Radiosurgical Thalamotomy for Essential Tremor: A Prospective Study with Blinded Assessment by a Movement Disorder Neurologist

Abstract

To prospectively evaluate the effectiveness and safety of radiosurgical thalamotomy in patients with Essential Tremor (ET). Patients underwent stereotactic radiation VIM thalamotomy by a dedicated Cobalt 60 intracranial radiosurgery platform in a fixed headframe. 130 Gy was prescribed to the 100% isodose point with single 4mm collimator. Effectiveness was evaluated using validated tremor rating scale: upper limb CRST Part B ratings (CRST) in comparison to baseline. To be eligible minimal CRST score of 2 in writing or drawing was required. Writing and drawing score assessments were conducted by a single movement disorder neurologist in a blinded fashion. Mean writing and drawing scores were statistically compared with paired t-test. A total of 213 cases (203 patients) were enrolled in the study, 7 cases (and individual patients) withdrew prior to treatment. The total number of thalamotomies performed was 206. Ten patients had right and left thalamotomies on study. Eleven patients underwent a contralateral thalamotomy but their initial thalamotomy was not a case in this study. 30 patients withdrew or were lost to follow-up, 2 patients were withdrawn due to not meeting medication criteria after treatment, 12 patients were withdrawn not meeting CRST rating criteria. Two patients were lost to follow-up immediately following the procedure (one of whom was a patient who underwent right and left staged procedures - no follow-up was obtained after the second procedure). 177 cases completed 6-month follow-up; 169 cases completed 1 year follow-up; 113 cases completed 2-year follow-up. For 189 total evaluable cases pre-treatment, drawing score mean was 2.86 +/- 0.84, pre-treatment writing score mean was 2.96 +/- 0.86. WRITING At one year: 143 cases (writing side targeted) mean writing score 1.28 +/-1.11 P<.01. 77% of cases improved by 1 point or greater. At two years: 102 cases 1.48+/-1.11, P<.01. 78% of cases improved by 1 point or greater. DRAWING At one year: 169 cases mean drawing score 1.42 +/-0.97, P<.01. 71% of cases improved by 1 point or greater. At two years: 113 cases mean drawing score 1.49+/-0.98, P<.01. 71% of cases improved by 1 point or greater. Cumulative side effects at 6 months and 1 year were seen in 17 of 175 of patients. 12 mild, 3 moderate and 2 severe. Mild side effects included numbness of the fingers, lip or hand and mild dysarthria. Severe side effects were 1 thalamic hemorrhage resulting in contralateral weakness. 1 patient developed foot drop and slurring of speech. Cumulative 2-year side effects were 15 mild, 3 moderate and 3 severe (1 additional thalamic hemorrhage). Stereotactic radiosurgical thalamotomy provided a significant reduction in tremor at 1 and 2 years. The treatment is an effective noninvasive treatment option worthy of consideration in many patients. The treatment has a low but non-zero risk of significant SEs.