Anatomical variations of the sphenoid sinus and its adjacent structures: a review of existing literature

Abstract

The sphenoid sinus, one of the posterior groups of sinuses, has long been regarded as a 'neglected sinus' due to the anatomical location, poor understanding and poor accessibility, till the advent of endoscopes and modern imaging techniques. Increasing knowledge and greater understanding of this sinus has permitted an evolution in surgical practices and boundaries. Various literatures of the past report a great variety of rates of pneumatization, rates of optic nerve protrusion and dehiscence, as well as internal carotid artery (ICA) protrusion and dehiscence. One similarity noted among these studies is that the rates vary according to the ethnicity of the patients. Recommendations have also been made along the way with regard to modified surgical techniques. This review aims to describe the pneumatization of sphenoid sinus and the topographical relation of the optic nerve and ICA in different populations.

Anatomical variants of surgically important landmarks in the sphenoid sinus: a radiologic study in Southeast Asian patients

“…The findings with regard to the sphenoid sinus in many of the CT and anatomical studies of the past describe a multitude of variations and highlight their findings in their respective populations [2,3,5]. Most of these results, however, are based on the Caucasian population and there are growing but limited data on the Asian population to fall back on.…”

“…The sphenoid sinus in turn can be used as a route to access the parasellar and sellar region, anterior skull base, clivus, cavernous sinus and petroclival region [2]. A highly pneumatized sinus with large cavity may be so extensive to envelope the surrounding structures, extend to the greater wing of the sphenoid or pterygoid process, that during opening of the sella, the neurovascular structures may risk being injured.…”

“…A highly pneumatized sinus with large cavity may be so extensive to envelope the surrounding structures, extend to the greater wing of the sphenoid or pterygoid process, that during opening of the sella, the neurovascular structures may risk being injured. Conversely, endoscopic transphenoidal approach will not be an option as a surgical route to the skull base and pituitary in conchal type of pneumatization in view of the fact that the cavity would be filled by cancellous bone and there would be no association with the sella turcica [2].…”

Protrusion of the Infraorbital Nerve into the Maxillary Sinus on CT: Prevalence, Proposed Grading Method, and Suggested Clinical Implications

“…7 The prevalence of internal carotid artery dehiscence and protrusion varies widely from 1.5% to 30% and 5.2% to 67%, respectively, with variation potentially depending on the study population. 6 Aeration of the anterior clinoid process has a reported prevalence of 12%-19%, 8,9 and when optic nerve protrusion is present, there is a 56% chance of ipsilateral anterior clinoid aeration. 9 Insertion of an intersphenoid sinus septum onto the carotid canal has been reported in 4.7%.…”

“…Most of the literature supports a prevalence of optic nerve dehiscence of 0.7%-8%. 6 Reported prevalence for optic nerve protrusion ranges from 8% to 35%, but no consensus definition exists for what constitutes protrusion, despite effort at developing a classification scheme. 7 The prevalence of internal carotid artery dehiscence and protrusion varies widely from 1.5% to 30% and 5.2% to 67%, respectively, with variation potentially depending on the study population.…”