This study aims to determine the microscopic anatomy of the layers of the lateral wall of the cavernous sinus (CS) and, in particular, intends to examine the location and relations of the dural openings on the deep layer. Forty sides of 20 formalin-fixed and fresh cadavers were dissected and their CS examined. In 12 cases we found an opening on the deep dural layer; however, in four of them the inferolateral trunk of the internal carotid artery (ICA) was identified through these dural openings. We noticed the trochlear nerve making a curve (5% of cases) or lying close to the ophthalmic nerve (12.5%) on the lateral wall. In one case, the triangular area described by Parkinson could not be exposed surgically. Our findings indicate the importance of the heterogeneous courses of the cranial nerves lying on the lateral wall and point to the significance of the dural openings, which can influence the etiology of neoplastic invasions originating from the CS.