Desenvolvimento auditivo na infância: protocolos padronizados e análise da Espectroscopia Funcional no Infravermelho Próximo (fNIRS)

Abstract

Introduction: Proper development of speech and language in childhood depends on the child’s ability to perceive and process auditory stimuli. Therefore, the assessment of auditory development is essential and must consider each child’s characteristics and specific factors, including the use of a cochlear implant (CI). Techniques such as Functional Near-Infrared Spectroscopy (fNIRS) have gained relevance for enabling the analysis of cortical activation in response to auditory stimuli, offering valuable insights into auditory maturation. Objectives: To characterize auditory development assessment methods in children based on standardized protocols and cortical responses measured by fNIRS; to identify commonly used auditory perception evaluation methods in young children with CIs; and to develop and test a protocol based on fNIRS to assess cortical auditory responses in children under five years of age. Methods: The study consisted of two parts: (i) a scoping review conducted according to PRISMA-ScR guidelines and registered on the OSF platform, with literature searches performed in the following databases: MEDLINE via PubMed, LILACS via BVS, Web of Science, SciELO, Scopus, and CINAHL via EBSCOHost; and (ii) a descriptive cross-sectional study involving 19 normal-hearing children aged between 12 and 54 months. Data collection included audiological assessment, application of the LittlEARs® Auditory Questionnaire, and registration of cortical auditory responses using fNIRS. Data were analyzed using MATLAB and HOMER2, focusing on oxyhemoglobin (HbO) and deoxyhemoglobin (HbR) concentrations. Results: Two independent articles were developed: "Methods for Assessing Auditory Development in Children with Cochlear Implants: A Scoping Review" and "Cortical Responses in Children to Different Auditory Stimuli: An Analysis Using Functional Near-Infrared Spectroscopy (fNIRS)." In the first (i), 2,098 studies were identified, and 58 were included after eligibility screening. Despite variability in the choice of assessment batteries—often selected at the discretion of professionals—the following tools stood out as well-established in the literature: the Meaningful Auditory Integration Scale/Infant-Toddler Meaningful Auditory Integration Scale (MAIS/IT-MAIS), Categories of Auditory Performance (CAP), Speech Intelligibility Rating Scale (SIR), Meaningful Use of Speech Scale (MUSS), and LittlEARs® Auditory Questionnaire (LEAQ). Behavioral tests such as the Early Speech Perception (ESP), Listening in Progress (LiP), and Glendonald Auditory Screening Procedure (GASP) were among the most used. Regarding objective tests, free-field audiometry remains the gold standard, while tests such as the Cortical Auditory Evoked Potential (CAEP) and Mismatch Negative (MMN) are gaining prominence. fNIRS emerges as a viable and complementary approach. In the second article (ii), an auditory stimulus protocol (pure tone, International Speech Test Signal – ISTS, and children's story reading) was developed for fNIRS data collection. It proved feasible, as it captured cerebral hemodynamic responses to auditory stimuli, showing differentiated neural activation patterns for each type of signal. The pure tone elicited more diffuse cortical activation, with changes in oxygenation observed in the temporal, parietal, occipital, and frontal regions. Both the ISTS and story reading showed bilateral activation in the temporal regions, a typical pattern in response to speech. Although there was variability in cortical region activation patterns among normal-hearing children in both HbO and HbR responses, group-level results concentrated in the medial and posterior temporal regions. Conclusion: Scientific literature highlights the importance of standardized tools – both objective and behavioral – for assessing auditory development in early childhood. The inclusion of fNIRS in this process represents progress in understanding brain functionality in response to auditory stimuli. However, it is crucial to establish clear assessment parameters in normal-hearing children before applying them to children with hearing loss.