Intra-operative evoked potential studies of newborn infants with myelomeningocele.

Somatosensory evoked potentials were studied in seven infants during surgery for repair of thoraco-lumbar myelomeningocele. All were operated on during the first 24 hours of life. Because anaesthetics were known to suppress somatosensory evoked potentials, narcotics and muscle relaxants were used for anesthesia. Before surgical dissection, stimulation of median nerves evoked cortical responses in five of the seven patients. After dissection, evoked potentials could be retrieved from the neural plaque with peroneal nerve stimulation in five of the seven infants. Stimulation of the neural plaque produced cortical responses in five of the seven but cortical responses with long latencies could be obtained from peroneal nerve stimulation in only two of the seven patients. In two patients lumbar-root stimulation distal to the plaque produced low-amplitude and delayed-latency cortical responses. These findings indicate that the distal nerves and neural plaque may have intact afferent connections with the cortex: therefore at surgical repair the neural plaque has been meticulously preserved.