Anatomical variations of sphenoid sinus based on computerized tomography (CT)

Objectives Currently in Sri Lanka otorhinolaryngologists are vastly involved in   functional endoscopic sinus surgery (FESS), while transsphenoidal approach to sellar lesions is becoming popular among neurosurgeons. There is a possibility of endoscopic supra sellar, lateral skull base and clival surgery to take off in near future although no sufficient database is available about the anatomical variations of the sphenoid sinuses of Sri Lankans. This research is aimed at filling this deficit. Design and Methods A cross sectional retrospective study of 200 CT scans of 0.5mm intervals of the ‘nose, paranasal sinus and brain” of Sri Lankans who were seen at district general hospital Trincomalee were analyzed. Details were collected regarding pneumatization, sellar budge, protrusion and dehiscence of the walls of maxillary nerve (MN), optic nerve (ON), vidian nerve (VN) and internal carotid artery (ICA) and the different types and attachment of the sphenoid sinus septum. Results We found no conchal pneumatization but 100% of the study population to have presellar area of the sphenoid body pneumatization, 87% to have sellar and 39.5% to have post sellar area of the sphenoid bone pneumatization. Superior extension of pneumatization into anterior clinoid process (ACP) was found among 13.5% and extension in to posterior clinoid process (PCP) in 4.5%. Lateral extension in to opticocarotid recess was found in 60% and pneumatization in to greater wing of sphenoid (GWS) was found in 42% while 13.5% had pneumatization of lesser wing of sphenoid (LWS). Anterior pneumatization extended in to vomer and ethmoid bones and was 25%and 19% respectively. Posterior extension in to clivus was 34.5% while pneumatization extended inferiorly in to pterygoid process in 54.5 %. The sellar bulge was well defined in 75.5% and not so in 24.5%. The Intersinus septum was absent in 0.5% while single Intersinus septum was present in 86.5% and 8% had a transverse septum. 29.5% had multiple Intrasinus septum while 64.5 % had accessory septa. Occurrence of protrusion and dehiscence in optic nerve, maxillary nerve, vidian nerve and internal carotid artery were, 54%, 8.5%, 24.5% and 79% and, 23%, 7%, 14% and 57.5% respectively. Conclusions The sinus anatomy has a racial difference and regional anatomy varies randomly. Posterior, inferior and lateral extensions of pneumatization could make orientation and relative positioning of vital structures confusing. Septal attachments to   vessels and nerves are much higher than appreciated previously. Individual study with greater attention to detail in CT scans is recommended prior to surgery to minimize complications.