Neurology Neurology

Parkinson's Features

Parkinson's disease is the second most common neurodegenerative disease. Its cardinal motor features form the TRAP mnemonic, but non-motor features dominate quality of life.

✦ The Mnemonic

"TRAP — Tremor, Rigidity, Akinesia, Postural instability"

Four cardinal motor features of Parkinson's disease

T Tremor Resting pill-rolling tremor (4–6 Hz); suppressed by movement; worse with stress; starts unilaterally

R Rigidity Lead-pipe rigidity (uniform throughout range); cogwheel = rigidity + tremor; passive movement

A Akinesia / Bradykinesia Slowness of movement initiation; small handwriting (micrographia); hypomimia (masked face)

P Postural instability Late feature; falls; shuffling gait; festination; difficulty turning; retropulsion

📚 Clinical Breakdown

Non-motor features often precede motor symptoms by years — hyposmia (anosmia), REM sleep behaviour disorder (acting out dreams — punching, kicking during sleep), constipation, depression, and autonomic dysfunction (orthostatic hypotension). These are caused by Lewy body pathology spreading beyond the substantia nigra.

Dopaminergic therapy: levodopa (with carbidopa/benserazide — DDCI) remains the gold standard. Dopamine agonists (pramipexole, ropinirole) are used in younger patients to delay levodopa-related dyskinesias. MAO-B inhibitors (rasagiline, selegiline) provide modest neuroprotective-like benefit.

Levodopa complications: after 5–10 years, most patients develop motor fluctuations — 'on-off' phenomenon (sudden freezing) and dyskinesias (involuntary writhing movements during peak drug effect). Deep brain stimulation (DBS) of the subthalamic nucleus significantly reduces fluctuations and dyskinesias in selected patients.

Tremor type Resting pill-rolling — suppressed by movement

Rigidity type Lead-pipe or cogwheel

First-line drug Levodopa + carbidopa/benserazide

Precedes motor symptoms Hyposmia, REM sleep disorder, constipation

⭐ Clinical Pearl

Parkinson's Plus syndromes: Progressive supranuclear palsy (PSP — vertical gaze palsy, falls backwards, axial rigidity), Multiple system atrophy (MSA — early autonomic failure, cerebellar or parkinsonian features), and Corticobasal degeneration (CBD — alien limb, apraxia, cortical sensory loss). None respond well to levodopa — distinguishing them from PD is important.

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