Sudden deafness is complete hearing loss that occurs all at once or within a period of three days. Sudden deafness is sometimes called sudden hearing loss syndrome or sudden sensorineural hearing loss (SSHL). Sudden deafness may affect both ears, but only affects one ear in ninety percent of the cases of sudden deafness.

The sudden hearing loss is most commonly noticed upon waking in the morning. The person may not notice the hearing loss until they attempt to use the affected ear such as while making a phone call. In addition to the hearing loss, people with sudden hearing loss syndrome may have a ringing in the ears or dizziness. The ringing in the ears is called tinnitus and may involve a variety of different, repetitive sounds or tones, not just ringing.

A sudden loss of hearing should be considered a medical emergency. Prompt medical attention increases the chance that the hearing can be treated or at least partially restored. There are numerous possible causes of sudden hearing loss. Some possible causes of sudden hearing loss are disease, lack of oxygen, tumors, poisoning, and head trauma. In most cases, the cause is never identified. Therefore, it may be described as idiopathic.

A physician can measure the hearing loss with a hearing test. Sudden hearing loss syndrome is characterized by a loss of hearing of thirty decibels. The thirty decibel level is half as loud as normal conversation. A person with sudden hearing loss syndrome has lost the ability to hear any sound below this level.

The standard treatment for sudden hearing loss syndrome is the administration of steroids. If a specific cause has been determined, the physician may be able to tailor the treatment to the cause. However, there is substantial debate over the best treatment for many causes of sudden deafness. Therefore, steroids remain the most common treatment. A low-salt diet may also be recommended for patients with sudden hearing loss syndrome.

Some cases of sudden deafness resolve on their own without medical treatment. This is called spontaneous recovery. When the person recovers their hearing without medical treatment, it usually occurs within three days.