Parkinson's Disease: Motor Fluctuations

Abstract

Motor fluctuations represent important late complications of Parkinson's disease treated with levodopa. Although treatment of these problems has improved with the emergence of numerous pharmacologic and surgical therapies, the various options can make it confusing. Pharmacologic treatment is the first step. Polytherapy is often the rule in this case with a variety of agents available as adjunctive therapy with levodopa. These adjuncts include dopamine agonists (bromocriptine, pergolide, pramipexole, ropinirole), catechol-O-methyltransferase (COMT) inhibitors (tolcapone), controlled-release formulations of levodopa, monoamine oxidase (MAO) B inhibitors (selegiline), and amantadine. The treatment can consist of any of a number of combinations of these agents. No single algorithm can be used in all patients; therapy should be individualized. Physicians treating these patients need to be well versed in late complication patterns as well as the medications chosen. In addition, optimal doses vary, and often patients are considered treatment failures and taken off medications before reaching that level. In the more complicated cases, patients should be evaluated by specialists in movement disorders. With this in mind, some guidelines are offered for the pharmacologic approach to patients with fluctuating responses to medications. For simple wearing off, controlled-release levodopa (Sinemet CR, Dupont Pharmaceuticals, Wilmington, DE), COMT inhibitors, MAO inhibitors, and dopamine agonists are reasonable options. For more complicated fluctuations, dopamine agonists with limits on levodopa are the first choice, especially when dyskinesia is present; when dyskinesia is not a factor, COMT inhibitors may be used. For dyskinesia specifically, dopamine agonists or addition of amantadine can be helpful. Surgery should be a treatment of last resort for patients in whom medical therapy fails. Patients who are candidates for medial pallidotomy should be fluctuators with severe dyskinesia and "off" periods that have not improved with pharmacologic therapy. Thalamic deep brain stimulation (DBS) should be used only in patients with tremor-predominant disease and severe intractable tremor that is unresponsive to medication and occurs not only at rest but with posture and action as well. Surgical therapy should be performed only in centers with surgeons experienced in stereotactic techniques and movement disorder specialists to ensure that the appropriate patients come to surgery and that complications are kept to a minimum. Dietary adjustment has a limited role in treating advanced Parkinson's disease.