Objective:

This report aims to demonstrate the benefit of bilateral ventral intermediate nucleus (VIM) deep brain stimulation (DBS) after unilateral focused ultrasound thalamotomy (FUS) on tremor and ataxia in one patient previously diagnosed with Essential Tremor now with suspected spinocerebellar ataxia type 38 (SCA38).

Background:

SCA38 is a rare, adult onset, autosomal dominant syndrome thought to present as a pure cerebellar ataxia. VIM and dentate nucleus DBS have been effective for tremor control and ataxia, respectively, in various SCAs. There are no DBS outcome studies for SCA38. Data on DBS outcomes after FUS are limited

Design/Methods:

We describe one patient with medication-refractory bilateral hand action tremor who underwent unilateral right FUS. Tremor recurred within 6 months. Over the following year the patient had worsening bilateral limb ataxia, mild gait ataxia, hypermetric saccades, subtle dysarthria, and neuropathy. Whole genome sequencing showed a variant of unknown significance in the ELOVL5 gene (c.331C>T, p.R111C), previously seen in one ataxic individual. The patient underwent bilateral VIM DBS for tremor control.

Results:

Pre-FUS Tremor Rating Scale (TRS) total score was 57 (A+B: Left 16, Right 14). Post-FUS TRS total score was 46 (A+B: Left 14, Right 13). Post-FUS SARA ataxia score was 9.5 (Left 7, Right 4). Right arm was immobilized due to injury at initial DBS programming visit. Baseline DBS OFF Left TRS A+B score was 10. DBS ON Left TRS A+B score was 5. Baseline DBS OFF Left SARA ataxia score was 6. DBS ON Left SARA ataxia score was 3. SARA gait, stance, and speech scores were unchanged by DBS.

Conclusions:

Though longer follow up is needed, this case contributes to the limited literature on SCA38 and its response to DBS. It highlights the potential of VIM DBS to alleviate tremor and ataxia in SCA38 and demonstrates successful DBS outcome after failed FUS in an unusual case.