Update on Parkinson's disease.

Parkinson's disease is a progressive degenerative disorder of the central nervous system. The hallmark physical signs are tremor, rigidity and bradykinesia. Idiopathic Parkinson's disease is caused by the progressive loss of dopaminergic neurons in the substantia nigra and nigrostriatal pathway of the midbrain. Secondary parkinsonism may be caused by certain drugs (e.g., metoclopramide and haloperidol) or by cerebrovascular disease (e.g., multiple lacunar strokes). The disease can usually be diagnosed based on the history and physical findings. Dopamine replacement is still considered the most efficacious treatment for Parkinson's disease, but dopamine agonists, formerly prescribed only as adjunctive therapy, are emerging as useful initial therapy. Other pharmacologic treatments include drugs that inhibit dopamine-metabolizing enzymes (monoamine oxidase-B and catechol O-methyltransferase). Injections of botulinum toxin can be helpful in patients with associated dystonia or blepharospasm. Surgery may be indicated for certain patients or when symptoms do not respond to medical therapy. Additional adjunctive therapies include physical therapy, nutritional counseling and techniques to help patients manage emotional and cognitive changes related to the disease.