A White Spot Around the Fissula Ante Fenestrum: A New Diagnostic Indicator for Otosclerosis

Background/Objectives: Since we started endoscopic stapes surgery, we have frequently noticed a white spot (WS) with a clear boundary on the bone surface around the fissula ante fenestrum (FAF) in otosclerosis cases. We investigated the significance of this surgical finding. Methods: We enrolled 27 cases of otosclerosis and 28 control cases of conductive hearing loss due to pathologies other than otosclerosis, both operated on endoscopically at the University of Tokyo Hospital. We retrospectively reviewed surgical videos to determine whether WS was present or absent. We examined the incidence of WS in otosclerosis cases and the controls and also in cases of otosclerosis, the presence or absence of WS was compared with the preoperative hearing level, preoperative air-bone gap, vasodilatation on the promontory, and a low-density area on high-resolution computed tomography (HRCT). Results: WS was present in 11 (41%) of 27 cases of otosclerosis but none in 28 control cases. There were no significant differences in patients' age and gender, the incidence of vasodilatation on the promontory, preoperative hearing level, or preoperative air-bone gap between otosclerosis cases with and without WS. Although a hypodense focus anterior to the oval window was more frequently present on HRCT in otosclerosis cases with WS (82%) than those without WS (56%), the difference in the incidence failed to reach significance (p = 0.10). Conclusions: We observed WS around the FAF only in cases of otosclerosis, indicating that WS is unique in otosclerosis. WS did not correlate with vasodilatation on the promontory, preoperative hearing level, or air-bone gap. A hypodense focus anterior to the oval window on HRCT tends to be more common in otosclerosis cases with WS.