Deep Brain Stimulation for Parkinson’s Disease
abstract & commentary
Source: Ardouin C, et al. Bilateral subthalamic or pallidal stimulation for Parkinson’s disease affects neither memory nor executive functions: A consecutive series of 62 patients. Ann Neurol 1999;46:217-223.
The last three years have seen an explosion of interest in deep brain stimulation for Parkinson’s disease. Of the possible targets, only pallidal and subthalamic nucleus (STN) stimulation address the major cardinal symptoms of bradykinesia, rigidity, and tremor. Although implantation of a deep brain stimulator into the internal palladium or STN is not currently approved in the United States, these procedures, and in particular STN stimulation, are being performed at academic centers and in clinical practice. Ardouin and colleagues’ review of the effects of bilateral stimulation on memory and executive functions is particularly important, as neurologists struggle with the question of who should and who should not undergo these procedures.
Pooling patients implanted with bilateral STN or pallidal stimulators in Grenoble and Paris, 62 consecutive Parkinson’s patients underwent a battery of neuropsychological tests before and after bilateral implantation of electrodes. Patients who underwent implantation were relatively young (average age < 55), with at least 12 years of Parkinson’s symptoms. All responded to levodopa, with characteristic severe motor fluctuations. In the "on" state, patients were independent, and in the "off" state they were incapacitated (Hoehn and Yahr > 4/5). Electrodes were implanted in a single operative sitting using neuroradiologic landmarks and an intraoperative microelectrode recording to define placement. All patients sustained a dramatic benefit in motor performance, although the benefit was greater in the STN group. Patients implanted with STN stimulators were also able to substantially reduce their daily requirement for levodopa to assess the late effects of bilateral stimulation. Patients with prior cognitive disturbance or hallucinations should probably not be considered as candidates. The conservative view would hold that STN stimulation should be performed in academic centers where resources are available for continuous neurological followup. The desperation of certain patients to undergo the procedure and the opportunity for considerable financial reimbursement in surgical fees may derail these plans. —sf (Dr. Steven Frucht is Assistant Professor of Neurology, Movement Disorders Division, Columbia-Presbyterian Medical Center.)
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