Hearing deficits correlated with the timing of systemic disturbance as indicated by primary incisor defects.

A correlation of hearing deficits and enamel defects was investigated in 18 children presenting to a pediatric neurology service for hearing evaluation. Eleven had enamel defects. Five had defects consistent with a systemic insult occurring as early as 14 weeks gestation, two between 29 to 33 weeks gestation, and four near term. Hearing loss was more severe in the five with enamel defects occurring in the mid-trimester (mean = 70 dB), than in the four subjects with defects occurring around term (mean = 23 dB) (t = 3.8; p less than 0.01). Of the remaining two subjects, one had normal hearing and the other had a moderate loss. A correlation was found between the average degree of hearing loss (in dB) versus the estimated time of systemic insult in weeks gestational age as indicated by position of the tooth defect (r = -0.78; p less than 0.01). Neurological profiles also differed with those having early defects being more severe. These findings suggest a differential susceptibility for developing audiological (and possibly other neurological) structures based on insult timing.