Page 20 - Delaware Medical Journal - January 2018
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Unusual Imaging Manifestations of Severe Bilateral Cochlear Otosclerosis: A Case Report
Katie Taylor, DO: Alberto Iaia, MD; Michael Teixido, MD; Francesco Agnello, MD; Gianvincenzo Sparacia, MD
Otosclerosis is characterized by abnormal bony growth at the otic capsule of the petrous bone, which can lead to profound hearing loss. Crosssectional imaging plays an important role in confirming the suspicion of otosclerosis and determining disease extent. Here the authors present some unusual imaging manifestations of a severe case of bilateral cochlear otosclerosis in a 68-year-old female presenting with gradual sensorineural hearing loss.
IntroductionOtosclerosis or
the abnormal growth of bone at the otic capsule, which typically
sound transduction through the conductive hearing system
into the cochlea.1 With an estimated prevalence of 1 percent, otosclerosis demonstrates inheritance through an autosomal dominant gene transmission with incomplete penetrance, but
may also occur sporadically.2 Caucasians in their second to
third decades of life are most commonly affected, with a female predilection of 2:1.3 Patients typically present with progressive bilateral conductive hearing loss. Clinical presentation widely varies depending on the extent of the disease and the exact anatomic location of involvement, in addition to conductive hearing loss, tinnitus, sensorineural hearing loss and balance instability are also frequently observed.1,2,4,5 The otic capsule is comprised of three layers: a thin endosteal layer, a middle layer
of combined endochondral and intrachondral bone, and an outer periosteal layer. The pathophysiology of this disease may affect occurs within the middle layer and progresses as a cycle of three phase, is characterized by active deposition of islets of osteoid tissue. This is subsequently followed by a subacute phase, which consists of an increase in resorptive osteoclastic activity, resulting in the spongiotic remodeling of bone. Within the later chronic- sclerotic phase, osteoblastic activity is more prominent, producing new bone with irregular features.5 This pathologic process may
be visualized by the clinician on otologic examination by the presence of a discolored, vascular hue along involved areas of the cochlear promontory, visible through the tympanic membrane (also known as Schwartze’s sign).5
Otosclerosis is described by the anatomic locations of involvement, either as fenestral or cochlear (also known as
retrofenestral). Fenestral otosclerosis is the most common
and is found in 85 percent of patients, while 15 percent
present with the cochlear type. Typically, disease progression posteriorly to involve both the oval window and margins of
the round window. Active disease then may continue to spread to the otic capsule. When disease involvement is limited to
oval window niche producing a characteristic pattern of conductive hearing loss. Cochlear otosclerosis is characterized as involvement of the inner ear and is more likely to produce a sensorineural hearing loss by interfering with the transmission of electrical stimulation from the cochlear inner hair cells to the spiral ganglion neurons.1,5 Rarely, cochlear otosclerosis will present without involvement of the perifenestral region.6 Treatment of hearing loss associated with otosclerosis
includes stapedectomy and placement of a stapes prosthesis
for fenestral otosclerosis, hearing aids for sensorineural loss, cochlear implantation to improve hearing in patients with severe cochlear involvement, or with bisphosphonate treatment to help arrest progression of cochlear disease.
the suspicion of otosclerosis and determining disease
tomography (CT) imaging that may indicate the success of surgical therapy. Obliteration of the round window may predict round window will be unable to undulate in coordination with the oval window during sound transduction. Additionally, cochlear implantation through the round window may likewise become more challenging with this presentation. It is also important to identify the height of the oval window niche, as narrow distances (< 1.4 mm on coronal CT reformats) may result in a more challenging surgery.5
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Del Med J | January 2018 | Vol. 90 | No. 1
Abstract
