SN12 SHORT NOTE 5M

Write a short note on parkinsonism, including essential tremor.

General Medicine · Final Professional

Definition

Parkinsonism is a clinical syndrome defined by bradykinesia together with at least one of rest tremor and rigidity. Parkinson's disease (PD) is the commonest cause, accounting for about 80%, and is a progressive neurodegenerative disorder characterised by loss of dopaminergic neurones in the substantia nigra pars compacta with Lewy bodies (intracytoplasmic inclusions of alpha-synuclein).

Symptoms appear when 60–80% of nigrostriatal dopaminergic neurones have been lost — which is why disease is well established at presentation.

Cardinal Features — "trap"

TRAP — cardinal features of parkinsonism

T = Tremor — rest tremor, 4–6 Hz, "pill-rolling", asymmetrical at onset, decreases with voluntary movement, increases with stress and distraction

R = Rigidity — "lead-pipe" increase in tone throughout the range; "cogwheel" when combined with tremor

A = Akinesia / bradykinesia — the essential feature: slowness with progressive decrement in amplitude on repetitive movement (finger tapping), micrographia, hypomimia (mask-like face), reduced arm swing, hypophonia

P = Postural instability — impaired righting reflexes, positive pull test, falls (a later feature; early falls suggest an alternative diagnosis)

Other motor features: festinating, shuffling gait with difficulty initiating (freezing) and turning en bloc; stooped posture; drooling; reduced blink rate.

Non-motor features — often preceding motor onset by years, and a major source of disability:

Hyposmia (very early), REM sleep behaviour disorder (acting out dreams — a strong predictor), constipation, and depression.
Later: cognitive impairment and dementia, hallucinations, anxiety, autonomic dysfunction (postural hypotension, urinary urgency, erectile dysfunction), pain, fatigue and sleep disturbance.

Causes of Parkinsonism

Idiopathic Parkinson's disease (80%).
Drug-induced — the commonest reversible cause: antipsychotics (typical and atypical), metoclopramide, prochlorperazine, flunarizine, sodium valproate, lithium. Characteristically symmetrical, with prominent tremor and a clear temporal relation to the drug.
Parkinson-plus syndromes: progressive supranuclear palsy (early falls, vertical gaze palsy, axial rigidity), multiple system atrophy (early autonomic failure, cerebellar or pyramidal signs), corticobasal degeneration (alien limb, marked asymmetry), dementia with Lewy bodies (early dementia with visual hallucinations and fluctuating cognition).
Vascular parkinsonism — "lower body parkinsonism", stepwise progression, poor levodopa response.
Others: post-encephalitic, Wilson's disease (essential to exclude in any patient under 50), normal pressure hydrocephalus, repeated head injury, carbon monoxide and manganese toxicity.

Essential Tremor — the Key Differential

Feature	Parkinson's disease	Essential tremor
Tremor type	REST tremor — present when the limb is supported and relaxed	POSTURAL and ACTION tremor — on holding a posture or performing a task
Frequency	4–6 Hz	6–12 Hz
Symmetry	Asymmetrical at onset	Bilateral, roughly symmetrical
Parts affected	Hands, legs, jaw, chin (head tremor is rare)	Hands, head (titubation) and voice are commonly affected
Effect of movement	Decreases with voluntary movement	Increases with movement, worse at the end of a task
Effect of alcohol	No effect	Characteristically improves markedly — a useful diagnostic clue
Family history	Uncommon	Positive in over half; autosomal dominant
Other signs	Bradykinesia, rigidity, postural instability	None — examination is otherwise normal
Treatment	Levodopa	Propranolol, primidone

Diagnosis

Parkinson's disease is a clinical diagnosis. Supportive features include asymmetrical onset, an excellent and sustained response to levodopa, and the presence of rest tremor. Red flags suggesting an alternative diagnosis: symmetrical onset, early falls, early dementia or hallucinations, early autonomic failure, vertical gaze palsy, cerebellar or pyramidal signs, rapid progression, and poor levodopa response.

Investigations are for exclusion rather than confirmation:

MRI brain (vascular disease, hydrocephalus, Parkinson-plus features)
serum caeruloplasmin, 24-hour urinary copper and slit-lamp examination for Kayser–Fleischer rings in any patient under 50 (Wilson's disease is treatable and must not be missed)
thyroid function
DaTscan (dopamine transporter imaging) where the distinction from essential tremor or drug-induced parkinsonism is genuinely uncertain.

Management of Parkinson's Disease

There is no disease-modifying therapy; treatment is symptomatic.

Levodopa with a peripheral decarboxylase inhibitor (carbidopa or benserazide) — the most effective drug for motor symptoms. Long-term use is complicated by motor fluctuations ("wearing off", "on-off" phenomenon) and dyskinesias, which is why initiation is sometimes deferred in younger patients — though delaying at the cost of function is no longer favoured.
Dopamine agonists (pramipexole, ropinirole, rotigotine patch) — useful in younger patients and as adjuncts; beware impulse control disorders (gambling, hypersexuality, compulsive shopping), which must be specifically asked about, plus somnolence, hallucinations and oedema.
MAO-B inhibitors (selegiline, rasagiline) — modest benefit, useful early or as adjunct.
COMT inhibitors (entacapone) — extend levodopa action in wearing-off.
Amantadine — for dyskinesia.
Anticholinergics (trihexyphenidyl) — for tremor in the young; avoid in the elderly because of confusion and cognitive impairment.
Advanced therapy: deep brain stimulation of the subthalamic nucleus or globus pallidus for motor fluctuations and dyskinesias with preserved levodopa responsiveness and no dementia; apomorphine infusion; intrajejunal levodopa gel.
Non-motor and supportive management is equally important: physiotherapy (gait and balance training, cueing strategies for freezing), occupational therapy, speech and language therapy, falls prevention, treatment of constipation, depression and REM sleep behaviour disorder, management of postural hypotension, and caregiver support.
Hallucinations and psychosis: reduce dopaminergic drugs where possible; if antipsychotics are required, use quetiapine or clozapine — never haloperidol or risperidone, which markedly worsen parkinsonism.

DANGER / REMEMBER

Never stop Parkinson's medication abruptly, including when a patient is admitted, made nil by mouth, or transferred between wards. Abrupt withdrawal can precipitate an akinetic crisis and a neuroleptic malignant-like syndrome with rigidity, hyperthermia, raised CK and renal failure. Levodopa doses must be given on time, every time — use a nasogastric tube, patch or apomorphine if the oral route is unavailable.

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