I thank Dr Obeso and his colleagues for their interest in my review and their comments related to my concern that previous lesions of the GPi might adversely affect the response to subsequent reinnervation or restorative therapies for PD. They correctly point out that the preoperative levodopa response generally predicts subsequent benefit from functional surgery. Although, as they state, patients undergoing unilateral pallidotomy maintain levodopa response on the lesion side, an alteration in this response has been described.1 Interestingly, they cite our long-term pallidotomy experience to support their argument, while in fact we found that pallidotomy improves contralateral off-period signs of parkinsonism, and that the bradykinesia may become less responsive to levodopa.2 A subsequent study in these patients suggested the possibility that the pallidotomy may have had a negative effect on the dopaminergic response as evaluated by a complex motor task.3 The potential for high-frequency deep brain stimulation involving the contacts placed in the ventral-most part of the GPi to block the anti-akinetic effects of levodopa raises a similar concern.4-6