Thalamic Deep Brain Stimulation for Dystonic Head Tremor: A Long‐Term Study of 18 Patients

Dystonic head tremor is a particular manifestation of dystonia, which is difficult to treat. Although deep brain stimulation (DBS) of the globus pallidus internus has been established as a treatment for different phenotypes of dystonia, its role in dystonic tremor has been debated. Although thalamic targets have been used for treatment of dystonic tremor of the extremities, there is limited experience with dystonic head tremor. Here, we present our experience with thalamic ventral intermediate (Vim) nucleus DBS in a consecutive series of patients providing long-term follow-up. Eighteen patients with dystonic head tremor as the leading symptom underwent the implantation of quadripolar DBS electrodes into the thalamic Vim. Patients' symptoms were evaluated with the Burke-Fahn-Marsden Dystonia Rating Scale motor (BFMDRS-M) and disability (BFMDRS-D) scores, and a modified Fahn-Tolosa-Marin Tremor Rating Scale (mFTMTRS), preoperatively, at short-term (3 months-2 years), and at long-term follow-up (>2 years). There was improvement in both tremor and dystonia rating scales. Tremor scores were reduced from a value of 7.94 preoperatively to 2.0 at short term (P < 0.001) and to 1.71 at long-term follow-up (P < 0.001). BFMDRS-M scores were reduced from 14.56 to 7.8 (P < 0.001) and to 7.0 (P < 0.001), and BFMDRS-D scores from 3.88 to 2.65 (P < 0.05) and to 2.71 (P < 0.05), respectively, during chronic stimulation. Our results indicate that Vim DBS is a safe and efficient treatment option for dystonic head tremor with stable long-term results. We suggest Vim DBS as an alternative to pallidal DBS in cases where head tremor is the leading symptom.