Sudden Hearing Loss: Symptoms, Causes & Treatment

What Is Sudden Hearing Loss?

Sudden hearing loss (SSNHL) is defined as a hearing reduction of at least 30 decibels across three consecutive frequencies, occurring within 72 hours. It is a medical emergency that requires immediate treatment with corticosteroids. Most cases affect only one ear and occur without warning.

Sudden sensorineural hearing loss, often called "sudden deafness," is a rapid loss of hearing function that typically occurs in one ear. The condition affects the inner ear (cochlea) or the auditory nerve, rather than the outer or middle ear. This distinguishes it from conductive hearing loss caused by earwax blockage or middle ear infections, which are generally more treatable.

The medical definition requires a specific threshold: hearing loss of at least 30 decibels (dB) across three or more consecutive frequencies on an audiogram. To put this in perspective, 30 dB is roughly the difference between normal conversation and whispering. Many patients describe the onset as waking up with significantly reduced hearing in one ear, or experiencing a sudden "pop" followed by hearing loss.

The condition affects both men and women equally, with peak incidence occurring between ages 43 and 53. However, it can occur at any age, including in children and the elderly. The overall incidence is estimated at 5-20 cases per 100,000 people annually, though this may be underreported as mild cases sometimes resolve spontaneously before medical attention is sought.

Types of Sudden Hearing Loss

Sudden hearing loss can be classified based on the pattern of frequency loss on the audiogram, which has important prognostic implications:

• Low-frequency hearing loss: Affects lower pitches primarily. Generally has the best prognosis for recovery.
• Mid-frequency hearing loss: Affects the middle range of hearing. Intermediate prognosis.
• High-frequency hearing loss: Affects higher pitches. Often has poorer recovery rates.
• Flat hearing loss: Affects all frequencies equally. Variable prognosis.
• Profound hearing loss: Severe loss across all frequencies (>90 dB). Worst prognosis for spontaneous recovery.

Understanding the type of hearing loss pattern helps physicians predict outcomes and may influence treatment decisions. Low-frequency hearing loss, for example, may respond better to corticosteroid treatment and has higher rates of spontaneous recovery compared to high-frequency or profound loss.

What Are the Symptoms of Sudden Hearing Loss?

The primary symptom is rapid hearing loss in one ear, often noticed upon waking. Associated symptoms include tinnitus (ringing) in 70-80% of cases, a feeling of ear fullness, and dizziness or vertigo in 20-60% of patients. Some describe hearing sounds as muffled or distorted.

The hallmark symptom of sudden hearing loss is a rapid decrease in hearing ability, typically affecting only one ear. Patients often discover the hearing loss suddenly - for example, when trying to use the phone on the affected ear, or upon waking in the morning. Some patients report hearing a "pop" or loud noise immediately before the hearing loss begins.

The hearing loss itself varies in severity. Some patients experience only mild difficulty hearing, while others have complete deafness in the affected ear. The loss typically reaches its maximum severity within hours to a few days, though by definition it must occur within 72 hours to be classified as "sudden."

Tinnitus and Ear Fullness

Tinnitus, or ringing in the ear, accompanies sudden hearing loss in approximately 70-80% of cases. The tinnitus may be described as ringing, buzzing, hissing, or roaring. It can be constant or intermittent and may persist even after hearing recovers. The presence of tinnitus itself does not necessarily indicate a worse prognosis.

Many patients also experience a sensation of fullness or pressure in the affected ear, similar to the feeling of having water in the ear after swimming or the pressure changes felt during airplane travel. This symptom can be misleading, as patients may initially attribute it to earwax or a minor ear infection.

Vertigo and Balance Problems

Between 20-60% of patients with sudden hearing loss also experience vertigo or dizziness. This occurs because the inner ear contains both the cochlea (responsible for hearing) and the vestibular system (responsible for balance). When the inner ear is affected, both systems may be impacted.

The presence of vertigo at the time of sudden hearing loss is generally associated with a poorer prognosis for hearing recovery. Patients with significant vertigo may have more extensive damage to the inner ear structures. However, the vertigo itself typically improves over time as the brain compensates for the vestibular dysfunction.

What Causes Sudden Hearing Loss?

In 85-90% of cases, the exact cause cannot be identified (idiopathic). Known causes include viral infections, vascular disorders affecting inner ear blood supply, autoimmune diseases, acoustic neuroma, head trauma, and ototoxic medications. Multiple mechanisms may contribute in a single case.

Sudden sensorineural hearing loss remains one of medicine's diagnostic challenges because the cause is unknown in the vast majority of cases. When a specific cause cannot be identified, the condition is termed "idiopathic sudden sensorineural hearing loss" (ISSHL). Despite extensive research, we still don't fully understand why the inner ear suddenly loses function in most patients.

