Sudden sensorineural hearing loss is defined as a loss of hearing in one or both ears occurring instantly – or sometimes rapidly within three days. It is caused by damage to the cochlea, the auditory nerve or both of these. It almost always affects only one ear.
There are several identifiable causes of sudden sensorineural hearing loss, often with serious implications. It can result from an acoustic neuroma or other intracranial tumour, from trauma, blasts and loud noise, barotrauma (SCUBA diving and flights), meningitis, herpes zoster, syphilis, immunological disease, AIDS, MS, Meniere’s disease, Lyme disease and stroke. In most of these the deafness may be gradual, but can also be sudden. This article will discuss idiopathic sudden sensorineural hearing loss – which occurs in 85% of cases.
Worst outcomes if missed
Delayed diagnosis – early referral to a specialist and correct diagnosis and treatment is important because after two to three weeks the remaining deafness is likely to be permanent.
Permanent deafness – it is important to remember that the overall effectiveness of existing treatments for idiopathic sudden sensorineural hearing loss is still unproven. Although the view of most ENT specialists is that treatment may well work, this has not yet been proven statistically because of lack of controlled trials of acceptable quality. But if the patient sees a specialist early they can get a face-to-face explanation of the problem as well as making an informed choice about any treatment.
- In the UK, idiopathic sudden sensorineural hearing loss is identified in five to 20 people per 100,000 a year. The true numbers are probably higher.
- It can occur at any age, but is most common around the age of 50.
- The deafness is almost always unilateral.
- Spontaneous recovery occurs in 50-70% of cases, usually within two to three weeks. It is more likely in milder cases than in profound deafness and when there is a high-frequency hearing loss or vertigo.
- The most probable causes of idiopathic sudden sensorineural hearing loss are URTI-related viral infections and microvascular obstruction to the blood flow in the cochlea. But it isn’t usually possible to confirm either of these for certain.
- Loss of hearing, usually in one ear, which occurs suddenly or is noticed over three days. It is essential to distinguish sudden sensorineural hearing loss from deafness because of wax or from the more common middle-ear problems after URTIs.
- The degree of deafness can vary from profound to mild. It can be mainly high frequency, low frequency or equal across the frequency range.
- Pain can be a feature and suggests a viral infection. The ear often feels full, under pressure or blocked.
- There can be a disturbance of balance in up to 50% of cases.
- Tinnitus is a symptom in at least 70% of cases.
- Sounds, especially speech and music, can be distorted. Loud sounds may be painful.
- There is usually nothing abnormal to see in the ear in idiopathic sudden sensorineural hearing loss, except when it is accompanied by a middle-ear infection.
- If the patient hums, the sound is louder in the ‘good’ ear, unlike in conductive deafness, when it’s louder in the deaf ear.
It is quite common for GPs to assume that sudden deafness is the result of wax, infection or fluid in the middle ear. Patients are given decongestants and told to come back in a few weeks if things aren’t better. Later, when a diagnosis of sudden sensorineural hearing loss is made, the patient can feel let down. Even though the effectiveness of treatment normally given is unproven, patients may get the impression that if the problem had been spotted sooner they might have been helped by treatment, instead of being deaf for the rest of their life.
Tuning fork tests can be used to distinguish between middle-ear conductive deafness and sudden sensorineural hearing loss as described below.
The aim of investigations is to identify treatable causes, as well as any series underlying problem.
- Tuning fork tests are usually diagnostic. Every surgery should have one (512Hz is best). The Weber test – where the base of the tuning fork is placed on top of the head – can help to distinguish sudden sensorineural hearing loss from middle-ear conductive deafness (the main differential diagnosis). In middle-ear conductive deafness the sound goes to the deaf ear. In sudden sensorineural hearing loss the sound goes to the good ear.
- Pure tone audiometry is the gold standard investigation and will make the diagnosis. Get one done in your surgery if you can, or refer the patient to a specialist urgently, if possible within days of onset.
- An ENT department will organise investigations and management of remaining hearing loss once the diagnosis is made.
- Normally an MRI is needed to exclude an acoustic neuroma or other intracranial pathology.
Early diagnosis of treatable or serious underlying disease is important. For idiopathic sudden sensorineural hearing loss, treatment is needed within two weeks of the onset of the deafness. Treatment is normally with a short course of oral steroids, 60mg of prednisolone reducing over a week, or an intratympanic injection of a steroid solution. Betahistine and antiviral agents such as aciclovir may also be given.
It must be said that for idiopathic sudden sensorineural hearing loss, the evidence supporting current treatment methods is not clear. There are several reasons for this.
- Any spontaneous recovery usually occurs within the same two-week window after the onset of deafness during which treatment is recommended.
- Treatments seem to work best if given within the same two weeks.
- Spontaneous recovery can occur within days. These patients may not think it’s worth seeing their doctor, so the episode is unrecorded. This reduces the number of subjects for trials of treatment.
- A Cochrane review showed that there have been no really conclusive randomised controlled trials of treatment. These are certainly needed.
Despite this, most patients, when asked, would prefer to have had active treatment, and may resent any delay in diagnosis. Audiological management of any permanent hearing loss – for example with hearing aids, and of tinnitus, hyperacusis, or poor balance – should also begin as early as possible to be effective. Cochlear implants can help some patients with unilateral profound sudden sensorineural hearing loss who also have intractable tinnitus.
Five key questions to ask
- Was your hearing normal before? Have you had previous ear problems?
- When did it start and how quickly did it come on?
- Do you have other symptoms – pain, tinnitus, poor balance? These will support the possibility of sudden sensorineural hearing loss.
- Do you have other health problems or medical treatment, for example aminoglycosides, or other ototoxic drugs?
- Have you been on a flight or been SCUBA diving recently? Barotrauma can lead to sudden sensorineural hearing loss.
Five red herrings
- A temporary middle or external ear problem of some kind is often wrongly assumed to be the cause.
- Presence of wax doesn’t exclude sudden sensorineural hearing loss.
- An inflamed looking ear drum doesn’t exclude sudden sensorineural hearing loss.
- If you can’t get a specialist outpatient appointment urgently, send the patient as an emergency to the local ENT clinic. If this is not possible send them to A&E to be seen during the next day or two
- Don’t assume that the cause is trivial and the deafness temporary – you wouldn’t if the patient had lost their sight!
Mr John Graham is a consultant ENT surgeon at the Royal National Throat, Nose and Ear Hospital in London and secretary-general of the European Society of Pediatric Otorhinolaryngology. Mr Graham is a trustee of Deafness Research UK.
Deafness Research UK is the national medical research charity for people with hearing loss, tinnitus and other hearing problems. The charity runs an advisory service for people with hearing problems:
Freephone 0808 808 2222, Monday-Friday 9.30-5.30 pm,
Patient information on SSHL can be found on their website.
Chau JK, Cho JW and Fritz DK. Evidence based practice: management of adult sensorineural hearing loss. Otolaryngologic clinics of North America, 2012;45;941-58
Wei BPC, Mubiru S and O’Leary S. Steroids for sudden sensorineural hearing loss. Cochrane database of systematic reviews. 2009.