Acute cochlear disorders: the combination of hearing loss, recruitment, poor speech discrimination, and tinnitus

The combination of hearing loss, recruitment, poor speech discrimination and tinnitus, which is characteristic of acute cochlear disorders, can be accounted for on the basis of a decoupling of hair cells from their drive system, the tectorial membrane. Decoupling may either be caused by a temporary reduction of ciliary stiffness (shown to occur during periods of noise-induced temporary threshold shifts) or by temporary and/or chronic ciliary pathology (demonstrated to exist in cases of antibiotic ototoxicity and in endolymphatic hydrops). Since ciliary coupling is elastic in nature, the decoupling is only partial. The hearing loss and the tinnitus are manifestations of the reduced coupling per se, the magnitude of the loss depending on the degree of decoupling and the number of hair cells involved. Recruitment and poor speech discrimination result from center-clipping of the signal waveform applied to an involved hair cell, the direct corollary of partial, ciliary decoupling.