2026 Poster Presentations
P357: OCCIPITAL INTERHEMISPHERIC TRANSTENTORIAL APPROACH TO THE CEREBELLOMESENCEPHALIC FISSURE AND SUPEROMEDIAL CEREBELLUM: A CLINICAL SERIES
Austin A Charles, BS1; Anna L Huguenard, MD2; Michael T Lawton, MD2; 1Creighton University School of Medicine, Phoenix, AZ; 2Department of Neurosurgery, Barrow Neurological Institute, Phoenix, AZ
The occipital interhemispheric transtentorial (OITT) approach provides direct access to the pineal region, posterior third ventricle, quadrigeminal cistern, and dorsal midbrain, yet contemporary case series remain limited. We present our institutional experience to evaluate its safety, effectiveness, and skull-base role in managing complex posterior incisural lesions.
We retrospectively reviewed nine patients who underwent OITT between 2021-2024 by a single surgeon at one institution. Pathologies included two arteriovenous malformations (AVM), four cerebral cavernous malformations (CCM), and three tumors: one meningioma, one solitary metastatic osteosarcoma, and one pineal parenchymal tumor of intermediate differentiation (PPTID). Candidacy for OITT approach was based on lesion involvement of the pineal region, posterior third ventricle, quadrigeminal cistern, or dorsal midbrain on preoperative magnetic resonance imaging (MRI) and/or angiography. Primary outcomes were extent of resection and postoperative length of stay (LOS). Technical nuances included lateral/park-bench positioning, wide posterior interhemispheric dissection with CSF release via callosal and quadrigeminal cisterns, and a tentorial incision parallel to the straight sinus to enter the posterior incisural space.
Median age was 53 years (range 19-69 years); five patients were male and four female. Mean lesion diameter was 1.15 cm (AVM), 1.30 cm (CCM), and 3.07 cm (tumor). Both AVMs were Spetzler-Martin Grade III. Gross total resection was achieved in 6/9 patients (67%); three patients (1 AVM, 1 CCM, PPTID) demonstrated small residual lesion on postoperative imaging. The residual AVM required Gamma Knife radiosurgery, but the residual CCM and PPTID did not require reoperation. No intraoperative complications were observed, and median postoperative LOS was 15 days (range 2-78). Two illustrative cases (vermal AVM and midbrain CCM) demonstrate corridor selection and operative strategy.
OITT approach affords effective exposure to lesions of the posterior incisural space and dorsal midline with high rates of complete or near-complete removal and favorable postoperative disposition. These data support OITT as a valuable skull base approach; modern navigation and intraoperative imaging further enhance its safety and broaden its indications.
