of resting tremor, bradykinesia, rigidity, postural instability)
• A presumptive regulatory framework that doesn't require nexus opinions for qualifying veterans (§ 3.309(e) for herbicide exposure)
• A rating structure that establishes a minimum 30 percent rating once the diagnosis is established, with additive ratings for manifestations

The convergence is what produces the 98.3 percent strong-nexus grant rate. Once the medical record supports a clean Parkinson's diagnosis, and once the service record supports covered exposure, the connection theory is structurally solid. The remaining work is the rating-level analysis of which manifestations get separately compensable ratings stacked on the 30 percent floor.

Agent Orange Presumption: 332 Cases (37% of Claims)

The Agent Orange presumption under 38 CFR § 3.309(e) is the single most important regulatory framework in the Parkinson's claim picture. Parkinson's disease was formally added to the § 3.309(e) presumptive list in 2010, and the addition was retroactive, meaning claims pending or previously denied could be re-adjudicated under the new presumption.

The Parkinson's-specific presumptive invocation in my dataset:

• Herbicide exposure (broader category): 332 cases
• Agent Orange specifically: 81 cases (these overlap with herbicide)
• Camp Lejeune: 41 cases
• Burn pit: 34 cases (an invoked exposure theory, not a Parkinson's disease presumption)

The herbicide / Agent Orange categories together account for the majority of presumptive invocations. For a veteran who served on the ground in Vietnam during the Vietnam War (or in specific other covered locations during covered periods), the herbicide presumption establishes that any qualifying disease on the § 3.309(e) list, including Parkinson's, is presumed connected to that service.

What the presumption removes from the claim:

• The nexus opinion requirement. The veteran doesn't have to prove the Parkinson's was caused by herbicide exposure. The link is presumed.
• The in-service event documentation requirement. The veteran doesn't have to document a specific incident or exposure event. Service in a covered location during a covered period establishes the exposure.

What the presumption still requires:

• A current diagnosis of Parkinson's disease or the broader statutory parkinsonism category added in 2021
• Documentation of qualifying service in a covered location during a covered period
• The disease manifesting at any time after service (no manifestation-period limit for Parkinson's, unlike some other Agent Orange conditions)

The connection-type breakdown in my dataset shows the presumptive lane is the dominant theory:

• Presumptive: 358 cases (40 percent of all cases with a coded connection theory), 44.7% grant
• Direct: 341 cases, 43.7% grant
• Secondary: 67 cases, 40.3% grant
• Small aggravation and other categories

Notice that the three primary lanes, presumptive, direct, secondary, are at structural parity. The presumptive lane is the highest at 44.7 percent, but only by 1 percentage point over direct (43.7%) and 4 points over secondary (40.3%). This is unusual. For most condition cornerstones, the presumptive lane runs 10-25 points above direct (sinusitis: 52.4% vs 30.5%; COPD: 43.2% vs 38.7%). For Parkinson's, the gap is essentially zero.

I think this happens because Parkinson's is a condition where the diagnosis itself is robust and well-supported across the dataset. Once Parkinson's is the established diagnosis, the connection theory matters less than it does for conditions where the diagnosis is contested. Veterans with clean Parkinson's diagnoses generally have either a presumptive lane available (herbicide, Camp Lejeune) or a direct lane available (documented in-service exposure or symptom onset), and either lane works at roughly the same rate.

The 41 Camp Lejeune cases reflect veterans who served at Camp Lejeune between 1953 and 1987 with documented exposure to contaminated water. The qualifying-service rule is in 38 CFR § 3.307(a)(7), and Parkinson's disease appears on the disease list in 38 CFR § 3.309(f), providing another presumptive lane for that specific veteran population.

DC 8004 Minimum 30%, Then Additive

The minimum-30% floor and how additives work

The rating schedule for Parkinson's at 38 CFR § 4.124a uses Diagnostic Code 8004 (paralysis agitans) as the primary code. The structural feature of DC 8004 that distinguishes it from most condition rating schedules is the minimum-30% floor.

The regulatory text under § 4.124a Note 2 specifies that conditions like Parkinson's are rated at the minimum 30 percent for the established diagnosis, with additional ratings allowed for residuals, which are separately compensable manifestations that affect specific body systems or functions.

