ABSTRACT
BACKGROUND AND OBJECTIVES: Electrically evoked middle latency response (EMLR) has several advantages over electrically evoked auditory brainstem response (EABR). The major component peaks of EMLR lie outside the region of stimulus artifacts and it reflects the activation of a more significant portion of the auditory pathway than EABR. It is known that several conditions alter the general morphology, amplitude, and latency of the waveforms of EMLR. The purpose of this study was to record and evaluate the effects of stimulation rate and pulse duration on detectability, latency and amplitude of EMLR in the cat. MATERIALS AND METHOD: EMLR was recorded in response to 9 experimental conditions-3 conditions of pulse duration (150, 200, 250 micron sec biphasic) at each of 3 conditions of stimulation rate (2, 6 and 10/sec)-after electrical stimulation at the round window in 7 cats. RESULTS: PA was identified in all conditions. PB was obtained from 17 of the 63 waves. The latency of PA was significantly shorter and the amplitude of PA was significantly larger for the stimulation rate of 10/sec and the pulse duraion of 250 micron sec compared with other conditions. CONCLUSION: We found that based on the present data, the optimal stimultion condition for EMLR in our laboratory was the stimulation rate of 10/sec and the pulse duration of 250 micron sec. This data can provide a basis for the appropriate stimulation condition of EMLR in human.
Subject(s)
Animals , Cats , Humans , Artifacts , Auditory Pathways , Cochlear Implantation , Electric Stimulation , Evoked Potentials, Auditory, Brain StemABSTRACT
BACKGROUND AND OBJECTIVES: Auditory neuropathy (AN) is a hearing disorder caused by desynchronous neural discharge of auditory nerve. The purpose of this study is to describe in detail various clinical manifestations of children with AN. SUBJECTS AND METHOD: The medical record of 18 children with AN were retrospectively reviewed. Demographic information, the findings of various examination including audiologic, radiologic, neurologic, and vestibular tests, and the outcomes of cochlear implantation were analyzed. RESULTS: There were 14 boys and 4 girls. The onset of hearing loss was ranged from birth to 2 years of age. Most children were diagnosed with bilateral AN based on positive otoacoustic emission (OAE) with absent ABR and they showed no changes in hearing thresholds. They had showed persistently preserved OAE and showed abnormal vestibular test results, and were not accompanied by peripheral neuropathy. In contrast, a small number of children had unilateral AN and had cochear microphonic instead of OAE. They showed changes in hearing threshold and showed disappearance of OAE, and were accompanied by peripheral neuropathy. Most children who received cochlear implants showed significant improvement in speech perception abilities. CONCLUSION: AN is a heterogeneous disorder that has some common characteristics in auditory function. Children with AN who are not benefited from appropriate auditory rehabilitation using a hearing aid can obtain significant improvement from cochlear implantation.
Subject(s)
Child , Female , Humans , Cochlear Implantation , Cochlear Implants , Cochlear Nerve , Evoked Potentials , Hearing , Hearing Aids , Hearing Disorders , Hearing Loss , Medical Records , Parturition , Peripheral Nervous System Diseases , Rehabilitation , Retrospective Studies , Speech PerceptionABSTRACT
No abstract available.