Most types of congenital and acquired hearing loss arise
from damage to, or loss of, cochlear hair cells or their
associated neurons. The incidence of heritable deafness is
high: one child in a thousand is born deaf; another one in a
thousand becomes deaf before adulthood [1,2]. Depending
on the age of onset, hearing impairment can affect oral
language acquisition, cognitive development and psychosocial
development. The prevalence of acquired hearing
loss is rising, as the population of the world increases
and ages and as noise pollution steadily increases. It is
estimated that one in three adults over the age of 65
has a handicapping hearing loss, making this condition
one of the most common chronic disorders, with more
than 250 million affected people worldwide in 2001