The minimum 30% covers the global disability picture of Parkinson's disease itself. The additive ratings can include:

• Resting tremor (rated under the appropriate cranial nerve or peripheral nerve code if functionally significant)
• Rigidity and bradykinesia affecting specific limbs
• Postural instability and balance impairment
• Cognitive decline (rated under § 4.130 mental disorders criteria if it meets the threshold)
• Speech impairment (rated under § 4.124a)
• Swallowing impairment (rated under digestive system criteria)
• Autonomic dysfunction (orthostatic hypotension, urinary incontinence, constipation)
• Mood disturbance secondary to Parkinson's (rated as a mental disorder if separately compensable)
• Sleep disturbance, particularly REM sleep behavior disorder

The combined rating math for a veteran with diagnosed Parkinson's plus several separately compensable manifestations can produce ratings well above 30 percent through the additive structure. A 30% base for Parkinson's plus 20% for severe tremor affecting both hands plus 30% for postural instability with documented falls plus 10% for swallowing impairment can combine using VA's combined-rating math to produce a substantial overall picture.

The rating distribution among granted cases in my dataset:

• 10%: 7 cases (these are pre-rating-revision cases or unusual coding)
• 30%: 54 cases (the modal grant tier, the DC 8004 floor)
• 40%: 6 cases
• 70%: 3 cases
• 100%: 9 cases

30% as the modal grant tier reflects DC 8004's minimum floor. The 100% schedular ratings (9 cases) reflect veterans whose Parkinson's progression and combined manifestations produce a totalizing disability picture. The 70% cases are mid-range progressions where the additive manifestations combine to a higher tier than the 30% floor alone.

What's missing from the rating distribution is the 50% and 60% tiers. These don't appear frequently in the Parkinson's-coded subset, because the rating schedule jumps from the 30% floor up through 70% to 100% as manifestations accumulate, rather than passing through 50% or 60% as natural intermediate tiers.

For a single veteran in 2026, the dollar values matter:

• 30%: $537.42 per month, $6,449 per year
• 70%: $1,759.19 per month, $21,110 per year
• 100%: $4,044.91 per month, $48,539 per year

The combined rating math from the additive manifestations is what produces the higher tiers in practice. A clean Parkinson's diagnosis with severe additive manifestations can move from the 30% floor to a 70% or 100% combined rating without ever leaving the structural framework of DC 8004 plus separately rated manifestations.

The Strongest Strong-Nexus Win Rate in the Data (98.3%)

The nexus quality breakdown for Parkinson's is the part of the analysis that surprised me most when I ran it.

• Strong nexus: 179 cases, 98.3% grant
• Adequate nexus: 185 cases, 69.2% grant
• Weak nexus: 154 cases, 0.0% grant
• Missing nexus: 164 cases, 0.0% grant
• Not applicable: 210 cases, 17.6% grant

98.3 percent. That is, of 179 cases with strong nexus, 176 were granted. The remaining 3 cases were denied for procedural reasons or for some condition-specific dispute that the data doesn't resolve cleanly.

For comparison, the strong-nexus grant rates I've measured across other condition cornerstones:

• COPD: 92.5%
• Sinusitis: 62.4% (lower because of the Note: my sinusitis subset has 362 strong-nexus cases, a larger sample with more variability)
• Chronic fatigue: 83.7%
• Spinal stenosis: 91.8%
• Pes planus: 80.0%
• Anxiety: 93.3%

Parkinson's at 98.3% sits at the top, by a clear margin. Why?

I think the explanation lives at the intersection of three factors:

First, the diagnosis is robust when it's made. Parkinson's disease has objective neurological examination findings (resting tremor with characteristic pill-rolling quality, bradykinesia, rigidity, postural instability), supportive response to levodopa, and well-established imaging biomarkers when needed. A confirmed Parkinson's diagnosis is rarely overturned at the Board because the underlying clinical picture is hard to mistake for something else. This is the opposite of the chronic fatigue picture, where the diagnosis itself is the contested ground.

Second, the presumption is mature law. Parkinson's has been on the § 3.309(e) Agent Orange presumptive list since 2010. The presumption has been litigated, applied, and refined over 15 years. Board members are comfortable with the framework, C&P examiners are familiar with the connection theory, and the regulatory text is clean.

Third, the strong-nexus cases tend to be highly developed. Veterans whose Parkinson's claims reach strong nexus typically have specialist neurology evaluations, supportive private medical opinions that explicitly engage with the herbicide exposure literature, and documentation of qualifying service. The selection into the strong-nexus category is heavily filtered by the level of documentation already in the file.

