Sphenoid sinus septations and their interconnections with parasphenoidal internal carotid artery protuberance: radioanatomical study with literature review

Introduction
Internal carotid artery (ICA) injury is the most dangerous and life-threatening complication in patients operated on due to parasellar tumors via a minimally invasive endoscopic endonasal approach. Sphenoid septal attachment to the ICA protuberance within the sphenoid sinus was found to be one of the anatomical risk factors for ICA injury during transsphenoidal surgery.

Aim
To determine the relationship between the sphenoid sinus septa and the parasellar or paraclival internal carotid artery prominence based on our own material and a literature review.

Material and methods
The axial plane scans of computed tomography angiography and a literature review of previously published papers on the septum variation and its connection with the ICA prominence are provided.

Results
Out of 100 sphenoid sinuses, 49 (49%) had at least one septum inserted at the ICA prominence. In the majority of cases 42 (86%) one septum was inserted at the prominence of one of the ICAs. In 7 (14%) cases, two separate septa were inserted at the prominences of both ICAs. Patients with multiple septa and those having an incomplete septum were at higher risk of at least one of them being inserted at the ICA prominence within the sinus. Including cases from the literature review, the average number of septa per patient was 1.42. The risk of intersection between the septum and the ICA prominence was 32%.

Conclusions
A significant percentage of the intrasphenoidal septa are inserted at the sphenoidal ICA protuberance.