Clinical application of evoked EEG responses in infants. III: congenital hypothyroidism.

Previous studies have shown a close relationship between maturation of the central nervous system and development of evoked EEG responses. In this study, 13 infants with congenital hyperthyroidism were examined between the ages of one week and 17 weeks in an attempt to evaluate the degree of developmental retardation and the influence of hormonal treatment. It was found that visual evoked responses were abnormal in 12 of the patients, the most common abnormality being an immature abnormal response pattern. Latency was increased significantly in 10 of the 11 patients who were diagnosed before the age of six months, but was normal in the remaining two who were diagnosed later. A significant reduction of photic driving occurred in only two patients; it was the sole abnormality in one of them. Both the response pattern and latency became normal during treatment. The authors conclude that recording visual evoked responses is a simple and useful method of evaluating cerebral function in congenital hypothyroidism, both before and during treatment.