[Long-term follow-up study of selective VIM-thalamotomy].

To evaluate the effect of the physiologically defined selective Vim-thalamotomy on tremor type Parkinson's disease (PA, 26 cases) and essential tremor (ESS-T, 16 cases), a long-term follow-up study was conducted. The follow-up time extended from 4 months to 7 years (mean: 3.6 years). On 42 cases a total of 49 operations (4 bilateral surgery and 3 reoperations) were carried out. After identifying kinesthetic neuron, the coagulative lesion was made by using Leksell's apparatus between two needles of 4 mm effective tip length located with 3 mm interval including the recording point. One coagulation (unit lesion) destroyed about 20 mm3 brain tissue taking account of the mechanical damage by the needles themselves. The unit lesion was added around an imaginary cylinder of 3 mm radius, until the tremor was abolished completely. On the basis of number of unit lesion and its extent within an imaginary cylinder, these 49 operations were divided into the following group. Group I (minimal lesion group): coagulative lesion of 1 to 3 units within a quadrant of the imaginary cylinder. Group II: 3 to 5 units within 1/2 to one cylinder. The early (14 days after operation) and the late results on the tremor were evaluated clinically and electromyographically by 4 different categories: complete abolition, slight residual, residual, and recurrence in a strict sense. The late results in 13 PA cases of group I (similar to the early results) were: 10 complete abolition, 2 slight residual and one recurred, this case was reoperated 3 months after first operation and therefore categolized in group II. The late results in 11 ESS-T cases of group I were: 6 complete arrest, 4 slight residual, and one recurred case, which had been reoperated 2 years after operation. Therefore in a total of 24 minimal lesioned cases with PA and ESS-T complete abolition in 16, slight residual in 6, and 2 reoperated cases. In these successful 22 cases with minimal lesion, the tremor was abolished without noticeable long-lasting side effect. In other 20 cases with PA and ESS-T of group II, the tremor was almost completely relieved and maintained. In conclusion, by radiographically and physiologically controlled selective Vim thalamotomy for Parkinsonian and essential tremor, it was shown that the effect of minimal lesion was valid and well maintained on the long-term follow-up base.