Sudden sensorineural hearing loss, commonly termed sudden deafness, is a rapid loss of hearing, a kind of “stroke” in the inner ear. “Sensorineural” indicates that the origin of hearing loss lies in the inner ear. Sudden sensorineural hearing loss (SSHL) is defined as a hearing loss of at least 30 dB at a minimum of three continuous frequencies and lasting at least three days. It is quite a common condition, with more than 65,000 new cases per year in the USA alone.
Sudden deafness frequently occurs in one ear rather than in both. But even if only one ear is affected, people are frightened, because – depending on the severity – they may lose the ability to localize sound, in other words, they may no longer be able to tell where a sound is coming from.
Spotting the signs of sudden deafness
Symptoms and first signs should be taken seriously. Many people suffering from sudden sensorineural hearing loss report waking up in the morning with a “full or popped ear”, feeling dizzy or hearing a loud ringing noise in the affected ear (tinnitus). If only one side is affected, some notice the hearing loss only when they use this ear for a telephone call or plug in headphones.
Causes of sudden sensorineural hearing loss
There are several causes for sudden deafness, however 90% of all cases come without an obvious, identifiable cause (“idiopathic”).
Causes that may lead to sudden hearing loss include viral infections, autoimmune diseases, neurological diseases like multiple sclerosis (MS), medication that is harmful for the ear (“ototoxic"), head trauma, stroke and blood circulation disorders.
Stress is another cause frequently associated with sudden deafness. Therefore, it is important to eliminate stress factors, if possible.
No matter what the cause of sudden deafness is, always remember to you seek medical advice as soon as possible if you experience any symptoms of sudden hearing loss.
Prompt treatment is important
Sudden hearing loss should be taken seriously. Patients experiencing symptoms should seek medical treatment as soon as possible and see a doctor immediately. Prompt recognition and treatment of sudden deafness improve chances of recovery and decreases the risk of a permanent hearing loss.
Half of the people with sudden deafness, recover some or all of their hearing spontaneously, especially those suffering only from mild symptoms. Of those who experience a moderate or severe hearing loss, only 20% regain their full hearing. Odds of recovering at least some hearing are much higher with prompt treatment. Delaying a visit to an ear specialist might greatly decrease the effectiveness of treatment.
Diagnosis of sudden deafness
Otolaryngologists or ENT specialists will first perform a medical evaluation to confirm the diagnosis and rule out a conductive hearing loss which can be accompanied by similar symptoms. Common diagnostic tests to distinguish between sensorineural and conductive hearing loss are:
- Otoscopy, an ear examination with an otoscope that gives information about the ear canal, the ear drum and parts of the middle ear
- Pure tone audiometry, a quick hearing test to identify hearing thresholds at various frequencies
- Speech audiometry, a hearing assessment that provides information about speech understanding
- Tympanometry, an objective test to assess the function of the middle ear
ENT specialists will obtain these audiometric data as a first step. Ideally this is done within the first two weeks after the symptoms occurred. Once clinicians have established the diagnosis of sudden deafness, magnetic resonance imaging (MRI) or computer tomography (CT) may be ordered to assess for the cause of the sudden deafness. This also allows the professionals to rule out any problems beyond the inner ear, i.e. stemming from the hearing nerve or the brain.
Another diagnostic test to evaluate their proper function is AABR, also called BERA, an automated objective hearing assessment.
Treatment of sudden deafness
Initially, ENT specialists usually offer corticosteroids for sudden sensorineural hearing loss. Very often, this is an effective treatment, especially when it is started within the first two weeks after the onset of illness. Steroids reduce inflammation and can be administered orally as pills or with an injection directly into the middle ear. This procedure is called intratympanic steroid therapy, and is performed when patients do not fully recover from sudden deafness after several weeks.
More recently, clinicians have started combining steroid therapy with a hyperbaric oxygen therapy, especially for patients who suffer from a severe to profound sudden hearing loss. There is growing evidence that this treatment method may improve hearing thresholds, ideally leading to a lower degree of hearing loss. Hyperbaric oxygen therapy is also used for other medical treatments, for example, for wound healing and for treatment of certain infections.
Vasodilators are another treatment option. These drugs dilate (or open) the blood vessels. The cochlea, the hearing organ in the inner ear, needs a lot of oxygen. A problem with the artery that provides oxygen to the cochlea, may result in hearing loss. Vasodilating drugs can remedy this oxygen problem and are therefore may be used for treating sudden deafness.