Concomitant Dehiscences of the Temporal Bone: A Case-Based Study

Abstract

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 also reported the relation between the dehiscence and pressure- or sound-induced vertigo (Tullio’s phenomenon). 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 regard 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 for repair. At 6 months from the procedure, hearing was preserved, and the vestibular symptoms disappeared.

Patient Sex Mediates the Influence of Patient Age on Superior Canal Dehiscence Repair Outcome

“…Hence, we deduce that osteopenia may also play a role in the outcome of SCD repair. Among cases for which thinning of the SSC roof is presumably driven by reduced estrogen levels, other regions of the temporal bone may also be osteopenic 28,29 . We speculate that this general osteopenia of the surrounding bony structures (beyond the dehiscent region) may be partially responsible for patients' symptoms at baseline, which would not be fully addressed by the SCD repair and thus would persist despite surgery.…”

“…Among cases for which thinning of the SSC roof is presumably driven by reduced estrogen levels, other regions of the temporal bone may also be osteopenic. 28,29 We speculate that this general osteopenia of the surrounding bony structures (beyond the dehiscent region) may be partially responsible for patients' symptoms at baseline, which would not be fully addressed by the SCD repair and thus would persist despite surgery. Osteopenia may also be associated with more delicate bony labyrinth and vestibular structures that are more prone to injury during surgical repair, thereby resulting in the lack of resolution, or even the onset of vestibular symptoms following surgery.…”

Asociación entre dehiscencia del canal semicircular superior y dehiscencia del tegmen tympani. Revisión narrativa cronológica

“…En la tomografía computarizada de alta resolución se mostró una dehiscencia bilateral del canal semicircular superior, aunque de mayor calibre en el lado en que predominaba la clínica descrita (izquierdo), así como dehiscencias izquierdas del tegmen timpánico y mastoideo con importante adelgazamiento del hueso temporal derecho. Debido a estos hallazgos, recomendaron un enfoque terapéutico qui-rúrgico a través de la fosa craneal media para lograr una exposición más amplia y precisa 32 . Kaufman y cols.…”

Association of the superior semicircular canal and tegmen tympani dehiscences and its relationship with the pneumatisation of the temporal bone

“…Given the increased likelihood of both defects, it is recommended that when one is diagnosed, the possibility of the other should be investigated, especially if otological meningitis or conduction hearing loss is present, before exploratory tympanic surgery or linked to vestibular symptoms [ 4 – 6 ].…”