Causes of hearing impairment in the Norwegian paediatric cochlear implant program

Abstract

Abstract

Severe to profound hearing impairment (HI) is estimated to affect around 1/2000 young children. Advances in genetics have made it possible to identify several genes related to HI. This information can cast light upon prognostic factors regarding the outcome in cochlear implantation, and provide information both for scientific and genetic counselling purposes. From 1992 to 2005, 273 children from 254 families (probands) were offered cochlear implants in Norway. An evaluation of the causes of HI, especially regarding the genes GJB2, GJB6, SLC26A4, KCNQ1, KCNE1, and the mutation A1555G in mitochondrial DNA was performed in 85% of the families. The number of probands with unknown cause of HI was thus reduced from 120 to 68 (43% reduction). Ninety-eight (46%) of the probands had an identified genetic etiology of their HI. A relatively high prevalence of Jervell and Lange-Nielsen syndrome was found. The main causes of severe and profound HI were similar to those found in other European countries. GJB2 mutations are a common cause of prelingual HI in Norwegian cochlear implanted children.

Sumario

Se estima que la hipoacusia (HI) severa a profunda afecta alrededor de 1/2000 niños pequeños. Los avances en la genética han hecho posible la identificación de varios genes relacionados con HI. Esta información puede proporcionar luz en los factores pronóstico relacionados con el resultado de los implantes cocleares, y dar información tanto para fines científicos como para asesoramiento genético. De 1992 a 2005, a 273 niños de 254 familias (propósitos) se les ofreció un implante coclear en Noruega. Una evaluación de las causas de la HI, especialmente de los genes GJB2, GJB6, SLC26A4, KCNQ1, KCNE1 y la mutación A1555G del DNA mitocondrial se realizó en 85% de las familias. El número de propósitos con causa desconocida de HI se redujo de 120 a 68 (reducción del 43%). Noventa y ocho (46%) de los sujetos tuvieron una causa genética identificada. Se encontró una prevalencia relativamente alta del Síndrome de Jervell and Lange Nielsen. Las principales causas de la HI severa a profunda fueron similares a las encontradas en los países Europeos. Las mutaciones de GJB2 son una causa común de hipoacusia pre-lingüística en niños noruegos con implante coclear.

Key Words:

• Connexin 26
• Genetics
• Severe and profound hearing loss
• Cochlear implantation

Acknowledgements

This work is in memory of my co-author and supervisor, Professor Sten Harris, who sadly and unexpectedly passed away during the conduction of the study.

A poster based on the same sample was presented at the 10th International Conference on Cochlear Implants and other Implantable Auditory Technologies, 10–12 April 2008 in San Diego, California, USA.

This project was supported by the Futura Foundation for Scientific Medical Research, Norway. The authors are grateful to the personnel at the cochlear implant team at Oslo University Hospital, Rikshospitalet for their cooperation while interviewing and examining their patients, Harald Strand for performing the mitochondrial mutation testing, Dr. Einar Hopp for valuable advice regarding interpretation of the radiological findings, the secretaries Mona Schoug, Inger Lise Høivik Pedersen, and Kirsten Børge-Ask Pay for administering the patients, and the registered nurses Karin Zymarikopoulos and Anne Heimly for assistance with the ECG screening. And finally, we thank the families for their participation in the study.

Declaration of Interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.