OBJECTIVETo evaluate the efficacy and safety of unilateral pallidotomy in treating Tourette syndrome (TS). The therapeutic electrophysiological mechanism of pallidotomy was analyzed according to the properties of GPi cells in TS.

METHODSTwenty-two patients underwent microelectrode-guided unilateral pallidotomy. All patients referred to surgery were previously failed with multiple non-surgical methods (psychopharmacological and behavioural therapy). Pre- and postoperative tic severities were rated by the Yale global tic severity scale (YGTSS). With the microelectrode recording technique, the properties of GPi cells in 6 patients were recorded and analyzed.

RESULTS(1) Postoperative scores of motor tics, phonic tics, overall impairment rating and global severity in YGTSS were significantly decreased (P < 0.01). The amelioration of phonic tics was less than motor tics. The follow-up data at 12 months revealed a stable efficacy. Five cases experienced transient complications included drowsiness, intracranial pneumatocele, incontinence, diplopia and slightly facial palsy after pallidotomy, there were no permanent complications such as death, intracranial, hematoma hemiplegia and visual field defect. (2) The discharge rates of GPi neurons ranged from 20 to 156 Hz, the discharge patterns include regular, irregularly bursting and clustering mode. The synchronizations of neuronal discharge in GPi with the activities of contralateral limbs were observed also by electromyogram recorded at the same term.

CONCLUSIONS(1) Pallidotomy is proven to be a safe and effective method to treat TS, it provides a significant immediate and short term reduction of tic severity in intractable Tourette' syndrome. The long term effect of pallidotomy is confirmed also. Pallidotomy is applied to those patients with high tics scores, severe self-injured behaviors or fail to medicine treatment. (2) The low discharge rate, abnormal firing pattern and synchronized neuron are the properties of GPi neurons in TS, and maybe the pathophysiological basement of tics. Eliminated the neurons with abnormal activity in GPi, and decreased the activity of CSTC circuits maybe the therapeutic mechanism of pallidotomy.