MATERIAL and METHODS: We conducted a retrospective study of 20 PD patients who underwent bilateral pallidal DBS placement with MER. There were 14 males and 6 females. The mean age at implantation was 67 years (range 42 - 80 years). Paired t-tests were used to compare initial imaging target coordinates versus final electrode coordinates based on intraoperative MER. United Parkinson's Disease Rating Scale (UPDRS) scores pre-operatively (medication off) and at 6 months post-operatively (medication off, stimulation on) and daily levodopa equivalents preoperatively and 6 months post-operatively were analyzed.

RESULTS: The mean difference between calculated imaging target and final electrophysiological target was 3 mm (SD + 1.53 mm; p < 0.0001) in the dorsal-ventral plane and 1.2 mm the axial plane, resulting in a calculated final electrophysiology-based target adjustment of 3.4 mm (SD = 1.4 mm). Patients' average daily levodopa equivalent dose dropped by 52% at six months post-operatively (SD=40.9; p = 0.002). UPDRS scores dropped 26.9 points six months postoperatively (SD=20.4; p = 0.0003).

CONCLUSION: In our experience intraoperative microelectrode recordings can facilitate final electrode placement. Keywords : Microelectrode recording, Parkinson's disease, Globus pallidus internus, Targeting, Deep brain stimulation, Brain mapping