Long-term efficacy and tolerability of bilateral pallidal stimulation to treat tardive dyskinesia

Objective: To confirm the efficacy and safety of deep brain stimulation (DBS) of the internal part of the globus pallidus in improving severe tardive dyskinesia (TD). Methods: Nineteen patients with severe pharmacoresistant TD were included. All were assessed at baseline and at 3, 6 (main outcome measure), and 12 months, and in the long term (6-11 years) for 14 patients, after bilateral pallidal DBS, using motor scales (Extrapyramidal Symptoms Rating Scale [ESRS], Abnormal Involuntary Movement Scale [AIMS]), cognitive scales, and a psychiatric assessment. At 6 months, a double-blind ESRS evaluation was performed in the stimulation "on" and stimulation "off" conditions. Results: At 6 months, all patients had a decrease of more than 40% on the ESRS. The efficacy of the procedure was confirmed by a double-blind evaluation. This improvement was maintained at 12 months (ESRS: decrease of 58% [21%-81%]; AIMS: decrease of 50% [7%-77%]) and in the long term (ESRS: decrease of 60% [22%-90%]; AIMS: decrease of 63% [14%-94%], n = 14). All the subscores of the ESRS (parkinsonism, dystonia, and chorea) and of the AIMS (facial, oral, extremities, and trunk movements) improved. Despite psychiatric comorbidities at baseline, cognitive and psychiatric tolerability of the procedure was excellent. No cognitive decline was observed and mood was improved in most of the patients. Conclusions: Pallidal DBS procedure should be considered as a therapeutic option in disabling TD refractory to medical treatment. Classification of evidence: This study provides Class II evidence that in patients with severe pharmacoresistant TD with implanted pallidal leads, the stimulation "on" condition significantly improved ESRS scores compared to the stimulation "off" condition.