Issues in Congenital Hearing Impairment
Tranebjaerg (2008) recently reviewed the genetic aspect of congenital hearing impairment. She noted that of all sensory disorders, hearing loss is the most prevalent. Further, more than half of all cases of congenital hearing loss are founded in genetic mutations. Of those, autosomal recessive inheritance patterns are the most common (perhaps 70% to 80%) and autosomal dominant represent the rest (perhaps 20%).
Obtaining a "genetic diagnosis" not only adds to the prognostic overview, but allows the professional to appropriately counsel the parents with regard to additional offspring.
Tranebjaerg notes that most countries in the "western" world screen for hearing loss at birth and so the age of detection (for children with moderate-severe-profound hearing loss) has dramatically decreased from approximately 2.5 years, to approximately 1-3 months.
Tranebjaerg reviews mutations and genotype/phenotype characteristics in her article, as well as detailed discussions addressing Connexin 26 (Cx 26) and the underlying genes; GJB6 and GLB2. Additionally, she addresses cochlear implants and the frequency of genetic mutations found in cochlear implant recipients.
For More Information, References and Recommendations:
The Genetics of Infant Hearing Loss. Centers for Disease Control and Prevention.
http://www.cdc.gov/ncbddd/ehdi/genetics.htm
Traanebjaerg, L., (2008): Genetics of Congenital Hearing Impairment: A Clinical Approach. International Journal of Audiology, Vol 47, pages 535-545.