Sudden Sensorineural Hearing Loss (SSNHL)

Sudden sensorineural hearing loss (SSNHL) is a medical emergency: rapid-onset unilateral hearing loss of at least 30 dB across three or more contiguous audiometric frequencies developing within 72 hours. Incidence ranges from 5 to 27 per 100,000 people per year, with peak onset between the ages of 43 and 53. In 85–90% of cases no definitive cause is ever identified — these are classified as idiopathic SSNHL. Early recognition and prompt treatment with corticosteroids can meaningfully improve hearing outcomes; delays beyond two to four weeks sharply reduce the chance of recovery.

Table of Contents

  1. What Is SSNHL?
  2. Causes and Risk Factors
  3. Symptoms and Clinical Presentation
  4. Diagnosis and Evaluation
  5. Prognosis and Recovery
  6. Treatment: Corticosteroids
  7. Intratympanic Steroid Therapy
  8. Adjunctive and Emerging Therapies
  9. Excluding Acoustic Neuroma
  10. Rehabilitation and Long-Term Management
  11. References & Research
  12. Featured Videos

What Is SSNHL?

The American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) defines SSNHL as a sensorineural hearing loss of 30 dB or greater across three or more contiguous pure-tone frequencies occurring within 72 hours. "Sensorineural" means the deficit arises in the cochlea (inner ear hair cells) or the auditory nerve (cranial nerve VIII) rather than in the middle ear ossicular chain — ruling out conductive causes such as cerumen impaction, otitis media, or otosclerosis.

What makes SSNHL an emergency is the tight window for steroid treatment. The cochlea and auditory nerve respond to corticosteroids if reached early; waiting a month dramatically reduces recovery odds. Yet many patients — and even some primary-care providers — initially dismiss sudden unilateral hearing loss as "a blocked ear" or "wax build-up," delaying specialist referral by days to weeks.

The deficit is almost always unilateral. Bilateral simultaneous SSNHL is rare and should raise suspicion for autoimmune inner ear disease, bilateral acoustic neuromas (neurofibromatosis type 2), or a systemic process such as sarcoidosis or syphilis.

Causes and Risk Factors

Despite decades of investigation, 85–90% of SSNHL cases remain idiopathic. Several pathophysiological mechanisms have been proposed and supported to varying degrees by evidence.

Viral Infection

The viral hypothesis is the most extensively studied. Herpes simplex virus type 1 (HSV-1) reactivation within the cochlea or auditory nerve is considered the most plausible viral cause: postmortem studies have demonstrated HSV-1 DNA in human cochlear and spiral ganglia, and mouse models show that intracochlear HSV-1 inoculation produces rapid sensorineural loss. Other implicated viruses include mumps (historically the most convincingly linked), measles, influenza A and B, cytomegalovirus (CMV), and varicella-zoster virus. Clinical trial evidence for antiviral therapy added to steroids has been disappointing, which has tempered confidence in the viral hypothesis as a primary, universal driver.

Vascular Occlusion

The cochlea is supplied exclusively by the internal auditory artery (a branch of the anterior inferior cerebellar artery), with no collateral circulation. Microvascular occlusion — from thromboembolism, vasospasm, or hypercoagulability — would produce immediate ischemic hair cell death, mimicking a cochlear stroke. Risk factors for vascular events (hypertension, diabetes, hyperlipidemia, smoking) appear more prevalent in SSNHL patients than controls. The abruptness of onset during sleep or awakening is consistent with a circulatory event, as is the observation that low-frequency hearing loss (supplied by the apical, terminal cochlear vasculature) carries a worse prognosis.

Autoimmune Inner Ear Disease

Autoimmune inner ear disease (AIED) accounts for a minority of SSNHL cases, but its identification matters because it is steroid-responsive and may recur bilaterally. Patients may show elevated anti-68-kDa heat shock protein antibodies or anti-endothelial cell antibodies on specialized panels. AIED should be suspected when SSNHL is bilateral, recurrent, associated with systemic autoimmune conditions (lupus, Cogan syndrome, Wegener's granulomatosis), or rapidly progressive over weeks.

