ACCURACY OF VENTROLATERAL THALAMIC NUCLEUS LOCALIZATION USING UNREFORMATTED CT SCANS AND THE B-R-W SYSTEM - EXPERIMENTAL STUDIES AND CLINICAL FINDINGS DURING FUNCTIONAL NEUROSURGERY

The accuracy with which the ventrolateral thalamic nucleus could be ta rgetted using the BRW stereotactic system and unreformatted axial CT i maging was evaluated in cadaver brains mounted in a skull. Ball bearin gs (1.82 mm diameter) were placed in the nuclei ventro intermedius (Vi m), ventro oralis anterior (Voa) and posterior (Vop) and the brains th en sectioned, the locations of the ball bearings relative to the anter ior (AC) and posterior commissures (PC) measured and evaluated with re ference to a Schaltenbrandt and Bailey stereotactic atlas. Targetting of the ventrolateral thalamic region was frequently accurate (77%) but because of errors in estimation of the AC-PC plane (mean forward angu lation of 9-degrees) some ball bearings were placed too deeply in the Fields of and Forel, zona incerta and rostral subthalamic nucleus. Ven trolateral thalamotomy using the BRW stereotactic system and unreforma tted axial CT imaging was undertaken in six patients with tremor due t o a range of pathologies. The tremor was abolished or altered in four patients whilst no lesion was made in the other two patients since no site that reduced the tremor, could be located. The surgical and clini cal implications of this study are discussed.