Parkinson's Disease Cardinal Motor Signs

The four cardinal motor features of idiopathic Parkinson's disease resulting from substantia nigra dopaminergic degeneration.

Loss of >= 70% of dopaminergic neurons in the substantia nigra pars compacta disrupts the basal ganglia direct (movement activating) and indirect (movement inhibiting) pathways, tipping the balance toward profound motor inhibition.

Systematic Breakdown

Tremor (Pill-Rolling at Rest)

4-6 Hz resting tremor, usually unilateral at onset, improving with purposeful voluntary movement and worsening with stress.

Rigidity (Cogwheel & Lead-Pipe)

Increased muscle tone throughout range of passive joint movement; superimposed tremor produces 'cogwheeling'.

Akinesia / Bradykinesia

Slowness of initiating and executing movements; masked facies (hypomimia), decreased blink rate, hypophonia, and micrographia.

Postural Instability

Impaired righting reflexes leading to frequent unprovoked falls; festinating shuffling gait with en bloc turning (late manifestation).

High-Yield Clinical Pearls & Exam Tips

Histopathology: Eosinophilic intracellular inclusions called Lewy bodies composed of alpha-synuclein.
Levodopa/Carbidopa remains the most effective symptomatic pharmacotherapy; Carbidopa blocks peripheral DOPA decarboxylase, minimizing nausea and maximizing CNS penetration.

Related Pharmaceuticals

Levodopa-Carbidopa Pramipexole Ropinirole Selegiline Entacapone

Related Clinical Conditions

Parkinson's Disease Progressive Supranuclear Palsy Multiple System Atrophy

Authoritative Sources: Adams and Victor's Principles of Neurology 11e · Movement Disorder Society Clinical Criteria

Parkinson's Disease Cardinal Motor Signs

Systematic Breakdown

Tremor (Pill-Rolling at Rest)

Rigidity (Cogwheel & Lead-Pipe)

Akinesia / Bradykinesia

Postural Instability

More Neurology Mnemonics

Cerebellar Lesion Localization: DANISH

Spinal Cord Syndromes: Brown-Séquard vs Anterior Cord

Cranial Nerves Sensory vs Motor: Rhyme

System Notice

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