Parkinson's disease: making the diagnosis, selecting drug therapies.

Parkinson's disease is a progressive neurodegenerative condition of unknown cause and with no known cure. The diagnosis is based on clinical findings of rest tremor, muscle rigidity, bradykinesia, and gait instability. Over 40% of patients develop a dementia syndrome that is largely distinct from Alzheimer's disease. Depression is common, also occurring in more than 40% of patients with PD. Careful evaluation in necessary to help distinguish Parkinson's disease from secondary causes of parkinsonism. Carbidopa/levodopa, dopamine agonists, and monoamine oxidase type B inhibitors are the mainstays of treatment. Anticholinergics and other agents may also be useful. Pharmacologic treatment must be carefully titrated to control symptoms and to avoid side effects. In advanced disease, dose-related dyskinesias, end-of-dose wearing-off effect, and unpredictable sudden motor fluctuations become very disabling and difficult to manage.