Abstract

T. S. Gee*, H. K. Pal, A. K. Aaijaz, I. Zul and A. K. Shamim

Cerebellopontine angle (CPA) tumors account for 10% of all intracranial tumors. The endoscopic approach to CPA is being used increasingly as the availability of variable angled endoscope allow for operative views of lesions at angles not visible by the microscope and it is minimally invasive. The authors present findings based on the endoscopic study performed on three cadaveric heads (six sides) through the retrosigmoid approach and 10 adult dried skulls. The CPA cistern was examined using MAHE 5.0 mm rigid endoscope at 0 and 30°viewing angles and morphometric assessment of the neurovascular structures visualized was carried out. A morphometric study on skulls was performed to measure key distances relevant to surgery of CPA lesions; these distances were measured from the sino-dural angle (SDA). The cranial CPA level contains the oculomotor, trochlear, trigeminal nerves and superior cerebellar artery. The middle CPA level contains the acoustic-facial bundle and provides access through an endoscopic corridor to the abducens nerve, anterior inferior cerebellar artery and vetebro-basilar junction. The caudal CPA level contains the lower cranial nerves (glossopharyngeal, vagus, accessory and hypoglossal) and the V4 segment of the vertebral artery. The thickness of III, IV, V and acoustic-facial bundle in their cisternal course ranged from 2.2 to 2.5 mm; 0.5 to 0.8 mm, 2.5 to 3.0 mm, and 2.0 to 2.5 mm respectively. The distance between the SDA-posterior lip of porus acousticus ranged from 31 to 37 mm (median 34 mm). SDA-Meckel’s cave distance was 46 to 52 mm (median 49 mm and SDA-petrous apex distance was 59 to 67 mm (median 61 mm). The authors conclude that understanding of endoscopic anatomy of cerebellopontine angle is very useful for skull base surgeon.