INTRACRANIAL COURSE AND RELATIONS OF THE HYPOGLOSSAL NERVE - AN ANATOMIC STUDY

This anatomic study describes the course and intracranial relations of the hypoglossal n. in 32 cadavers. The rootlets of the nerve emerged as a fan-shaped distribution (23.44%) or in two bundles (76.56%) and c onverged towards the hypoglossal canal in the subarachnoid space befor e piercing the dura mater. In 76.57% of cases the rootlets pierced the dura mater in two separate apertures, less commonly through the same aperture (21.87%), and in I are cases through three individual apertur es, as in one of our cases. The distance between the two apertures var ied from 0.6 mm to 8.7 mm. Commonly, the two bundles converged togethe r and left the skull through one foramen in the skull. However, in som e cases (28.12%), the hypoglossal canal was divided in two by a small bony spicule. In 23.45% of cases the initial course of the posterior i nferior cerebellar a. (PICA) passed between the two bundles of the hyp oglossal n. before ascending towards the lateral border of the fourth ventricle.