Spinal somatosensory evoked potentials in cervical cord lesions

Short-latency somatosensory evoked potentials (SEPs) to median and ulnar nerve stimulation were studied in 17 patients with cervical cord lesions of different sites and origins. Spinal cord lesions involving the 6th and 7th cervical segment led to an attenuation or loss of the cervical response after stimulation of the median nerve, whereas lesions at C8/D1 only affected the cervical response evoked by ulnar nerve stimulation. The third component of the neck-SEP (N13) was exclusively involved in some cases. More extensive lesions additionally abolished the second component (N11). Spinal cord lesions above the 6th cervical segment caused some dissociation of the simultaneously recorded responses at C7 and C2, with preserved responses at C7 and disturbed or absent evoked potentials at C2.