Supracerebellar Infratentorial Variant Approaches to the Intercollicular Safe Entry Zone

OBJECTIVE: To describe and compare surgical exposure through microsurgical cadaveric dissection of the intercollicular region afforded by the median, paramedian, and extreme-lateral supracerebellar infratentorial (SCIT) approaches. METHODS: Ten cadaveric heads were dissected using SCIT variant approaches. A neuronavigation system was used to determine tridimensional coordinates for the intercollicular zone in each route. The areas of surgical and angular exposure were evaluated and determined by software analysis for each specimen. RESULTS: The median surgical exposure was similar for the different craniotomies: 282.9 +/- 72.4 mm(2) for the median, 341.2 +/- 71.2 mm(2) for the paramedian, and 312.0 +/- 79.3 mm(2) for the extreme-lateral (P = 0.33). The vertical angular exposure to the center of the intercollicular safe entry zone was also similar between the approaches (P = 0.92). On the other hand, the horizontal angular exposure was significantly wider for the median approach (P < 0.001). CONCLUSIONS: All the SCIT approaches warrant a safe route to the quadrigeminal plate. Among the different variants, the median approach had the smallest median surgical area exposure but presented superior results to access the intercollicular safe entry zone.