[A case of cavernous sinus epidermoid: anatomical classification and surgical approach]

Epidermoid rarely appears in the cavernous sinus. We encountered a 41-year-old man with left abducens nerve palsy. A round-shaped, low-density lesion on CT was located lateral to the left cavernous sinus with a compressed and thinned lateral wall of the sphenoid sinus. We could not identify cranial nerves in the cavernous sinus, which was found to be packed with a non-enhanced, high-intensity tumor on both T1 and T2 MRI. Part of the tumor capsule and its pearly contents were removed with an intradural subtemporal approach, and an inner membranous layer with cranial nerves and a tumor capsule were seen at the bottom of the tumor cavity. Postoperatively, complete cure was achieved. Reviewing similar cases, we found 18 cavernous sinus epidermoids:extracavernous type in 5;interdural in 10;and intracavernous in 3. The interdural type could be further divided into two subtypes:superficial cavernous sinus and inner membranous types. The present case belongs to the former. Frontotemporal and subtemporal procedures via both intra- and extradural approaches are relatively safe for lesions except for the intracavernous type, because cranial nerves are not located in the lateral wall of the tumor. MRI provides more useful information on cranial nerves and aid in choosing a better treatment strategy.