Head Trauma-Induced Superior Semicircular Canal Dehiscence Syndrome

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.