![]() ĭespite of progress and availability of modern genetic tests and imaging technologies, the etiology of many cases of congenital or acquired ANSD is still unknown.ģ. ANSD might be also acquired letter in life as a result of late-onset genetic-based mechanisms or due to an autoimmune reaction. MRI testing reviled that the electrophysiological picture of congenital ANSD might be also due to the hypoplastic cochlear nerve (cochlear nerve deficiency). Genetic testing of patients with ANSD during the last two and half decades revealed more than 20 genes associated with that type of hearing loss. Also, risk factors for the development of ANSD include hyperbilirubinemia, congenital cytomegalovirus infection, asphyxia, and low birth weight. The mechanism of ANSD among these children is due to incomplete myelinization and affected inner hair cells, as it was demonstrated in postmortem histology -inner hair cells were affected much more than outer hair cells. ANSD risk is higher among children that were born at 32 or earlier gestational week. About half of the cases of ANSD in children are diagnosed in those who were born premature. Etiology of auditory neuropathy spectrum disorderĭespite of electrophysiological commonality of ANSD, there is a broad spectrum of audiological clinical features, which come from different possible pathophysiological mechanisms due to different etiology of ANSD. Elucidating the etiology and/or patophysiology of hearing loss mechanisms in these children might help to choose an optimal rehabilitation approach and predict rehabilitation outcomes. Therefore, ANSD is characterized by a different course and results of rehabilitation, which in many cases are difficult to predict. This electrophysiological picture might reflect the presence of pathology of the auditory system of various etiologies in any site in the auditory system from the inter hair cells (IHC) to the brain stem (including synapses, dendrites of spiral ganglion neurons, spiral ganglion neurons themselves, the auditory nerve). Electrically evoked brainstem potential testing after cochlear implantation seems to be applicable and useable tool to predict potential CI outcomes and to choose optimal rehabilitation trace.Īuditory neuropathy spectrum disorder (ANSD) is an electrophysiological label, that incorporates patients with hearing loss of different etiologies and pathogenesis but united based on the presence of pre-neural cochlear responses such as otoacoustic emission (OAE) and cochlear microphonics (CM) and absent or grossly abnormal auditory brain steam responses (ABRs). ![]() Electrophysiological methods (electrocochleography, electrically evoked brainstem potentials) might help to localize the site of lesion in hearing system and therefore help to predict rehabilitation outcomes. ![]() But there are still auditory neuropathy spectrum disorder cases with unknown etiology and site of the lesion. Modern genetic approaches, such as whole genome and whole exome sequencing, reveal etiology of auditory neuropathy spectrum disorder in many cases. More than 20 genes related to auditory neuropathy spectrum disorder phenotype are known already. Genetic testing, especially in cases without obviously perinatal hearing loss risk factors, might help to understand etiology and pathophysiology, whether it is synaptopathy or neuropathy therefore, it becomes possible to predict rehabilitation outcomes. ![]() Some patients with auditory neuropathy spectrum disorder undergo cochlear implantation, but it is not always possible to foresee the results of rehabilitation. Reviling the etiology or at least pathophysiology of auditory neuropathy spectrum disorder is crucial for choosing rehabilitation pathway and predicting rehabilitation outcomes. ![]()
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