Morphometric Variations of Sphenoidal Air Sinuses in Human Cadavers

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Background: The sphenoid sinuses are difficult to approach directly, so a transnasal approach is preferred. Due to the variable extent of pneumatization, there are variations in the size and shape of sphenoid ostium. These sinuses are related to many important structures, and they produce surface impressions on sinus walls. There are very few cadaveric studies that describe sphenoid sinuses morphometrically and their relation to nearby important structures. Hence, this study was undertaken to study the morphological variations of sphenoid sinuses; to measure the dimensions of the sphenoid sinuses; to classify the sphenoid sinuses and to study the variations of relation of important structures along the walls of the sphenoid sinuses. Methodology: The present study was performed on 25 formalin-fixed cadavers (50 hemisections). The morphometric anatomy of the sphenoid sinuses was studied by taking midline sagittal sections of the head, neck, and face regions in cadavers. Anteroposterior depth (infrasellar) and vertical height (presellar) of the sinus were measured. Based on the morphology of the sinus, they were grouped into conchal, presellar, sellar, and postsellar types. Surface impressions made by the carotid artery and optic nerve on the lateral wall of the sinus were observed. Results: The most common type of sphenoid sinuses was the sellar variety (68%), with conchal being the least common (0%). Most of the sinuses (88%) were divided by the intersinus septa. A round-shaped ostium of the sphenoid air sinus was found to be common (56%). Impressions of the internal carotid artery and optic nerve into the lateral wall of the sinus were prominent in highly pneumatized sphenoid sinuses. Conclusions: Variations observed are mainly due to variable pneumatization of the sphenoid bone. The degree of pneumatization will result in protrusion of the surrounding structures such as internal carotid artery and optic nerve into the sinus wall. The extent of pneumatization will determine the degree of protrusion of surrounding structures.