Hereditary factors account for a large portion not only of congenital and early onset deafness, but also of progressive bilateral hearing loss. Identification of probands having similar phenotype is difficult because many genes are involved and different mutations can cause similar phenotypes. Progress in this field is also difficult due to paucity of clinical criteria and the vagueness of definitions used by the different professionals involved. For syndromal hearing loss, the main obstacle in obtaining a homogeneous series of families is the difficulty of finding a sufficiently large number of subjects affected by the same disorder, as usually, these conditions are rare. For non-syndromal hearing loss, the research strategy must be designed to accommodate genetic heterogeneity and careful clinical documentation, using uniform protocols and definitions, distinguishing subgroups.
Extensive collaboration is usually necessary.
This project was carried out dividing centre members into study subgroups, which although interactive and in connection with one another, have the task of developing a particular line of research. The co-ordinated action of clinicians and geneticists favoured and hastened the discovery of genes responsible of hearing impairment as well as lead to better understanding of hearing physiology. Data were useful in programming medical costs and services for diagnosis, care and rehabilitation. The CRS is involved in European basic research projects as contract holder on behalf of the European Commission and in co-operation with renowned research centres all over Europe.