Objective: According to the literature, bony dehiscence at the lateral wall of the sphenoid
sinus is reported to be rare. However, authors have experienced frequent bony dehiscence
of sphenoid sinus in patients with sphenoid fungus ball. Therefore, this study evaluated
the prevalence of bony dehiscence of sphenoid sinus according to pathology.
Methods: This is a single-center study with retrospective analysis during January 2017 to
January 2019. First, patients who had been treated with sphenoid fungus ball (SFB)
were recruited. This was followed by recruitment of age- and sex-matched patients
with bilateral chronic rhinosinusitis (CRS) or with pituitary adenoma (PA). Presence
and width of the bony defect were measured in the coronal section of paranasal sinus
CT scan with 2 mm thickness in the bone setting. For sphenoid fungus ball, the ipsilateral
side was selected for analysis, and for others, side of analysis was selected randomly.
Results: In total, 65 patients were analyzed (27 SFB, 15 PA, 23 CRS). All bony defects were
located medial to foramen rotundum and superior orbital fissure, just anterior to
opticocarotid recess. In SFB, bony defects were present in 74.1% (20/27) and were
significantly more frequent compared with PA (20%) and CRS (26.1%; p < 0.001). The width was highest in SFB (1.24 ± 6.96 mm) followed by CRS (0.79 ± 0.18
mm) and PA (0.72 ± 0.32 mm). However, the difference was not significant (p = 0.304). Bony ostitis was most frequently observed in SFB (88.8%) followed by CRS
(56.5%) and PA (0%). Logistic regression revealed that the presence of bony defect
was more dependent on the presence of ostitis rather than on sinus pathology. During
the study period, three patients with SFB presented with invasive fungal sinusitis.
In two patients, lateral wall defect was the route on invasion to the skull base.
Conclusion: Sphenoid sinus lateral wall defect is more frequently observed when the bony ostitis
is present. In SFB in which bony ostitis is common, this bony defect could be a route
of skull base invasion.