Influence of pure tones audiometric threshold on EABR latency

2-way ANOVAs (audiogram type / duration of deafness) were conducted to study whether the auditory loss for tones before implantation, as revealed by an audiogram, had an influence on EABR latency. The audiometric and deafness duration groups presented in Table I were used. There were significant differences for wave IIIe (F = 6.4, df = 1, p = 0.013) and wave Ve (F = 3.5, df = 1, p = 0.004) but not for interval IIIe-Ve (F = 0.1, df = 1, p = NS). Figure 9 displays latencies of wave IIIe (9a), wave Ve (9b), and interval IIIe-Ve (9c) with respect to audiometric threshold groups. Analysis of variance for the type of audiogram and duration of deafness showed significant interactions for wave IIIe (F = 28.9, df = 1, p < 0.001), wave Ve (F = 12.0, df = 1, p < 0.001), and interval IIIe-Ve (F = 9.1, df = 1, p = 0.003). Post hoc comparisons (Student-Newman-Keuls test) were significant for audiometric groups of subjects with more than seven years of deafness for wave IIIe (p < 0.005), wave Ve (p < 0.001) and interval IIIe-Ve (p < 0.001). ANOVAs’ normality tests passed for analysis about wave IIIe (p = 0.068), wave Ve (p > 0.05) and interval IIIe-Ve (p > 0.05), while the equal variance test failed for wave IIIe (p = 0.004) and wave Ve (p = 0.01) and passed for interval IIIe-Ve (p > 0.05).

Figure 9. Mean latencies of EABR waves IIIe (a), Ve (b), and interval IIIe-Ve (c) averaged across all subjects and electrode sites according to two groups defined according to the level of auditory loss before implantation. Group 1: subjects had hearing loss less than 100 dB HL for 500, 1000, 2000, and 4000 Hz tones; group 2: subjects had hearing loss above 100 dB HL for 500, 1000, 2000, and 4000 Hz tones. Vertical bars show the standard error around each mean. * represents significant differences among groups of electrodes (p < 0.05).