Cerebrovascular Pathology Treated via the Oculomotor-Tentorial Triangle

Background Pathology in the region of the basilar apex, anterior midbrain, and interpeduncular and ambient cisterns may be accessed anteriorly via an orbitozygomatic (OZ) craniotomy. Previously described triangles to access this region include the opticocarotid triangle (OCT), the carotid-oculomotor triangle (COT), and supracarotid triangle (SCT). The oculomotor-tentorial triangle (OTT), bordered medially by CN3, laterally by the tentorium, and posteriorly by the temporal lobe, is less well described. The purpose of this review was to describe all vascular pathology treated via the OTT.

Methods This is a retrospective review of all patients with vascular pathology treated via the OTT from 1998 to 2017 by the senior author. Patients were grouped together based on pathology/surgical procedure and included aneurysms within the OTT, bypasses performed within the OTT, and brainstem cavernous malformations (CMs) and dural AVFs accessed through the OTT. The majority of patients were approached via an OZ craniotomy, wide Sylvian fissure split, and temporal lobe mobilization.

Results The total study population included 62 patients. Eighteen patients had aneurysms within the OTT (7 P1–P2, 9 P2, and 2 P3). Thirteen aneurysms were saccular, 4 dolichoectatic, and 1 fusiform. Twelve aneurysms were clipped, 2 wrapped, 2 proximally occluded, 1 trapped, and 1 trapped with bypass. Bypass was performed for 24 patients with pathology outside the OTT (3 cases of VBI, 13 basilar trunk, 4 basilar apex, 2 PCA (P1), and 2 SCA aneurysms). Bypasses included 11 M2 MCA-RAG-P2 PCA, 8 STA-P2 PCA or –s1 SCA, 2 V3 VA-RAG-s1 SCA, 1 ATA-s1 SCA, and 1 SCA-PCA side by side. Sixteen patients had brainstem CMs resected (10 midbrain, 5 upper pons, 1 interpeduncular cistern). A Kawase approach was incorporated for three of the five CMs in the upper pons. Four patients had tentorial region dAVFs ligated.

Conclusion The OTT can be used to approach a wide variety of vascular pathologies in the region of the basilar quadrification and anterior midbrain. Wide Sylvian fissure split and posterolateral retraction of the temporal lobe move the triangle's posterior border and expand the area of the triangle.