Today I want to look at an autoimmune disorder that is organ specific. I haven’t seen many disorders that affect the ear, so let’s see what this one is all about. Did you know that until recently it was thought that the inner ear could not be attacked by the immune system? I assumed that there isn’t any part of the body that can’t be affected by an autoimmune disorder.
There are a few words in this post that need some defining, so we know what is being talked about .
- Sensorineural hearing loss caused by a lesion or disease of the inner ear or the auditory nerve.
- Vestibular – relating to a vestibule, particularly that of the inner ear, or more generally to the sense of balance.
- Cytokine – any of a number of substances, such as interferon, interleukin, and growth factors, that are secreted by certain cells of the immune system and have an effect on other cells.
- Interferon – a protein released by animal cells, usually in response to the entry of a virus, that has the property of inhibiting virus replication.
- Interleukin – any of a class of glycoproteins produced by leukocytes for regulating immune responses.
- Glycoprotein – any of a class of proteins that have carbohydrate groups attached to the polypeptide chain.
- Antigen – a toxin or other foreign substance that induces an immune response in the body, especially the production of antibodies.
Autoimmune inner ear disease (AIED) is an unusual form of progressive non-age-related sensorineural hearing loss and sometimes vertigo. It is caused by antibodies or immune cells which are attacking the inner ear. It occurs in both ears with cochlear and vestibular symptoms that progress over a period of weeks to months and affects hearing, and often balance function, in both ears.
What are the Symptoms of AIED?
- Hearing loss leading on to severe deafness
- Dizziness or problems with your balance
- Fullness in your ear
- Tinnitus (ringing, roaring, or hissing in your ear)
- Vertigo (a sense that you’re spinning)
About 50% of patients with AIED have symptoms related to balance (dizziness or unsteadiness).
AIED is rare, probably accounting for less than 1% of all cases of hearing impairment or dizziness.
Click to watch. This is an easy to understand explanation.
What Causes AIED?
The cause of AIED is generally assumed to be related to either antibodies or immune cells that cause damage to the inner ear. There are several theories as to how these might arise, analogously to other autoimmune disorders:
- Bystander damage: Damage to the inner ear causes cytokines to be released which provoke (after a delay) additional immune reactions. This theory might explain the attack/remission cycle of disorders such as Meniere’s disease.
- Cross-reactions: Antibodies or rogue T-cells cause accidental inner ear damage because the ear shares common antigens with a potentially harmful substance, virus, or bacteria that the body is fighting off.
- Intolerance: The body may not know about all of the inner ear antigens, and when they are released (perhaps following surgery or an infection), the body may wrongly mount an attack on the “foreign” antigen.
- Genetic factors: Genetically controlled aspects of the immune system may increase or otherwise be associated with increased susceptibility to common hearing disorders, such as Meniere’s disease. Read more.
Another great explanation. Click to watch.
How is AIED Diagnosed?
The diagnosis is based on:
- findings on physical examination
- blood tests
- and the results of hearing and vestibular tests. As auditory neuropathy can present with a progressive bilateral sensorineural hearing loss, ABR testing should be done in persons with enough hearing for the test to be practical.
- Otoacoustic emission tests can be done in those in whom ABR testing cannot be done due to severely impaired hearing.
- ECOG (electrocochleography) testing may also be useful.
How is AIED Treated?
For a more in depth lecture on how to treat AIEDs, click here.