Influence of pure tone audiometric threshold on ELAR latency

A series of 2-way ANOVAs (audiogram type / duration of deafness) was conducted to study whether the pure tone audiometry (PTA) loss before implantation, as revealed by an audiogram, had an influence on ELAR latency. This analysis also allows investigation of whether the potential effect of the degree of auditory loss is linked to the duration of deafness. There were significant differences for N1 (F = 6.9, df = 1, p = 0.011) and almost for P2 (F = 3.8, df = 1, p = 0.056) but not for interval N1-P2 (F = 0.6, df = 1, p = NS). Figure 7 displays latencies of N1 (a), P2 (b), and interval N1-P2 (c) with respect to audiometric threshold groups. Analysis of variance for the type of audiogram and duration of deafness showed no significant interactions for neither N1 (F = 3.1, df = 1, p = 0.083), P2 (F = 2.3, df = 1, p = 0.14), nor interval N1-P2 (F = 0.2, df = 1, p = 0.68). ANOVAs’ normality tests passed for analysis of N1 (p = 0.1), and interval N1-P2 (p > 0.06) and failed for P2 (p = 0.001), while the equal variance test passed for P2 (p > 0.05) and interval N1-P2 (p = 0.07) but failed for N1 (p = 0.008).

Figure 7. Mean latencies of ELAR waves N1 (a), P2 (b), and interval N1-P2 (c) averaged across all subjects and electrode sites as a function of two groups defined according to the level of auditory loss before implantation. Group A1: subjects had hearing loss less than 100 dB HL for 500, 1000, 2000, and 4000 Hz tones; group A2: subjects had hearing loss above 100 dB HL for the same frequencies. Vertical bars show the standard error around each mean. * represents significant differences among groups of electrodes (p < 0.05).
Figure 7. Mean latencies of ELAR waves N1 (a), P2 (b), and interval N1-P2 (c) averaged across all subjects and electrode sites as a function of two groups defined according to the level of auditory loss before implantation. Group A1: subjects had hearing loss less than 100 dB HL for 500, 1000, 2000, and 4000 Hz tones; group A2: subjects had hearing loss above 100 dB HL for the same frequencies. Vertical bars show the standard error around each mean. * represents significant differences among groups of electrodes (p < 0.05).