Central auditory nervous system problems may be isolated or associated with more pervasive processes and conditions which closely interact with other sensorimotor modalities as well as “top down” cognitive functions. 6Ĭentral auditory testing clinically evaluates the integrity of the CANS and provides a “bottom up” sensory cognitive approach to learning and behavioural problems as well as an index to neuropathological constellations. 5 The young brain has an inherent ability for plasticity: the forebrain sensory representations may change in response to altered receptors, sensory environment, or use and learning. 4 In children, myelination and maturation continue until 10–12 years of age. The CANS is characterised by an intrinsic “redundancy”-that is, an extensive interaction of its structures that is responsible for the resistance of the system to exhibit deficits on standard auditory testing in the presence of a lesion. 4 The cerebral hemispheres are connected by the corpus callosum. The cortical and subcortical auditory areas mainly consist of Heschl's gyrus, the planum temporale (extending from the posterior aspect of Heschl's gyrus to the end of the Sylvian fissure), and the Sylvian fissure with the insula. The superior olivary complex, lateral lemniscus and inferior colliculus, medial geniculate body, and reticular formation are important relay stations. The central auditory nervous system (CANS) extends from the cochlear nucleus in the brain stem to the auditory cortex. 3Īnatomy of the central auditory nervous system 2 Despite the frequency of the problem, a systematic approach to the diagnosis and rehabilitation of APD in children has only started emerging over the past 30 years, as a result of developments in basic sciences emphasis has shifted from identification of the lesion that causes the disorder to identification of the impaired individual's difficulties and their appropriate remediation. 1Ī rough prevalence estimate for auditory processing disorders (APD) in childhood is 7%. These auditory deficits have been collectively termed “auditory processing disorders”, in order to incorporate in the term the interaction between peripheral and central pathways. Hearing impairment(s) arising from pathology of the brain may have detrimental consequences on a child's life if untreated however, diagnostic and management strategies for these “central” hearing impairments in childhood are rarely implemented. Hearing is a complex process that orchestrates transduction of the acoustic stimulus into neural impulses by the ears, transmission of the neural impulses by the auditory nerves to the brain, and perceptual registration and cognitive elaboration of the acoustic signal by the brain as well as conscious perception of the sound.
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