Tremor reduction and quality of life after deep brain stimulation for multiple sclerosis-associated tremor

Tremor is an important cause of disability and poor quality of life amongst multiple sclerosis (MS) patients. We assessed the outcomes of ventral intermediate (VIM) nucleus deep brain stimulation for the treatment of multiple sclerosis (MS)-associated tremor at a single centre in a prospective fashion.

Sixteen patients (9 female, 7 male) with a mean age of 41.7 years (range 24-59) underwent surgery. The median duration of MS prior to surgery was 6.5 years and median duration of tremor prior to surgery was 4 years. Case selection was by multidisciplinary assessment with carers, therapists, neurosurgeons and movement disorder neurologists. Tremor was scored pre-operatively and at 6 to 12 months post operatively using Bain and/or Fahn-Tolosa-Marin systems. The Euro-Qol 5D tool was used to assess quality of life before and after surgery.

The mean tremor reduction was 39 % with a range between 0 and 87 %. Five of 16 patients achieved at least 50 % tremor reduction and 11 of 16 achieved at least 30 % tremor reduction at last follow up, mean 11.6 months (range 3-80). Tremor was significantly reduced as rated by Bain scores (Wilcoxon matched pairs, Z = 3.07, p = .002) and tended to significance as rated by Fahn scores (Wilcoxon matched pairs, Z = 1.85, p = 0.06). Sub-analysis of activities of daily living measures from the Fahn system showed post operative improvement in feeding (statistically significant), hygiene, dressing, writing and working. Mean visual analogue scores (0-100) of patient reported well-being increased from 54.6 to 57.4 post operatively with a trend to significance (Student's t-test, t = 1.26, p = 0.2). Euro-Qol 5D utility values increased following surgery with a trend to significance which was greater in the group with at least 50 % tremor reduction than in those with none or at least 30 % tremor reduction.

VIM DBS may reduce severe, disabling tremor in patients with MS. This tremor reduction tends to be associated with improved quality of life and function in those who respond. Patient reported outcome measures may not correlate with physician rated clinical outcome such as tremor scoring systems and more subtle assessment of these patients is required.