[Anatomic rationale for a transmaxillary access to the cavernous sinus]

W. Couldwell et al. were the first to propose a transmaxillary access to the cavernous sinus in 1997. The authors showed that this approach was low-invasive and cosmetic and it ensured visualization of different nervous formations of the cavernous sinus and the intracavernous segment of the internal carotid artery. This study was undertaken to study microsurgical anatomy, to simulate a transmaxillary access, to demonstrate its expediency, and to assess the use of endoscopic techniques when this access was applied. The study was conducted in 3 steps: 1) a craniometric study on 33 skulls and 25 craniograms to examine the craniological and geometric parameters of the anatomy of the osseous structures included into the transmaxillary access; 2) simulation of the access on the osseous structures of the skull (2 sides); by including anterior and posterior maxillotomy and bone drilling-out around the round foramen; 3) microsurgical preparation--dissection was performed on 3 head samples (5 sides) at the Laboratory of Microneurosurgical Anatomy, Acad. N. N. Burdenko Research Institute of Neurosurgery, Russian Academy of Medical Sciences. Endoscopy was tested when the transmaxillary access was applied. The results were as follows: 1. The depth of the access failed to correlate with the shape of the skull. The operative observation angle averaged 18-23 degrees. 2. Simulation of the transmaxillary access on the dried skull made it possible to visualize the medial portion of the infratemporal fossa, by enlarging the pterygpid-maxillary fissure. The bone drilling-out boundaries for the skull base were defined. 3. Microsurgical dissection after removal of the posterior maxillary sinus wall and opening the pterygopalatine fossa. The topography of the maxillary artery and nerve was studied. After drilling out the bone of the skull base, the lower wall of the cavernous sinus was crescent. The cavernous sinus was opened as far as possible both above the maxillary nerve and between the second and third branches of the trigeminal nerve.

1. The access is deep and narrow, yet low-traumatic. 2. It may be the access of choice in removing a small pathological focus in the pterygopalatine fossa, round foramen or lower portions of the cavernous fossa. 3. The access may be used to approach the medial portion of the infratemporal fossa. 4. The described stepwise microsurgical anatomy and internal guiding lines in the retromaxilllary space permit one to perform surgical operations with confidence. 5. With this access, there is no guidance over the great vessel (internal carotid artery). 6. The access passes through the vestibule of the mouth; in this connection its application is undesirable at surgery for intradural abnormalities.