To report outcomes of MRI guided focused ultrasound (MRgFUS) unilateral ventral intermediate nucleus (VIM) thalamotomy in tremor-predominant Parkinson’s disease (PD) patients at a single institution.

MRgFUS thalamotomy of the VIM is an emerging non-invasive therapy approved for tremor-predominant PD. There are limited data on treatment outcomes and adverse effects from MRgFUS for PD. In select patients, MRgFUS can be a surgical treatment option for medication refractory tremor in PD.

Patients with PD who underwent unilateral MRgFUS VIM thalamotomy at a single institution were included. The Unified Parkinson’s Disease Rating Scale (UPDRS), global improvement questionnaires and adverse events were assessed at baseline and the most recent follow-up visit (range 2-13.5 months).

Twelve patients underwent unilateral MRgFUS VIM thalamotomy. Two patients had transient improvement and subsequently went on to obtain deep brain stimulation. Ten patients (8 male) had a mean follow-up of 8.1 ± 4.1 months. The mean age at time of surgery was 74.8 ± 8.6 years (62.7-88.5). Average disease duration was 6.1 ± 4.7 years (1.7-14.8). UPDRS motor score improved from 38.5 at baseline to 33.6 (12.8%, p=0.007) and UPDRS tremor score improved from 8.1 at baseline to 4.6 (43%, p=0.005). At last follow-up 8/10 (80%) patients noted moderate-marked global improvement, 1/10 (10%) reported mild improvement and 1/10 (10%) indicated mild worsening.

Adverse events included gait difficulties which typically improved or resolved by 2 months. One individual developed acute thalamic edema with significant postural instability, but had subsequent improvement prior to passing away 2 months later. Another patient died 8 months after MRgFUS which was felt unrelated to his surgery.

Unilateral MRgFUS thalamotomy is safe and effective treatment for tremor predominant PD. Two patient deaths in our cohort were felt unrelated to the MRgFUS procedure. Short term gait difficulties are a common adverse effect, but typically resolve over time.