The 154 cases with weak nexus and 0.0 percent grant rate, and the 164 cases with missing nexus and 0.0 percent grant rate, are the inverse selection. These are cases where the medical record doesn't support a clean Parkinson's diagnosis, the connection theory is unclear, or the file is missing pieces the Board needs to decide. When the file is in that state, the case doesn't grant regardless of how sympathetic the underlying situation is.

The 210 not-applicable cases reflect appeals where the nexus question wasn't reached (rating-level disputes, jurisdictional issues, procedural questions). The 17.6 percent grant rate there reflects rating-increase claims and similar disputes that turn on tier-level analysis rather than connection theory.

Why Direct Connection Loses Less Than 1% Below Presumptive (43.7% vs 44.7%)

The structural parity between direct and presumptive Parkinson's claims is worth unpacking.

For most condition cornerstones, the presumptive lane substantially outperforms the direct lane. The presumption removes the hardest part of the case, the nexus opinion, and the resulting grant rate is meaningfully higher. Sinusitis runs 22 points higher on presumptive. COPD runs 4-5 points higher. Chronic fatigue runs 4 points higher (but on a low base).

Parkinson's runs 1 percentage point higher on presumptive (44.7%) than direct (43.7%). The gap is essentially nonexistent.

I think this is because of three things:

First, direct Parkinson's claims often have strong medical opinions even without the presumption. Veterans whose neurologists are comfortable diagnosing Parkinson's are often the same veterans whose neurologists are willing to engage with the connection theory and write substantive nexus opinions. The direct lane for Parkinson's is therefore stocked with relatively high-quality medical opinions, even when the presumption doesn't apply.

Second, the rating structure is the same regardless of lane. Whether service connection is established by presumption or by direct nexus, the rating is the same. DC 8004 floor of 30% plus additive manifestations. There's no rating advantage to the presumptive lane.

Third, the population of Parkinson's claimants is more uniform than the population of, say, sinusitis claimants. Parkinson's is largely a Vietnam-era condition. Most appellants are similarly situated demographically and clinically. The variance that produces big presumptive-vs-direct grant-rate gaps in conditions like sinusitis (where the populations using each lane look very different from each other) is muted for Parkinson's.

What this means for veterans practically: the choice of connection theory matters less for Parkinson's than it does for almost any other condition. If you have a herbicide-presumptive lane available, use it because it's structurally cleaner and removes the nexus opinion requirement. If you don't have a presumptive lane available, the direct path works almost as well, because the clinical picture is robust and the medical opinions tend to be substantive.

The Diagnosis Gap: Parkinsonism vs Parkinson's

The denial-reason breakdown for the 275 denied Parkinson's cases:

• severity_insufficient: 65
• diagnosis_missing: 54
• nexus_gap: 46
• service_connection_missing: 37
• procedural_issue: 22
• in_service_event_missing: 21
• other: remainder

Diagnosis-missing at 54 cases (about 20 percent of denials) is meaningful, though much smaller proportionally than for chronic fatigue (70 percent). The denials are spread more evenly across categories than for any other cornerstone I've analyzed.

The diagnosis-missing cases for Parkinson's reflect a specific clinical distinction that matters for the regulatory framework: Parkinson's disease (idiopathic Parkinson's, the most common form) is a specific entity, distinct from the broader category of "parkinsonism," which includes a range of conditions with overlapping movement-disorder features. Parkinsonism includes:

• Drug-induced parkinsonism (from antipsychotics, antiemetics, or other dopamine-blocking medications)
• Vascular parkinsonism (from cerebrovascular disease)
• Atypical parkinsonian syndromes (progressive supranuclear palsy, multiple system atrophy, corticobasal syndrome)
• Post-encephalitic parkinsonism
• Toxin-induced parkinsonism

These conditions share clinical features with Parkinson's disease but are distinct diagnostic entities. Some of them, particularly the atypical parkinsonian syndromes, don't respond to levodopa the way Parkinson's disease does, and the long-term progression and prognosis differ.

Before 2021, the regulatory herbicide list named "Parkinson's disease" specifically. Veterans with parkinsonism that didn't quite meet the criteria for idiopathic Parkinson's were at risk of having their claims denied on diagnostic grounds. The broader condition wasn't yet in the statute, even if it produced similar movement-disorder symptoms.

