At least 1 in 1000 children are born with hearing impairment. Around 50% of congenital hearing loss is genetic in origin, and late-onset hearing loss can also have a genetic cause. Hearing loss is classified based on criteria such as genetic or environmental cause, time of onset, age of onset, clinical presentation, anatomic defect, pathology, severity, frequency affected, and whether it is unilateral or bilateral. There are three types of anatomic defects - conductive, sensorineural, or mixed - and these can arise from syndromic conditions, which involve other symptoms, or nonsyndromic conditions.

1. DEAF MUTISM

2.  The incidence of congenital hearing
impairment is at least 1 child in every 1000
born.
 A hearing impairment commonly involves
damage to or loss of cochlear hair cells; this is
referred to as a sensorineural hearing loss
(SNHL).

3.  It is estimated that at least 50% of congenital
hearing impairment has a genetic origin.
 Late-onset hearing loss can also be caused by
genetic defects.
 As understanding of the genetics of deafness
increases, the role of the otolaryngologist in
diagnosing, interpreting, and managing this
form of hearing loss has mandated a basic
understanding of genetics.

4.  Hearing Loss Classification
 Criteria Classification Comment
 Genetic hereditary
 Environmental Nonhereditary
 Multifactorial
 Time of onset Congenital At birth
 Acquired Late-onset
 Age of onset prelingual before speech
development
 Postlingual after speech
development

5.  Clinical presentation non syndromic hearing loss only
 Syndromic hearing loss with symptoms
 Anatomic defect conductive external and middle ear
 Pathology
 Sensorineural inner ear pathology
 Mixed
 Severity mild 20-40db
 Moderate 41-55db
 Moderately severe 56-70db
 Severe 71-90db
 Profound >91db
 Frequency loss low frequency <500Hz
 Mid frequency 501-2000Hz
 High requency >2000Hz
 Ear affected unilateral
 Bilateral
 Prognosis stable
 Progressive

6.  .There are three types of anatomic defects—
conductive, sensorineural, or a combination
of both (mixed)
 and these defects may arise from syndromic
or nonsyndromic conditions
 . Syndromic and nonsyndromic conditions
can be subclassified by inheritance pattern as
autosomal dominant, autosomal recessive, X-
linked, mitochondrial, or complex.