Cortical Auditory Event-Related Potentials and Categorical Perception of Voice Onset Time in Children With an Auditory Neuropathy Spectrum Disorder

A systematic review of acoustic change complex (ACC) measurements and applicability in children for the assessment of the neural capacity for sound and speech discrimination

OBJECTIVE

The acoustic change complex (ACC) is a cortical auditory evoked potential (CAEP) and can be elicited by a change in an otherwise continuous sound. The ACC has been highlighted as a promising tool in the assessment of sound and speech discrimination capacity, and particularly for difficult-to-test populations such as infants with hearing loss, due to the objective nature of ACC measurements. Indeed, there is a pressing need to develop further means to accurately and thoroughly establish the hearing status of children with hearing loss, to help guide hearing interventions in a timely manner. Despite the potential of the ACC method, ACC measurements remain relatively rare in a standard clinical settings. The objective of this study was to perform an up-to-date systematic review on ACC measurements in children, to provide greater clarity and consensus on the possible methodologies, applications, and performance of this technique, and to facilitate its uptake in relevant clinical settings.

DESIGN

Original peer-reviewed articles conducting ACC measurements in children (< 18 years). Data were extracted and summarised for: (1) participant characteristics; (2) ACC methods and auditory stimuli; (3) information related to the performance of the ACC technique; (4) ACC measurement outcomes, advantages, and challenges. The systematic review was conducted using PRISMA guidelines for reporting and the methodological quality of included articles was assessed.

RESULTS

A total of 28 studies were identified (9 infant studies). Review results show that ACC responses can be measured in infants (from < 3 months), and there is evidence of age-dependency, including increased robustness of the ACC response with increasing childhood age. Clinical applications include the measurement of the neural capacity for speech and non-speech sound discrimination in children with hearing loss, auditory neuropathy spectrum disorder (ANSD) and central auditory processing disorder (CAPD). Additionally, ACCs can be recorded in children with hearing aids, auditory brainstem implants, and cochlear implants, and ACC results may guide hearing intervention/rehabilitation strategies. The review identified that the time taken to perform ACC measurements was often lengthy; the development of more efficient ACC test procedures for children would be beneficial. Comparisons between objective ACC measurements and behavioural measures of sound discrimination showed significant correlations for some, but not all, included studies.

CONCLUSIONS

ACC measurements of the neural capacity to discriminate between speech and non-speech sounds are feasible in infants and children, and a wide range of possible clinical applications exist, although more time-efficient procedures would be advantageous for clinical uptake. A consideration of age and maturational effects is recommended, and further research is required to investigate the relationship between objective ACC measures and behavioural measures of sound and speech perception for effective clinical implementation.

Reconsidering commonly used stimuli in speech perception experiments

This paper examines some commonly used stimuli in speech perception experiments and raises questions about their use, or about the interpretations of previous results. The takeaway messages are: 1) the Hillenbrand vowels represent a particular dialect rather than a gold standard, and English vowels contain spectral dynamics that have been largely underappreciated, 2) the /ɑ/ context is very common but not clearly superior as a context for testing consonant perception, 3) /ɑ/ is particularly problematic when testing voice-onset-time perception because it introduces strong confounds in the formant transitions, 4) /dɑ/ is grossly overrepresented in neurophysiological studies and yet is insufficient as a generalized proxy for "speech perception," and 5) digit tests and matrix sentences including the coordinate response measure are systematically insensitive to important patterns in speech perception. Each of these stimulus sets and concepts is described with careful attention to their unique value and also cases where they might be misunderstood or over-interpreted.

[Auditory neuropathy and prematurity: modern view of the issue (literature review)]

Auditory neuropathy spectrum disorder (ANSD) is a specific auditory disorder caused by dysfunction of periphery part of the auditory system, in which the function of the outer hair cells is preserved, but the afferent input at the cochlear level suffers due to the pathology of the inner hair cells, neurons of the spiral ganglion and/or the auditory nerve, as well as synaptic contact between them. As a result, a specific condition is formed, in which a patient's otoacoustic emissions and/or cochlear microphonics are present, auditory brainstem responses are abnormal or absent, the discrepancy between the hearing level and the electrophysiological data, poor speech perception which may not correlate with the hearing thresholds. ANSD is a multifactorial disease. One of the main risk factors is perinatal pathology and, in particular, prematurity. The possible factors associated with prematurity that provoke the onset of the disease, features of the pathogenesis, clinical and audiological peculiarities of ANSD in premature infants, contemporary approaches to the habilitation of such patients are discussed in the article. The necessity of an individual, patient-oriented approach to the treatment of premature infants with ANSD is substantiated; such an approach should be based both on the genesis of the disorder, taking into account possible points of lesion in the auditory system, and the developmental peculiarities of a premature baby considering the presence of concomitant diseases associated with prematurity. In the article attention is focused on the main directions of habilitation work with such children, including a multidisciplinary approach, regular careful monitoring of the auditory, speech and language skills, intensive psychological and speech therapist support, the choice of an adequate way of intervention and its improvement as necessary.

Cortical Auditory Plasticity Following Cochlear Implantation in Children With Auditory Neuropathy Spectrum Disorder: A Prospective Study

OBJECTIVES

The cortical auditory evoked potential (CAEP) can provide an insight into the maturation of the central auditory nervous system by recording the auditory cortex responses to speech stimuli. This study aimed to explore the central auditory system development in children with auditory neuropathy spectrum disorder (ANSD) using cochlear implants (CIs) and to find the correlation of CAEP biomarkers with speech perception.

METHODS

This study was performed on 23 children with prelingual deafness, diagnosed with ANSD, as well as 23 children with prelingual deafness, without ANSD as the control group. All children underwent unilateral CI before the age of 3 years. Children with ANSD were classified into two groups, based on their CAEP results prior to implantation: children with a clear CAEP response (ANSD-I) and children without an identifiable CAEP (ANSD-II). The P1 component of CAEPs and speech intelligibility rating (SIR) were recorded before the initial device activation (baseline) and at 6, 12, and 24 months postimplantation.

RESULTS

The P1 CAEP responses were present in all children in the control group, while they were recorded in only 52% of ANSD children before the CI surgery. The longitudinal analysis revealed a significant reduction in the P1 latency and a significant improvement in the P1 amplitude across different time points in all study groups. However, the P1 latency and P1 amplitude were significantly shorter and larger in the control group than the ANSD group, respectively. Also, children in the ANSD-I group exhibited a slightly shorter P1 latency, a larger P1 amplitude, and a higher SIR score than the ANSD-II group after 2 years of follow-up. The P1 CAEP latency was significantly correlated with the SIR score.

CONCLUSION

The CAEP can be used as an objective indicator of auditory cortical maturation and a predictor of speech perception performance in implanted children with ANSD.