- Design
- Retrospective clinicopathological study
- Population
- 61 autopsy-confirmed Parkinson's disease cases, Parkinson's UK Brain Bank
- Primary outcome
- Correlation of Braak stage with clinical progression indices
- Effect
- No correlation with H&Y at death (ρ 0.146, 95% CI −0.11 to 0.39) or disease duration
Researchers reviewed 61 autopsy-confirmed Parkinson's disease cases with Braak staging from the Parkinson's UK Brain Bank. Mean age at death was 79, disease duration 13.5 years and Hoehn and Yahr stage at death 4.0.
Braak stage did not correlate with Hoehn and Yahr stage at death, disease duration, age at death or brain weight. Co-pathology was the rule: tau in the entorhinal cortex in 82%, small vessel disease in 60%, amyloid in 58% and amyloid angiopathy in 25%.
The Braak model, in which Lewy pathology spreads in a predictable order, is often taught as a map of clinical progression. In this cohort it was not one. For clinicians, the frequent co-pathology may matter more: most patients with long-standing Parkinson's carry Alzheimer-type and vascular changes that may shape their late decline.
- Do not explain a patient's stage of Parkinson's to them in terms of Braak stage — it did not match clinical severity.
- Most patients had tau, amyloid or small vessel disease as well as Lewy pathology.
- Treat vascular risk factors in Parkinson's; small vessel disease was present in 60%.
- Consider mixed pathology when cognition declines in late Parkinson's disease.
Why it matters
It challenges a widely taught model of Parkinson's progression and points to co-pathology as part of late decline.
Don't overread it
Sixty-one cases is small, and by the time of death most patients were at advanced stages, limiting the range to detect a correlation.
The statistics, in plain English
A Spearman correlation (ρ) of 0.146 with a 95% interval of −0.11 to 0.39 means no clear relationship; the interval includes zero and rules out only a strong one.
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