Several theories attempt to explain idiopathic cases. The most prominent hypotheses involve viral infection, vascular compromise (reduced blood flow to the cochlea), or autoimmune attack on the inner ear. In reality, multiple mechanisms may work together, and different patients may have different underlying causes even when presenting with similar symptoms.

Viral Infections

Viral infection is one of the leading theories for idiopathic sudden hearing loss. Several viruses have been implicated, including herpes simplex virus (HSV), varicella-zoster virus (the virus causing chickenpox and shingles), cytomegalovirus (CMV), mumps, measles, rubella, and influenza viruses. These viruses may directly damage the cochlea or auditory nerve, or trigger an inflammatory response that causes secondary damage.

Supporting evidence includes the observation that sudden hearing loss often occurs following upper respiratory infections, and that higher rates are seen during viral epidemics. Post-mortem studies have occasionally found viral particles in the cochlea of patients who had sudden hearing loss. However, proving viral causation in individual cases remains difficult.

Vascular Causes

The cochlea is supplied by a single end-artery (the labyrinthine artery) with no collateral circulation. This makes it vulnerable to ischemia (reduced blood flow). Any interruption in blood supply, even briefly, can cause permanent damage to the sensitive hair cells that convert sound into electrical signals.

Vascular causes may include small vessel disease, vasospasm, microemboli (tiny blood clots), or conditions that increase blood viscosity. Patients with cardiovascular risk factors - including hypertension, diabetes, high cholesterol, and smoking - may have slightly higher rates of sudden hearing loss, though the relationship is not definitively established.

Autoimmune Inner Ear Disease

In some cases, the body's immune system may attack the inner ear tissues. Autoimmune inner ear disease (AIED) can cause sudden or rapidly progressive hearing loss, often bilateral (affecting both ears) and sometimes fluctuating. Patients with other autoimmune conditions - such as rheumatoid arthritis, lupus, or Sjogren's syndrome - may be at higher risk.

AIED responds to immunosuppressive treatment, particularly corticosteroids, which is one reason why steroids are the first-line treatment for sudden hearing loss of unknown cause. If autoimmune disease is suspected, longer courses of steroids or other immunosuppressants may be considered.

Identifiable Causes

In approximately 10-15% of cases, a specific cause can be identified. These include:

• Acoustic neuroma: A benign tumor on the vestibular nerve. Present in 1-3% of sudden hearing loss cases. MRI is recommended to rule this out.
• Meniere's disease: Inner ear disorder causing episodes of vertigo, fluctuating hearing loss, tinnitus, and ear fullness.
• Head trauma: Injury can damage the cochlea or cause perilymph fistula (leakage of inner ear fluid).
• Ototoxic medications: Certain antibiotics (aminoglycosides), chemotherapy drugs (cisplatin), loop diuretics, and high-dose aspirin can damage hearing.
• Multiple sclerosis: Can affect the auditory nerve in rare cases.
• Lyme disease: Bacterial infection transmitted by ticks that can affect the inner ear.
• Syphilis: Can cause hearing loss in its later stages.

When Should You See a Doctor for Sudden Hearing Loss?

Seek medical attention immediately if you experience sudden hearing reduction in one or both ears. This is a medical emergency - treatment should ideally begin within 24-72 hours. Contact an ENT specialist or visit an emergency department the same day symptoms begin. Do not wait to see if hearing returns on its own.

Time is the most critical factor in sudden hearing loss treatment. Research consistently shows that patients who begin treatment within the first few days have significantly better outcomes than those who delay. The window for effective treatment narrows substantially after two weeks, and after one month, treatment is unlikely to provide meaningful benefit.

Unfortunately, many patients delay seeking care, often assuming the symptoms are due to earwax, allergies, or a minor infection that will resolve on its own. This delay can have permanent consequences. Every day that passes without treatment may reduce the likelihood of recovery.

Where to Seek Care

If you experience sudden hearing loss, you should seek care from an otolaryngologist (ENT specialist) as soon as possible. If you cannot get an immediate ENT appointment, go to an emergency department. Emergency physicians can begin steroid treatment while arranging ENT follow-up and audiometry testing.

Explain to medical staff that you have sudden hearing loss and that this is considered a medical emergency requiring urgent treatment. Some facilities may not be familiar with the time-sensitive nature of this condition, so advocating for prompt evaluation is important.

How Is Sudden Hearing Loss Diagnosed?

Diagnosis requires audiometry testing showing at least 30 dB hearing loss across three consecutive frequencies. An MRI scan is recommended to rule out acoustic neuroma. Blood tests may be ordered to check for infections, autoimmune conditions, and vascular risk factors. Physical examination excludes middle ear problems.

