Introduction: The ambient cistern is an arachnoid complex that extends from 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 exists. 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.

Methods: A subtemporal approach was performed in six brain hemispheres. A qualitative and quantitative analysis were made. The linear exposition of the vascular structures and the surgical exposure area were evaluated.

Results: 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 104.8mm2 for ST and 210.5 for STh (p=0.0001). Regarding to endoscope assistance the medial area, ST was 81.0mm2 and STend was 176.2mm2 (p=0.038). For the total area of exposure, we obtained a value of 210.5mm2 for ST and a value of 391.3mm2 for STend (p=0.041).

Conclusions: 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.

Patient Care: We suggest an alternative and less invasive surgical approach with endoscope assistance compared to the traditional microscopic approach.

Learning Objectives: By the conclusion of this session, participants should be able to: 1) Evaluate advantages of an endoscopic approach to the temporal region; 2) Identify a wider surgical exposure with endoscopic assistance compared to the traditional microsurgical approach

References: 1- Figueiredo EG, Beer-Furlan A, Welling LC, Ribas EC, Schafranski M, Crawford N, et al. Microsurgical Approaches to the Ambient Cistern Region: An Anatomic and Qualitative Study. World Neurosurg. 2016;87:584-590. / 2- Figueiredo EG, Beer-Furlan A, Nakaji P, Crawford N, Welling LC, Ribas EC, et al. The Role of Endoscopic Assistance in Ambient Cistern Surgery: Analysis of Four Surgical Approaches. World Neurosurg. 2015 ;84(6):1907-1915.