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Atypical parkinsonism
Parkinsonism that responds poorly to levodopa, with early falls, early autonomic failure, gaze palsy or early dementia, suggests a "Parkinson-plus" syndrome — PSP, MSA, dementia with Lewy bodies or corticobasal degeneration — rather than Parkinson's disease.
Why it matters in the exam
Questions describe a patient with parkinsonism and add "one clue": backward falls in the first year and downgaze palsy (PSP), a fall in blood pressure on standing, urinary incontinence and cerebellar signs (MSA), visual hallucinations, fluctuating alertness and severe sensitivity to antipsychotics (Lewy bodies), or an "alien" hand and one-sided apraxia (corticobasal degeneration). They also test drug-induced parkinsonism (antipsychotics, metoclopramide), in which DaT-SPECT is normal, and poor levodopa response as a warning sign. A dangerous distractor is giving haloperidol to a hallucinating patient with Lewy bodies. The general principle: Parkinson's disease usually starts on one side, with rest tremor and a good, lasting response to levodopa, whereas the atypical syndromes progress faster, respond weakly or briefly to levodopa, and carry a worse prognosis. The diagnosis is largely clinical, and MRI helps by showing typical atrophy.
Key points
- Poor levodopa response and early flags suggest atypical parkinsonism.
- PSP: vertical gaze palsy and early backward falls.
- MSA: early autonomic failure with parkinsonism or ataxia.
- Lewy bodies: early dementia, hallucinations and fluctuations — severe antipsychotic sensitivity.
- Drug-induced parkinsonism is symmetric, with a normal DaT-SPECT.
Summary table
| Syndrome | Distinguishing clues | Imaging or treatment |
|---|---|---|
| PSP (progressive supranuclear palsy) | Vertical supranuclear gaze palsy (mainly downward), backward falls in the first year, axial rigidity, "surprised" stare | Midbrain atrophy ("hummingbird sign"); poor levodopa response |
| MSA (multiple system atrophy) | Early autonomic failure (orthostatic hypotension, urinary incontinence), parkinsonism or ataxia, stridor | "Hot cross bun" sign in the pons; treat orthostatic hypotension (midodrine, fludrocortisone) |
| Dementia with Lewy bodies | Dementia before parkinsonism or within a year, visual hallucinations, fluctuations, REM sleep behaviour disorder | Cholinesterase inhibitors; avoid typical antipsychotics |
| Corticobasal degeneration | Asymmetric rigidity, apraxia, "alien" hand, cortical sensory loss, myoclonus | Supportive care |
| Drug-induced parkinsonism | Symmetric, after antipsychotics, metoclopramide or prochlorperazine | Normal DaT-SPECT; stop the drug |
A free exam question
לפי MCKEITH CRITERIA לאבחנת DEMENTIA WITH LEWY BODIES , איזה מהבאים אינו CORE FEATURE ? (the question as examined, in Hebrew)
- א. פלקטואציות בערנות ובריכוז
- ב. הזיות ויזואליות חוזרות
- ג. מחשבות שווא סיסטמיות
- ד. פרקינסוניזם ספונטאני
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Sources
- MDS Clinical Diagnostic Criteria for Progressive Supranuclear Palsy (Höglinger et al., Movement Disorders), 2017 — Core clinical features
- MDS Criteria for the Diagnosis of Multiple System Atrophy (Wenning et al., Movement Disorders), 2022 — Clinically established MSA
- Fourth Consensus Report of the DLB Consortium (McKeith et al., Neurology), 2017 — Core clinical features
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.