[Intra-sphenoidal prolapse of the internal carotid artery. Computed tomography of 300 sinuses]

Endonasal sphenoidotomy is a high risk operation: fatal complications due to direct lesion to the internal carotid artery have been reported. We conducted a prospective analysis of carotid prolapse within the sphenoid cavity in order to draw attention to this dangerous anatomic variant.

Tomodensitometry of the sinuses was performed in 150 patients (mean age 35 years; range 20-70) with inflammatory nasal symptoms of less than one year duration (mean 5.2 months). Cases with benign or malignant tumours, polyposis or a past history of sinus trauma were excluded. Transversal sections were analyzed by one radiologist and one ear-nose-throat specialist. The diagnosis of carotid prolapse was defined as an intrasphenoid protrusion of the artery at least as long as one-third of its circumference. Results of the analysis were expressed as percent for 300 sinuses.

Prolapse of the internal carotid was found in 20.3% of the sinuses (n = 61). In all cases a thin (> 1 mm) bony structure surrounded the artery. No prolapse was observed into the posterior ethmoid cells.

Intrasphenoid prolapse of the internal carotid artery is a major risk factor in nasal and sinus surgery. The high incidence (1 out of 5 sinuses) indicates the need for routine preoperative imagery to reduce surgical risk.