Eric L. Slattery, Timothy E. Hullar, and Lawrence R. Lustig

Unilateral sudden hearing loss is often dramatic and can cause the patient to urgently seek a medical consultation. Though often the result of benign disease, this symptom can nonetheless be the result of serious intracranial pathology, such as a tumor or acute vascular event. The associated symptoms and signs that may accompany the hearing loss will often provide clues to the diagnosis. In most cases, audiologic and imaging studies are required to pinpoint the diagnosis.

Sensorineural Hearing Loss: Inner Ear

Idiopathic Sudden Sensorineural Hearing Loss

As the name implies, idiopathic sudden sensorineural hearing loss (ISSHL) presents with a sudden onset, unilateral sensorineural loss. By definition, the hearing loss should occur over three contiguous frequencies, in less than 3 days, with at least 30 dB of loss in each frequency. There are no other associated symptoms required for diagnosis, although patients often report concurrent or antecedent symptoms of an upper respiratory tract infection. A magnetic resonance imaging (MRI) scan is warranted, as rarely this presentation is caused by a skull base tumor, such as a vestibular schwannoma.

Barotrauma

Barotrauma may result from lifting a heavy weight, straining, scuba diving, flying in an unpressurized aircraft, or blunt trauma. It is also common in patients undergoing hyperbaric oxygen therapy. Barotrauma is more likely to occur in those with an acute upper respiratory infection. Otalgia is usually present, and if the tympanic membrane perforates, otorrhea may be present. Fluid and/or blood may also accumulate behind the drum, and the accumulation of blood (hemotympanum) will appear dark brown, purple, or red.

If a sensorineural hearing loss arises after one of these inciting pressure change events, several diagnoses must be entertained, including the presence of a perilymphatic fistula at the oval window, round window, or some other site. Dizziness and tinnitus will often accompany the sensorineural hearing loss. A fistula test with pneumatic otoscopy may be suggestive of this diagnosis, but there is no definitive diagnostic examination available, except for surgical exploration. Other possibilities include inner ear membrane break and pneumolabyrinth(usually from rapid ascent during diving).

Iatrogenic middle and inner ear injury can result from minor surgeries (eg, myringotomy), middle ear and mastoid surgeries, and inner ear surgeries. Further iatrogenic injury can result from surgeries not directed toward the ear, including posterior and middle fossa craniotomies and regional head and neck surgeries, such as parotidectomies. If the trauma is limited to the external auditory canal, tympanic membrane, and/or ossicles, a sudden conductive hearing loss may ensue. If the trauma directly or indirectly injures the inner ear or auditory nerve, then sensorineural hearing loss would result. In either case, tinnitus, vertigo, otalgia, facial paralysis, and/or otorrhea could result as well.

Noise-Induced Hearing Loss