The Contribution of Speech-Evoked Cortical Auditory Evoked Potentials to the Diagnosis and Measurement of Intervention Outcomes in Children with Auditory Processing Disorder

Abstract

Cortical auditory evoked potentials (CAEPs) are included in guidelines for assessment of auditory processing disorder (APD), but their diagnostic value and their use as a measure of treatment effectiveness have not been fully explored. The current study has three main aims: (1) to assess if there are differences in CAEPs recorded in quiet and in noise in children with APD compared to a control group of typically developing (TD) children, (2) to investigate the test-retest reliability of CAEPs, and (3) to determine whether participation in discrimination or language with or without support of personal frequency modulation (FM) resulted in significant changes in auditory function as measured by CAEPs. Fifty-five children with APD and 22 TD children age 7 to 13 years participated. There were group differences between TD children and children with APD for CAEP P1 and N250 amplitudes. CAEPs assessed on two occasions (separated by 7 to 10 days) showed a significant reduction in N250 amplitude on the second visit, highlighting the importance of establishing a stable baseline for CAEPs to more clearly delineate the effects of training from other factors influencing measurements. Participants with APD were randomly assigned to five treatment groups, including a no training group, two groups receiving discrimination training (one of these also used personal FM), and two groups receiving language training (one of these also used personal FM). N250 amplitudes changed during the baseline period, in the absence of any specific training, and hence a control group alone is insufficient for establishing intervention effectiveness; establishing a stable pretraining baseline for electrophysiological (and other) outcome measurements is also important. After 6 weeks training, children with APD in the discrimination treatment group showed a further significant change in N250 amplitudes, beyond the change that occurred during the baseline period. These results are limited by the small numbers of participants in each treatment group; however, the finding of some CAEP changes after training is consistent with published evidence for cortical changes after short-term auditory training.