Clinico-anatomical relationships between the internal carotid artery and sphenoid sinus usingcomputed tomography

Unexpected and sometimes inexplicable massive haemorrhage arising from intracranial injury to the internal carotid artery (ICA) is a life-  threatening complication of endoscopic transsphenoidal skull base surgeries. Pre-interventional computed tomography (CT) assessment of the  anatomical relationships between the ICA and the sphenoid sinus is necessary to understand and prevent this complication. The aim of this study  was to determine the normal anatomical variations between the sphenoid sinus and internal carotid artery using CT and evaluate their relationship  with sinus dimensions. The CT scans of 323 sphenoid sinuses of patients aged 18 to 80 years were retrospectively studied. The images were taken  with a GE Bright Speed Multi detector Helical CT Scanner and viewed using the Digital Imaging and Communication in Medicine (DICOM) viewer. The  anteroposterior, craniocaudal and transverse diameters were measured and used to determine sinus volume. Protrusion of the ICA into the  sinus cavity, dehiscence, and presence of septal ttachments to the sinus walls bordering the ICA were studied. The prevalence of ICA protrusion, dehiscence of sinus wall, and septal attachment were 28.48%, 17.34% and 13.93% respectively. There was a statistically significant relationship  between protrusion of ICA and the anteroposterior and transverse sinus diameters. The relationship between dehiscence of the wall over the ICA  and sinus volume as well as the transverse diameter was statistically significant. A careful CT identification of these normal but potentially  dangerous variations between the ICA and the wall of the sphenoid sinus prior to surgery is essential for a safe cranial base endoscopic  transsphenoidal procedure.