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.