Objective: To assess the feasibility and tolerance of staged bilateral Gamma Knife thalamotomy (GKT) for Essential Tremor (ET)

Background: Unilateral GKT is an established treatment for severe tremors. However, essential tremor is usually bilateral. The persistence of contralateral tremor may induce an impairment in activities of daily living (ADL). Bilateral procedures with thermocoagulation were contraindicated because of the risk of balance, cognitive or speech problems. As the lesion induced by radiosurgery within the VIM is progressive and limited, we proposed a prospective study on staged bilateral GKT. Here are the preliminary results.

Methods: 23 patients (10 women, mean age70yo) with severe ET who had benefit from a first GKT (GKT1) and who had a severe permanent contralateral tremor were included. Patients were included if there was no impairment in their balance or speech and if the neuropsychological assessment was stable. The 2nd GKT (GKT2) was performed at least 18 months after the first GKT. Patients were assessed before and quarterly for at least 12 months after GKT2, with tremor rating scale, neuropsychological and gait/balance assessments, speech assessment and MRI. VIM lesioning was performed with Leksell Gamma unit with a single exposure through a 4mm collimator. Radiosurgical dose was 130Grays.

Results: here are the preliminary results for 13 patients who completed the study at 1 year. Tremor score on the treated hand was improved by 63%. The improvement of ADL was 64%. Cognitive score and gait assessment were stable. No patient had hypophonia or dysarthria. Two patients were not significantly improved. One patient had a side effect related to GKT2. She developed hemiataxia and dysarthria induced by a hyperresponse pattern 11months after GKT.

Conclusions: These preliminary results on staged bilateral GKT for severe ET in a selected cohort of patients show that the procedure is feasible without a major risk of cognitive or balance problems. However, a longer follow-up is needed to confirm these results.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/staged-bilateral-gamma-knife-thalamotomy-for-severe-essential-tremor/