Analysis of the Thresholds of FSABR Electrophysiological Stimulation Air and Bone in Infants from 2 to 6 Months of Age

Introduction: The electrophysiological evaluation is important in the identification and quantification of hearing loss before 6 months of life in the infant. An important electrophysiological evaluation is the frequency-specific auditory brainstem responses (FSABR) to confirm the hearing thresholds, so that hearing disorders are detected early, with greater precision the site of injury, and providing better prognosis.

Objectives: This study aims to describe electrophysiological thresholds by air and bone stimulation in full-term infants with normal hearing.

Methods: The evoked otoacoustic emissions and immittance measurements were carried out. Then, FSABR was carried out by air and bone conduction at frequencies between 500 Hz and 4,000 Hz. How electrophysiological threshold was considered the lowest intensity at which wave V was identified and replicated by the examiner.

Results: The sample comprised 35 full-term infants, of both genders, aged between 2 and 6 months. All had normal otoacoustic emissions type A tympanometry curve and presented acoustic reflexes in both the ears. In the study FSABR, comparing air and bone conduction, it was observed that the results of bone conduction are higher. In the frequency of 500 Hz, older infants showed lower values in both the pathways, air and bone; however, at 4 kHz there was no association with age.

Conclusion: The latency times obtained by bone conduction decrease with increasing age of the infant at 0.5 Hz. The FSABR by bone conduction is a reliable test that aids in the diagnosis and prognosis of hearing impairment.

Keywords: Evoked potential hearing, infants, bone, hearing tests, hearing loss.