We read with great interest the timely review by Dr Lang1 on the surgical treatments for Parkinson disease (PD) and agree with his overall conclusion regarding the limitations of the available data and the lack of well-controlled clinical trials to unequivocally demonstrate the therapeutic efficacy of the surgical procedures currently in use for PD. However, we would like to take issue with his final argument, which suggested that prior lesions of the basal ganglia may reduce the likelihood of responding to the restorative therapies that may become available in the near future. This is a fundamental concern, particularly in younger patients, who are generally the best candidates for surgical treatments. We think, however, this theoretical concern is supported neither by the available data nor by our own experience. Preoperatively, the ability of a patient to benefit from dopaminergic cell transplantation, or any other surgical procedure for PD, has been accurately predicted by the patient's ability to respond to levodopa. Indeed, the "levodopa test" is widely used as part of the Core Assessment Program for Intracerebral Transplantation.2 A poor or null response to levodopa has been consistently associated with failure to improve following dopamine cell grafting,3 pallidotomy,4 and subthalamic nucleus (STN) deep brain stimulation.5 During postoperative assessments, patients undergoing unilateral pallidotomy maintain their levodopa response on the lesioned and unlesioned sides.6 Patients undergoing bilateral STN deep brain stimulation also maintain a robust levodopa response.7
Obeso JA, Rodriguez MC, Guridi J, et al. Lesion of the Basal Ganglia and Surgery for Parkinson Disease. Arch Neurol. 2001;58(7):1165–1166. doi:
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