Hereditary Hearing Loss And Testing

The basic unit of everything we are has to do with genetics. Our genes contain DNA (deoxyribose nucleic acid), a double helix of coded strands that contain information about our ancestors. These genes contain info such as height, eye and hair color. They also contain the family history of illness and disease. Having a family history of hearing loss or deafness puts everyone down the line at risk for this condition. This is called hereditary hearing loss.

Hearing loss can be described as the inability to hear sounds in our environment. There are four types of hearing loss, which are conductive, sensorineural, mixed, and central. These hearing loss types can be syndromic or nonsyndromic, and can happen before language development (prelingual) or after language development (post lingual).

An important factor is determining if hearing loss is before birth (congenital) or after birth (acquired). It's severity and location must also be diagnosed in order for the correct treatment to be administered for relief of symptoms to occur.

The severity of hearing loss is measured in decibels. The higher the numbers, the more severe the hearing loss. Hearing loss is graded as:

• Mild (26-40 dB)


• Moderate (41-55 dB)


• Moderately severe (56-70 dB)


• Severe (71-90 dB)


• Profound (90 dB)

How is hereditary hearing loss diagnosed?

Physiologic testing includes:

• Auditory brainstem response testing (ABR, also known as BAER, BSER).


• Auditory steady-state response testing (ASSR).


• Evoked otoacoustic emissions (EOAEs)


• Immittance testing (tympanometry, acoustic reflex thresholds, acoustic reflex decay)

Audiometry: Behavioral testing and pure tone audiometry

• Behavorial testing includes behavioral observation audiometry (BOA) and visual reinforcement audiometry.


• Pure-tone audiometry (air and bone conduction) determines of the lowest sound heard.


• Air conduction audiometry is testing sounds through earphones


• Bone conduction audiometry presents sounds through a vibrator or tuning fork.

Audioprofile records several audiograms from one person at different times, but may include different members of the same family. Comparing numerous audiograms, the age-related progression of hearing loss can be viewed within these families.

Environmental Causes:

Acquired hearing loss in children commonly results from prenatal infections, such as:

• Toxoplasmosis


• Rubella


• Cytomegalic virus


• Herpes

Acquired hearing loss in adults is mainly due to extreme noise exposure.

Hereditary Causes:

Syndromic hearing loss: Is related to abnormalities of the external ear or other organs, and may account for up to 30% of prelingual deafness. Syndromes of hereditary hearing loss include:

• Waardenburg syndrome (WS)


• Branchiootorenal syndrome


• Stickler syndrome


• Neurofibromatosis 2

Nonsyndromic hearing loss: Is associated with abnormalities of the middle ear and inner ear.

Determining if hearing loss is hereditary may require genetic testing of all family members, as well as viewing medical histories if direct physical examination can not be performed. The good news is that most all hearing loss can be treated or specific accommodations can be made to improve communication for individuals diagnosed with with hereditary hearing loss.

by Barb Hicks RN/LMT