© J Hear Sci, 2017; 7(3): 9–25 DOI: 10.17430/904674 MIDDLE EAR MUSCLE DYSFUNCTION AS THE CAUSE OF MENIERE’S DISEASE ADEF Contributions: Andrew Bell A Study design/planning B Data collection/entry C Data analysis/statistics John Curtin School of Medical Research, Australian National University, Canberra, D Data interpretation E Preparation of manuscript Australia F Literature analysis/search G Funds collection Corresponding author: Andrew Bell, JCSMR, 131 Garran Road, Australian National University, Canberra, ACT 2601, Australia, e-mail:
[email protected] Abstract The symptoms of Meniere’s disease form a distinct cluster: bouts of vertigo, fluctuating hearing loss, low-frequency tinnitus, and a feeling of pressure in the ear. Traditionally, these signature symptoms have pointed to some sort of pathology within the inner ear itself, but here the focus is shifted to the middle ear muscles. These muscles, the tensor tympani and the stapedius, have generally been seen as serving only a secondary protective role in hearing, but in this paper they are identified as vigilant gate-keepers – constantly monitoring acoustic input and dynamically adjusting hearing sensitivity so as to enhance external sounds and suppress internally generated ones. The case is made that this split-second adjustment is accomplished by regulation of inner ear pressure: when the middle ear muscles contract they push the stapes into the oval window and increase the pressure of fluids inside the otic capsule. In turn, hydraulic pressure squeezes hair cells, instantly adjusting their sensitivity. If the middle ear muscles should malfunction – such as from cramp, spasm, or dystonia – the resulting abnormal pressure will disrupt hair cells and produce Meniere’s symptoms.