Third Window Syndrome: Surgical Management of Cochlea-Facial Nerve Dehiscence

Abstract

Objective: This communication is the first assessment of outcomes after surgical repair of cochlea-facial nerve dehiscence (CFD) in a series of patients. Pre-and post-operative quantitative measurement of validated survey instruments, symptoms, diagnostic findings and anonymous video descriptions of symptoms in a cohort of 16 patients with CFD and third window syndrome (TWS) symptoms were systematically studied. Study design:Observational analytic case-control study.Setting: Quaternary referral center.Patients: Group 1 had 8 patients (5 children and 3 adults) with CFD and TWS who underwent surgical management using a previously described round window reinforcement technique. Group 2 had 8 patients (2 children and 6 adults) with CFD who did not have surgical intervention.Interventions: The Dizziness Handicap Inventory (DHI) and Headache Impact Test (HIT-6) were administered pre-operatively and post-operatively. In addition, diagnostic findings of comprehensive audiometry, cervical vestibular evoked myogenic potential (cVEMP) thresholds and electrocochleography (ECoG) were studied. Symptoms before and after surgical intervention were compared.Main outcome measures: Pre-vs. post-operative DHI, HIT-6, and audiometric data were compared statistically. The thresholds and amplitudes for cVEMP in symptomatic ears, ears with cochlea-facial nerve dehiscence and ears without CFD were compared statistically.Results: There was a highly significant improvement in DHI and HIT-6 at pre-vs. post-operative (p < 0.0001 and p < 0.001, respectively). The age range was 12.8-52.9 years at the time of surgery (mean = 24.7 years). There were 6 females and 2 males. All 8 had a history of trauma before the onset of their symptoms. The mean cVEMP threshold was 75 dB nHL (SD 3.8) for the operated ear and 85.7 dB (SD 10.6) for the unoperated ear. In contrast to superior semicircular canal dehiscence, where most ears have abnormal ECoG findings suggestive of endolymphatic hydrops, only 1 of 8 operated CFD ears (1 of 16 ears) had an abnormal ECoG study. Wackym et al. Surgery for Cochlea-Facial Nerve DehiscenceConclusions: Overall there was a marked improvement in DHI, HIT-6 and symptoms post-operatively. Statistically significant reduction in cVEMP thresholds was observed in patients with radiographic evidence of CFD. Surgical management with round window reinforcement in patients with CFD was associated with improved symptoms and outcomes measures.

Perilymphatic Fistula: A Review of Classification, Etiology, Diagnosis, and Treatment

“…CFD and another dehiscence (76). Like CCD, CFD is visible on high resolution CT imaging, but not all individuals with visible CFD on imaging will have associated symptoms.…”

“…Like CCD, CFD is visible on high resolution CT imaging, but not all individuals with visible CFD on imaging will have associated symptoms. Direct surgical treatment of the dehiscence carries a risk of deafness and facial nerve paralysis-round window reinforcement is an alternative procedure that is effective at reducing vertigo and headache symptoms with fewer risks to important nerves (76).…”

Biomechanics of Third Window Syndrome

“…High-resolution computed-tomography images of the temporal bone revealed dehiscence of the bone above the superior semicircular canal, and imaging was considered the gold standard for diagnosis for a number of years. However, a high rate of false-positive on CT imaging (14)(15)(16)(17)(18)(19) motivates the use of physiological indicators of SSCD prior to CT imaging (20), with the most common tests described in subsequent sections. Under current guidelines, patients must present with at least one audiovestibular symptom for a formal diagnosis (21).…”

“…Other instances of third window syndrome include dehiscence in the posterior or lateral canal and present with clinical symptoms similar to SSCD, though their etiologies can be different (26). The clinical presentation is not specific to the site of a bony defect, and a high-resolution CT is necessary to establish the exact site of dehiscence (20). Other origins include perilymphatic fistula, enlargement of inner ear windows such as the vestibular aqueduct, cochlea-facial nerve dehiscence, and otosclerosis of the internal auditory canal (9,20,(27)(28)(29)(30).…”

Audiovestibular Quantification in Rare Third Window Disorders in Children

“…Regardless of the anatomical location of the pathological third window, i.e., whether it is a direct physical connection between the middle and the inner ear or between the inner ear and the cranial cavity, these disorders generate typical third window features that include conductive hearing loss, sound, or positive pressure induced dizziness (Tullio's or Hennebert's phenomenon), disequilibrium, autophony, and conductive dysacusis [magnified perception of sounds generated by the body, e.g., gaze evoked tinnitus (3)] in addition to occasional oscillopsia, phonophobia, pulsatile tinnitus, and high amplitude, low threshold vestibular evoked myogenic potentials (4). These are called third window effects; however, although observation of these symptoms constitute the diagnostic criteria, some of them may be absent, especially depending on the functional status of the audiovestibular system (5).…”