MRI-guided ultrasound thalamotomy may reduce essential tremor

Image: PD 

1. MRI-guided ultrasound thalamotomy improved essential tremor symptoms in a small group of patients. 

2. A substantial subset of study subjects experienced sensory disturbances following treatment. 

Evidence Rating Level: 2 (Good) 

Study Rundown: This pilot study demonstrates that MRI-guided transcranial ultrasound thermo-ablation can induce lesions in the deep brain and improve symptoms in patients with refractory essential tremors. Patients also reported improved quality of life. Treatment benefits persisted up to one year – the maximum follow-up time. Side effects included sensory disturbances such as paresthesia and temporary unsteadiness, although one study subject reported persistent dysesthesia. This small study was not powered to determine whether this new modality has any net clinical advantage over existing treatments such as stereotactic radiotherapy and deep-brain stimulation. Results are also susceptible to bias due to the open-label nature. A future blinded randomized trial might address these issues.

Click to read the study, published today in NEJM

Relevant Reading: A comparison of Continuous Thalamic Stimulation and Thalamotomy for Suppression of Severe Tremor

In-Depth [open-label, uncontrolled pilot study]: This is a pilot study that evaluates the feasibility of MRI-guided focused ultrasound thalamotomy in treating refractory essential tremors. This open-labeled study included 15 patients without a control group. The maximum follow-up time was 12 months.

The primary clinical end point was the hand sub-score of the Clinical Rating Score for Tremor. The hand sub-score improved from 20.4±5.2 at baseline to 4.3±3.5 at 3 months and 5.2±4.8 at 12 months. The total score also improved from 54.9±14.4 at baseline to 24.3±14.8 at 12 months. Patients reported improved quality of life, as measured by the Quality of Life in Essential Tremor Questionnaire (37% vs. 12%, P=0.001).

The sample size was too small to draw definitive safety conclusions. A significant subset of patients experienced sensory disturbances, most commonly paresthesia of the face or fingers. The paresthesia was persistent in four patients. Some patients reported temporary unsteadiness without objective change on the neurological exam. One patient had persistent dysesthesia of his dominant index finger.

By Xiaozhou Liu and Mitalee Patil

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