The William M. (Mac) Thornberry National Defense Authorization Act for Fiscal Year 2021 changed this. Section 9109 added "parkinsonism," the broader category, to the statutory herbicide presumption in 38 USC § 1116. The 2022 PACT Act added hypertension and MGUS to that disease list and expanded covered herbicide locations; it was not the law that added parkinsonism.

For veterans whose diagnostic picture is "parkinsonism, etiology unclear" or "atypical parkinsonian syndrome," conditions that produce Parkinson's-like symptoms but don't meet strict idiopathic Parkinson's criteria, the 2021 statutory expansion opened a presumptive lane that wasn't available before then.

The 54 diagnosis-missing denials in my dataset partially predate the 2021 expansion. Some of those denials may warrant review under the broader statutory category, subject to the effective-date and readjudication rules that apply to the individual claim.

FY2021 NDAA: Parkinsonism Broadens the Door

The FY2021 NDAA added parkinsonism, bladder cancer, and hypothyroidism to the statutory herbicide disease list. The 2022 PACT Act made different changes: it added hypertension and MGUS and expanded the locations that qualify for presumed herbicide exposure.

The sequence matters:

• In 2010, VA added Parkinson's disease to 38 CFR § 3.309(e).
• In 2021, the FY2021 NDAA added parkinsonism to 38 USC § 1116.
• In 2022, the PACT Act added MGUS and hypertension and expanded herbicide-covered locations.

For veterans whose claims predate the 2021 change and were denied on diagnostic grounds because parkinsonism didn't quite fit the Parkinson's disease label, the expanded statute may matter. The correct effective-date and readjudication rules depend on the claim history; the expansion should not be described as a 2022 PACT Act benefit.

What the parkinsonism expansion may capture:

• Vietnam-era veterans with vascular parkinsonism or drug-induced parkinsonism whose initial Parkinson's disease claims were denied
• Veterans with atypical parkinsonian syndromes (PSP, MSA, CBD) who couldn't reach the idiopathic Parkinson's diagnosis
• Veterans with mixed neurological pictures where the diagnostic picture didn't crystallize into idiopathic Parkinson's

The 34 burn-pit-coded Parkinson's cases in the dataset reflect an exposure theory invoked in the decisions, not a parallel disease presumption. Section 1119 presumes covered toxic exposure, but Parkinson's disease and parkinsonism are not listed in 38 USC § 1120 or 38 CFR § 3.320. Covered toxic exposure can support direct development, including a medical examination and opinion under 38 USC § 1168 when its requirements are met.

The 2021 parkinsonism expansion and the PACT Act's later covered-location changes are still working through the data. My dataset includes cases decided through 2025, but appellate lag means the grant-rate impact will not be clear until more decisions accumulate.

Lay Statements Worth 23 Points

Lay statements quoted in the Board's decision are a meaningful grant-rate predictor for Parkinson's:

• Lay statement quoted: 430 cases, 50.9% grant
• Lay statement not quoted: 445 cases, 27.4% grant

A 23-point gap. This is consistent with the broader pattern I see across condition cornerstones. Quoted lay statements grant at meaningfully higher rates than non-quoted ones, with gaps typically running 15-30 points.

For Parkinson's specifically, the lay statements that the Board engages with tend to describe:

• Onset and progression of motor symptoms (when tremor started, when bradykinesia became noticeable, when balance issues began)
• Functional impact (effects on activities of daily living, employment, fine motor tasks like writing or buttoning clothes, driving)
• Treatment response and side effects (levodopa response, dyskinesias, "on-off" phenomena)
• Caregiver observations (when applicable, spouse or family statements describing the progression the veteran can't fully describe)
• Specific incidents (falls, near-misses, episodes of freezing, autonomic symptoms)

What weak lay statements look like:

• Generic descriptions ("my Parkinson's has been getting worse")
• Symptom-only without functional context
• Lack of specificity on timeline or progression

The 430 cases with quoted lay statements grant at 50.9 percent, above the overall 38.2 percent rate. The lay-statement variable is particularly useful for Parkinson's because the rating-level analysis often depends on documenting the severity and frequency of specific manifestations (tremor, postural instability, autonomic symptoms), and the lay statement can fill descriptive gaps that clinical visits sometimes miss.

This matters more at the rating phase than at the connection phase. Once service connection is established (either by presumption or by direct nexus), the rating-level work is figuring out which separately compensable manifestations are present and how severe they are. The lay statement that describes the daily symptom picture in detail can support higher additive ratings beyond the 30% DC 8004 floor.

