Involuntary Movements: Tremors, Chorea, Myoclonus — What They Mean Neurologically

When a patient presents with abnormal involuntary movements, the neurological examination focuses on characterising the movement pattern — because different patterns arise from different brain structures and indicate different diagnoses. Calling all involuntary movements "tremors" is like calling all rashes "eczema" — the category is too broad to guide management.

Tremor

Rhythmic, oscillatory movement. The timing reveals the diagnosis: Resting tremor (present at rest, diminishes with action) — Parkinson's disease: the "pill-rolling" 4–6 Hz tremor is the prototype. Action tremor (present during voluntary movement) — includes postural tremor (essential tremor — 8–12 Hz; hands, head, voice), kinetic tremor (worsening during finger-nose test — cerebellar disease), and intention tremor (worsening toward the target — specific to cerebellar disease).

Chorea

Irregular, unpredictable, flowing, "dance-like" movements — flowing from one body part to another. The patient cannot sustain a grip (milkmaid grip). Causes: Huntington's disease; Sydenham's chorea (post-streptococcal — in children, following rheumatic fever); drug-induced (OCP, antipsychotics); Sydenham's chorea; thyrotoxicosis; antiphospholipid syndrome.

Myoclonus

Sudden, brief, lightning-fast muscle jerks — much faster than tremor. Can be physiological (hiccups; hypnic jerks — the startle on falling asleep) or pathological. Pathological myoclonus: cortical myoclonus (EEG correlate — from cortical irritability); subcortical (essential myoclonus, progressive myoclonic epilepsies); spinal cord (segmental myoclonus — rhythmic, spinal origin). Asterixis (the "liver flap" — inability to maintain sustained posture) is sometimes called "negative myoclonus" — seen in metabolic encephalopathy (hepatic, renal).

Hemiballismus

Violent, large-amplitude, flinging movements of one arm or leg — dramatic and highly specific. Caused by a lesion in the subthalamic nucleus — most commonly a small lacunar stroke. Usually improves spontaneously; treated acutely with haloperidol or tetrabenazine. Sri Anand CNC, Chanda Nagar, Hyderabad. Call +91 90633 66983.