Sudden Sensorineural Hearing Loss

Understanding Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSHL), sometimes called sudden deafness, is defined as a rapid loss of hearing of at least 30 decibels across three or more consecutive frequencies, occurring within 72 hours or less. It most commonly affects one ear (unilateral) and can range from a mild reduction in hearing clarity to complete deafness in the affected ear. SSHL is classified as a medical emergency — and with good reason. The window for effective treatment is narrow, and delays in seeking help can significantly reduce the chances of hearing recovery.

In the United Kingdom, SSHL is estimated to affect approximately 5 to 20 people per 100,000 each year, according to data referenced by the British Society of Audiology (BSA) and NICE. However, the true incidence is likely higher, as some cases are misdiagnosed as ear wax, a cold, or Eustachian tube dysfunction, or are simply not reported because the hearing recovers spontaneously before medical attention is sought. SSHL can occur at any age but is most commonly diagnosed in adults aged 40 to 60, with roughly equal rates in men and women.

Despite its dramatic presentation, SSHL remains underrecognised. Many people — and some healthcare professionals — do not immediately realise that sudden hearing loss in one ear warrants the same urgency as other acute medical events. Understanding the signs, knowing what to do, and acting quickly can make the difference between recovery and permanent hearing loss.

How Sudden Hearing Loss Presents

The onset of SSHL is often sudden and striking. Many people describe one of two classic scenarios:

• Waking up deaf in one ear — the person goes to bed with normal hearing and wakes to find that one ear has lost hearing overnight. They may first notice it when holding the phone to the affected ear or when they cannot hear an alarm on that side
• A sudden "pop" or "bang" — some people hear a loud pop, crack, or rushing sound immediately before their hearing drops. This may occur during everyday activities with no obvious trigger

In approximately 90% of cases, SSHL affects only one ear. The accompanying symptoms can provide important clues about the severity and underlying mechanism:

• Tinnitus — ringing, roaring, buzzing, or hissing in the affected ear is present in around 70% of cases. The tinnitus may be the first symptom the person notices, with hearing loss recognised shortly afterwards
• Aural fullness — a feeling of pressure, blockage, or "stuffiness" in the ear, which is why SSHL is sometimes initially mistaken for ear wax build-up or a cold
• Vertigo or dizziness — present in approximately 30-40% of cases. When vertigo accompanies SSHL, it may suggest more extensive damage to the inner ear and is generally associated with a less favourable prognosis for hearing recovery
• Distorted or "tinny" sound — even sounds that can still be heard in the affected ear may sound distorted, hollow, or unnatural

It is crucial to recognise that a sudden change in hearing — even if it feels like it might just be a blocked ear — should be treated as potentially serious until proven otherwise.

Causes of SSHL

One of the most challenging aspects of SSHL is that, in the majority of cases, no specific cause is ever identified. The breakdown is approximately:

• Idiopathic (unknown cause) — 85-90% of cases. In these cases, a viral or vascular mechanism is strongly suspected but cannot be confirmed. The theory is that a viral infection of the inner ear, or a disruption to the blood supply to the cochlea (which is supplied by a single small artery with no collateral circulation), causes sudden damage to the delicate sensory structures
• Identifiable cause — 10-15% of cases, including:
  • Viral infections — mumps, measles, herpes simplex, herpes zoster (Ramsay Hunt syndrome), cytomegalovirus, and influenza have all been associated with SSHL
  • Autoimmune inner ear disease — the body`s immune system attacks the inner ear, sometimes as part of a systemic autoimmune condition
  • Vascular events — disruption to the blood supply of the cochlea, potentially related to cardiovascular risk factors such as diabetes, hypertension, or hyperlipidaemia
  • Acoustic neuroma (vestibular schwannoma) — a benign tumour on the hearing and balance nerve. SSHL is the presenting symptom in approximately 10-20% of acoustic neuroma cases, which is why MRI scanning is an essential part of the investigation
  • Meniere`s disease — can occasionally present with sudden hearing loss as part of an acute attack
  • Ototoxic medications — certain drugs, including some antibiotics, chemotherapy agents, and high-dose aspirin, can damage the inner ear
  • Head trauma — a blow to the head or barotrauma (pressure injury from diving or flying) can cause sudden cochlear damage

Regardless of the suspected cause, the management approach is similar: urgent steroid treatment to reduce inflammation and give the inner ear the best chance of recovery.

The Urgent Treatment Pathway

Time is the single most critical factor in the treatment of SSHL. Every hour that passes without treatment reduces the likelihood of hearing recovery. Here is what you should do — and what to expect — if you or someone you know experiences sudden hearing loss.

Step 1: Seek Medical Attention Immediately

Do not wait to see if the hearing comes back on its own. Contact one of the following the same day:

• Your GP — request an emergency or same-day appointment. Make clear that you have experienced sudden hearing loss and that it may be a medical emergency
• NHS 111 — if your GP surgery is closed or you cannot get a same-day appointment, call 111 for urgent advice
• A&E — if you cannot access a GP or 111 in a timely manner, attend your nearest emergency department. While A&E may not seem like the natural choice for hearing loss, SSHL is a genuine emergency and they can initiate steroid treatment

Step 2: Steroid Treatment Within 72 Hours

UK and international guidelines, including NICE Clinical Knowledge Summaries and the BSA, recommend that oral corticosteroids should be started as soon as possible, ideally within 72 hours of symptom onset. The standard treatment is a course of high-dose oral prednisolone, typically starting at 1mg per kilogram body weight per day (usually 40-60mg daily), tapered over two to three weeks. Starting steroids within the first 48 hours is associated with the best outcomes; starting beyond 72 hours significantly reduces the chance of recovery, though some benefit may still be gained up to two weeks after onset.