What I Can't Tell You From This Data

Honest limits matter, particularly for a condition with this much regulatory complexity.

I can't tell you whether your specific neurological diagnosis will be characterized as idiopathic Parkinson's disease, parkinsonism, or an atypical parkinsonian syndrome. The diagnostic question requires neurological examination, response to dopaminergic medication, and sometimes imaging or biomarker studies. That's a clinical question for a movement-disorder specialist, not something aggregate data can resolve.

I can't tell you whether your service qualifies under the Agent Orange presumption. The covered locations and periods are specific. Boots-on-ground service in Vietnam, the Korean DMZ during certain periods, certain Royal Thai bases, and a few others. Blue Water Navy veterans gained presumptive eligibility in 2019 under the Blue Water Navy Vietnam Veterans Act. The PACT Act expanded some categories further. Whether your specific service file qualifies depends on what the VA's exposure tracking shows and what your records confirm.

I can't tell you whether your case should use the herbicide presumption, the Camp Lejeune presumption, or direct connection. That depends on the specific covered service in your record. Burn-pit or other covered toxic exposure can support direct development, but it is not a Parkinson's disease presumption under § 1120 or § 3.320. Some veterans have more than one valid lane available; others have none. The presumptive vs direct gap is small for Parkinson's, but a valid presumption is structurally cleaner when available.

I can't tell you which of your manifestations will qualify for separately compensable ratings beyond the 30% DC 8004 floor. The additive ratings depend on the clinical documentation of each manifestation, the severity, and the rating-schedule criteria for that specific symptom category. A neurology specialist's evaluation that documents each manifestation separately is what supports the combined rating math.

I can't tell you whether the 2021 statutory parkinsonism expansion will benefit your specific case. The answer depends on the prior decision, the current diagnosis, and the applicable effective-date or readjudication rules.

What the data can tell you is the structural shape of this claim. The 98.3 percent strong-nexus grant rate is real and is the highest I've measured. The Agent Orange presumption is mature and works when invoked appropriately. The DC 8004 floor of 30 percent is the schedular baseline, with additive manifestations producing higher combined ratings. And the 2021 statutory expansion broadened the diagnosis category in ways that haven't fully worked through the data yet.

Three Things to File a Parkinson's Claim Right

If I were filing or appealing a Parkinson's claim today, the three pieces of the file that would matter most:

One: A specialist neurology evaluation that documents the diagnosis with the recognized criteria. A movement-disorder specialist, neurologist, or comprehensive neurological evaluation that addresses the UK Brain Bank or MDS diagnostic criteria for Parkinson's disease, or accurately identifies a broader parkinsonism diagnosis under 38 USC § 1116, is the foundation of the claim. The 98.3 percent strong-nexus grant rate is reachable when the diagnostic record is clean and supports the connection theory. Generic neurological notes that say "Parkinson's, on medication" don't produce strong nexus. Substantive specialist evaluations that engage with the diagnostic criteria and document the clinical picture do.

Two: A presumptive framework invocation when available, with the supporting service documentation. If you performed herbicide-covered service, the herbicide presumption under 38 USC § 1116 applies to Parkinson's disease and parkinsonism; 38 CFR § 3.309(e) also expressly lists Parkinson's disease. If you served at Camp Lejeune during the qualifying period, use the service rule in § 3.307(a)(7) and the Parkinson's disease listing in § 3.309(f). Covered PACT Act service does not create a burn-pit presumption for Parkinson's. The direct lane at 43.7 percent remains available if no disease presumption applies.

Three: Comprehensive documentation of the manifestations for the rating-level analysis. The 30 percent DC 8004 floor is what the base diagnosis produces. The combined rating with separately compensable manifestations is where the higher numbers come from. Document each manifestation (resting tremor, rigidity, bradykinesia, postural instability with falls, speech impairment, swallowing difficulties, autonomic symptoms, cognitive changes, mood disturbance, sleep disturbance) in clinical records and through lay statements with specific examples. The 50.9 percent grant rate when lay statements are quoted reflects veterans whose lay evidence described the symptom picture with the specificity the rating-level analysis requires.

If your initial Parkinson's claim was denied before the 2021 statutory change because the diagnostic picture didn't quite fit idiopathic Parkinson's, the broader parkinsonism category may affect a new or reviewed claim. The governing effective-date and readjudication rules are claim-specific.