Perilymphatic Fistula

A tear in the round or oval window membrane allows perilymph to leak into the middle ear, disrupting the pressure and ionic environment of the cochlea. Fistulas typically follow physical exertion (heavy lifting, straining), barotrauma (scuba diving, air travel, blowing the nose forcefully), or head trauma. Patients often report a "pop" at the moment of hearing loss onset and may have associated positional vertigo.

Retrocochlear Tumors

Acoustic neuroma (vestibular schwannoma) presents as SSNHL in approximately 1–3% of cases — a small but clinically critical proportion. The tumor compresses or infiltrates cochlear blood supply or nerve fibers, producing sudden loss. This is the primary reason MRI with gadolinium is non-negotiable in the workup of every patient with SSNHL: missing an acoustic neuroma that is treatable in its early stages has serious long-term consequences. Other CPA tumors (meningioma, epidermoid cyst) can also present this way.

Ototoxic Medications

Aminoglycoside antibiotics (gentamicin, amikacin, tobramycin), platinum-based chemotherapy (cisplatin, carboplatin), loop diuretics (furosemide at high doses), quinine and its derivatives, and high-dose salicylates can each cause acute cochlear toxicity. Drug-induced SSNHL is usually bilateral but can be asymmetric. A thorough medication history is essential in every SSNHL workup.

Symptoms and Clinical Presentation

The hallmark is sudden unilateral hearing loss, most commonly noticed on awakening in the morning — a pattern consistent with a vascular or viral event occurring during sleep. The hearing loss may develop over minutes to hours rather than instantaneously.

Associated Symptoms

What SSNHL Does Not Cause

Pain, facial weakness, facial numbness, dysphagia, or diplopia are not features of isolated SSNHL and should prompt evaluation for a central or brainstem cause (multiple sclerosis, posterior fossa stroke, CPA tumor with CN V or VII involvement).

Diagnosis and Evaluation

The AAO-HNS 2019 Clinical Practice Guideline provides a clear diagnostic roadmap. The objectives are: (1) confirm sensorineural rather than conductive loss; (2) exclude identifiable and treatable causes; (3) rule out retrocochlear tumor.

Tuning Fork Tests

Bedside Rinne and Weber tests take under two minutes and immediately distinguish conductive from sensorineural loss. In SSNHL, Weber lateralizes to the better (unaffected) ear — the opposite of conductive loss, where Weber lateralizes toward the affected ear. Rinne is positive (AC > BC) bilaterally in SSNHL.

Comprehensive Audiogram

Pure-tone audiometry (250–8000 Hz air conduction + bone conduction) combined with speech discrimination (word recognition score, WRS) is the essential diagnostic test. The audiogram confirms sensorineural loss, defines its severity and frequency pattern, establishes a baseline for monitoring recovery, and helps guide prognosis. Low-frequency loss carries a better prognosis than high-frequency or flat loss.

Tympanogram

A type A tympanogram (normal middle-ear compliance) confirms that the ossicular chain is intact and rules out middle-ear effusion or eardrum perforation as the cause of hearing loss.

MRI with Gadolinium — Non-Negotiable

Every patient with SSNHL must have gadolinium-enhanced MRI of the internal auditory canals and posterior fossa unless there is a documented contraindication (renal failure, severe gadolinium allergy). Thin-slice (≤3 mm) T1-weighted post-contrast sequences through the cerebellopontine angle (CPA) and internal auditory canal (IAC) will detect acoustic neuromas as small as 2–3 mm. Because acoustic neuroma is present in 1–3% of SSNHL patients and is surgically curable at an early stage, missing it is a sentinel event. The 2019 AAO-HNS guideline upgraded MRI from an option to a strong recommendation specifically because earlier guidelines allowed ABR screening to substitute — ABR misses small intracanalicular tumors at an unacceptable rate.

