Outcomes of transmastoid resurfacing for superior canal dehiscence using a cartilage overlay technique

Spontaneous Tegmen Tympani Dehiscence: Causes and Treatment of Conductive Hearing Loss

OBJECTIVE

Conductive hearing loss (CHL) commonly arises in patients with spontaneous dehiscence of the tegmen of the temporal bone with meningoencephalocele (SME). The aim of this study was to further investigate 1) the potential mechanisms for CHL in this setting; 2) hearing outcomes following surgery to address SME, and 3) the possible causes of persistent CHL following surgery.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS AND INTERVENTION

Seven patients (six female; nine ears) who underwent middle cranial fossa repair of SME and were found to have a tegmen tympani dehiscence from October 2010 to September 2014 were included in the study.

MAIN OUTCOME MEASURES

Pre- and postoperative pure-tone audiometry.

RESULTS

Eight of nine ears (89%) had audiometric hearing loss at presentation. Seven ears (78%) had an air bone gap of ≥15 dB; all of these had an encephalocele traversing the tegmen tympani defect, four had a middle ear effusion, and three had a simultaneous superior semicircular canal dehiscence (SSCCD). The CHL resolved postoperatively in four of seven ears. Two of the three ears with persistent CHL had SSCCD. Attic ossicular fixation was identified in the other patient and the CHL resolved after ossiculoplasty.

CONCLUSIONS

CHL associated with SME can be attributed preoperatively to ossicular chain fixation and synchronous SSCCD as well as the more commonly cited cerebrospinal fluid effusion and prolapse of meningoencephalocele onto the ossicular chain. Persistent postoperative CHL can also occur due to SSCCD and ossicular fixation by adhesions.

Ambient Pressure Tympanometry Wave Patterns in Patients With Superior Semicircular Canal Dehiscence

Importance: Superior semicircular canal dehiscence (SSCD) is a treatable condition, but current diagnostic modalities have numerous limitations. Clinicians would benefit from an additional tool for diagnostic workup that is both rapid and widely available. Objective: To assess the utility of ambient pressure tympanometry (APT) in the diagnostic workup of SSCD by determining the sensitivity and specificity of APT for SSCD in comparison to other diagnostic modalities. Design: Retrospective cohort study of patients who underwent APT and temporal bone computerized tomography (CT) scans from May 2017 to July 2018. Setting: Tertiary referral center. Participants: APT was performed as part of routine audiological testing on adult patients. We retrospectively analyzed all patients who received both APT and temporal bone CT scans, and divided ears into SSCD and non-SSCD groups based on the presence or absence of radiographic SSCD. Ears with other radiographic findings that could affect tympanic membrane compliance were excluded. Exposures: All patients in this study underwent APT and temporal bone CT scans. Some patients also underwent pure tone audiometry and vestibular evoked myogenic potentials (VEMPs). Main Outcomes and Measures: The primary outcome measures were sensitivity, specificity, and risk ratio of APT for SSCD. Secondary outcome measures include sensitivity of VEMPs and supranormal hearing thresholds. Results: We describe 52 patients (70 ears) who underwent APT and CT imaging (mean age 47.1 years, 67.1% female). APT detected SSCD with 66.7% sensitivity and 72.1% specificity. In symptomatic patients, sensitivity was 71.4% and specificity was 75%. VEMPs performed best at detecting SSCD when defining a positive test as oVEMP amplitude >17 μV, with a sensitivity of 68.2%, similar to APT (p > 0.99). The combination of APT and VEMPs increased sensitivity to 88.9%, better than APT alone (p = 0.031) and trending toward better than VEMPs alone (p = 0.063). Conclusions and Relevance: Rhythmic wave patterns on APT are associated with SSCD and may raise suspicion for this condition in conjunction with consistent results on other diagnostic modalities. Although clinical utility requires confirmation in a larger prospective study, APT is a simple, rapid, and widely available tool warranting further study.