Mild impairment of neuro-otological function in early treated congenital hypothyroidism

Pure tone audiometry, tympanometry, acoustic stapedial reflex thresholds (ASRTs), and auditory evoked brain stem responses (AEBRs) were carried out in 38 children with early treated congenital hypothyroidism aged 10-12 years, together with tests of vestibular function (electronystagraphy, rotational, and caloric tests). Sensorineural hearing loss with thresholds of greater than 15 dB was detected in 18 children (10 at 8 kHz only); only two children had more than 40 dB hearing loss, each in one ear. Raised ASRTs were found in eight children and two children had abnormal AEBRs. Of the 29 children tested, 12 had an abnormality of vestibular function. Although not significant at the 5% level, there was a tendency for the abnormalities to be more prevalent and severe in the children with more severe hypothyroidism, as judged by pretreatment plasma thyroxine. It is concluded that (i) mild abnormality of hearing is still common in children with congenital hypothyroidism despite early treatment but this is much less severe than that found before neonatal screening and (ii) mild abnormalities of vestibular function may be common in early treated congenital hypothyroidism.