Effect of cervical spinal cord lesions on early components of the median nerve somatosensory evoked potential.

Clinical interpretation of median somatosensory evoked potentials (SEPs) is usually based on latency measurements of selected waveforms. The "cervicomedullary" potential (N14) is commonly recorded by measuring the voltage difference between cervical spine and frontal electrodes. This cervicomedullary potential is actually a composite waveform that is generated by several distinct neural structures. We present evidence that placement of additional recording electrodes to delineate the multiple cervical components of the median SEP enhances ability to detect and localize cervical cord lesions.