Introduction:
Autoimmune inner ear disease is extremely an uncommon condition and its prevalence is about 15 in 100,000 individuals. If only the inner ear is affected, it is regarded as ‘primary’ and considered ‘secondary’ if it accompanies a larger autoimmune disorder that affects the entire body. Examples of such disorders include systemic lupus erythematosus, an autoimmune disease characterized by connective tissue inflammation; rheumatoid arthritis, a condition affecting the joints and causing pain and inflammation; sarcoidosis, the formation of small inflammatory cell clusters in the body; and various others. This condition is often common in middle-aged women.
How Does the Ear Function?
The ear comprises three parts namely the outer, middle, and inner ear. The outer ear continues inside into the ear canal. The eardrum acts as a protective barrier, separating the ear canal from the middle ear. The middle ear contains small bones that assist in transmitting sound vibrations to the inner ear. The inner ear comprises the auditory (hearing) nerve, which connects with the brain.
The sound from a source sends sound waves or vibrations into the air. These travel through the opening of the ear, then through the ear canal, and hit the eardrum, making it vibrate. These vibrations are transferred to the small bones in the middle ear, which further transfer them to the auditory nerve present in the inner ear. In the inner ear, the vibrations are transformed into nerve impulses that reach the brain directly. Subsequently, the brain processes these nerve impulses as auditory sensations, perceiving them as sounds such as speech, music, or the sound of a horn.
How Was Autoimmune Inner Ear Disease (AIED) Found?
Until recent times, the prevailing belief was that the immune system could not target or impact the inner ear. However, studies have found that the tissue that surrounds the endolymphatic sac (a fluid-filled balloon-shaped structure in the inner ear) comprises necessary elements that could trigger an immunological reaction. The inner ear also has the potential to set off an autoimmune response to sensitized cells that can pave their way into the cochlea through the circulatory system.
What Are the Reasons for Autoimmune Inner Ear Disease (AIED)?
In the context of health, an autoimmune disease is characterized by the body's immune system erroneously targeting its own healthy cells. In AIED, the immune system makes an attack on the protein present in the inner ear called coachline by manufacturing and releasing antibodies against these proteins. The reason for its occurrence is not fully known. According to the American Academy of Otolaryngology-Head and Neck Surgery Foundation (AAO-HNS), it is usually found in individuals who suffer from one or more autoimmune conditions. These autoimmune disorders can happen in groups of two to three diseases.
How Do the Symptoms of Autoimmune Inner Ear Disease (AIED) Manifest?
In individuals with AIED, hearing loss sets in one ear and gradually progresses to the other. The duration of this process may range from several weeks to several months. The symptoms of AIED are as follows:
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Dizziness or issues with balance.
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Tinnitus (ringing, hissing, or roaring sound in the ear).
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Vertigo (a feeling of spinning or motion that is usually described as dizziness).
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Fullness in the ear.
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Hearing that can improve and deteriorate randomly.
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Symptoms of systemic autoimmune disease may be experienced like muscle aches, low-grade fever, swelling and redness, fatigue, and so on.
Occasionally, AIED can be mistaken for another inner ear condition known as Meniere's disease, which also leads to hearing loss and is characterized by episodes of vertigo. Though both conditions include similar symptoms like tinnitus and poor balance, the major difference lies in the fact that Meniere’s disease affects only a single ear.
What Factors Increase the Risk of Developing Autoimmune Inner Ear Disease (AIED)?
Individuals with other autoimmune disorders are susceptible to developing AIED when compared with those who do not have any autoimmune conditions. AIED may be associated with the following autoimmune diseases:
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Systemic lupus erythematosus is an autoimmune disease where inflammation occurs in the connective tissues.
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Rheumatoid arthritis is a condition that affects the joints, causing inflammation and pain.
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Ulcerative colitis (a long-term inflammatory bowel disease that results in inflammation of the digestive tract).
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Scleroderma (long-term tightening and hardening of the skin and connective tissues).
How Can Autoimmune Inner Ear Disease (AIED) Be Diagnosed?
Since AIED is very rare, there are no specific protocols to diagnose the condition. The condition is usually diagnosed by healthcare professionals when other conditions or symptoms have been eliminated. The following diagnostic tests may be employed by the physician:
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Serial audiograms test may be done to assess the hearing over a period of several months.
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Vestibular testing can assess balance. However, this is time-consuming.
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Imaging techniques like magnetic resonance imaging (MRI) can show the anatomy of the inner ear structure which can aid in eliminating other issues in the cochlea.
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An important diagnostic method is the blood test. A blood test is done to detect if the levels of T cells in the blood are elevated since these cells act against the antigens in the inner ear.
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Other laboratory tests include estimation of erythrocyte sedimentation rate (an indicator of inflammation), rheumatoid factor (an indicator of rheumatoid arthritis), anti-nuclear antibody titer (to determine the presence of lupus or other autoimmune conditions), leukocyte migration inhibition test, quantitative immunoglobulin determination, lipid panel (to check dyslipidemias), and so on.
How Can Autoimmune Inner Ear Disease (AIED) Be Treated?
The treatment is based on factors like age, lifestyle, the severity of symptoms, tolerance to medication, and overall health of the individual. A few treatment options include:
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Corticosteroids: Initiating the treatment with corticosteroids like Prednisone can rapidly reduce inflammation. The response of the individual to corticosteroids will be observed by the physician. If the symptoms begin to fade with the intake of corticosteroids, then the condition could be diagnosed as AIED. In emergencies, oral steroids may be given. Steroid injections may also be administered through the eardrum, directly into the middle ear. Corticosteroids commonly exhibit side effects such as elevated blood pressure, mood fluctuations, headaches, weight gain, and fluid retention.
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Immunosuppressants: Immunosuppressants are agents that retard the reaction of the immune system. Immunosuppressants are prescribed to treat autoimmune diseases as well as to avoid the body from rejecting organ transplants. A commonly used immunosuppressant in the treatment of AIED is Methotrexate which is also used in chemotherapy. Side effects associated with the use of immunosuppressants are fatigue, high blood pressure, diabetes, weight gain, and an elevated chance of acquiring infections.
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Biologics: Those who are irresponsive to corticosteroids may be treated with biologics. Biologics are medications that are obtained from living organisms. Examples include Golimumab and Rituximab. A review found that biologics may be effective like corticosteroids and can aid in reversing hearing loss and can be used as a maintenance medication in those who want to switch from corticosteroids. Because of how biologics work on the immune system, biologics may be associated with an increased risk of infection.
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Hearing Devices: Hearing devices may be used to overcome the hearing loss caused by AIED. A cochlear implant is a small electronic device designed to enhance hearing by stimulating the cochlear nerve. This implant comprises an internal component that is positioned in the inner ear and an external component that is situated behind the ear. Cochlear implants are specifically preferred in those with severe hearing loss or those with specific patterns of hearing loss. Comparatively, hearing aids are less invasive and can be removed when not required.
Conclusion:
Autoimmune inner ear disease is characterized by the immune system targeting and attacking healthy cells within the inner ear, representing an autoimmune condition. Since it is a very rare condition, there are no specific diagnostic methods to diagnose AIED. Medications are available to keep the immune system under control. In certain cases, the dosages and types of medications need to be adjusted depending on factors like drug resistance or side effects. AIED usually takes 3 to 90 days to develop but the hearing loss can occur suddenly. The onset of sudden hearing loss necessitates urgent medical attention as it is deemed a medical emergency. One must consult a physician as early as possible if they experience sudden hearing loss to prevent permanent hearing loss.
