[Objective auditory evaluation by evoked potentials]

We have analyzed 1300 Auditory Brain-Stem Response Audiometry exams. The patients were distributed according to criteria related to age, clinical presentation, hearing impairment risk-factors and hearing thresholds. The results were divided into five groups of hearing thresholds: normal hearing (threshold response obtained up to 25 dBHL); mild hearing loss (25-50 dBHL); moderate hearing loss (50-70 dBHL); severe hearing loss (70-90 dBHL); and without response to acoustic stimuli. We have studied the risk-factors related to gestation, delivery and neonatal period, family history of hearing loss, hearing apparatus malformations, craniofacial anomalies, certain modalities of infectious diseases, hearing impairment associated syndromes, and the use of some kind of drugs. Cerebral palsy, neuropsychomotor development retardation and cases without known antecedents were also studied. The main results of our study show: 82.8% incidence of hearing impairment; the late performance of examinations to evidence a definite hearing loss as 54.1% of the examined patients were at ages ranging from one to three years old; 54.0% of total cases have not presented any language development; the risk-factor "Congenital Rubeola" has the expressive incidence of 14.8% and the distribution of this value into hearing threshold ranges has shown an exponential increase which demonstrates a close correlation between that disease and hearing impairment.