Abstract
The relationship between the volume of sphenoid sinus (SS) and the prevalence of internal carotid artery (ICA) and optic nerve (ON) protrusions in the SS was studied by using high-resolution CT imaging. The ICA and ON protrusions in SS were observed in randomly selected normal head CT scanning images from 350 adult subjects. Ac-cording to the incidence of ICA protrusion, three groups were divided into no ICA protrusion (70.75%), unilateral protrusion (8.68%) and bi-lateral protrusions (20.57%). The ON protrusion accounted for 16% in 350 subjects and accom-panied absolutely with ICA protrusion, but ICA protrusion appeared without accompanying with ON protrusion. The SS volume depended upon the protrusions in it and showed statistical dif-ferences, without ICA protrusion, the smallest size (11.16 ± 1.60) cm3; the unilateral protrusion, medium size (14.20 ± 1.80) cm3 and the bilateral protrusion, the largest size (25.03 ± 2.21) cm3. By observing 3D reconstructed models of ON and SS, we found ON was adjacent to SS (46%) and to posterior ethmoid sinuses (44%). The current study indicates that SS volume is varied with numbers of the protrusions and that ON location varies with the pneumatization of SS. Our results provide an anatomical basis to the surgeries for SS and its surrounding structures.
Highlights
With the advance of the endoscopic endonasal transsphenoidal approach, it is possible to make it instead of removal of pituitary by trans-skull cavity, for endoscopic pituitary via the sphenoid sinus, and for some operations needed to be expand to sellar region, suprasellar lesions, cavernous sinus, clivus and et al SS is surrounded by important structures, such as, internal carotid artery (ICA), optic nerve (ON), et al [1]
According to the morphological feature, the protrusions into SS were divided to three types when the SS was observed in the axial plane (Figure 1) on the CT scan images from 350 subjects (Figure 1(A)), no ICA protrusion the in the SS (247 subjects, 70.75%), unilateral protrusion (31 subjects, 8.68%, Figure 1(B)), and bilateral protrusions (72 subjects, 20.57%, Figure 1(D))
The anterior clinoid process (ACP) cavity with pneumatization became bigger in 24 sides because they were fused to the SS (Figure 2(D))
Summary
With the advance of the endoscopic endonasal transsphenoidal approach, it is possible to make it instead of removal of pituitary by trans-skull cavity, for endoscopic pituitary via the sphenoid sinus, and for some operations needed to be expand to sellar region, suprasellar lesions, cavernous sinus, clivus and et al SS is surrounded by important structures, such as, internal carotid artery (ICA), optic nerve (ON), et al [1]. Anatomical and radiological studies dealt with the sphenoid sinus and its surrounding structures based on cadavers or CT studies in these years. Several literatures have documented the dimensions, septation, pattern of SS pneumatization, SS surrounding structures [3,4,5], prevalence of protrusions [6] and the relation between pneumatization and protrusions [7]. These studies provided important information for surgeries in this area and promoted advancement of the surgery as well. We accomplished volumetric measurement of SS by using 3D image reconstruction based on conventional two-dimensional CT images and the types were divided according to the numbers of ICA protrusion in SS, and the relation between the number of the ICA pro-
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