GPAtlas🧭 When to suspect
Parkinson's disease is a chronic, progressive neurodegenerative condition caused by loss of the dopamine-producing cells of the substantia nigra. It is the commonest cause of parkinsonism, but the diagnosis is clinical – made by a specialist using the UK Parkinson's Disease Society Brain Bank Clinical Diagnostic Criteria – and there is no blood test or scan that confirms it in primary care.
Suspect parkinsonism in anyone with the insidious onset of bradykinesia (the mandatory feature) plus at least one of: rigidity, a 4–6 Hz resting tremor (classically "pill-rolling"), or postural instability not explained by primary visual, vestibular, cerebellar or proprioceptive dysfunction. Asymmetry of signs at onset is a key supportive feature.
Crucially, non-motor symptoms often predate the motor signs by years – hyposmia or anosmia, rapid eye movement (REM) sleep behaviour disorder, constipation and depression. The GP's task is to recognise parkinsonism, exclude reversible mimics, and refer quickly and untreated; do not start anti-parkinsonian medication in primary care.
| Supports idiopathic Parkinson's disease | Suggests an alternative (atypical or secondary parkinsonism) |
|---|---|
| Asymmetrical onset and persistent asymmetry | Symmetrical signs from the outset |
| Resting tremor, "pill-rolling", 4–6 Hz | Tremor absent, or a prominent action/postural tremor |
| Slowly progressive over years | Rapid progression |
| Sustained, excellent levodopa response | Poor or absent levodopa response |
| Normal early cognition and autonomic function | Early falls/postural instability → progressive supranuclear palsy (PSP); early dementia, fluctuating cognition or visual hallucinations → dementia with Lewy bodies (DLB); early severe autonomic failure → multiple system atrophy (MSA); vertical (supranuclear) gaze palsy → PSP |
Risk rises with age; other associations include male sex, a family history of Parkinson's disease, and certain pesticide/toxin exposures. A recent dopamine-antagonist drug (antipsychotic or antiemetic) or significant cerebrovascular disease should always prompt consideration of drug-induced or vascular parkinsonism instead.
Source: NICE NG71
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