Commentary

As medicine becomes more sophisticated and we find ourselves increasingly interested in the molecular genetics underlying function and disease, we tend to forget the critical importance of anatomy. Writing more than 100 years ago, the director of the U.S. Patent Office noted that everything that could be invented had been. The absurdity of this statement is obvious. That we continue to learn from more detailed study of anatomy is not as self-evident. We tend to feel that anatomy stopped with Galen, or at least with Vesalius. On the contrary, fine anatomic studies still provide insights into both normal physiology and pathological processes that can occur as a result of disease or as a consequence of surgical intervention. Needless to say surgery remains applied anatomy.

The cavernous sinus and its surrounding anatomy are fascinating areas that have received increasing scrutiny as surgical intervention has become more aggressive. This study builds on the microscopic dissections by Umansky and others that better define our knowledge of the course of the cranial nerves in the parasellar region. The concept of a sleeve surrounding the cranial nerves as they enter the area of the cavernous sinus is not new. It is well recognized that the third cranial nerve has a sleeve that often extends substantially within the lateral wall of the cavernous sinus. Petroclival meningiomas likely gain access to the lateral wall of the cavernous sinus via this sleeve. Similarly, meningiomas originating from the area of the clivus may follow the course of the sixth cranial nerve. The interesting distinction between nourishment from the microvascular circulation supplied by branches of the meningohypophyseal and inferolateral trunk and that supplied by the surrounding cerebrospinal fluid will probably have substantial bearing on the protection of the sixth cranial nerve during surgical intervention. It is hoped that this study and others will help us to protect the cranial nerves as we look for better surgical and nonsurgical methods of treating pathology in the parasellar region.