Microinjection of lidocaine into human thalamus: a useful tool in stereotactic surgery.

A new method was developed to aid in the localization of the optimal site for a permanent lesion in movement disorder patients undergoing stereotactic thalamotomy. The method involved making small injections of a local anesthetic into the thalamus, which was also useful in assessing any possible side effects that could potentially arise from the lesion. Initial results indicate that 0.5 to 2-microliters injections of 2% lidocaine at appropriate sites in the thalamic ventrocaudal or ventrointermedius nucleus can produce a temporary marked suppression of tremor. In most cases the lidocaine induced effects mimicked those produced by high frequency electrical stimulation delivered to the same site. However, lidocaine had no effect at some sites where stimulation arrested tremor. This technique promises to be useful not only in the treatment of motor disorder patients but also in other cases where functional localization prior to lesioning is desirable.