Sudden sensorineural hearing loss (SSHL) happens when the nerve pathways in your inner ear are damaged rapidly, usually within hours. In about 90% of cases, no specific cause is ever identified. The remaining 10% can be traced to a range of triggers, from viral infections to disrupted blood flow in the inner ear. Clinically, SSHL is defined as a drop of at least 30 decibels across three connected sound frequencies within 72 hours.
How Common SSHL Is and How It Presents
SSHL affects roughly 5 to 27 people per 100,000 each year. Most people notice it the moment they wake up or when they try to use a phone on the affected side. It almost always hits one ear. Many people also experience tinnitus (ringing), a feeling of fullness in the ear, or dizziness alongside the hearing drop.
Because the onset is so fast, people sometimes assume it’s just earwax or allergies. That delay matters. The greatest window for spontaneous improvement is the first two weeks, and treatment started within that window produces the best outcomes.
Viral and Infectious Causes
Viral infection is one of the most frequently suspected triggers, even when it can’t be confirmed with certainty. The idea is that a virus inflames or directly damages the delicate structures of the inner ear or the nerve that carries sound signals to the brain.
Several virus families have been linked to SSHL. The herpes virus family is the most studied group, and it includes herpes simplex types 1 and 2, varicella zoster (the virus behind chickenpox and shingles), cytomegalovirus, and Epstein-Barr virus. Mumps has been connected to sudden deafness in both clinical observations and blood-based studies, and measles and rubella carry associations as well. Respiratory viruses, adenoviruses, and certain other viral families have also been implicated based on patient histories and antibody testing.
In many of these cases, the hearing loss appears during or shortly after a viral illness. Some researchers believe the virus itself invades inner ear tissue, while others think the immune response triggered by infection does the damage.
Blood Flow Disruption to the Inner Ear
Your inner ear depends on a single, tiny artery with no backup blood supply. That makes it extremely vulnerable. Even a brief interruption in blood flow can starve the cochlea of oxygen and cause permanent damage.
Several vascular problems can cause that interruption: a blood clot (thrombosis), a small particle blocking the artery (embolus), a spasm that temporarily narrows the vessel, or simply reduced blood flow from cardiovascular disease. The sudden, abrupt nature of the hearing loss matches what you’d expect from a vascular event, which is one reason researchers find this explanation compelling.
Animal and human studies of inner ear tissue after blood vessel blockage show a predictable pattern: bleeding inside the cochlea occurs first, followed by scarring and eventually hardening of the tissue. A large study comparing nearly 74,000 people with high cholesterol to the same number of age-matched controls found that the high-cholesterol group was 1.62 times more likely to develop sudden hearing loss. That finding reinforces the connection between cardiovascular health and inner ear function.
Autoimmune Conditions
Sometimes the immune system mistakenly attacks the inner ear. This can happen on its own or alongside a broader autoimmune disease. Among people diagnosed with autoimmune inner ear disease, 15 to 30% also have a systemic autoimmune condition such as rheumatoid arthritis, lupus, ulcerative colitis, or a blood vessel inflammation called polyarteritis nodosa.
A rare condition called Cogan syndrome, which causes inflammation in both the eyes and the inner ear, is another recognized autoimmune cause. When autoimmune disease is the culprit, hearing loss may fluctuate or affect both ears over time, which can help distinguish it from other causes.
Physical Trauma and Pressure Changes
A tear or hole in the thin membranes separating your air-filled middle ear from your fluid-filled inner ear is called a perilymph fistula. When this happens, fluid leaks from the inner ear into the middle ear, changing the pressure balance that your hearing and balance systems rely on.
Perilymph fistulas can result from:
- Head or ear trauma, such as a blow to the head
- Barotrauma, from rapid pressure changes during flying, scuba diving, heavy lifting, or even childbirth
- Acoustic trauma, like a gunshot fired close to the ear
- A punctured eardrum
- Straining, including blowing your nose extremely hard
These causes are among the more identifiable triggers for SSHL because there’s usually a clear event the person can point to.
Tumors and Structural Problems
A benign growth on the nerve connecting the inner ear to the brain, often called an acoustic neuroma, is one of the identifiable structural causes doctors screen for. These tumors grow slowly, but they can compress the nerve or its blood supply enough to cause sudden hearing changes. This is a key reason imaging is part of the workup for SSHL, even though tumors account for a small fraction of cases.
Why Most Cases Remain Unexplained
Despite the list of known causes above, 90% of SSHL cases are classified as idiopathic, meaning no cause is found after testing. This isn’t because doctors aren’t looking hard enough. The inner ear is tiny, deeply embedded in bone, and nearly impossible to biopsy in a living person. Blood tests, imaging, and hearing tests can rule out specific causes, but the inner ear often doesn’t reveal its secrets through standard diagnostics.
Researchers believe that many idiopathic cases likely involve viral inflammation or vascular disruption that simply can’t be confirmed with current tools. The immune-mediated theory also remains plausible for a subset of unexplained cases.
How SSHL Is Treated
Oral steroids are the standard first-line treatment. The typical approach is a course lasting 7 to 14 days followed by a gradual taper over a similar period. Treatment ideally starts within two weeks of symptom onset. After four to six weeks, the chances of meaningful improvement drop significantly.
If oral steroids don’t work, or if someone can’t take them, steroid injections delivered directly through the eardrum into the middle ear are used as a backup. Research suggests that combining these injections with oral steroids may produce better hearing recovery than oral steroids alone. As a standalone rescue option for people who didn’t respond to the first round of treatment, injections show variable but sometimes meaningful benefits.
Without any treatment at all, somewhere between 32 and 65% of people experience at least some spontaneous recovery. That’s a wide range, and outcomes depend heavily on how severe the initial loss is, the person’s age, and whether dizziness is present (dizziness tends to signal a worse prognosis). Full recovery is possible but far from guaranteed, which is why early treatment matters.
What Affects Your Outlook
Timing is the single biggest factor you can control. People treated within the first two weeks consistently do better than those who wait. The severity of the initial hearing drop also plays a major role: mild to moderate losses recover more often than profound ones. Younger patients generally fare better than older ones, and the absence of dizziness at onset is a favorable sign.
If hearing doesn’t fully return, hearing aids or, in cases of severe loss, cochlear implants can restore functional hearing for most people. Ongoing tinnitus is one of the more persistent aftereffects, even in people whose hearing partially recovers.