Meniere’s disease (MD) may well be caused by middle ear muscles behaving badly. This debilitating inner ear disease is characterized by episodes of vertigo, hearing loss, tinnitus and ear fullness of which the trigger is still unknown. The concept of endolymphatic hydrops (raise in the fluid pressure of the inner ear) is commonly accepted to be the explanation of what occurs in the inner ear, regardless of the trigger.
A new interesting theory has lately been advocated. The explanation is that the pressure in the inner increases (endolymphatic hydrops) may occur due to the inappropriate and abnormal contraction of the middle ear muscles, in particularly the tensor tympani muscle. Two of the smallest muscles in the human body are found in the middle ear. The stapedial muscle connects to the stapes (stirrup) and contraction with tilting of the stapes occurs reflexively to loud sound, protecting the inner ear to noise induced damage. The tensor tympani muscle on the other hand reacts to a lot of different triggers, such as the patient’s own voice, chewing and swallowing and also aim to protect the inner ear to sound. When the tensor tympani contracts the stapes is forced inwards. Momentarily it protects the inner ear by dampening the sound.
Abnormal sustained contraction of the tensor tympani muscle with sustained inward displacement of the stapes unfortunately causes sustained increased inner ear pressure with compression of the outer hair cells and the generation of the symptoms of MD. Why this abnormal and often sustained muscle contraction (dystonia) occurs is not known.
If indeed future research shows that the middle ear muscles are to blame a logic approach would be to medically or surgically reduce the contraction. Care should be taken into making a decision on treatment as cutting or paralyzing the muscle may lead to other problems such as hypersensitivity to noise and hearing loss.
