Sudden hearing loss is a hearing loss that occurs within minutes or may develop rapidly over the course of 3 days or less. Sudden hearing loss may be divided into two different types:
- Sudden conductive or
- Sudden sensorineural (nerve deafness) loss.
Sensorineural hearing loss (SNHL) indicates an abnormality of the cochlea, auditory nerve, or higher aspects of central auditory perception or processing (for more information regarding the difference between conductive and sensorineural hearing loss please see “Hearing Loss”
A sudden loss of hearing should be evaluated as soon as possible to determine the cause of the hearing loss. A sudden conductive hearing loss is often easily correctable. A sudden sensorineural hearing loss, however, is a medical emergency and must be treated as soon as possible to try to increase the chance of hearing improvement.
Sudden Conductive Hearing Loss
Some common causes of sudden conductive hearing loss include (with their associated treatment in parenthesis):
- ear wax impaction (removal in the physician’s office)
- acute outer or middle ear infection (antibiotic drops and/or antibiotic pills)
- trauma to the ear canal (possible surgery)
- trauma to the ear drum or middle ear bones (surgery/hearing aid).
Sudden Sensorineural Hearing Loss
As mentioned previously, sudden sensorineural hearing loss is considered a medical emergency. There is a much higher chance of hearing improvement in sudden sensorineural hearing loss if treatment is started within 7 days of onset of the hearing loss.
Sudden sensorineural hearing loss may vary from a mild to a profound hearing impairment. Sudden sensorineural hearing loss is most commonly defined as a loss of at least 30 dB in three consecutive frequencies, with the hearing loss developing over 3 days or less. The disorder has an estimated incidence of 5 – 20 cases per 100,000 population, with about 4000 new cases per year in the United States.
The following is a list of the most common causes of sudden sensorineural hearing loss:
- Unknown cause (up to 90% of cases)
- Lyme’s disease
- Autoimmune disease
- Meniere’s disease
- Acoustic neuroma
- Multiple sclerosis
There are various proposed theories as to the cause of idiopathic (unknown cause) sudden hearing loss.
The most common theories as to the cause of sudden sensorineural hearing loss include viral infection (causing swelling in the inner ear), vascular occlusion (blockage of blood flow to the inner ear), and intralabyrinthine membrane breaks (a break of the delicate membranes in the inner ear). At present, the majority of evidence points to some type of swelling (also known as inflammation) in the inner ear as the most common cause of sudden sensorineural hearing loss.
A herpes type virus is believed to be the most common cause of sudden sensorineural hearing loss. The herpes virus lays dormant in our bodies and reactivates for an unknown reason.
Because the majority of sudden sensorineural hearing loss is believed to be of some type of inner ear or hearing nerve inflammation, oral steroids have been used to treat the condition.
Most of the treatments studied in randomized controlled trials can be divided into three different categories: 1) corticosteroid treatment; 2) specific antiviral therapy; and 3) specific treatment of vascular insufficiency. The justification for steroid treatment is based upon a presumed inflammatory process within the inner ear. Such inflammation might arise from a viral infection, an autoimmune mechanism, or even as a result of changes from an area of ischemia (lack of blood flow). In other words, steroid therapy is non-specific and may be beneficial in cases of differing causes. Antiviral therapy has not been found to be helpful for sudden sensorineural hearing loss.