Noninvasive Thalamotomy for Refractory Tremor by Frameless Radiosurgery.

ABSTRACT Objective We sought to determine whether a more widely accessible, non-invasive frameless approach to radiosurgical thalamotomy would improve objective measures of refractory essential or parkinsonian tremor without added toxicity compared to reports of frame-based radiosurgery. Methods We conducted a single-arm pilot observational prospective trial of adult patients with essential or parkinsonian tremor from 2013 to 2019 and report results at one-year follow-up. Patients were treated with frameless unilateral radiosurgical ablation of the thalamic ventral intermediate nucleus to a maximum dose of 160 Gy. Treatment response was measured by the Fahn-Tolosa-Marin (FTM) tremor rating scale and the Quality of Life in Essential Tremor or Parkinson's Disease Questionnaire obtained prior to treatment and at 3, 6, 9, and 12 months. Results Thirty-three patients, including 23 with essential tremor and 10 with Parkinson's disease, were enrolled. Overall treatment response rate per FTM was 83% (n=15/18) at 6 months. There was a marked improvement in tremor, with average total FTM reduction of 21% at 3 months (from 46 to 30 points, p=0.003) and 41% at 6 months (from 46 to 24 points, p=0.001). At 6 months, functional decline had regressed by 54% (from 15 to 7 points, p=0.001). Quality of life improved by 57% (p=0.001) at 6 months in patients with essential tremor, and patients with Parkinson's Disease had unchanged quality of life. At one-year follow-up, grade 2 neurologic adverse events were observed in 6% (n=2/33) of patients without any grade ≥ 3 events. Conclusion Noninvasive, frameless radiosurgical thalamotomy may be a feasible treatment for patients with refractory tremor and demonstrates short-term safety at one-year follow-up. This pilot study provides promising preliminary descriptions of efficacy, and definitive estimates of long-term safety and benefit require further study with longer follow-up.