Stereotactic thalamotomy in the treatment of essential tremor of the upperextremity: reassessment including a blinded measure of outcome

The effectiveness of high frequency stimulation of the thalamic nucleus ven tralis intermedius (Vim-HFS) for treatment of tremor has been studied by bl inded assessment. The effectiveness of thalamotomy for essential tremor of the upper extremity by use of a blinded measure of outcome is now reported. Thalamotomy was performed in 21 patients (three operated on bilaterally) w ith medically intractable, essential tremor. Assessments of function, handw riting/drawing, and tremor amplitude were done before and at 3 and 12 month s after surgery. The handwriting/drawing score was rated by a neurologist b linded to patient identity, laterality, and operative status. By comparison with baseline, both the total functional score and the total score from bl inded assessment of handwriting/drawing improved significantly at 3 and 12 months after surgery. The two scores were significantly correlated, suggest ing that the blinded assessment is a good predictor of a total disability f rom tremor. Complications after unilateral thalamotomy included transient d ysarthria, permanent perioral numbness, and permanent mild disequilibrium i n one patient each. Permanent mild dysarthria occurred in two of three pati ents operated bilaterally. Thus a blinded assessment of outcome establishes that unilateral thalamotomy is an effective, safe procedure for the treatm ent of essential tremor.