Abstract
Semicircular canal dehiscence (SCD) is a condition of the inner ear wherein the temporal bone adjacent to the vestibular apparatus thins or erodes completely. It has no clear epidemiological predisposing factors that have been identified to date. Its diagnosis is made difficult by a clinical presentation that often overlaps with other pathologies of the ear. Symptoms of SCD are believed to result from a “third-window” phenomenon, which disrupts the transmission of acoustic energy in the inner ear. Symptoms, when present, may change or worsen over time, confounding the diagnosis. We present a case of SCD of the posterior canal that mimicked Meniere’s disease for several decades. We also discuss the clinical findings that may steer clinical suspicion towards this diagnosis.
1
Introduction
Semicircular canal dehiscence (SCD), first identified in the superior canal, has been also described in the posterior canal bearing a similar presentation . Diagnosis is difficult as SCD can be asymptomatic. Furthermore, this is complicated by the fact that many of its symptoms are common to more frequently encountered etiologies. Much of the symptomatology originates from an inappropriately triggered vestibular ocular reflex, but often is indistinguishable from other inner ear processes. Here, we report a case of posterior SCD treated for several decades as Meniere’s disease.
2
Case report
A 65-year-old woman presented for follow-up of long-standing hearing loss and a diagnosis of Meniere’s disease. She initially presented about 25 years earlier with right-sided hearing loss and bilateral aural fullness along with dizziness and nausea with head-turning. Audiometry at that time had revealed a sensorineural hearing loss (SNHL) in the right ear. Over the years, she also developed conductive hearing loss (CHL) in the right ear as well as new-onset SNHL in the left.
An updated audiometric assessment showed significant progression of a mixed-loss pattern in the right ear and moderate progression of SNHL in her left ear since prior examination 3 years earlier. Tympanometry and ABR testing had been normal at each testing event over the years. The rest of the past history and review of systems were negative for any pertinent abnormalities.
On examination, her right ear was sensitive to loud sounds but not associated with vertigo. High-resolution CT of the temporal bones was performed with representative images from both ears illustrated in Figs. 1–3 .
The CT images demonstrated bilateral high riding jugular bulbs with the right bulb eroding into the posterior semicircular canal and causing bony dehiscence. In addition, the right jugular bulb was found to be extending into the middle ear cavity through a bony dehiscence. The other semicircular canals did not show any dehiscence bilaterally.
Since the patient had not experienced any spells of vertigo for many years, her primary complaint was hearing loss. No treatment of the lesion was recommended but she was referred for possible amplification.
2
Case report
A 65-year-old woman presented for follow-up of long-standing hearing loss and a diagnosis of Meniere’s disease. She initially presented about 25 years earlier with right-sided hearing loss and bilateral aural fullness along with dizziness and nausea with head-turning. Audiometry at that time had revealed a sensorineural hearing loss (SNHL) in the right ear. Over the years, she also developed conductive hearing loss (CHL) in the right ear as well as new-onset SNHL in the left.
An updated audiometric assessment showed significant progression of a mixed-loss pattern in the right ear and moderate progression of SNHL in her left ear since prior examination 3 years earlier. Tympanometry and ABR testing had been normal at each testing event over the years. The rest of the past history and review of systems were negative for any pertinent abnormalities.
On examination, her right ear was sensitive to loud sounds but not associated with vertigo. High-resolution CT of the temporal bones was performed with representative images from both ears illustrated in Figs. 1–3 .
