Etiology of hearing impairment (HI) is complex and comprises genetic and environmental factors. Currently, the background of genetic hearing impairment is an area of intensive research and we are witnessing fast progress in this field. The story has begun in 1997 when the DFNB1 locus was discovered with GJB2 and GJB6 genes causative for almost 50% of cases of recessive, profound, prelingual hearing loss. Nowadays, we have much more possibilities for dissecting the reason of HI, but proper assessment of clinical symptoms is essential for selecting the most optimal diagnostic pathway. In the first stage, the detailed characteristic of hearing loss including its level established by pure tone audiometry (PTA) or auditory brainstem responses (ABR), age of onset, and other helpful features as progressive or no progressive type should be provided. Subsequently, the presence or absence of accompanying symptoms should be established and followed by a detailed analysis of pedigree. In addition, modern assistive algorithms such as AudioGene, Face2Gene, and POSSUM are also discussed. Taking into account the variety of causative genes and pathogenic variants underling hearing loss, searching for causative genes, after exclusion of the DFNB1 variants, should be performed with multigenic panels based on next-generation sequencing technology.
Part of the book: An Excursus into Hearing Loss