Head Trauma-Induced Superior Semicircular Canal Dehiscence Syndrome.

Abstract

Radiologic superior semicircular canal dehiscence (SSCD) is not an uncommon finding, while many patients remain asymptomatic. We aimed to highlight minor head trauma as a risk factor for evolution into a clinically significant SSCD syndrome and provide the audiovestibular findings. A retrospective chart review study in a tertiary referral medical center was conducted. Patients were identified from the Province of Ontario Workplace Safety and Insurance Board database, 1998-2025. Each patient underwent a comprehensive assessment comprising history, physical examination, audiovestibular testing, and CT to confirm radiological dehiscence. Twelve patients were identified. Median age was 41 years (Interquartile range 38-48). The most common mechanism of injury was a fall. Direction of impact was primarily temporal. Three patients suffered a contrecoup injury pattern. All patients sustained an immediate hearing loss. Immediate autophony was reported in 10 patients. A Tullio phenomenon was reported in six cases. Hennebert sign and bone conduction hyperacusis were found in 8 and 7 patients, respectively. Pure tone audiometry showed classic low-frequency bone conduction supra-thresholds with mild to moderate air conduction hearing loss in 7 patients. When tested, vHIT showed a unilateral relative reduction in gain of the superior semicircular canal in all cases when compared to the contralateral SSC (average mean of 0.81 vs. 0.92, p < 0.001). Average SP/AP ratios were significantly higher among the SSCD ears compared to contralateral controls (0.40 vs. 0.19, respectively, p < 0.001). Seemingly mild head trauma may be enough to convert anatomically predisposed patients into a clinically symptomatic SSCD syndrome.