DBS in tremor with dystonia: VIM, GPi or both? A review of the literature and considerations from a single-center experience.

Background: Deep brain stimulation (DBS) is an established treatment for dystonia and tremor. However, there is no consensus about the best surgical targeting strategy in patients with concomitant tremor and dystonia. Both the thalamic ventral intermediate nucleus (VIM) and the globus pallidus pars interna (GPi) have been proposed as targets. Few cases using them together in a double-target approach have also been reported.

Methods: We reviewed the literature on this topic, summarizing results of different target choices. Additionally, we retrospectively report a case series of nine patients with sporadic dystonia and severe tremor treated with a double-target strategy at our center. Outcome measures were the Burke-Fahn-Marsden Dystonia Rating Scale (BFM) and Eq-5d scale.

Results: In published studies of patients with dystonia and tremor, VIM-DBS is highly effective on tremor but raise some concerns about dystonia's control, while GPi-DBS is more effective on dystonia but does not always relieve tremor. GPi + VIM-DBS shows good efficacy but is rarely reported and reserved for selected patients. In our patients, the double-target strategy obtained a significant and durable improvement in tremor, dystonia, and quality of life. Additionally, compared with a cohort of patients with tremor treated with VIM-DBS only, significantly lower frequency and intensity of VIM stimulation were required to control tremor.

Conclusion: Our findings and published evidence seem to support the double-targeting approach as a safe and effective option in selected patients with tremor-dominant dystonia. This strategy appears to provide a more extensive control of either dystonia or tremor and may have a potential for limiting stimulation-related side effects.