Bottom Line

Parkinson's disease is rated under 38 CFR § 4.124a, Diagnostic Code 8004, with a minimum 30% rating for the established diagnosis and additive ratings for separately compensable manifestations including tremor, rigidity, postural instability, speech, swallowing, autonomic dysfunction, mood, and cognitive changes. Across 892 BVA cases, the grant rate is 38.2%, and the strong-nexus grant rate is 98.3%, the highest single strong-nexus rate I've measured for any condition cornerstone in my dataset. Parkinson's disease is a presumptive condition for veterans with qualifying herbicide exposure under 38 CFR § 3.309(e), and the FY2021 NDAA added the broader parkinsonism category to 38 USC § 1116. Camp Lejeune provides a separate Parkinson's disease presumption under §§ 3.307(a)(7) and 3.309(f). Parkinson's disease and parkinsonism are not burn-pit disease presumptions under § 1120 or § 3.320. The 30% DC 8004 floor combined with additive manifestation ratings produces the higher combined ratings in practice; the modal granted rating is 30%, but 9 cases in this dataset reached 100% through the additive structure. Lay statements that describe the daily symptom picture with specificity drive a 23-point grant-rate gap. For all Parkinson's claimants, the specialist neurology evaluation is what supports the diagnosis and, when a direct lane is needed, the nexus.

Methodology and Limitations

• Data source: Outcome statistics, nexus-quality coding, denial-reason classification, connection-type tagging, and rating-tier distribution are drawn from Claim Raven's analysis of 101,518 condition records drawn from 49,876 Board decisions, including 892 Parkinson's disease cases. Rating schedule framework is drawn from 38 CFR § 4.124a, Diagnostic Code 8004 (paralysis agitans), and the Note 2 minimum-rating framework. The herbicide presumption is from 38 USC § 1116 and 38 CFR § 3.309(e); the broader parkinsonism category was added to the statute by the FY2021 NDAA. The Camp Lejeune framework is from 38 CFR §§ 3.307(a)(7) and 3.309(f). Sections 1119, 1120, 1168, and 38 CFR § 3.320 are cited only to distinguish direct toxic-exposure development from a disease presumption. 2026 VA disability compensation rates referenced for context (100% single vet = $4,044.91/month; 70% = $1,759.19/month; 30% = $537.42/month).
• Sample size: 892 BVA decisions involving Parkinson's disease, with outcomes split 38.2% granted (341), 30.8% denied (275), 30.9% remanded (276). Connection-type subdivisions cover 358 presumptive, 341 direct, 67 secondary, and a small aggravation remainder. Presumptive subcategories include 332 herbicide invocations, 81 Agent Orange specifically (overlapping with herbicide), 41 Camp Lejeune, and 34 burn pit. Rating-tier distribution among grants reflects 79 cases where a tier was clearly identified.
• Classification approach: Cases coded as "parkinsons" based on the condition extraction from BVA decisions. The data does not consistently distinguish idiopathic Parkinson's disease from other parkinsonian syndromes; some classifications may reflect the broader parkinsonism category, particularly for decisions after the 2021 statutory change. Nexus-quality coding (strong/adequate/weak/missing/not_applicable) is based on the Board's treatment of the medical opinion language.
• Limitations:
• The 892 Parkinson's cases reached the BVA. Claims granted at the regional office without appeal aren't in this dataset, and the overall VA grant rate for Parkinson's is almost certainly higher than 38.2%.
• The 98.3% strong-nexus grant rate reflects 179 cases. While this is a meaningful sample, the strong-nexus category is heavily selected. These are cases where the medical opinion is robust enough to be classified as strong, which correlates with other features of the file being well-developed.
• The 2021 statutory parkinsonism expansion took effect partway through the dataset's coverage. The full impact on grant rates may not be visible until more later cases accumulate.
• The distinction between idiopathic Parkinson's disease and the broader parkinsonism category is not always cleanly identified in the data. Some atypical parkinsonian syndromes (PSP, MSA, CBD) may be coded as Parkinson's in the dataset.
• Rating-tier distribution reflects the 79 cases where a tier was clearly coded. The combined-rating math from additive manifestations is not separately broken out. The 30% modal tier reflects DC 8004 alone, and higher tiers reflect the combined rating with manifestations.
• The Agent Orange presumption framework has evolved since 2010 (Blue Water Navy 2019, PACT Act 2022); some cases in the dataset were decided under earlier versions of the framework.
• These observations describe BVA patterns. They are not predictions of individual outcomes.