Evoked potentials and quantitative thermal testing in spinal cord injury patients with chronic neuropathic pain.

OBJECTIVE Neuropathic pain (NP) is a common symptom following spinal cord injury (SCI). NP may be associated with altered processing of somatosensory pathways in dermatomes rostral to the injury level. To explore this possibility, the characteristics of contact heat evoked potentials (CHEPs) and quantitative thermal testing (QTT) were studied at and above the lesion level in SCI patients with NP. The goal was to determine processing abnormalities correlated with data from clinical evaluations. METHODS Thirty-two subjects with chronic NP, 22 subjects without NP and 16 healthy control subjects were studied. Warm and heat pain thresholds were determined both at and above SCI level. CHEPs were recorded above SCI level and subjects rated their perception of evoked heat pain using a numerical rating scale. RESULTS CHEPs were not different between the three groups. Evoked pain perception in SCI subjects with NP was significantly higher than in SCI subjects without NP and healthy controls. Heat pain threshold was significantly lower in subjects with NP in comparison to both groups. CONCLUSIONS Our findings indicate that processing of somatosensory inputs from dermatomes rostral to the injury level is abnormal in SCI subjects with NP. SIGNIFICANCE SCI somatosensory processing alteration may contribute to the understanding of the mechanisms underlying NP and secondary changes to NP in SCI.