Concomitant dehiscences of the temporal bone: a case-based study

Otic capsule dehiscences create a pathological third window in the inner ear that results in a dissipation of the acoustic energy consequent to the lowered impedance. Superior semicircular canal dehiscence (SSCD) was identified by Minor et al. in 1998 as a syndrome leading to vertigo and inner ear conductive hearing loss. The authors reported the relation between the dehiscence and pressure- or sound-induced vertigo (Tullio phenomenon). The pathophysiology of this entity still remains controversial. Prevalence rates of SSCD in anatomical studies range from 0.4 to 0.7 % with a majority of patients being asymptomatic. The observed association with other temporal bone dehiscences, as well as the propensity toward a bilateral or contralateral near-dehiscence, raises the question of whether a specific local bone demineralization or systemic mechanisms could be considered. The present report regards a case of a patient with a previous episode of meningitis, with a concomitant bilateral SSCD and tegmen tympani dehiscence from the side of meningitis. The patient was affected by dizziness, left moderate conductive hearing loss and pressure/sound-induced vertigo. Because of disabling vestibular symptoms, the patient underwent surgical treatment. A middle cranial fossa approach allowed to reach both dehiscences on the symptomatic side, where bone wax and fascia were used. At 6 months from the procedure, hearing was preserved and the vestibular symptoms disappeared.