Brain stem auditory evoked potentials: Effects of ovarian steroids correlated with increased incidence of Bell's palsy in pregnancy

Abstract

To investigate the effect of ovarian steroids on the brain stem during changes of estrogen and progesterone blood levels, we recorded brain stem auditory evoked potentials with increased stimulus rates from 26 women treated for sterility by menotropins (Pergonal and Metrodin). These women were divided into three groups according to their estrogen and progesterone blood levels. The brain stem auditory evoked potential results revealed a significant delay of peak III only, with an increased stimulus rate in the group with the highest estrogen level. Estrogen may cause a brain stem synaptic impairment, presumably because of ischemic changes, and thus also may be responsible for a higher incidence of Bell's palsy during pregnancy.

Pre- and Postovulatory Auditory Brainstem Response in Normal Women

“…It has also been hypothesized that estrogen is responsible for electrolyte imbalance and thereby disturbing the inner ear function [30]. Moreover, it is believed to be responsible for brainstem synaptic impairment, presumably by producing ischemic changes [5] that may influence cochlear blood flow and potentially hearing functions [23]. The decreased latency in the postovulatory phase ABR in the present study might be due to the effects of progesterone on hearing pathway.…”

“…High estrogen level, small brain size and shorter auditory pathway [3,4] in female seems to be responsible for better hearing in female than in male as suggested by the findings of most of the studies. Others suggest that higher estrogen level delays in peak III appearance, due to brainstem synaptic impairment (via ischemic changes), resulting in a higher incidence of Bell's palsy during pregnancy [5].…”

“…Wide variation is observed in different parameters of ABR at different phases of menstrual cycle. There is increase in wave latencies (WLs) of all waves in midcycle and decrease in latencies in midluteal phase with the smallest latencies occurring during menstruation, Interpeak latencies (IPLs) and amplitude follow the same trend [4][5][6][7][8][9]. Estrogen has been suggested to be responsible for delaying the conduction by influencing GABA release at the level of polysensory association areas of brain [6].…”

Sudden (reversible) sensorineural hearing loss in pregnancy

“…The second explanation would be due to hormonal changes affecting level of oedema [3][4][5][6]. Finally another explanation could be of a vascular interruption [7]; this could be due to physical changes within the body during pregnancy and birth. Each of these three explanations will be examined in turn.…”

“…Raised perilymphatic pressure [14] is often associated with variation in the hormone levels of women with menstrual irregularities, pregnancy and the menopause and the presumed patency of the cochlear aqueduct. Some authors also attribute neurological impairments during pregnancy, such as cranial nerve palsy/ facial paralysis, to electrolyte balance and hormone fluctuations [4,6,7,15].…”