Imaging in otosclerosis: A pictorial review

Abstract

Otosclerosis is an otodystrophy of the otic capsule and is a cause of conductive, mixed or sensorineural hearing loss in the 2nd to 4th decades of life. Otosclerosis is categorised into two types, fenestral and retrofenestral. Imaging plays an important role in the diagnosis and management of otosclerosis. High-resolution CT (HRCT) of the temporal bone using 1-mm (or less) thick sections is the modality of choice for assessment of the labyrinthine windows and cochlear capsules. MRI has limited application in the evaluation of the labyrinthine capsules but is useful for assessment of the cochlear lumen prior to cochlear implantation in patients with profound hearing loss. The treatment of fenestral otosclerosis is primarily surgical with stapedectomy and prosthesis insertion. Patients with retrofenestral otosclerosis and profound hearing loss are treated medically using fluorides, but may derive significant benefit from cochlear implantation. This pictorial review aims to acquaint the reader with the pathology and clinical features of otosclerosis, the classical imaging appearances on CT and MRI, a radiological checklist for preoperative CT evaluation of otosclerosis, imaging mimics and a few examples of post-stapedectomy imaging and complications.Teaching points• Otosclerosis causes conductive, sensorineural and mixed hearing loss in adults.• HRCT of the temporal bone is the diagnostic imaging modality of choice.• Stapedectomy is used to treat fenestral otosclerosis.• Fluorides and cochlear implantation are used to treat retrofenestral otosclerosis.

Diagnostic efficacy and therapeutic impact of computed tomography in the evaluation of clinically suspected otosclerosis

“…When otosclerosis was demonstrated, clinically relevant features of the distribution were documented in 16 % of cases. Firstly, otosclerotic foci involving the round window have been associated with increased pre-and post-surgical bone conduction thresholds, particularly when there is marked round window obliteration [3,9], and such involvement may compromise the efficacy of stapedectomy [10]. Round window extension was present in 10 % of our cases.…”

Imaging Review of the Temporal Bone: Part II. Traumatic, Postoperative, and Noninflammatory Nonneoplastic Conditions

“…Early on, the type of hearing loss is almost always conductive in nature. Later on, mixed hearing loss or sensorineural hearing loss sets in as the disease progresses in extent (50). The otic capsule is normally com posed of an inner layer of endosteum, an outer layer of periosteum, and a middle layer of persistent primary en dochondral bone.…”

“…Thus otosclerosis is also re ferred to as "otospongiosis," and this phase is referred to as the vascular phase of otosclerosis. As the disease progresses or becomes inactive, the "spongy" areas recalcify, becoming less vascular and more sclerotic (50). The most common location to be involved in otosclerosis early on is around the em bryologic fissula ante fenestram, a thin fold of embryonic cartilage and con nective tissue in a small cleft just ante rior to the oval window (51,52).…”

“…Retrofenes tral otosclerosis rarely occurs without fenestral involvement, and patients al most never have isolated sensorineural hearing loss. membrane, and absence of middle ear inflammation (50). Imaging is helpful for confirming the diagnosis, determining the extent of oval window involvement, assessing for a retrofenes tral component, and excluding clinical mimickers such as superior semicircu lar canal dehiscence.…”

“…The oval window is narrowed and the stapes footplate is thickened (Fig 21). The formation of thickened bony plaques may lead to complete obliteration of the oval window, seen in 2% of cases (50), referred to as obliterative fenestral otosclerosis (Fig 22). Retrofenestral locations (beyond/behind the region of the oval window) should be examined for signs of involvement as well, as this may alter clinical man agement.…”