Thalamic stimulation in patients with multiple sclerosis: long-term follow-up

Background: We assessed the long-term effect of deep brain stimulation (DBS) in patients with multiple sclerosis (MS).

Methods: Nine patients with MS-induced tremor underwent placement of a DBS electrode in the thalamus. All patients were referred from the tertiary MS center at the New Jersey Medical School. Intraoperative macrostimulation was performed under local anesthesia before permanent implantation. Preoperative and postoperative evaluation included magnetic resonance imaging (MRI), the Extended Disability Status Scale (EDSS), the Bain-Finchley tremor scale, neuropsychological testing and patient assessment of the benefit from surgery.

Results: There were no surgical complications. Follow-up ranged from 9 to 48 months (mean 32 months). EDSS scores averaged 7.2 before surgery, 6.8 at 6 months after surgery and 7.8 at late follow-up. Tremor scores averaged 5.4 before surgery, 1.7 at 6 months after surgery and 2.1 at late follow-up. Four patients who had significant tremor reduction at 6 months had severe MS progression afterwards, and one was lost to late follow-up. Another patient, in whom excellent tremor control was obtained, developed increasing stimulation-induced fatigue, and the implant was removed at his request. The 3 other patients have maintained a worthwhile benefit from DBS. MRI scans did not show any new MS plaques in relation to the electrode, although imaging was consistent with disease progression in all patients. Neuropsychological testing showed a mild to moderate decline in cognitive function consistent with disease progression.

Conclusions: Chronic thalamic stimulation decreases tremor in patients with MS. However, this improvement does not correlate with improvement in objective measures of function. Any actual benefit may be limited in most patients by the progression of underlying disease. DBS for relief of tremor in patients with MS should be considered only in carefully selected patients with relatively stable disease, in whom upper extremity tremor is a disabling symptom.