Endoscopic Endonasal Approach to Meckel's Cave

Background: External approaches to Meckel's cave and the petrous segment of the internal carotid artery (ICA) offer excellent exposure but are associated with neurological, functional, and cosmetic morbidities. Only a few articles report endoscopic endonasal exposure of Meckel's cave. Our aim is to describe an endoscopic approach to Meckel's cave. Anatomical relationships and predictable morbidities based on anatomy are discussed.

Material and Methods: Four cadaveric heads (eight sides) were dissected with 0° endoscopy through a transnasal, transmaxillary approach; a Caldwell-Luc approach was performed if lateral manipulation of instruments was hampered by the lacrimal bone.

Results: A large maxillary antrostomy was performed and the sphenopalatine artery identified; the posterior and superior walls of the maxillary sinus were removed, and the internal maxillary artery and maxillary nerve (V2) entering foramen rotundum were identified. Lateral to the pterygoid buttress, the medial attachment of the lateral pterygoid muscle was dissected and the mandibular nerve (V3) entering the foramen ovale was exposed. A large sphenoidotomy was performed and the cavernous ICA located in the carotid sulcus. The vidian nerve and V2 were followed retrogradely by removing pterygoid bone enabling identification of foramen lacerum, petrous carotid, and Gasserian ganglion in Meckel's cave. Additional bone was removed on the medial side of foramen ovale to expose the V3 retrogradely to the Gasserian ganglion, which was followed posteriorly to the retrogasserian root.

Conclusions: The endoscopic approach affords the same exposure as historical external approaches with significantly less morbidity based on anatomical dissections. Indications include benign lesions of the pterygopalatine fossa, infratemporal fossa, and Meckel's cave with minimal intracranial extension. Biopsy of malignant tumors in the above-mentioned regions is also indicated. Limitations of the technique and morbidity based on anatomical dissection will be discussed.