Somatosensory evoked potentials and auditory brain-stem responses in congenital hypothyroidism. I. A longitudinal study before and after treatment in six infants detected in the neonatal period.

We report the results of a longitudinal study of auditory brain-stem responses (ABRs) and somatosensory evoked potentials (SEPs) performed in 6 children with congenital hypothyroidism. These infants were detected by the Quebec Network for Genetic Medicine and treated early. ABRs and SEPs were recorded both before and 2 weeks after the initiation of therapy and at 6 months of age. Before treatment, for SEP, we found increased wave N19, P22 latencies and N13-N19, N19-P22 interpeak latencies (IPLs) in congenital hypothyroid (CH) children. For ABR, there were increased wave I latencies with normal I-V IPLs. Substitutive therapy improved these abnormalities although this improvement was more evident after a shorter period of time for ABRs than for SEPs. Even at 6 months, 2 CH children still showed increased N13-N19 IPLs. Both had very low serum T4 levels at the time of diagnosis and one had also a very small knee surface area, both criteria indicating a severe hypothyroidism. It will be interesting to verify if initial and persisting increase of N13-N19 IPL is associated with later neuropsychological problems.