Laboratory Testing

Routine blood work is indicated to screen for systemic causes: complete blood count (CBC) with differential, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP), fasting lipids, fasting glucose, and thyroid-stimulating hormone (TSH). Where clinically indicated: FTA-ABS or RPR (syphilis — a treatable cause of sudden hearing loss), antinuclear antibody (ANA) and anti-dsDNA (lupus/AIED), and coagulation studies (lupus anticoagulant, antiphospholipid antibodies) in young patients or those with vascular risk factors. Lyme serology in endemic regions. Routine viral titers have no proven clinical utility and are not recommended by the 2019 guideline.

Vestibular Function Testing

Video head impulse test (vHIT) or caloric testing (ENG/VNG) quantifies vestibular end-organ function. Reduced or absent caloric response on the affected side is consistent with labyrinthine involvement. This does not change the immediate management but establishes a baseline and predicts vestibular rehabilitation needs.

Prognosis and Recovery

Spontaneous partial recovery occurs in 32–65% of patients and complete recovery in 22–35%. The wide range reflects heterogeneity in etiology, timing of treatment, and definitions of "recovery." The following are established prognostic indicators:

Better Prognosis

Worse Prognosis

Patients should be counseled that maximum recovery typically occurs within the first two weeks of treatment and that gains are unlikely after six weeks. If hearing does not recover sufficiently for conversational function, amplification (hearing aid) or, in the case of profound unilateral loss, a bone-anchored hearing aid (BAHA) or CROS device may be appropriate.

Treatment: Corticosteroids

Oral corticosteroids are the first-line, guideline-endorsed treatment for idiopathic SSNHL. The 2019 AAO-HNS guideline made oral steroids a strong recommendation, backed by multiple randomized controlled trials and systematic reviews showing meaningful improvement in hearing outcomes compared with placebo or watchful waiting.

Regimen

The most commonly used protocol is prednisone 1 mg/kg/day (maximum 60 mg/day) for 10–14 days, followed by a taper over 5–7 days. Some centers use methylprednisolone dosing equivalents. Dexamethasone (0.75 mg dexamethasone equals ~5 mg prednisone) is sometimes preferred due to its lack of mineralocorticoid activity in patients with fluid-sensitive conditions.

Timing

Treatment should begin as soon as possible after diagnosis — ideally within 24–48 hours of onset and no later than two weeks. The 2019 guideline states that the benefit window closes approximately four weeks from onset; treatment after this point may still be offered as "salvage" but the evidence base for late treatment is weaker.

Contraindications and Precautions

High-dose systemic steroids are problematic for patients with uncontrolled diabetes (glucose dysregulation), poorly controlled hypertension, active peptic ulcer disease, active or latent tuberculosis, or recent systemic infection. In these patients, intratympanic (IT) steroids are the preferred alternative, providing high local cochlear drug concentration without significant systemic exposure.

Intratympanic Steroid Therapy

Intratympanic corticosteroid injection delivers dexamethasone or methylprednisolone directly through the tympanic membrane into the middle ear space, where the drug diffuses through the round window membrane into the perilymph. Perilymphatic drug concentrations achieved by IT injection are 10–40 times higher than those achieved by equivalent systemic doses, while systemic absorption is negligible.

Primary IT Therapy

IT steroids are offered as primary treatment for patients who cannot tolerate or refuse systemic steroids. Multiple randomized trials — most notably the multicenter trial by Rauch et al. (2011, PMID 21205966) — found IT dexamethasone non-inferior to oral prednisone in hearing recovery rates at two months, establishing IT injection as a legitimate first-line option rather than a second choice.

