**2.3 Position of damage**

	- b1. congenital causes such as rubella, syphilis, Usher syndrome, Alport Syndrome, Waardenburg syndrome and autosomal dominant and recessive sensorineural deafness [Friedman et al., 2003].
	- b2. acquired factors: Infections such as measles, cytomegalovirus, bacterial meningitis, autotoxicity of drug consumption, noise pollution including long-term exposure, presbycusis and sudden idiopathic HL [Willems, 2004].
