Stereotactic posterioventral pallidotomy improves balance control as assessed by computerized posturography.

Postural instability is arguably the most debilitating symptom of Parkinson's disease (PD). Recently, posterioventral pallidotomy/pallidoansotomy (PVP) has been advocated to improve a multitude of symptoms associated with PD. Dyskinesias, rigidity and bradykinesia are the most talked about improved symptoms, but posture and gait are also affected after PVP. To analyze the effect of PVP on postural control, 14 patients with PD were prospectively studied using a computerized dynamic posturography machine. Seven males and 7 females underwent a total of 18 procedures, 6 left PVP, 6 right PVP, 2 bilateral and 2 had Vim thalamotomies in addition to PVP. Data were collected pre- and postoperatively after a 12-hour drug-free interval ('off' period) and 1-2 h after medications ('on' period). Postoperative analyses were performed between 1 and 3 months postoperatively. As a group, patients' balance, in the off period, improved after surgery in a dynamic setting. Prior to surgery, patients' anterior-posterior sway exceeded their stability limits (patient fell) on 31% of the trials. After surgery, the fall rate decreased to 23%. Anterior-posterior sway decreased significantly (p < 0.05) postoperatively when the platform was sway referenced. In comparing the effect of surgery in decreasing sway with that of medication preoperatively, improvement after surgery (off period) was better than the preoperative on period (p < 0.05). Patients also improved in ostoperative off state when compared to preoperative off state with the platform sway referenced (p < 0.05), controlling for improvement in dyskinesia-induced imbalance. In conclusion, PVP improves standing balance performance better than that achieved with medications preoperatively. Since central input parameters were improved, the mechanism of PVP may be centralized.