Peripheral nerve conduction studies in passively addicted neonates.

Neurologic signs dominate the manifestations of the neonatal abstinence syndrome (NAS). To help delineate this dysfunction, peripheral nerve conduction studies (NCS) were made in 25 neonates born to methadone-maintained mothers; 12 of the mothers abused other controlled substances concomitantly. Median and common peroneal motor nerve conduction velocities (NCV) in these infants were normal, both at three to seven days and three to four weeks of age, and were unaffected by maternal drug intake pattern, severity of neonatal abstinence symptoms, treatment with either camphorated tincture of opium or phenobarbital, intrauterine growth retardation, or abstinence-associated seizurer. Electromyographic findings were normal in 21/23 infants; two others showed minimal partial denervation, characterized by fibrillations and positive sharp waves. NCV in the NAS may enhance gestational age assessment and therefore increase validity of neurobehavioral follow-up. Our studies continue to point to a central rather than a peripheral motor dysfunction exhibited by passively addicted infants at birth, which may persist on two-to-five-year follow-up.