Sudden sensorineural hearing loss

Sensorineural hearing loss may be either sensory (affecting the sense organ of hearing in the cochlea) or neural (affecting the nervous pathways which connect the cochlea to the hearing centres in the brain).

Generally, sensorineural hearing loss is described as sudden if you notice a drop in your hearing instantaneously or over a short period not exceeding three days. You may notice a popping sound when it happens, or you may detect it when you first wake up or try to use the impaired ear. Sudden Sensorineural Hearing Loss (SSHL) is a medical emergency and you will need to contact your doctor immediately.

People with Sudden Sensorineural Hearing Loss often describe themselves as 'deafened'. They may also say they have an 'acquired hearing loss'. If you lose your hearing after learning to speak, you are said to have 'post-lingual hearing loss'.

What should you do if you lose your hearing suddenly?

If you think you have a sudden hearing loss in one or both ears, you need to see your GP (family doctor) and ask for an urgent referral to an ear, nose and throat (ENT) specialist. If you can't see your GP, and you have a severe sudden hearing loss, you should go to your nearest hospital accident and emergency department.

What causes sudden sensorineural hearing loss?

Sudden Sensorineural Hearing Loss with no known cause

Most of the time the cause is unknown - it is only possible to establish a firm cause of Sudden Sensorineural Hearing Loss in about 15% of cases. The remaining 85% are referred to as idiopathic (with no known cause). In the majority of these idiopathic cases, the hearing is affected in only one ear (unilateral) and will improve spontaneously. It can be tempting, therefore, to adopt a 'wait-and-see' policy, but you should be seen by a specialist as soon as possible if you experience Sudden Sensorineural Hearing Loss, because it is important to establish a diagnosis since treatment may be needed if a specific cause is found.

In an attempt to find a reason for these idiopathic cases of hearing loss, two main theories have been advanced. The first theory is that it may be of viral origin, as some viruses are known to damage the hearing, and a viral infection seems to precede the hearing loss in some cases. The second theory is that it may be due to some vascular defect (relating to blood vessels). There is no conclusive proof to support either view.

Infections

Meningitis is one of the commonest causes of severe or profound acquired deafness in infants and children. Hearing loss due to meningitis usually affects both ears (bilateral). Anybody who has suffered from meningitis, especially a child, should have their hearing tested as soon as possible after recovery.

Measles and mumps are also associated with Sudden Sensorineural Hearing Loss. In measles, the loss is usually moderate to profound and bilateral, whereas in mumps it usually affects only one ear. The herpes zoster virus may on rather rare occasions produce a Sudden Sensorineural Hearing Loss accompanied by weakness of the facial muscles and vertigo. This so-called Ramsay Hunt syndrome may affect adults who have been close to children with chicken pox, which is caused by the same virus.

Some infections are confined to the ear itself. Labyrinthitis is an inflammation of the inner ear, caused by bacterial or viral infection, which can make you feel dizzy, give you tinnitus (ringing in the ears), and can lead to sensorineural hearing loss, but usually only in one ear. Bacterial labyrinthitis often results in permanent hearing loss.

Head injuries

Head injuries, especially those associated with a fractured skull, may produce profound and often permanent hearing loss. Even where there is no fracture, sensorineural hearing loss may occur, caused by damage to the central nervous system or the inner ear itself.

Noise

Noise-induced hearing loss is usually gradual in onset and can be prevented by wearing appropriate ear protection. However, sudden hearing loss may occur from exposure to excessively loud noises, for example from blast injuries (from a nearby explosion) or from firearms and fireworks, especially in enclosed spaces. This sudden hearing loss can range from total deafness in one or both ears to a relatively minor high-frequency loss. In these latter cases, the hearing may recover spontaneously in time.

Ear surgery

Sensorineural hearing loss may occur after any surgical procedure on the ear, and the degree of risk depends on many factors. These include the nature of the procedure, the underlying disease and the skill of the surgeon. The hearing loss may occur immediately, in the few days following the operation, or even many years later. It is important to balance the potential benefits of surgery against the risks to hearing, and these issues should be discussed with your specialist.

Barotrauma

Barotrauma may occur when the ear is exposed to sudden pressure changes, as in flying or diving. Most commonly, the middle ear is affected, causing a conductive hearing loss. It is rarer for the inner ear to be involved, but sensorineural hearing loss can occur if the membrane of the round window (one of the two windows which separate fluid in the inner ear from air in the middle ear) ruptures, causing a leakage of perilymph (one of the inner ear fluids).

Immunological disorders

Disorders affecting the immune system may have a role in causing Sudden Sensorineural Hearing Loss but the link is, at best, uncertain. There is a certain amount of debate over the diagnosis of the condition known as Autoimmune Inner Ear Disease (AIED), its relationship with Sudden Sensorineural Hearing Loss, and potential treatments, but it probably accounts for less than one per cent of all cases of hearing loss. Sudden deafness has been known to occur in established autoimmune diseases such as rheumatoid arthritis and diabetes. However, there is no evidence that rheumatoid arthritis or diabetes cause sudden deafness; they are common conditions and it is likely that some people who have them also happen to develop idiopathic Sudden Sensorineural Hearing Loss.

Ototoxicity

Sudden Sensorineural Hearing Loss is sometimes attributed to ototoxic drugs (drugs that may damage the inner ear) and rare cases have been reported following the use of (for example) gentamicin (an antibiotic). However, the deafness related to ototoxicity is more often gradual than sudden, and is often preceded by tinnitus. Drugs that are known to cause permanent hearing loss are usually given only when no other alternative exists for treating a life-threatening disease. If your doctor prescribes ototoxic drugs, you should discuss with them how this might affect your hearing.

