Assessment of Children by Speech ABR

Hearing loss in children can result in cognitive deficits in the central areas which are dependent upon hearing, therefore responsible for delay in speech development, poor language skills and disorders in psychological and mental behavior. It will also cause a decrease of the intellectual ability and socio-economic position of the child.

In children aged 3.5 years and older, pure tone audiometry is performed to determine the exact frequency-specific hearing threshold.

To obtain the auditory threshold in younger children, Skoe and Kraus reported that the auditory brainstem response has proven to be a clinically useful tool for assessing neural function at the brainstem level and is most commonly elicited by clicks or tone-bursts.

However, recent research has established that complex stimuli can also elicit the response such as Music, complex tones, and speech stimuli . A speech stimulus is particularly useful, as it can provide clues as to how temporal and spectral features are preserved in the brainstem.

The human soundscape is characterized by complex sounds with rich harmonic structure, dynamic amplitude modulations and rapid spectro-temporal fluctuations. This complexity is represented by temporal and spectral neural code within the auditory brainstem, two broad classes of time-locked responses can be defined namely transient and sustained responses .

Although complex sounds consist of both sustained and transient features, the response to a complex sound is not necessarily predictable from the response to click auditory brainstem response . For these reason, further studies had gradually transitioned to using sounds as stimuli as they are more complex .

The click auditory brainstem response is a clinical tool to assess the neural functionality of the auditory brainstem. The use of verbal stimuli in auditory brainstem response protocols has provided important information of how the speech stimuli are processed by the brainstem structure .

The perception of speech sounds seems to begin in the brainstem, which has an important role in the reading process and the phonological acquisition . Speech auditory brainstem response assessment allows the identification of fine-grained auditory processing deficits associated with real world communication which do not appear in click evoked auditory brainstem response .

The verbal stimulus most widely used in speech auditory brainstem response is a syllable composed of a consonant and a vowel , usually the syllables da. The verbal assessment provides information about how the speech syllable is encoded by auditory system. The trace of the speech auditory brainstem response can be identified in two parts:

The onset and the frequency following response . The first part represents the consonant and the second part represents the vowel .

So speech auditory brainstem response can be used as an objective measure of the hearing function, one of the great advantages of this method is that it is not influenced by environmental issues, which can disrupt the behavioral assessments . Even the best behavioral tests can be affected by multiple factors such as attention, motivation and alertness or fatigue .

Moreover, altered responses of speech auditory brainstem response may be associated with impaired speech perception specially in noise. These changes can cause a negative impact on communication and serious consequences for academic success in children. complex auditory brainstem response can also help to identify those individuals who are most likely to benefit from auditory training .