Parkinson's Disease

The tremor that stops when the patient reaches for a cup — and the shuffle that starts before anyone notices — make Parkinson's a disease where what the patient ISN'T doing reveals the diagnosis.

Parkinson's disease results from progressive loss of dopamine-producing neurons in the substantia nigra. Dopamine normally balances acetylcholine in the basal ganglia to produce smooth, coordinated movement. When dopamine drops, acetylcholine dominates unopposed, producing the four cardinal features: resting tremor (pill-rolling, disappears with intentional movement), rigidity (cogwheel or lead-pipe), bradykinesia (most disabling motor feature), and postural instability (late feature, biggest fall risk). The disease is more than motor — autonomic dysfunction causes orthostatic hypotension, constipation, and urinary retention. Dysphagia reduces automatic swallowing, contributing to drooling and aspiration risk. Depression affects up to 50% of patients. Carbidopa-levodopa remains the gold standard; carbidopa prevents peripheral conversion of levodopa so more reaches the brain. Timing doses precisely matters — protein competes with levodopa for absorption, so high-protein meals should not coincide with medication. On-off phenomena and dyskinesias emerge with long-term levodopa use. The nurse monitors for freezing episodes, fall risk, aspiration from dysphagia, and medication effectiveness measured by improved mobility and reduced tremor.

Key Distinctions

Don't confuse resting tremor (Parkinson's — stops with purposeful movement) with intention tremor (cerebellar disorders — worsens when reaching for a target). Students mix up bradykinesia with paralysis — the patient can move, but initiation and speed are impaired. Postural instability is a LATE finding, not an early one; early Parkinson's presents with unilateral resting tremor and subtle bradykinesia.

Clinical Pearl

TRAP the diagnosis: Tremor at rest, Rigidity, Akinesia/bradykinesia, Postural instability. If the tremor disappears when they move, think Parkinson's.