The recovery from AP adaptation in sensorineural hearing loss.

CONCLUSIONS: 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. OBJECTIVE: This study aimed to detect the AP recovery pattern in SNHL. METHODS: 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. RESULTS: 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.

Electrocochleographic findings in recurrent idiopathic sudden sensorineural hearing loss.

CONCLUSION: The main differences in electrocochleography (ECochG) between recurrent and nonrecurrent idiopathic sudden sensorineural hearing loss (iSSNHL) were the high prevalence of an abnormally increased action potential (AP) recovery (iR) in nonrecurrent iSSNHL and the very low prevalence of iR in recurrent iSSNHL. An enhanced SP/AP ratio, low AP threshold, low initial hearing level, and up-sloping type of audiogram appear to be favorable prognostic factors in recurrent iSSNHL. OBJECTIVES: This study aimed to characterize differences in ECochG findings and other confounding prognostic factors between recurrent and nonrecurrent iSSNHL and to estimate how these findings are related to hearing outcome in recurrent iSSNHL. METHODS: ECochG was performed transtympanically in 23 and 42 ears with recurrent and nonrecurrent iSSNHL, respectively. AP recovery was measured using a paired-click stimulation paradigm. Differences in ECochG findings associated with confounding prognostic factors between recurrent and nonrecurrent iSSNHL, and between three outcome groups were assessed. RESULTS: iR was significantly more common in nonrecurrent iSSNHL (16 ears) than in recurrent iSSNHL (1 ear). In the outcome of recurrent iSSNHL, the prevalence rates of an enhanced summating potential (SP)/AP ratio, lower AP threshold, lower initial hearing level, and up-sloping type of audiogram were significantly higher in the cure group than in the improvement and no-recovery outcome groups.

Prognostic evaluation of electrocochleography in idiopathic sudden sensorineural hearing loss.

CONCLUSION: Abnormal action potential (AP) recovery from adaptation was manifested as increased recovery (iR) or decreased recovery (dR) relative to the normal recovery range. dR was not analyzed statistically due to the very small number of cases. iR is considered an unfavorable prognostic indicator, whereas a normal AP recovery (nR), enhanced SP/AP ratio (≥0.35), and lower AP threshold are favorable prognostic indicators for idiopathic sudden sensorineural hearing loss (iSSNHL). OBJECTIVES: This study aimed to determine the prognostic efficacy of AP recovery examinations associated with other electrocochleography (ECochG) findings in iSSNHL. METHODS: ECochG was performed transtympanically in 58 iSSNHL ears. AP recovery was measured by a paired-click stimulation paradigm, and hearing outcome was classified into three groups. Additionally, the relationships of other confounding prognostic factors to hearing outcomes were assessed. RESULTS: iR was significantly more common in the no-recovery group, while nR and an enhanced SP/AP ratio were significantly more common in the cure and improvement groups. The AP threshold was significantly lower in the cure group than in the other two groups. The other confounding prognostic factors generally showed similar trends to those reported previously.