Identification of neonatal hearing impairment: hearing status at 8 to 12 months corrected age using a visual reinforcement audiometry protocol.

OBJECTIVES: 1) To describe the hearing status of the at-risk infants in the National Institutes of Health-Identification of Neonatal Hearing Impairment study sample at 8 to 12 mo corrected age (chronologic age adjusted for prematurity). 2) To describe the visual reinforcement audiometry (VRA) protocol that was used to obtain monaural behavioral data for the sample. DESIGN: All neonatal intensive care unit infants and well babies with risk factors (including well babies who failed neonatal tests) were targeted for follow-up behavioral evaluation once they had reached 8 mo corrected age. Three thousand one hundred and thirty-four (64.4%) of the 4868 surviving infants returned for at least one behavioral hearing evaluation, which employed a well-defined VRA protocol. VRA thresholds or minimum response levels (MRLs) were determined for speech and pure tones of 1.0, 2.0, and 4.0 kHz for each ear using insert earphones. RESULTS: More than 95% of the infants were reliably tested with the VRA protocol; 90% provided complete tests (four MRLs for both ears). Ninety-four percent of the at-risk infants were found to have normal hearing sensitivity (MRLs of 20 dB HL) at 1.0, 2.0, and 4.0 kHz in both ears. Of the infants, 2.2% had bilateral hearing impairment, and 3.4% had impairment in one ear only. More than 80% of the impaired ears had losses of mild-to-moderate degree. CONCLUSIONS: This may be the largest study to attempt to follow all at-risk infants with behavioral audiometric testing, regardless of screening outcome, in an effort to validate the results of auditory brain stem response, distortion product otoacoustic emission, and transient evoked otoacoustic emission testing in the newborn period. It is one of only a few studies to report hearing status of infants at 1 yr of age, using VRA on a clinical population. Successful testing of more than 95% of the infants who returned for the VRA follow-up documents the feasibility of obtaining monaural behavioral data in this population.

Tympanometric gradient measured from normal preschool children.

Tympanometric gradient is a quantitative expression of the shape of a tympanogram in the vicinity of the peak. Previous work suggests that gradient measures may be diagnostically and prognostically useful in the assessment and management of middle ear disease. However, since almost all previous work on the subject was performed on tympanograms recorded in 'arbitrary compliance units' which are not comparable to the physical admittance units provided by currently available instrumentation, at this point the tympanometric gradient can only be viewed to be a potentially-useful clinical measure. In this investigation, eight tympanometric gradient measures were calculated from tympanograms obtained from normal preschool age children. The measures were evaluated on the basis of distribution characteristics, relation to static admittance, and effect of pump speed. One of the measures--the pressure interval defined by a 50% reduction in peak eardrum admittance--appears to be the procedure of choice. Measurements obtained from abnormal ears are needed to evaluate the clinical utility of this measurement.

Recognition masking-level differences for 10 CID W-1 spondaic words.

Psychometric functions for the S omicron N omicron and S pi N omicron conditions and masking level differences were obtained for a subgroup of 10 words having the largest masking-level differences of 36 CID W-1 spondaic words. The mean masking-level difference obtained from 36 young normal adults was 9.4 dB with a standard deviation of 1.2 dB. The smallest masking-level difference of 7.4 dB was suggested as the low cut-off for normalcy. A shorter version of the masking-level difference procedure was suggested for clinical implementation. The subgroup of 10 words may permit a wider separation between normal and abnormal performance, and thus may enhance the clinical utility of the masking-level difference task for speech recognition. Because the magnitude of the masking-level difference will vary with the materials and procedures used, each clinic must establish its own norms.