Contribution of neurophysiological guidance to stereotactic posteroventralpallidotomy for Parkinson's disease

The usefulness of microrecording guidance to adequately place pallidotomy l esions is not thoroughly accepted. We have analysed in 23 consecutive Parki nsonian patients the deviation of the first recording track (FRT), which wa s directed to the theoretical stereotactic target, from the sensorimotor ar ea of the internal pallidum, the internal capsule and the center of the les ion. Standard stereotactic co-ordinates were calculated applying a digitize d brain alias adapted to neuro-imaging techniques. The first recording trac k (FRT) was located out of the sensorimotor area of the pallidum in 13 case s and out of the internal pallidum in 11 cases. In four of these cases the FRT was within the fibers of the internal capsule. The FRT was displaced po steriorly in 9 patients, anteriorly in 11, medially in 9 and laterally in 9 . The mean deviation was 1.8 mm (+/-1.5) in the medial-lateral axis, and 2. 5 mm (+/-1.9) in the antero-posterior plane. In none of the patients the ce nter of the lesion was co-incident with the theoretical anatomical target. The center of the lesion presented a mean deviation from the theoretical an atomical target of 1,4 mm (+/-1,1) in the medial-lateral, plane, and 2.5 mm (+/-1.3) in the antero-posterior plane. In addition, 8 patients presented a deviation from the theoretical anatomical target of more than 3 mm in the antero-posterior plane (mean 4.2 +/- 0.7 mm) and 4 patients presented devi ation in the medial-lateral plane of more than 3 mm (mean 3,4 +/- 0,2 mm). Lesion location was checked by magnetic resonance imaging. All patients imp roved to a similar extent to that previously reported by the other groups p erforming pallidotomy under neurophysiological guidance. At 3 months follow -up, pallidotomy ameliorated contralateral bradykinesia in the off conditio n by 41%, rigidity by 38%, tremor by 52% and dyskinesias by 92%. No major s ide effects were noted. We conclude that microrecording guidance is a usefu l tool for avoiding damage to adjacent structures and to precisely localize the sensorimotor area of the internal pallidum in order to obtain optimal clinical results.