Deep-Brain Stimulation for Parkinson's Disease

A 72-year-old right-handed man with a 12-year history of Parkinson's disease presents with a diminished response to medication and right-sided dyskinesia (involuntary movements). During the past several years, he has been taking multiple drugs for Parkinson's disease, including a monoamine oxidase inhibitor, amantadine, a dopamine agonist, and carbidopa-levodopa. He reports that with his current regimen, which includes 1.5 tablets of 25/100 carbidopa-levodopa taken every 2 hours, he has marked reductions in tremor, rigidity, and bradykinesia and substantial improvement in his walking. Despite multiple interval and dose adjustments, however, he also reports 6 hours per day of off time, when his symptoms are unresponsive to his current medication regimen. In addition, he has severe, disabling right-sided dyskinesia 4 hours per day. Symptoms affecting his left side are mild and not bothersome. His cognition is excellent, his neurologic examination is otherwise normal, and he has no other coexisting medical conditions. His neurologist refers him to a neurosurgeon for consideration of deep-brain stimulation.