Ménière's Disease

Ménière's Disease affects about one in every two thousand adults in the UK population. It is a late-onset disease usually starting between the ages of 30-50 years. Ménière's Disease is characterised by severe attacks of vertigo combined with fluctuating deafness, tinnitus and a feeling of pressure in the affected ear. Attacks often start without warning and can lead to loss of confidence, anxiety and sometimes depression.

Other causes

Less common causes of Sudden Sensorineural Hearing Loss include an acoustic neuroma, which is a benign tumour. The hearing loss associated with acoustic neuroma is usually gradual and often unnoticed, but may be sudden in as many as 10% of cases. Even rarer is the neurological condition of multiple sclerosis, in which 'plaques' of the disease may affect parts of the brainstem associated with hearing. The diagnosis of this condition is made by electrical tests of brainstem function and a magnetic resonance imaging (MRI) scan, and fortunately the hearing often recovers spontaneously.

How can sudden sensorineural hearing loss be treated?

As with any medical condition, treatment depends upon the cause, when the cause is known. As the cause is not known in so many cases of Sudden Sensorineural Hearing Loss, the treatment strategies may vary, being dependent on the doctor's observation and experience.

Sudden Sensorineural Hearing Loss where the cause is unknown

Although hearing returns to normal or near-normal in about 70% of these cases, "failure to investigate patients will inevitably lead to a missed diagnosis and a missed opportunity for treatment" (Booth ). Hence, in all such cases, urgent investigation is required.

Where cases of Sudden Sensorineural Hearing Loss may be due to a virus or vascular disorder, a wide range of treatments have been recommended, but none have had convincingly beneficial results. However, some viral infections respond to anti-viral agents like acyclovir, and in the Ramsay Hunt syndrome short-term treatment with steroids and acyclovir is justified if started early enough, as it may lead to a reversal of the hearing loss to near-normal thresholds.

There is no evidence of cardiovascular disease in the majority of patients suffering from Sudden Sensorineural Hearing Loss, but there are certain 'vascular' conditions which may occasionally cause sudden deafness. These include reduced blood flow in the cochlea and disorders of coagulation (clotting) of the blood. Research is being carried out on the potential value of carbogen inhalation in such cases, carbogen being a mixture of 95% oxygen and 5% carbon dioxide. So far no value has been proven.

Sudden Sensorineural Hearing Loss with a known cause

In many cases of Sudden Sensorineural Hearing Loss, there is no effective treatment for the hearing loss itself, but further loss may be reduced and occasionally the hearing may even be restored by preventive measures. For example, the adverse effects of ototoxic drugs may be halted and to some extent reversed if the patient stops taking that particular drug (in consultation with a medical advisor) and replaces it with a different agent. Similarly, the risk of noise-induced hearing loss can be greatly reduced by appropriate ear defenders, and the use of helmets undoubtedly reduces the risk of deafness in skull fractures due to head injuries. Finally, timely surgery for the 'dangerous' type of middle ear infection will prevent what is called suppurative labyrinthitis, which occurs if the infection spreads to the inner ear.

When a perilymph leak (a leak of one of the inner ear fluids) is suspected, bedrest is advised for up to five days. If there is no improvement in the hearing after that period, surgical exploration of the ear is needed, with repair of the leak when possible.

In cases of Ménière's Disease, most forms of medical treatment are aimed at controlling the crippling attacks of vertigo, while preserving the hearing if at all possible. In severe cases, if attacks persist despite medication, a Consultant may advise surgery. A number of different operations have been devised, some to reduce pressure in the inner ear, others to diminish or abolish the abnormal impulses passing from ear to brain. For more information about Ménière's Disease, see the Deafness Research UK factsheet on this topic.

Coping with sudden sensorineural hearing loss

Deafness is without doubt one of the most poorly understood of all disabilities and it attracts little sympathy from the hearing majority.

In a 2002 survey by Deafness Research UK, 40 per cent of people questioned about the impact of hearing loss on their relationships said that communication with their partners had become more difficult. One in four said they now had to miss out on social events. This sense of isolation is often compounded by the need to wear a visible hearing device. When the hearing loss occurs suddenly, the shock and sense of loss can be overwhelming.

If you experience a sudden hearing loss, you may go through a range of emotions including denial, hope (for a cure or improvement), anger, isolation, acceptance, embarrassment and resolve. Other people may react to your hearing loss by feeling awkward, embarrassed or unsympathetic. You may feel embarrassed about it yourself. It is important to be open and honest with the people around you, and explain what you want them to do. With time, and with the right sort of professional support, as well as the support of your friends and family, you should find that you become more skilled at being aware of your environment and communicating. As your skills grow you will feel more in control and you might find that you are able to adapt your leisure interests, social life and hobbies to your hearing loss.

There are many sources of information and advice available to help you adjust to your hearing loss. Deafness Research UK, Hearing Concern and RNID all provide a range of factsheets, and there may be a local support group you can join. The Link Centre for Deafened People provides a wide range of resources, services and support for deafened people. Hearing Therapists and lipreading classes can also be valuable sources of support.

Further reading

More detailed medical information about Sudden Sensorineural Hearing Loss can be found in Ballantyne's Deafness (6th Edition), edited by John Graham and Mike Martin, and published by Whurr Publishers Ltd, 196 Compton Terrace, London N1 2UN.

Acknowledgments

Deafness Research UK would like to thank Mr Gavin Morrison of St Thomas's and Guy's Hospitals and Mr John Ballantyne, CBE, FRCS, for their valuable contributions to this section.