Salvage IT Therapy

For patients who complete oral steroid therapy with incomplete recovery, salvage IT steroids (initiated within 4–6 weeks of onset) can recover additional hearing. The 2019 guideline makes salvage IT therapy a strong recommendation for incomplete responders, recognizing that it offers meaningful benefit with an excellent safety profile.

Procedure

The injection is performed in the office under topical anesthesia. Dexamethasone (10–24 mg/mL) or methylprednisolone (40–62.5 mg/mL) is injected into the posterior-inferior quadrant of the middle ear, with the patient positioned with the treated ear upward for 30 minutes afterward to maximize round window contact. A course of 3–4 injections over two weeks is typical.

Adjunctive and Emerging Therapies

Antiviral Agents

Given the viral hypothesis of SSNHL, antivirals (acyclovir, valacyclovir) were widely prescribed as adjuncts to steroids for decades. However, three rigorous randomized controlled trials — including the large multicenter trial by Tucci et al. (2002) — failed to demonstrate any benefit of antivirals beyond steroids alone for idiopathic SSNHL. The 2019 AAO-HNS guideline gives a strong recommendation against routine antiviral therapy in patients without evidence of an active herpesvirus infection. Antivirals remain appropriate for SSNHL secondary to herpes zoster oticus (Ramsay Hunt syndrome), where viral etiology is confirmed.

Hyperbaric Oxygen Therapy

Hyperbaric oxygen (HBO) therapy — breathing 100% oxygen at 2–3 atmospheres — may improve cochlear oxygenation and complement steroid therapy by counteracting the ischemic component of SSNHL. A Cochrane meta-analysis (Bennett et al., 2012, PMID 22972073) found a statistically significant improvement in hearing thresholds with HBO combined with conventional therapy, particularly for severe loss. However, study quality was heterogeneous and access to hyperbaric facilities is limited. The 2019 guideline considers HBO an option rather than a standard recommendation.

Vasodilators and Rheological Agents

Carbogen inhalation (5% CO₂ / 95% O₂), pentoxifylline, dextran infusion, and prostaglandin E1 analogues have been studied in SSNHL based on the vascular hypothesis. No high-quality RCT evidence supports routine use of any vasodilator or rheological agent; these treatments remain in investigational or regional use (particularly in Germany and Japan).

Neuromodulation

Emerging approaches include cochlear implantation for patients with profound permanent SSNHL, bone-anchored hearing systems (BAHA, Osia) for single-sided deafness, and CROS/BiCROS hearing aids to route sound from the dead ear to the functioning ear. These are rehabilitation tools rather than treatments for the underlying condition.

Excluding Acoustic Neuroma

Every clinician evaluating SSNHL must keep acoustic neuroma in the differential at all times. The key facts:

The practical message: do not delay MRI. Begin steroid treatment immediately — waiting for MRI results while the treatment window closes is the wrong trade-off. Order both concurrently. If MRI reveals an acoustic neuroma, ENT and neurosurgery referral follows; if MRI is negative, the diagnosis of idiopathic SSNHL is confirmed and treatment continues.

Rehabilitation and Long-Term Management

For patients with persistent hearing loss after maximal medical therapy, rehabilitation options depend on the degree of residual function:

Mild-to-Moderate Residual Loss

Conventional behind-the-ear or in-the-canal hearing aids amplify sound and improve speech understanding in noise. Modern digital aids with directional microphones and noise suppression are highly effective for sensorineural loss patterns.

Profound Unilateral Loss (Single-Sided Deafness)

Single-sided deafness (SSD) impairs sound localization, hearing in noise from the affected side, and understanding speech in reverberant environments. Options include:

Tinnitus Management

Persistent tinnitus after SSNHL is common. Referral to audiology for sound therapy, tinnitus retraining therapy (TRT), or cognitive behavioral therapy (CBT) should be offered. Hearing aid amplification alone reduces tinnitus awareness in many patients by enriching the acoustic background and reducing auditory deprivation in the cortex.

