1191. Quantitative analysis of ipsilateral and contralateral supracerebellar infratentorial and occipital transtentorial approaches to the cisternal pulvinar: laboratory investigation

Authors: Xiaochun Zhao; Qing Sun; Sirin Gandhi; Leandro Borba Moreira; Evgenii Belykh; Claudio Cavallo; Daniel Valli; Ali Tayebi Meybodi; Peter Nakaji; Michael Lawton; Mark Preul (Phoenix, AZ)

Introduction: The cisternal pulvinar is a challenging surgical location. The 4 surgical approaches for reaching the pulvinar without cortical transgression include ipsilateral supracerebellar infratentorial approach (iSCIT), contralateral supracerebellar infratentorial approach (cSCIT), ipsilateral occipital transtentorial approach (iOCTT), contralateral occipital transtentorial/falcine approach (cOTFA). This study quantitatively compared these approaches in terms of surgical exposure and maneuverability. Methods: Each of the 4 approaches was performed in 8 specimens. A 6-sided anatomic polygonal region was configured over the cisternal pulvinar, defined by 6 reachable anatomic points in different vectors. Multiple polygons were subsequently formed to calculate the areas of exposure. Surgical freedoms of each approach were calculated as the maximum allowable working area at the proximal end of a probe, with the distal end fixated at the posterior pole of the pulvinar. Areas of exposure, surgical freedoms and the working distances of all approaches were compared. Results: No significant difference was found amongst the 4 different approaches with regards to the operative distance, surgical freedom, or medial exposure area of the pulvinar. cSCIT provides a larger lateral exposure area (39±9.8mm 2 ) than iSCIT(19±10.3mm 2 ), iOCTT(19±8.2mm 2 ) and cOTFA(28±7.3mm 2 ). The total exposure area of cSCIT(75±23.1mm 2 ) is larger than iOCTT(43±16.4mm 2 ) and iSCIT(40±20.2 mm 2 ) approaches. Conclusion: cSCIT approach is the preferable approach among the 4 compared approaches, demonstrating better exposure to the cisternal pulvinar than ipsilateral approaches and larger lateral exposure than cOTFA. Both contralateral approaches described (cSCIT, cOTFA) provided enhanced lateral exposure to the pulvinar. OTFA had larger exposure to the lateral portion of the pulvinar than OCTT. Medial exposure and maneuverability were not different in all approaches. The shorter length of tentorium may negatively impact an ipsilateral approach as the cingulate isthmus and parahippocampal gyrus tend to protrude, in which case they can obstruct access to the cisternal pulvinar ipsilaterally.