The diagnosis of sudden sensorineural hearing loss is based on three key elements: the patient's history, physical examination, and audiometric testing. The history should establish the rapid onset (within 72 hours), unilateral nature (usually), and associated symptoms like tinnitus or vertigo.

Audiometry

Audiometry (hearing testing) is essential for diagnosis. The test measures hearing thresholds across different frequencies and can distinguish between sensorineural hearing loss (inner ear or nerve) and conductive hearing loss (outer or middle ear). The diagnostic criterion for sudden hearing loss is a sensorineural loss of at least 30 dB in three or more consecutive frequencies.

Pure tone audiometry plots hearing ability on an audiogram, showing which frequencies are affected and how severely. This information helps classify the type of hearing loss (low-frequency, high-frequency, flat, or profound) and provides a baseline for monitoring recovery with treatment.

MRI Scan

MRI (Magnetic Resonance Imaging) of the internal auditory canals and brain is strongly recommended for all patients with sudden hearing loss. The primary purpose is to rule out acoustic neuroma (vestibular schwannoma), a benign tumor that can cause sudden or progressive hearing loss. Acoustic neuroma is found in approximately 1-3% of sudden hearing loss cases.

MRI can also identify other structural causes such as stroke, multiple sclerosis plaques, or other tumors. While the AAO-HNS guidelines recommend MRI, some physicians may proceed with treatment first and obtain MRI subsequently, as the tumor grows slowly and would not affect immediate management.

Blood Tests

Blood tests may be ordered to investigate potential causes, though they are not always required for initial treatment. Commonly ordered tests include:

• Complete blood count (CBC)
• Inflammatory markers (ESR, CRP)
• Blood glucose and HbA1c (diabetes screening)
• Lipid panel (cholesterol)
• Thyroid function tests
• Autoimmune markers (ANA, rheumatoid factor) if autoimmune disease suspected
• Syphilis serology
• Lyme disease testing if endemic area

These tests rarely change immediate management but may identify underlying conditions requiring separate treatment or suggesting a specific cause for the hearing loss.

What Is the Treatment for Sudden Hearing Loss?

High-dose oral corticosteroids (typically prednisone 1mg/kg/day for 10-14 days with tapering) are the primary treatment. Intratympanic steroid injections may be used as initial treatment or as salvage therapy. Hyperbaric oxygen therapy may provide additional benefit. Treatment should begin as soon as possible, ideally within 72 hours.

Corticosteroids are the mainstay of treatment for sudden sensorineural hearing loss. While the evidence base is not as strong as we would like, steroids remain the standard of care recommended by clinical practice guidelines. They work by reducing inflammation in the inner ear and may help restore blood flow or reduce immune-mediated damage.

Oral Corticosteroids

The typical treatment regimen is high-dose oral prednisone or prednisolone at 1 mg per kilogram of body weight per day (usually 60 mg daily for most adults), continued for 10-14 days and then gradually tapered over 1-2 weeks. Some physicians use methylprednisolone instead. The high initial dose is thought to maximize the anti-inflammatory effect during the critical early treatment window.

Patients should be monitored for steroid side effects, which may include elevated blood sugar (particularly important in diabetics), mood changes, insomnia, increased appetite, stomach irritation, and elevated blood pressure. Short courses of steroids are generally well-tolerated, but patients with diabetes, uncontrolled hypertension, active infections, or peptic ulcer disease require careful management.

Intratympanic Steroid Injections

Intratympanic (IT) steroids involve injecting corticosteroids (usually dexamethasone or methylprednisolone) directly through the eardrum into the middle ear, from where they diffuse into the inner ear. This approach delivers high concentrations of steroids directly to the cochlea while minimizing systemic side effects.

IT steroids may be used in several scenarios:

• As initial therapy: Particularly for patients who cannot take oral steroids due to diabetes, glaucoma, or other contraindications
• As combination therapy: Together with oral steroids for potentially enhanced effect
• As salvage therapy: When oral steroids alone have not produced adequate recovery (typically after 2-4 weeks)

The AAO-HNS guidelines recommend offering intratympanic steroids as salvage therapy when initial treatment fails. Some centers use IT steroids as primary treatment, particularly for patients who cannot tolerate oral steroids.

Hyperbaric Oxygen Therapy

Hyperbaric oxygen therapy (HBOT) involves breathing 100% oxygen in a pressurized chamber. The theory is that increased oxygen delivery to the cochlea may help heal damaged tissue. A Cochrane review found moderate evidence that HBOT may improve hearing when used in addition to steroid treatment.

HBOT is typically administered as a series of sessions (often 10-20 treatments) over 1-2 weeks. Access to HBOT facilities is limited in many areas, and the treatment is time-consuming and expensive. Current guidelines suggest it may be offered as an adjunct therapy, particularly for patients with more severe hearing loss.