Vestibular Rehabilitation

Patients with persistent imbalance or dizziness after SSNHL benefit from vestibular rehabilitation therapy (VRT) — a structured program of gaze stabilization, balance, and habituation exercises designed to accelerate central vestibular compensation. A physical therapist or audiologist trained in vestibular rehabilitation should lead this program.

References & Research

Key Research Papers

  1. Stachler RJ, Chandrasekhar SS, Archer SM, et al. Clinical practice guideline: sudden hearing loss. Otolaryngol Head Neck Surg. 2012;146(3 Suppl):S1–S35. PMID: 22383545
  2. Chandrasekhar SS, Tsai Do BS, Schwartz SR, et al. Clinical Practice Guideline: Sudden Hearing Loss (Update). Otolaryngol Head Neck Surg. 2019;161(1_suppl):S1–S45. PMID: 31369519
  3. Rauch SD, Halpin CF, Antonelli PJ, et al. Oral vs intratympanic corticosteroid therapy for idiopathic sudden sensorineural hearing loss: a randomized trial. JAMA. 2011;305(20):2071–2079. PMID: 21205966
  4. Wilson WR, Byl FM, Laird N. The efficacy of steroids in the treatment of idiopathic sudden hearing loss. A double-blind clinical study. Arch Otolaryngol. 1980;106(12):772–776. PMID: 7002129
  5. Battaglia A, Burchette R, Cueva R. Combination therapy (intratympanic dexamethasone + high-dose prednisone taper) for the treatment of idiopathic sudden sensorineural hearing loss. Otol Neurotol. 2008;29(4):453–460. PMID: 18323753
  6. Bennett MH, Kertesz T, Perleth M, Yeung P, Lehm JP. Hyperbaric oxygen for idiopathic sudden sensorineural hearing loss and tinnitus. Cochrane Database Syst Rev. 2012;10:CD004739. PMID: 22972073
  7. Nakashima T, Itoh A, Misawa H, Ohno Y. Clinicoepidemiologic features of sudden deafness diagnosed and treated at university hospitals in Japan. Otolaryngol Head Neck Surg. 2000;123(5):593–597. PMID: 11077347
  8. Bing D, Wang DY, Lan L, et al. Intratympanic dexamethasone for sudden sensorineural hearing loss after failure of systemic therapy: our experience. Eur Arch Otorhinolaryngol. 2012;269(6):1557–1563. PMID: 21972124
  9. Kuhn M, Heman-Ackah SE, Shaikh JA, Roehm PC. Sudden sensorineural hearing loss: a review of diagnosis, treatment, and prognosis. Trends Amplif. 2011;15(3):91–105. PMID: 22158661
  10. Byl FM Jr. Sudden hearing loss: eight years' experience and suggested prognostic table. Laryngoscope. 1984;94(5 Pt 1):647–661. PMID: 6325838
  11. Chau JK, Cho JJ, Fritz DK. Evidence-based practice: management of adult sensorineural hearing loss. Otolaryngol Clin North Am. 2012;45(5):941–958. PMID: 22980682
  12. Koskas P, Kania R, Herman P, Tran Ba Huy P. Prognostic value of electrocochleography in idiopathic sudden sensorineural hearing loss. Audiol Neurootol. 2011;16(6):364–370. PMID: 21346341

Back to Table of Contents

Research Papers

The following PubMed topic searches retrieve current peer-reviewed literature on Sudden Sensorineural Hearing Loss.

  1. SSNHL corticosteroid treatment
  2. Intratympanic steroid injection SSNHL
  3. SSNHL prognosis and spontaneous recovery
  4. Sudden hearing loss acoustic neuroma MRI workup
  5. SSNHL viral and vascular etiology
  6. SSNHL hyperbaric oxygen therapy
  7. Single-sided deafness cochlear implant BAHA
  8. Idiopathic SSNHL randomized controlled trials

Back to Table of Contents

Connections

Back to Table of Contents