Neurophysiological study of peripheral nerves in newborn infants with congenital hypothyroidism. Value in the surveillance of replacement therapy

The authors studied prospectively with electrophysiological means, peripheral nerve maturation of 18 neonates with congenital hypothyroidism compared to 18 controls. Before replacement therapy, a large reduction of sural nerve action potential amplitude and of Hoffmann's reflex was observed. It was accompanied by a moderate reduction in nerve conduction velocity. These results imply a myelinic and even more an axonal pathology. It is related to the anatomical type of hypothyroidism and to serum T4 deficiency. It is transient and disappears after 6 months of hormonal replacement therapy. In conclusion, this study gives new informations on the consequences of congenital hypothyroidism on peripheral nerves.