Sudden Sensorineural Hearing loss

Sudden hearing loss (SHL) is defined as greater than 30 dB hearing reduction, over at least three contiguous frequencies, occuring over 72 hours or less. It occurs most frequently in the 30 to 60 year age group and affects males and females equally.

SHL is usually unilateral (that is, it affects only one ear); and is often accompanied by tinnitis. vertigo, or both. The amount of hearing loss may vary from mild to severe, and may involve different parts of the hearing frequency range. SHL may be temporary or permanent. About one third of people with SHL awaken in the morning with a hearing loss.

Causes:

Many theories have been put forward but there is no conclusive evidence available proving a particular cause for this condition.

Although some hold that this disease is generally idiopathic (of unknown cause), viral disease appears to be the basis for about 60% of all cases of SHL.

The vascular theory holds that partial or complete blockage of the blood circulation of the inner ear may cause idiopathic sudden SNHL.

Vascular spasm has also been implicated as a factor in sudden hearing loss, due to a reported association between migraine headaches and a temporary, reversible hearing loss.

The third theory is based on the rupture of the delicate inner ear membrane and fistulae of the round and/or oval window. Round and oval window ruptures are reported to occur when pressures from within (cerebrospinal pressure) or without (middle ear pressure) suddenly increase causing breaks in the cochlear membrane, resulting in sudden hearing loss. Often, there is a history of strenuous physical activity or straining, or sudden changes in barometric pressure, such as in flying or scuba diving.