The recovery from AP adaptation in sensorineural hearing loss

An abnormally slower action potential (AP) recovery from adaptation (decreased recovery, dR) was characteristically detected in many ears with sensorineural hearing loss (SNHL) but not Meniere's disease and idiopathic sudden SNHL. We assumed that this abnormal AP recovery from adaptation was attributed to an imbalance in the distributions of auditory neurons with high and low spontaneous firing rates. The significant difference of initial hearing level between dR and normal AP recovery groups (nR) was assumed to partially result from AP recovery being determined by the inner hair cell synapse, and not from outer hair cells.

This study aimed to detect the AP recovery pattern in SNHL.

Electrocochleography (ECochG) was performed transtympanically in 30 patients with SNHL. AP recovery was measured by a paired click stimulation paradigm as a function of inter-click intervals from 5 to 100 ms.

The high prevalence of dR (9 of 30 ears) appears to be a characteristic ECochG finding in SNHL. Initial hearing level differed significantly between dR and nR groups.