Compound muscle action potentials in newborn infants with spina bifida

The aim of this study was to investigate the relationship between compound muscle action potentials (CMAPs) and neurological impairment in newborn infants with spina bifida. Thirty-one newborn infants (17 males, 14 females, mean gestational age 39 wks [SD 2]; mean birthweight 3336 g [SD 496]) with spina bifida were investigated at a median age of 2 days (range 1-18 d). Motor and sensory impairment and muscle stretch reflexes were assessed and neuroimaging was performed. CMAPs were recorded from the tibialis anterior muscle and the gastrocnemius muscle after percutaneous electrical nerve stimulation. CMAPs were obtained in almost all infants. The area under the curve of the CMAP (CMAP-area) was associated with motor and sensory impairment and with the presence of muscle stretch reflexes, but not with the morphological level of the spinal anomaly. These associations were stronger for the gastrocnemius muscle than for the tibialis anterior muscle. In conclusion, the CMAP-area correlates with neurological impairment in neonatal spina bifida and provides an estimate of residual motor neuron function in affected spinal segments. The assessment of CMAPs after percutaneous electrical nerve stimulation is recommended as an additional instrument to the clinical neurological examination and imaging studies.