Localization accuracy of AC-PC line and functional pallidal target using BRW stereotactic implementation system and axial CT scanning : an experimental study

BACKGROUND: Ventriculography is still considered an unavoidable step for functional target localization, even though this method is invasive and requires stereotactic rooms, orthogonal frames, and parallax-free X-ray equipment. In this experimental study, the authors investigated the feasibility of performing stereotactic lesions using a conventional, widely employed frame, such as the Brown-Roberts-Wells (BRW) apparatus, and computerized axial tomography (CAT) imaging. METHODS: Five ex vivo models consisting of cadaveric brains enclose in a plastic shell were fixed in a BRW frame. A simple BRW implementation was used to ensure more symmetrical placement of the basal ring. Two-millimeter plastic balls were inserted at the level of the anterior (AC) and posterior commissures (PC) and at the target in the pallidus. Their final position was measured on the anatomical specimens and compared with Schaltenbrand Atlas maps. RESULTS: The error in estimating the length of the intercommissural line ranged from 0.5 mm to 2.0 mm, with a maximum backward angulation of four degrees in predicting the AC-PC plane. Upon dissection, in four out of five cases, the balls were found within the area of the pallidus defined by Laitinen for posteroventral pallidotomy. CONCLUSIONS: The authors conclude that anatomical identification of the AC-PC line and the pallidus target, using the BRW stereotactic system and CAT axial images alone offers sufficient accuracy. They suggest that functional neurosurgery for movement disorders could be safely and successfully carried out without ventriculography if neurophysiological monitoring is also employed.