Effects of Residual Hearing on the Auditory Steady State Response for Cochlear Implantation in Children

BACKGROUND AND OBJECTIVES: We aim to explore the effects of residual auditory steady state response (ASSR) on cochlear implantation (CI) outcomes in children lacking auditory brainstem responses (ABRs). SUBJECTS AND METHODS: We retrospectively reviewed the data of child CI recipients lacking ABRs. All ears were divided into two groups: with residual ASSR and without ASSR. For each frequency, the T- and C-levels and the electrical dynamic ranges of postoperative 3-month and 1-year mappings were compared between the groups. To evaluate speech perception, patients who received simultaneous bilateral CIs were divided into two groups: group 1 exhibited responses at all frequencies in both ears; in group 2, at least one ear evidenced no response. The Categories of Auditory Perception (CAP) and Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS) scores were compared between the groups. RESULTS: We enrolled 16 patients. At 2 kHz, the postoperative 3-month and 1-year T-levels of patients with residual hearing were lower than those of hearing loss group (p=0.001, p=0.035). In residual hearing group, the ASSR threshold correlated positively with the postoperative 1-year T-level (p=0.012, R² =0.276) and C-level (p=0.002, R² =0.374). Of 10 simultaneous bilateral CI recipients, 5 exhibited ASSRs at all frequencies and the other 5 showed no response at ≥1 frequency. The latter had higher CAP scores at the postoperative 1-year (p=0.018). CONCLUSIONS: In children exhibiting hearing loss in ABR testing, residual hearing at 2 kHz ASSR correlated positively with the post-CI T-level. Those with ASSRs at all frequencies had significantly lower CAP scores at the postoperative 1year. CI should not be delayed when marginal residual hearing is evident in ASSR.

Auditory evoked potentials: predicting speech therapy outcomes in children with phonological disorders

OBJECTIVES: This study investigated whether neurophysiologic responses (auditory evoked potentials) differ between typically developed children and children with phonological disorders and whether these responses are modified in children with phonological disorders after speech therapy. METHODS: The participants included 24 typically developing children (Control Group, mean age: eight years and ten months) and 23 children clinically diagnosed with phonological disorders (Study Group, mean age: eight years and eleven months). Additionally, 12 study group children were enrolled in speech therapy (Study Group 1), and 11 were not enrolled in speech therapy (Study Group 2). The subjects were submitted to the following procedures: conventional audiological, auditory brainstem response, auditory middle-latency response, and P300 assessments. All participants presented with normal hearing thresholds. The study group 1 subjects were reassessed after 12 speech therapy sessions, and the study group 2 subjects were reassessed 3 months after the initial assessment. Electrophysiological results were compared between the groups. RESULTS: Latency differences were observed between the groups (the control and study groups) regarding the auditory brainstem response and the P300 tests. Additionally, the P300 responses improved in the study group 1 children after speech therapy. CONCLUSION: The findings suggest that children with phonological disorders have impaired auditory brainstem and cortical region pathways that may benefit from speech therapy. .

ACOUSTIC INJURY OF GUINEA PIGS CAUSED BY ~60Co?-RAY / 第二军医大学学报

The head of guinea pig was irradiated with 60Co?-ray and a single dose of irradiation was 90 Gy and 70 Gy in two groups, respectively.Two h after irradiation, the threshold shifts were 12.5 dB and 9 dB, and the auditory cortical evoked response (ACER) maximum post-irradiation amplitude exceeded the maximum prc-irradiation value by 20% and 37%.Six h later, the threshold shift increased to 37 dB and the maximum amplitude decreased to the level of pre-irradiation in the 70 Gy group.Right auditory bulla area was irradiated with a total dose of 45 Gy in a course of six fractions in two weeks.Fourteen d after irradiation, the threshold shift of auditory brainstem evoked response(ABR)was 11.8 dB.Hjstolo-gical observation using scanning electron microscope showed that only outer hair cells in the basal coil of the cochlea were destroyed 6 h after irradliation in the 90 Gy group.But outer hair cells in all coils of the cochlea were found to be destroyed 16 h after irradiation.In the 45 Gy group, 14 d after irradiation, outer hair cells in all coils of the cochlea were damaged and no inner hair cells were injured severely.

Effect of Noise on the Auditory Center / 第二军医大学学报

Adult guinea pigs with normal Preyer's reflexs were used in this experiment and were divided into three groups according to the intensity of noise and exposure time. Auditory brainstem evoked response was recorded before and after exposure to noise. Clicks were presented monaurally at a rate of high (50 Hz) as well as low (10 Hz). The superior olive and inferior colliculus were observed under the electron microscope after the guinea pigs were exposured to 110dB noise for 30 min. The average shift of wave Ⅳ amplitude-intensity function curve was more than that of wave I after exposure to intensive noise. The difference value of wave Ⅴ latency from low (10 Hz) to high (50 Hz) stimulus click rate decreased and was negatively co related with the exposure time. Ⅰ-Ⅴ, Ⅲ -Ⅴ and Ⅳ-Ⅴ interpeak latencies were shorter after exposure to noise. The mitochondria and neurilemma swelling were found in the superior olive and inferior colliculus after exposure. Some mechanisms of the changes of auditory center were discussed in this paper.