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Audiological assessment of eleven congenital hypothyroid infants before and after treatment
M François1, P Bonfils, J Leger
1ORL Department, Hôpital Robert Debré, Faculty Bichat, University Paris VII, France.
Insights
Congenital hypothyroidism in newborns may not affect outer hair cell function, but can impact auditory nerve pathways. Early treatment leads to normal hearing thresholds in most infants by 12 months.
Area of Science:
- Pediatrics
- Audiology
- Endocrinology
Background:
- Congenital hypothyroidism (CH) is a condition present at birth that can lead to developmental issues if untreated.
- Auditory function in newborns with CH requires thorough evaluation to identify potential hearing impairments.
- Previous research has yielded conflicting results regarding the effects of CH on auditory system development.
Purpose of the Study:
- To assess the audiological status of newborns diagnosed with congenital hypothyroidism before initiating treatment.
- To investigate the impact of CH on different parts of the auditory pathway, including outer hair cells and auditory nerve function.
- To evaluate the effectiveness of early treatment for CH on hearing outcomes in infants.
Main Methods:
- Audiological evaluation of 11 newborns with CH prior to treatment.
- Measurement of evoked otoacoustic emissions (OAEs) to assess outer hair cell function.
- Auditory brainstem response (ABR) testing to evaluate the auditory nerve pathway.
- Behavioral hearing tests at 9-12 months of age for treated infants.
Main Results:
- Evoked otoacoustic emissions were present bilaterally in 9 out of 11 newborns, suggesting normal outer hair cell function.
- Auditory brainstem responses revealed a prolonged wave I in 6 newborns, indicating potential auditory nerve pathway abnormalities.
- Following treatment, all children exhibited OAEs in at least one ear by 9-12 months.
- Normal auditory thresholds (≤20 dB) were observed in 9 out of 11 treated children by 9-12 months of age.
Conclusions:
- Newborns with congenital hypothyroidism may have normal outer hair cell function despite potential auditory nerve pathway involvement.
- Early treatment of congenital hypothyroidism appears to be effective in normalizing hearing thresholds by infancy.
- Regular audiological monitoring is crucial for infants with CH to detect and manage hearing issues.
Abstract:
Eleven congenital hypothyroid newborns were consecutively referred for audiological evaluation before any treatment. Evoked otoacoustic emissions were present bilaterally in 9 newborns. These results suggest the normality outer hair cells and contrast with results obtained in experimental studies. The auditory brainstem responses in 6 newborns showed a prolonged wave I, as previously reported by other authors. At 9 to 12 months of age, all children treated had evoked otoacoustic emissions in at least one ear. In 9 cases, the auditory threshold was normal (equal to or below 20 dB) as determined by behavioural tests.