Non-genetic factors can account for about 25% of permanent hearing loss in children. Non-genetic factors known to cause permanent hearing loss can include:
- maternal infections, such as rubella (German measles), cytomegalovirus, or herpes simplex virus;
- low birth weight;
- birth injuries;
- toxins including drugs and alcohol consumed by the mother during pregnancy ;
- complications associated with the Rh factor in the blood/jaundice;
- maternal diabetes;
- toxemia during pregnancy;
- lack of oxygen (anoxia);
- cochlear malformations (Mondini's dysplasia); and.
- outer/middle ear malformations (atresia, stenosis).
Genetic factors (hereditary) are thought to cause more than 50% of all hearing loss. Hearing loss from genetic defects can be present at birth or develop later on in life. Most genetic hearing loss can be described as autosomal recessive or autosomal dominant. Other, rarer types of genetic hearing loss include X-linked (related to the sex chromosome) or mitochondrial inheritance patterns.
Genetic syndromes have a group of signs and symptoms that together indicate a specific disease. There are many genetic syndromes that include hearing loss as one of the symptoms. In fact, 20% of babies with genetic hearing loss have a syndrome. Examples include:
- Down syndrome;
- Usher syndrome;
- Treacher Collins syndrome;
- Crouzon syndrome;
- Alport syndrome;
- Sickle cell disease;
- Tay Sachs;
- Waardenburg syndrome;
- Pendred's syndrome (Large Vestibular Aqueduct).
Acquired hearing loss is a hearing loss that occurs after birth. The following are examples of conditions that can cause permanent acquired hearing loss in children:
- ear infections;
- ototoxic medications;
- chicken pox;
- large vestibular aqueduct;
- head injury; and
- noise exposure.