Objective: To review outcomes of the thalamic deep brain stimulation (DBS) in patients with cerebellar outflow and midbrain tremor.

Background: DBS of the ventral intermediate nucleus of thalamus (Vim) was approved for the treatment of medically refractory essential tremor (ET) and Parkinson-related tremor in 1997. However, the use of Vim DBS for other types of tremor especially cerebellar outflow and midbrain tremor has not been well studied.

Methods: A retrospective database review of cases with cerebellar outflow and midbrain tremor who underwent Vim DBS at our institution between 1998 and 2015. We categorized cases based on their pre-operative brain MRIs into 2 groups: lesional and non-lesional. Lesional refers to focal lesions on MRI e.g. infarct, hemorrhage, demyelination from multiple sclerosis (MS) or traumatic brain injury (TBI). Non-lesional refers to absence of focal lesions other than cerebellar and/or subcortical atrophy e.g. cerebellar degenerative diseases.

Results: We identified 19 patients who met the inclusion criteria. 12 cases are lesional (5 MS, 4 TBI, 1 midbrain infarction, and 2 ruptured aneurysms) and 7 cases are non-lesional (1 FXTAS, 1 Friedreich’s ataxia, 1 multiple system atrophy cerebellar type (MSA-C), and 4 idiopathic cerebellar degeneration). All underwent unilateral Vim DBS, except for the patient with MSA-C who got staged bilateral DBS. In a non-lesional group, 4 patients (57%) had sustained marked benefit in tremor control, 1 patient had minimal improvement, and 2 patients had initial good benefit that waned after several months. Only 1 out of 5 MS patients (20%) had sustained tremor control, 3 patients had initial benefits for 1-2 years and 1 patient lost to follow up after 3 months. 3 out of 4 TBI patients (75%) had sustained good tremor control whereas 1 patient (25%) had initial benefit for 2 years. The patient with midbrain infarction had good tremor control but later DBS was removed due to infection. Both patients with aneurysmal rupture had only minimal benefits.

Conclusions: Our data suggest that most patients with TBI and more than half of patients with cerebellar degeneration experienced sustained symptomatic improvement in tremor following Vim DBS. Tremor suppression occurred less consistently in patients with MS or hemorrhage. A randomized studies are warranted to better understand the effects of Vim DBS on cerebellar outflow and midbrain tremor.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/thalamic-deep-brain-stimulation-for-cerebellar-outflow-tremor-and-midbrain-tremor-a-case-series/