Treatments Not Recommended

Several treatments have been studied but are not currently recommended due to insufficient evidence or lack of proven benefit:

• Antiviral medications: Despite the viral theory, antivirals like acyclovir or valacyclovir have not shown benefit in clinical trials and are not routinely recommended.
• Vasodilators: Medications to improve blood flow have not demonstrated consistent benefit.
• Anticoagulants: Blood thinners have not proven effective for sudden hearing loss.
• Rheological agents: Medications to reduce blood viscosity lack sufficient evidence.

What Is the Prognosis and Recovery Rate?

With prompt treatment, approximately 32-65% of patients experience partial or complete hearing recovery. Factors associated with better outcomes include mild initial hearing loss, early treatment (within 72 hours), absence of vertigo, younger age, and low-frequency hearing loss pattern. Recovery typically occurs within the first 2-4 weeks.

The prognosis for sudden hearing loss varies considerably between patients. Broadly speaking, approximately one-third of patients recover completely, one-third have partial recovery, and one-third have no significant improvement despite treatment. These figures have improved somewhat with earlier recognition and treatment, but outcomes remain unpredictable for individual patients.

Factors Affecting Prognosis

Several factors are associated with better or worse outcomes:

Favorable prognostic factors:

• Mild to moderate initial hearing loss (less than 70 dB)
• Low-frequency hearing loss pattern
• Early treatment initiation (within 72 hours)
• Younger age
• Absence of vertigo at onset
• Upsloping audiogram configuration

Unfavorable prognostic factors:

• Profound hearing loss (>90 dB)
• High-frequency or flat hearing loss pattern
• Delayed treatment (more than 2 weeks)
• Older age
• Presence of vertigo at onset
• Downsloping audiogram configuration

Timeline of Recovery

When recovery occurs, it typically happens within the first 2-4 weeks of treatment. Some patients experience rapid improvement within days, while others show gradual improvement over several weeks. Recovery after 4-6 weeks is less common, and significant recovery after 3 months is rare.

Patients who show early signs of improvement (within the first 2 weeks) generally have a better overall prognosis. Serial audiometry is typically performed to monitor recovery - commonly at 2 weeks, 4 weeks, and 3 months after onset.

Living with Permanent Hearing Loss

For patients with permanent hearing loss after sudden SSNHL, several options can help restore functional hearing:

• Hearing aids: Amplification devices can help patients with mild to moderate residual hearing loss.
• CROS hearing aids: For patients with unilateral profound hearing loss, CROS (Contralateral Routing of Signal) systems route sound from the deaf ear to the hearing ear.
• Bone-anchored hearing devices: Alternative to CROS systems for unilateral hearing loss.
• Cochlear implants: For patients with bilateral profound hearing loss or poor hearing aid benefit, cochlear implants can restore hearing sensation.

Tinnitus that persists after sudden hearing loss can be managed with sound therapy, cognitive behavioral therapy, tinnitus retraining therapy, or hearing aids with tinnitus masking features.

Can Sudden Hearing Loss Be Prevented?

There is no proven way to prevent idiopathic sudden hearing loss. However, maintaining cardiovascular health, avoiding ototoxic medications when possible, protecting ears from loud noise exposure, and promptly treating ear infections may reduce some risk factors. The most important "prevention" is seeking immediate treatment if symptoms occur.

Because the cause of most sudden hearing loss cases is unknown, specific prevention strategies are limited. However, addressing modifiable risk factors and maintaining general ear health may help reduce risk:

Cardiovascular Health

Given the possible vascular component of sudden hearing loss, maintaining cardiovascular health is prudent. This includes managing blood pressure, controlling blood sugar levels (particularly important for diabetics), maintaining healthy cholesterol levels, not smoking, and regular physical activity. While these measures haven't been proven to prevent sudden hearing loss specifically, they support overall health and blood flow to all organs, including the inner ear.

Avoiding Ototoxic Substances

Certain medications can damage hearing. If you require treatment with potentially ototoxic drugs (such as aminoglycoside antibiotics, certain chemotherapy agents, or loop diuretics), your healthcare provider should monitor your hearing during treatment. Discuss alternatives with your doctor when possible.

Noise Protection

While noise exposure typically causes gradual hearing loss rather than sudden loss, protecting your hearing from loud sounds is still important. Use hearing protection in noisy environments, keep personal audio devices at moderate volumes, and avoid prolonged exposure to loud noise.

Prompt Treatment of Ear Conditions

Ear infections and other ear conditions should be treated promptly to prevent complications that might affect hearing. This is particularly important for middle ear infections, which can sometimes progress to involve the inner ear.

Frequently Asked Questions