Pre- and postovulatory auditory brainstem response in normal women

Studies with ovarian hormones on auditory brainstem response (ABR) have conflicting reports although women have ABR shorter than men. This study compared ABR between pre- and postovulatory phases of menstrual cycle in consenting 40 healthy female volunteers (age 19 ± 2.35 years). The study was conducted under standard laboratory conditions (room temperature 26 ± 2°C) using Neuropack (Nihon Kohden machine, NM-420S; H636, Japan) and earphone dynamic receiver ELEGA (Type DR-531; no.237, Japan) in sound proof room. Ears were stimulated simultaneously using standard protocol. ABR was recorded in pre- and postovulatory phases. Ovulation was estimated by measuring basal body temperature. The ABR wave latencies (WLs) I, II, III, IV, V and inter-peak latencies (IPLs) I-III, III-V, I-V were compared between the two phases of menstrual cycle using paired t test. The postovulatory phase had shorter WL V (5.71 ± 0.18 ms vs. 5.81 ± 0.19 ms, p < 0.01), IPL III-V (1.89 ± 0.16 ms vs. 1.94 ± 0.19 ms, p < 0.05), and I-V (3.88 ± 0.16 ms vs. 3.95 ± 0.18 ms, p < 0.05) than in preovulatory. Other WLs and IPLs showed decreasing trend in postovulatory phase. ABR is better in postovulatory phase as compared to preovulatory phase probably due to progesterone hormone which might be involved in modulating auditory hearing pathway at postovulatory phase.