Definition – A group of CNS degenerative diseases associated with involuntary movements or abnormalities of skeletal muscle tone and posture. They can be broadly classified as hypokinetic (too little) or hyperkinetic (too much) movement disorders.

Pathophysiology of Parkinson’s Disease (PD; Hypokinetic Movement Disorder) – The predominant area of involvement is basal ganglia, which are primarily inhibitory in function. Affects the dopamine-producing cells (substantia nigra and locus ceruleus) of basal ganglia, resulting in degeneration of nigrostriatal pathway and thereby causing decreased dopamine in the corpus striatum. This results in loss of inhibitory input to the cholinergic system, allowing excessive excitatory output.

Etiology – Unknown. The most common movement disorder is Parkinson’s disease, affecting 1% of the population over 50 years of age. Incidence is 20/100,000 per year. Male:female ratio is 3:2. Associated with pesticide and herbicide use; 5% to 10% is hereditary (five genes identified so far).

Treatment – Medical or surgical.

The goal of medical treatment is to increase dopamine action and decrease cholinergic effect. A guiding principle is to start treatment when symptoms interfere with performing ADLs.