Introduction:

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Autoimmune hearing loss is a rare form of sensorineural hearing loss characterized by intermittent hearing loss of unknown origin.

Compared to sudden sensorineural hearing loss, this type of hearing loss has a slower onset, typically occurring within 3 to 90 days.

While hearing fluctuations may not occur simultaneously in both ears, both ears are affected, and about half of the patients experience dizziness during the onset.

Some of these patients also have concomitant systemic autoimmune diseases such as rheumatoid arthritis, polyarteritis nodosa, systemic lupus erythematosus, and ulcerative colitis.

They often have a clear family history of autoimmune diseases, but autoimmune hearing loss is usually not observed in multiple family members.

Causes and Pathogenesis

The internal lymphatic sac is the only part of the inner ear with a lymphatic vascular network, containing lymphocytes, monocytes, and plasma cells, providing an immune defense system for the inner ear.

Immune cells enter the bone labyrinth through the spiral vein in the bony canal or through lymphatic vessels and small veins around the lymphatic sac.

Immune reactions involving humoral and cellular immunity or both can cause inner ear dysfunction and are considered to be the main causes of autoimmune hearing loss.

Thus, autoimmune factors have been recognized as one of the etiologies of certain inner ear diseases, including Meniere's disease, sudden deafness, and acute vertigo.

Clinical Manifestations

Onset usually occurs between the ages of 20 and 40, with a course of several weeks or months, and a higher incidence in females.

Hearing loss presents as rapidly progressive sensorineural hearing loss, often asymmetrically affecting both sides.

Damage can also involve the vestibule, with accompanying dizziness, ear fullness sensation, and tinnitus.

Diagnosis

Due to the deep location of the inner ear within the skull, it is not possible to perform immunopathological examination of the inner ear. Currently, there are no universally recognized criteria for the diagnosis of autoimmune inner ear diseases. Diagnosis mainly relies on patient symptoms, audiological examinations, special laboratory tests, and response to corticosteroid treatment.

In general, all patients with idiopathic, rapidly progressive bilateral hearing loss should be considered for the possibility of autoimmune hearing loss.

However, in some cases, symptoms may appear in one ear months or even years before affecting the other ear.

In cases where Meniere's disease triad is present (vestibular dysfunction, low-frequency fluctuating hearing loss, and tinnitus), autoimmune hearing loss should also be considered, especially when the other ear is rapidly affected within a short period of time.

Treatment Methods

Currently, the main treatment methods for autoimmune hearing loss include:

Immunosuppressants: Corticosteroids are the mainstay of treatment for autoimmune hearing loss. These drugs effectively reduce vasculitis lesions. Cyclophosphamide can reduce cellular immune reactions and decrease inflammatory cell infiltration around the tympanic membrane and the lymphatic sac. If there is improvement in hearing, medication should be continued until stability is achieved, gradually tapering off while monitoring for side effects and complications.

Intratympanic Steroid Injections: Due to the side effects of corticosteroids and the severe cytotoxicity of immunosuppressants, their use is limited. Directly injecting corticosteroids into the inner ear through the round window membrane can increase drug concentration and avoid systemic side effects.

Vascular Replacement: Another option for treating autoimmune hearing loss may be vascular replacement, which can help maintain hearing in some patients. However, vascular replacement is only a temporary treatment that temporarily removes self-antibodies from the patient's bloodstream. It has limitations in terms of treatment costs and recurrence issues.

Autoimmunity is one of the causes of sudden or progressive sensorineural hearing loss. The coexistence of many systemic autoimmune diseases with inner ear diseases indicates that autoimmunity can damage the inner ear.

Currently, the diagnosis of autoimmune hearing loss mainly relies on clinical manifestations, audiological and laboratory examinations, as well as the response to immunosuppressant treatment.

Autoimmune hearing loss is one of the few inner ear diseases that can be improved or stabilized with appropriate treatment for hearing and vestibular dysfunction. However, there is still no definitive method for diagnosis and treatment, requiring further research.