Anatomical considerations of the wall and cavity of the cavernous sinus *
< Object > Whether the cavernous sinus is an unbroken venous channel or a venous plexus has long been a matter of controversy. Although the ability to make a direct approach to the cavernous sinus has increased, several points remain unclear about its anatomy, such as the relationship between the lateral wall and the cranial nerves or venous spaces. In particular, whether the inner membranous layer appears after opening of the dura propria is of importance to neurosurgeons. The author studied the heads of 38 adult cadavers to clarify these problems. < Methods > The cavernous sinuses and surrounding structures were removed en bloc from 38 cadaveric heads. Then, using a surgical microscope, the author dissected the heads and made a histological investigation. Vascular injections were also done in some cases. < Result > The development of the venous spaces in the cavernous sinus varies and these spaces in the cadaveric heads used in this study were classified into three types ; a well developed type (66%), a moderately developed type (21%) and a poorly developed type (13%). The well developed type, which is the most common type, is generally imaged as a large, trabeculated venous space. In contrast, the poorly developed type is imaged just as a venous plexus. By studying the coronary section, the lateral wall was found to be composed of only two layers ; that of the dura propria and the interstitial layer of the venous plexus. Arteries and cranial nerves run through this interstitial layer. This thin loose connective tissue layer may be thought to be an independent membrane in cases with a large venous space, < Conclusion > The cavernous sinus is a venous plexus located in the epidural space of the parasellar region. It should be understood that the region generally called the cavernous sinus is the region containing a venous plexus and its interstitial layer, the internal carotid artery and its branches, and cranial nerves. (Accepted on October 5, 1998) Kawasaki Igakkaishi 24 (3) : 161-172, 1998
