The Location Of Effective Lesions In The Thalamus After Gamma Thalamotomy For The Treatment Of Tremor

Keywords: thalamotomy, gamma knife, tremor, technique, anatomy

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     We performed Gamma knife thalamotomy on 18 cases of tremor dominant Parkinson disease and essential tremor based on the measurement data of optimal lesions in the thalamus using MRI guided electrophysiologically controlled selective thalamotomy. The location of effective lesions in the thalamus for the treatment of tremor was analyzed using stereotactic MRI.
     Eighteen patients in total including 9 tremor dominant Parkinson patients and 9 essential tremor patients were treated. Patients ranged in age from 66 to 89 years old (mean age: 75.6).
     Gamma knife thalamotomy was performed using Leksell’s apparatus aided by thin slice MRI, Surgiplan and space ATLAS. The target point was selected in the radiologically identified VLp nucleus of human thalamus (Hirai and Jones,1989) for control of tremor. The target point was decided on the basis of measurement data of optimal locations of 12 coagulative lesions in the thalamus treated previously in our institution using MRI guided electrophysiologically controlled selective thalamotomy. A single isocenter exposure with the 4 mm collimator helmet of the Leksell gamma knife was used to make the lesions. The maximum dose was 130-140 Gy. The follow up period was 36-85 months (mean 63 months).
      Symptoms of the patients improved gradually. Three months later, fifteen out of 18 patients were aware of the improvements in tremor. One year later, tremor were improved by 50-90% in tremor scores in all patients and become stable. The radiosurgical lesions were usually identified in T2 weighted MRI of 3 months after treatment and gradually increased up to 2-3 years. .
     This is a retrospective study.
     The overall results are satisfactory, being 85% successful without any noticeable complications. The target area of the effective lesions after gamma thalamotomy for the treatment of tremor was located in 40-50 % of the thalamic length to compensate the individual difference
     Gamma thalamotomy can be safely applied to patients with tremor. Lesions located in optimal areas in radiologically identified thalamic nuclei provide relief from tremor in selected cases.


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