The N3 potential and the efferent cochlear pathway in profound sensorineural hearing loss.

OBJECTIVE: This study aimed to evaluate the presence of the N3 potential (acoustically evoked short latency negative response) in profound sensorineural hearing loss, its association with the cervical vestibular evoked myogenic potential and the relationship between both potentials and loss of auditory function. METHODS: Otological examinations of 66 ears from 50 patients aged from 4 to 36 years were performed, and the vestibular evoked myogenic potential and auditory brainstem response were measured. RESULTS: The N3 potential was recorded in 36 out of 66 ears (55 per cent) and a vestibular evoked myogenic potential was recorded in 34 (52 per cent). The N3 potential was recorded in 23 out of 34 ears (68 per cent) with a vestibular evoked myogenic potential response and absent in 19 out of 32 ears (59 per cent) without a vestibular evoked myogenic potential response. The presence of an N3 potential was significantly associated with a vestibular evoked myogenic potential response (p = 0.028), but there was no significant difference in the latency or amplitude of the N3 potential in either the presence or absence of a vestibular evoked myogenic potential. CONCLUSION: The presence of an N3 potential in profound sensorineural hearing loss with good or poor vestibular function can be explained by the contribution of the efferent cochlear pathway through olivocochlear fibres that join the inferior vestibular nerve. This theory is supported by its early latency and reversed polarity, which is masked in normal hearing by auditory brainstem response waves.

Hepatitis B virus infection in upper and lower Egypt.

The relative prevalence of hepatitis B surface antigen (HBsAg), anti-HBs, and anti-hepatitis B virus core antigen (HBc), as markers of hepatitis B virus infection, among 1,866 apparently healthy residents of two Egyptian provinces representing Upper and Lower Egypt populations was determined using solid-phase radioimmunoassay (SPRIA). The prevalence rate of HBsAg in the Egyptian population was moderately high (10.1%); it was higher in the Upper Egypt (11.7%) than the Lower Egypt (8.0%) population and more frequent in young adults--especially those of Upper Egypt--and males than females in both populations. The prevalence of anti-HBs gradually increased with age; it was higher in the Lower Egypt (51.1%) than the Upper Egypt (41.7%) population, and it was higher in females than males. A remarkably high infection rate, as shown by the prevalence of anti-HBc, was found in both populations (88.0%), with minor variations depending on age, sex, and geographic area.