Define immune mediated inner ear disease (IMIED; also known as autoimmune inner ear disease)
IMIED is a syndrome characterized by rapidly progressive, bilateral SNHL that can be responsive to immunosuppressive therapy. It is often accompanied by vertigo (50%), tinnitus, and a sense of aural fullness. It may exist as a primary illness or be associated with a systemic autoimmune disease (30% of cases). Although believed to be autoimmune, definitive evidence of an autoimmune etiology is lacking.
Caution should be taken to distinguish IMIED from idiopathic sudden SNHL, a very common cause of acute SNHL that is unilateral, rapidly progresses over 72 hours, usually not associated with vestibular symptoms, and commonly improves within 2 weeks (65% of cases) irrespective of treatment (although corticosteroids are frequently used). It is estimated that 85% of such cases are idiopathic (with up to 5% developing Ménière’s disease years later). All patients with sudden SNHL should be evaluated for secondary causes (15% of cases) including infection (HSV, VZV), vascular insult (vasculitis, APS, hypercoagulable diseases, atherosclerotic disease), medications, neoplasm (including those causing localized retrocochlear disease), and immune-mediated diseases. Patients with unilateral SNHL have diminished ability to hear a tuning fork and localize the sound during a Weber test (tuning fork on forehead) to the good ear. When they hum, the sound localizes to the good ear as well.
