Less is more: Parahippocampal resection or endoscopic assistance in ambient cistern surgery? Qualitative and quantitative assessment of subtemporal approach

The ambient cistern is an arachnoid complex that extends from the crural cistern to lateral border of cerebral colliculi. The subtemporal approach has been recognized as the best access to reach pathologies in the ambient cistern, however many disadvantages exist. The present work aims to analyze quantitatively the area of exposure provided by the subtemporal access. The objective is to evaluate if there are advantages of using the neuroendoscope in conventional subtemporal access when compared to the subtemporal access with resection of the parahippocampal gyrus. A subtemporal approach was performed in six brain hemispheres. Qualitative and quantitative analyses were made. The linear exposition of the vascular structures and the surgical exposure area were evaluated. The linear exposure to the posterior cerebral artery was 5.95 for subtemporal access (ST) and 13.6 for subtemporal access with resection of the parahippocampal gyrus (STh) (p = 0.019). The total exposure area was 104.8 mm2 for ST and 210.5 for STh (p = 0.0001). Regarding endoscope assistance the medial area, ST was 81.0 mm2, and STend was 176.2 mm2 (p = 0.038). For the total area of exposure, we obtained a value of 210.5 mm2 for ST and a value of 391.3 mm2 for STend (p = 0.041). In conventional subtemporal access, the use of the neuroendoscopes avoids the need for resection of the parahippocampal gyrus for better visualization of the ambient cistern structures.