Effect of electrical stimulation of the thalamic Vim nucleus on hand tremor during stereotactic thalamotomy

Objective: The aim of this study was to analyze the correlation between neuronal responses in the thalamic ventralis intermedius (Vim) nucleus to peripheral, natural stimulation and the modulation of tremor by electrical stimulation during stereotactic thalamotomy.

Design and methods: The authors studied 36 patients with hand tremor using a microelectrode. The responses of tremor to electrical stimulation were analysed electromyographically. Sixty stimulation sites were divided into three groups.

Results: Group A (20 sites) where responses to stretching of the contralateral forearm muscles were recorded. Group B (26 sites) where responses to stretching of the other muscles of the upper extremity were recorded. Electrical stimulation at sites in groups A and B temporarily suppressed the contralateral tremor, but the minimum current intensity to suppress tremor at sites in group A was less than that in group B. Electrical stimulation in group C (14 sites), where kinesthetic responses of contralateral lower extremity were recorded, resulted in increased amplitude of hand tremor. Selective coagulation including the area of tremor suppression resulted in abolition of the tremor in all patients.

Conclusions: These results suggest that the most effective site for thalamotomy may also be suitable for chronic stimulation in the Vim nucleus.