**7. Genetic evaluation**

The main problem in the diagnosis of disorders such as deafness is its heterogenicity. Genetic study of HL has considerable benefits for patients which are as follows:


Genetic evaluation should be considered for children with newly diagnosed loss of hearing especially if no specific cause is determined. For example, there is no need for genetic evaluation of the family of a child with HL due to meningitis; although, they may need assurance of not transmitting the disease to the next generation. Genetic evaluation includes several steps:


Based on previous studies, deaf people have positive assortive marriage; it is estimated that 90% of deaf individuals marry deaf. Depending on the pattern of inheritance they might have a deaf child. For example if both parental recessive alleles are similar, there is 100% chance of having a deaf child; and if one of the parents carry a dominant form of HL and the other carry the recessive form of HL the chance would be 50% for the dominant gene.

Early diagnosis of HL is important in gaining speech progression and social skills of the children which would lead to better life of these individuals and would later help them in cochlea implant. Hereditary or genetic understanding of the causes of HL is important. The benefits of this understanding and knowledge, not only allows physicians to help the families of at risk but also may help in treatment and control of HL. Sometimes it is possible to prevent hearing loss from worsening. HL may be one of the clinical signs of a syndrome and if the genetic cause of HL is determined it may help to predict and treat other clinical complications [Extivill et al., 1998].
