Objective: The clinical course and long term outcome up to 5 years post surgery of a sample of 4 patients with medical refractory HT who underwent DBS of the thalamic ventral intermediate nucleus (VIM) are presented.

Background: Holmes Tremor (HT) is characterized by a disabling large amplitude rest, postural and kinetic tremor. The response to medical therapies is often poor and deep brain stimulation (DBS) of thalamic targets might offer a more effective tremor reduction. However, there are only limited data regarding the long term clinical outcome of patients with HT after DBS.

Methods: Tremor severity was quantified by two blinded raters using the Fahn-Tolosa-Marin (FTM) tremor rating scale on video examinations from baseline visit, 4-6 months (stimulation ON/OFF) and 3-5 years (stim ON) post surgery. Life quality was measured by using the the Bain and Findley tremor activities of daily living (ADL) self-assessment. Electrode positions were located in preoperative MRI scans after fusioning with postoperative cranial computertomographic scans.

Results: Between 2002 and 2008 four patients (two with ischemic lesions of the posterior thalamus, one with hypertensive intracerebral bleeding of the ventroposterior thalamus and one with a posttraumatic lesion of the dorso-lateral thalamus) underwent implantation of DBS electrodes into the VIM. One patient did not show any clinical response to stimulation and postoperative MRI revealed a mislocalization of the electrode. After two years revision surgery was performed and in the course of this the electrode was finally explanted. In the other 3 patients baseline mean FTM score was 38 (minimum-maximum: 21-55) and ADL score was 41 (40-42). After 4 to 6 months post surgery the mean FTM score in stimulation ON was 23 (18-27; mean improvement 39%) and ADL score was 37 (31-43; 11% improvement). After 3 to 5 years the mean FTM score was 28 (20-45; 26% improvement compared to baseline) and ADL score was 45 (40-52; 11% worsening compared to baseline).

Conclusions: Out of 4 patients only 2 had a clear tremor reduction (>30%) in the FTM scale within six months post surgery. In the long term over 5 years in these 2 patients a clear tremor reduction compared to baseline was maintained. The clinical outcome after VIM DBS in HT seems very variable and the electrode localization may play an important role.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/long-term-clinical-outcome-after-deep-brain-stimulation-of-the-thalamic-vim-in-holmes-tremor-a-case-series/