Variations of sphenoid and related structures

The aim of this study was to delineate the precise relationship between the sphenoid sinus and internal carotid artery and the optic nerve, as well as to assess incidence of the anatomic variations of these structures. A revi ew of 92 paranasal sinus tomographic scans was made for anatomic variations of the sphenoid sinus and related bony and neurovascular structures. Coron al and axial tomographic sections were obtained with 2.5-mm section thickne ss. We assessed the protrusion of the internal carotid artery (ICA) and the optic nerve (ON) into the sphenoid sinus, bone dehiscence of these structu res, and pneumatization of the anterior clinoid process (ACP) and pterygoid recess (PR), as well as the variations of the sphenoid sinus septum. The p rotrusion of the ICA into the sphenoid sinus was found in 24 (26.1%) patien ts. An ON protrusion was present in 29 (31.5%) patients. Pneumatization of the PR was encountered in 27 (29.3%) patients. There was not a statisticall y significant relationship between the pneumatization of the PR and ICA pro trusion into the sphenoid sinus (chi(2) = 0.258, p = 0.168). A significant relationship between the ACP pneumatization protrusion of the ON into the s phenoid sinus found (chi(2) = 0.481, p = 0.007). Preoperative recognition; on of the anatomic variations by the radiologist is beneficial for identifi cation of the limits of dissection. This is particularly important in the s phenoid sinus I area where extensive pneumatization of the skull base bones may distort the anatomic configuration. Therefore, axial and coronal CT se ctions should always be obtained prior to any surgery in the sphenoid area.