Sudden sensorineural hearing loss: the 72-hour emergency

What sudden sensorineural hearing loss is

Sudden sensorineural hearing loss (SSHL), sometimes called sudden deafness, is the rapid onset of hearing loss originating in the cochlea (inner ear) or auditory nerve rather than in the outer or middle ear. The standard clinical definition requires a loss of 30 decibels or more across at least three consecutive audiometric frequencies, developing over 72 hours or less.

The NIDCD estimates that SSHL affects approximately one to six people per 5,000 each year in the United States, though because many cases go unreported or are misattributed, the true incidence may be higher. It occurs most often in adults in their 40s and 50s, though it can affect people of any age.

SSHL is classified as a medical emergency by the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS). Time-sensitive treatment substantially affects the probability of hearing recovery.

Why it is an emergency

Hearing is processed by the cochlear hair cells and the neurons of the auditory nerve, both of which are exquisitely sensitive biological structures with limited capacity for regeneration. When cochlear blood supply is compromised or when inflammatory or viral damage begins, the window for intervention that can reverse or limit that damage is narrow.

AAO-HNS clinical practice guidelines, most recently updated in 2019, recommend that patients presenting with SSHL receive oral corticosteroids as primary treatment. Steroids are thought to reduce cochlear inflammation and edema. The evidence base supports starting steroids as promptly as possible, with multiple studies suggesting that treatment begun within the first 24 to 48 hours is associated with better outcomes than treatment delayed by one or more weeks.

This is why the first 72 hours are the critical window described in the guideline: not because recovery is impossible after that point, but because the probability of meaningful hearing recovery appears to decrease the longer treatment is delayed.

Symptoms

The most common presentation is sudden hearing loss in one ear, often noticed upon waking or appearing very rapidly during the course of the day. Associated symptoms may include:

• A sense of aural fullness (the ear feels blocked or pressurized)
• Tinnitus, which may appear at the same time as the hearing loss or very shortly after
• Dizziness or vertigo, in a significant minority of cases

When vertigo accompanies SSHL, it tends to indicate more severe or extensive inner ear involvement. AAO-HNS guidelines note that the presence of vertigo at onset is associated with a less favorable hearing recovery prognosis, though outcomes vary considerably between individuals.

Why most cases have no identified cause

When full evaluation finds no systemic or local cause, the condition is called idiopathic SSHL. Idiopathic cases account for the majority of SSHL presentations.

Proposed mechanisms for idiopathic SSHL include viral infection of the cochlea or eighth nerve (similar to the proposed mechanism of Bell’s palsy affecting the facial nerve), microvascular events that transiently reduce blood flow to the stria vascularis or spiral ganglion, and immune-mediated cochlear damage. None of these mechanisms has been definitively proven as the dominant cause in human idiopathic SSHL, which is one reason the steroid treatment approach targets the anti-inflammatory and immunosuppressive pathway that could be relevant across multiple possible etiologies.

Evaluation and workup

Anyone presenting with suspected SSHL should receive prompt audiologic evaluation including pure-tone audiometry and speech recognition testing to confirm and characterize the hearing loss, and tympanometry to exclude a conductive component. An otolaryngologist or emergency physician typically coordinates the initial evaluation.

The AAO-HNS guideline recommends against routine CT scanning but does recommend MRI with gadolinium contrast to rule out a retrocochlear cause, particularly vestibular schwannoma. A minority of SSHL cases are the presenting symptom of a vestibular schwannoma, and MRI is the only reliable way to detect or exclude it. Because emergency MRI may not be immediately available in all settings, guidelines allow for MRI to follow the initiation of treatment rather than precede it.

Blood tests to evaluate for autoimmune, infectious (including Lyme disease in endemic areas), and vascular risk factors may be ordered depending on clinical context and patient history.

Treatment approaches

Oral corticosteroids, typically prednisone, are the first-line treatment supported by AAO-HNS guidelines. Standard courses last approximately 10 to 14 days.

Intratympanic (IT) steroid injection, which delivers steroids directly through the eardrum into the middle-ear space where they can diffuse into the cochlea, is recommended as an option for patients who cannot take systemic steroids due to medical contraindications such as uncontrolled diabetes, significant hypertension, or peptic ulcer disease. IT steroids are also used as salvage therapy for patients who do not recover hearing with initial oral steroids.

Hyperbaric oxygen therapy (HBOT) is used as an adjunctive treatment in some European countries and is included in guidelines in some jurisdictions. The evidence base is considered less robust than for corticosteroids, and availability varies substantially between healthcare systems.

The AAO-HNS guideline advises against certain treatments that were historically offered but lack supporting evidence, including antiviral medications (unless there is specific evidence of herpes zoster infection as the cause), thrombolytic agents, and vasoactive substances.

Recovery and prognosis

Recovery from SSHL ranges from complete to partial to absent, and prediction for any individual is difficult. Population-level data suggests that roughly one third of patients recover fully, one third partially, and one third have persistent significant hearing loss, though these figures are approximations and vary across studies depending on how recovery is defined and measured.

Factors generally associated with better prognosis include low-frequency or flat audiometric patterns (compared to high-frequency or total loss), prompt treatment initiation, younger age, and absence of vertigo at onset. These are population-level associations, not individual predictions.

For people who do not recover sufficient hearing, the management path moves to hearing rehabilitation. This can include conventional hearing aids for mild to severe residual loss, bone-anchored hearing devices for specific audiometric configurations, or cochlear implantation in selected cases of profound loss. Audiologists and ENT specialists guide this part of the care pathway.

What to do

If hearing loss develops suddenly in one ear, accompanied or not by tinnitus or ear fullness, the appropriate response is to seek urgent medical evaluation, not to wait and see whether it resolves spontaneously. The NHS UK and NIDCD both advise seeking care as quickly as possible, emphasizing that SSHL is a medical emergency even when it presents without pain or other alarming symptoms.

If symptoms persist or change, see an audiologist or physician.