Sensorineural Hearing Loss (SNHL)
The Molecular Genetics Laboratory, in partnership with the Ear and Hearing Center, helps patients and families understand the diagnostic evaluation process for hearing loss.
SNHL has many causes. For most children, the cause is not obviously known, and your ear specialist (pediatric otologist) will take a thorough medical history and perform a physical examination.
Genetic factors account for hearing loss in over half of children with SNHL. Genetic hearing loss is related to the passage of genes that cause hearing loss through a family.
The two main forms of genetic hearing loss are:
- Syndromic − Hearing loss in association with other medical problems. About 30 percent of children with SNHL have syndromic hearing loss. Many of the syndromes associated with SNHL can be diagnosed by talking with and examining the child and family.
- Nonsyndromic − Hearing loss without associated medical problems. Nonsyndromic hearing loss accounts for about 70 percent of children with SNHL. Genetic testing is an important diagnostic tool in the evaluation of children with nonsyndromic SNHL.
Nongenetic factors are also important contributors to SNHL and include:
- Infections (meningitis, cytomegalovirus [CMV], syphilis)
- Hyperbilirubinemia (jaundice at birth)
- Medications (aminoglycoside antibiotics, cisplatin chemotherapy)
- Trauma (skull fractures)
- Immune dysfunction (autoimmune inner ear disease)
- Blood dyscrasias (hypercoagulable states, sickle cell disease)
A child with SNHL may have different types of diagnostic tests to determine the cause of hearing loss.
These tests might include:
- Routine laboratory urine and blood tests
- Imaging studies (CT and MRI)
- Specialized laboratory tests including genetic tests
In addition to undergoing various medical tests, a child may be referred to a geneticist (or other specialist) for further evaluation to determine the cause of hearing loss.