INTRAUTERINE ONSET OF A MONONEUROPATHY - PERONEAL NEUROPATHY IN A NEWBORN WITH ELECTROMYOGRAPHIC FINDINGS AT AGE ONE-DAY COMPATIBLE WITH PRENATAL ONSET

Mononeuropathies are unusual at birth, and electromyographic (EMG) def inition the first day of life has not been reported previously. Althou gh neonatal mononeuropathies may be related to obstetric complications , prenatal mechanisms also merit consideration. We report an infant, b orn with a peroneal neuropathy, whose EMG was performed 18 h after bir th. An isolated peroneal nerve lesion with lack of compound muscle act ion potential and the presence of fibrillation potentials, confined to the tibialis anterior muscle, suggested a primary intrauterine mechan ism for this mononeuropathy. Because of an infant's small size, the te mporal profile used in adults for appearance of EMG signs of wallerian degeneration may not apply. Inaccurate conclusions may result if the EMG standards for timing adult nerve injury are applied to newborns. T o our knowledge, previous published cases of neonatal mononeuropathies have not included babies whose first EMG was performed before age 4 d ays, Therefore, an EMG study shortly after birth needed to be accompli shed if strong support for the hypothesis of a prenatal onset were to be generated, Our findings are compatible with an intrauterine onset o f this baby's peroneal neuropathy. (C) 1996 John Wiley & Sons, Inc.