The surgery will be performed with the patient awake. Two simultaneous microelectrode tracks will be used for each DBS electrode to be implanted. If neither electrophysiological recording is adequate, additional MER tracks may be performed. Macro-stimulation will also be used to evaluate for clinical efficacy and stimulation induced side effects. The DBS electrode will be placed into the track with the optimal electrophysiological and clinical findings. The identical procedure will be followed for the contralateral side. A post-operative stereotactic CT scan will be performed to assess lead location and evaluate for intracranial bleeding.