Objective: To determine the long-term clinical outcomes and optimal stimulation sites of globus pallidus internus deep brain stimulation (GPi DBS) in patients with medically refractory tardive dystonia and dyskinesia (TDD).

Background: Tardive syndromes (TS) are drug-induced movement disorders that are potential complications of exposure to dopamine receptor blocking agents, including antipsychotic drugs and certain antiemetics. In addition to classic tardive dyskinesia, characterized by repetitive oro-bucco-lingual movements, TS include dystonia, akathisia, tics, and chorea. TDD are often disabling and may persist despite withdrawal of the offending agent. The medical treatment is frequently difficult and unsatisfactory, and medically refractory cases remain a major therapeutic challenge. Prior studies have shown that GPi DBS can provide substantial benefit in treating TDD, however, data on long-term outcomes and optimal stimulation sites are still limited.

Method: We performed a retrospective, unblinded study of eighteen patients (9 men and 9 women) with medically refractory TDD who underwent GPi DBS surgery between 2000 and 2024. Clinical outcomes were assessed using the Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS), and the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) for patients with prominent tardive cervical dystonia.

Results: The mean age at onset of TDD was 42.0 ± 15.4 years, and the mean duration of TDD prior to surgery was 9.0 ± 8.1 years. The mean BFMDRS score improved by 64.1 ± 30.8 % at short- term follow-up (11.1 ± 3.4 months, n=14), 83.8 ± 14.1 % at mid-term follow-up (36.3 ± 5.1 months, n=11), and 88.0 ± 16.8 % at long-term follow-up (62.5 ± 7.6 months, n=7) compared with preoperative scores. The mean TWSTRS score improved by 43.8 ± 31.7 % (n=7), 60.8 ± 26.0 % (n=5), 69.0 ± 35.6 % (n=4), respectively, at the corresponding time points. There were no persistent adverse effects related to DBS. A detailed analysis of the optimal stimulation sites is ongoing.

Conclusion: GPi DBS appears to be a safe and effective treatment for medically refractory TDD, providing sustained long-term symptomatic benefit. Our findings suggest that earlier surgical intervention could be considered in patients with medically refractory TDD to achieve earlier symptomatic relief and durable long-term benefit.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/the-long-term-efficacy-of-globus-pallidus-deep-brain-stimulation-in-tardive-dystonia-and-dyskinesia/