Step 3: Urgent ENT or Audiology Referral

Your GP should arrange an urgent referral to an ENT specialist or emergency audiology service within 24 hours. An urgent audiogram is essential to confirm the diagnosis, determine the severity and pattern of hearing loss, and establish a baseline for monitoring recovery. The audiogram typically shows a unilateral sensorineural hearing loss — often with a characteristic pattern that may provide clues about the underlying cause.

Intratympanic Steroids as Salvage Therapy

If oral corticosteroids fail to produce improvement, or if the patient cannot take oral steroids due to medical contraindications (such as poorly controlled diabetes, active peptic ulcer disease, or certain psychiatric conditions), intratympanic steroid injections may be offered as salvage therapy. This involves injecting a concentrated steroid solution (usually dexamethasone or methylprednisolone) directly through the eardrum into the middle ear, from where it diffuses into the inner ear at much higher local concentrations than can be achieved through oral medication.

Intratympanic injections are typically given as a series of two to four treatments over one to two weeks. The procedure is carried out in an outpatient clinic under local anaesthesia and takes around 20-30 minutes. While it may sound daunting, most patients report only mild discomfort. Evidence suggests that intratympanic steroids can improve outcomes in patients who have not responded to oral treatment, and some UK centres now offer them as a first-line treatment alongside oral steroids for severe SSHL.

Investigation: MRI and Ruling Out Acoustic Neuroma

An MRI scan of the internal auditory canals with gadolinium contrast is recommended for virtually all patients with SSHL. The primary reason is to rule out acoustic neuroma (vestibular schwannoma), a benign tumour on the hearing and balance nerve. Acoustic neuroma is found in approximately 1-3% of patients presenting with sudden hearing loss, making MRI an essential part of the diagnostic workup.

The MRI should ideally be arranged within a few weeks of the initial presentation. In addition to acoustic neuroma, MRI can identify other structural causes such as demyelinating disease (multiple sclerosis), cochlear abnormalities, or vascular malformations. If MRI is contraindicated (for example, due to a pacemaker or metallic implant), a CT scan or auditory brainstem response (ABR) test may be used as alternative investigations.

Prognosis and Recovery

The prognosis for SSHL is often described using the "rule of thirds":

• Approximately one-third of patients recover fully, with hearing returning to normal or near-normal levels
• Approximately one-third recover partially, with some improvement but residual hearing loss
• Approximately one-third have little or no improvement, with the hearing loss remaining permanent

Several factors influence the likelihood and extent of recovery:

• Speed of treatment — patients who receive corticosteroids within 48-72 hours have significantly better outcomes than those treated later
• Severity of initial loss — mild to moderate SSHL has a better prognosis than severe or profound loss
• Age — younger patients generally recover more completely than older patients
• Presence of vertigo — SSHL accompanied by vertigo tends to have a less favourable prognosis, possibly indicating more extensive inner ear damage
• Audiometric pattern — low-frequency hearing loss tends to recover better than high-frequency or flat losses
• Underlying cause — SSHL caused by Meniere`s disease or autoimmune conditions may have a different recovery trajectory compared to idiopathic cases

Most recovery occurs within the first two to four weeks, though some improvement can continue for up to three months. If hearing has not recovered by three months, the loss is generally considered permanent.

Living with Permanent Unilateral Hearing Loss

For those who do not recover hearing after SSHL, adjusting to permanent single-sided deafness (SSD) or unilateral hearing loss can be challenging. Common difficulties include:

• Difficulty localising sound — the brain relies on input from both ears to determine where sounds are coming from. With hearing in only one ear, localisation becomes unreliable
• Struggling in noisy environments — the "head shadow" effect means sounds arriving from the deaf side are attenuated, making it harder to follow conversation when noise comes from that direction
• Listening fatigue — the constant extra effort required to hear with one ear can be mentally and physically exhausting
• Persistent tinnitus — tinnitus in the affected ear often remains even after the acute phase has resolved

Fortunately, there are effective hearing solutions for unilateral hearing loss:

• CROS hearing aids — a microphone worn on the deaf ear picks up sounds and wirelessly transmits them to a receiver on the hearing ear, helping to overcome the head shadow effect. Available through NHS audiology services and private providers such as Boots Hearingcare, Specsavers Audiology, and Hidden Hearing
• Bone-anchored hearing aids (BAHA) — a surgically implanted device that transmits sound through the skull bone directly to the functioning inner ear. BAHAs are available on the NHS and are particularly effective for people with profound single-sided deafness
• Conventional hearing aids — if there is residual hearing in the affected ear (partial recovery), a standard hearing aid may provide sufficient amplification

A hearing aid fitting consultation can help determine which solution is most appropriate for your specific pattern of hearing loss. Support from the RNID and peer support groups for people with single-sided deafness can also be invaluable in adjusting to life with unilateral hearing loss.

If you experience a sudden change in hearing in one or both ears, do not delay — seek urgent medical attention the same day. Early treatment saves hearing. Find an audiologist near you for ongoing hearing support and rehabilitation.