When sensorineural hearing loss occurs in the context of an inflammatory condition, it is referred to most appropriately as immune-mediated inner ear disease (IMIED).
May be associated with disturbances of balance as well as hearing loss because the inner ear mediates vestibular function as well as hearing.
May occur as a primary inner ear problem or as a complication of a recognized inflammatory condition such as Cogan syndrome, granulomatosis with polyangiitis, Susac syndrome, giant cell arteritis, Sjögren syndrome, and others.
Symptoms include tinnitus, vertigo, nausea, and difficulties with two issues related to hearing: acuity and speech discrimination.
Sensorineural hearing loss (SNHL) is an idiopathic inflammatory disorder that occurs either as a primary form of disease limited to the ear or secondary to another known immune-mediated condition that affects other organs, as well. The anatomy of the inner ear is shown in Figure 50–1. SNHL is a common feature of some primary forms of vasculitis (eg, Cogan syndrome, granulomatosis with polyangiitis [formerly Wegener granulomatosis], giant cell arteritis). SNHL also occasionally occurs in association with systemic autoimmune disorders such as systemic lupus erythematosus (SLE) and Sjögren syndrome.
Anatomy of the temporal bone and audiovestibular apparatus. AN, auditory nerve; C, cochlea; ES, endolymphatic sac; OC, ossicular chain; SCC, semicircular canals; V, vestibule. (© 2000 John H. Stone, MD, MPH.)
Because hearing loss is often not the sole feature of this syndrome—vertigo, tinnitus, and a sense of aural fullness often occur as well—and because the symptoms respond frequently to immunosuppression, immune-mediated inner ear disease (IMIED) is the preferred term for this disorder when symptoms and signs are confined entirely to the ear. Devastating disabilities including profound deafness and severe vestibular dysfunction are potential sequelae of IMIED. Yet if diagnosed promptly, IMIED is amenable to treatment. Unfortunately, the prognosis is difficult to gauge except in the setting of profound, sustained SNHL, in which case significant recovery of hearing is unlikely.
Little is known for certain about the mechanisms of injury to the inner ear in any condition associated with SNHL, because biopsy of the cochlea is not possible without causing irreversible injury. Some data from autopsy studies of patients with primary immune-mediated inner ear disease—generally obtained after patients had received substantial courses of immunosuppression before death—suggest that both antibody-mediated injury to the stria vascularis and vascular occlusion impair the metabolic processes that support hearing transduction. For patients who experience IMIED in the setting of a systemic vasculitis, for example, granulomatosis with polyangiitis, the basis of tissue injury is presumably inflammatory disease of the small blood vessels.
Several characteristics distinguish IMIED from other syndromes of inner ear dysfunction. First, its time course is relatively rapid. IMIED is analogous to rapidly progressive glomerulonephritis in that inner ear inflammation progresses to severe, irreversible ...