INTRODUCTION
Congenital hearing loss is hearing loss that is present at birth. Since hearing loss is not easily diagnosed at birth or during infancy and it has profound consequences on a person's development, it is important to consider hearing loss in patients at risk. A high risk register has been developed for those newborns who may have hearing loss.
The important factor in congenital hearing loss is the earlier the hearing loss is discovered, the sooner treatment can begin and the better the outcome.
Newborns who have one or more of the following are at risk for hearing loss:
(1) Family history of hearing loss
(2) Congenital infection ('torches')
(3) Anatomic malformations of the head and neck
(4) Low birthweight (<1500 gms)
(5) Hyperbilirubinemia
(6) Meningitis
(7) Asphyxia, low APGAR scores
(8) Ototoxic medications.
Any neonate with one or more of the above must be considered at risk for hearing loss and tested as soon as possible. This usually involves an auditory brainstem reponse test (see notes on audiology). The Department of National Health of Canada has stated, "infants manifesting any risk criterion for hearing loss should be screened under direct supervision of an audiologist or otologist preferably prior to discharge from hospital and before three (3) months of age - but not later than six months of age".
Approximately one half (50%) of congenital hearing loss is due to genetic abnormalities. Two thirds (66%) are autosomal recessive, one third (33%) are autosomal dominant and three per cent (3%) are X linked. These usually cause a sensorineural type of hearing loss of variable severity.
The etiology in roughly twenty-five per cent (25%) of patients with congenital hearing loss is unknown. It is useful for families to receive genetic counselling if a family member has congenital hearing loss.
DIAGNOSIS
The diagnosis of congenital hearing loss begins with a complete history including a search for risk factors mentioned previously. Also helpful in diagnosis of hearing loss is the development of speech milestones (refer to pediatric development notes). Before one can speak, one has to be able to hear. A physical exam is performed next with special attention to the ears, nose, throat and head and neck. Audiologic testing follows to document the type and severity of the hearing loss. This may include tympanometry, auditory brainstem evoked responses or other specialized tests. Occasionally a CT scan is helpful for visualization of cochlear abnormalities or tumors of the C.N.S. that may be causing hearing loss. Screening tests for congenital infections, hypothyroidism and other metabolic disorders are beneficial in selected patients.
TREATMENT
Treatment is aimed at the type and severity of the hearing loss. It may include surgery if the problem is easily correctible, but more often involves the fitting of hearing aids. Surgery for such abnormalities as external auditory canal atasia or usually postponed until adolescence ( the patient wears a hearing aid until then). Once a child has been diagnosed as having hearing loss, the child is assessed for specialized education programs and speech therapy. Once again, the family usually benefits from family and genetic counselling.
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All contents copyright (C) 1998.
Queen's University
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Revised: May 18, 1998.URL: http://meds-ss10.meds.queensu.ca/medicine/otolaryngology/