Somatosensory findings in patients with spinal cord injury and central dysaesthesia pain.

OBJECTIVE To determine whether central pain in patients with spinal cord injury is only dependent on the lesioning of spinothalamic pathways. METHODS In sixteen patients with spinal cord injury and central dysaesthesia pain, somatosensory abnormalities in painful denervated skin areas were compared with somatosensory findings in normal skin areas as well as in non-painful denervated skin areas. RESULTS The threshold values for detection of thermal (heat, cold, heat pain, or cold pain) and tactile stimulation were significantly changed in denervated skin areas although there were no significant differences in the threshold values between painful and non-painful denervated skin areas. The reductions of sensations of touch, vibration, joint position, and two point discrimination in painful and non-painful denervated skin areas were not significantly different. Allodynia (pain caused by non-noxious stimulation) and wind up-like pain (pain caused by repeatedly pricking the skin) were significantly more common in painful than non-painful denervated skin areas. CONCLUSIONS Because pain and thermal sensory perception are primarily mediated to the brain via spinothalamic pathways, whereas the sensations of touch, vibration and joint position are primarily mediated by dorsal column-medial lemniscal pathways, the results indicate that central pain is not only dependent on the lesioning of either dorsal column-medial lemniscal pathways or spinothalamic pathways. The findings of abnormal evoked pain (allodynia and wind up-like pain) may be consistent with the experimental findings of hyperexcitability in nociceptive spinothalamic tract neurons, that may be involved in the pathogenesis of central pain.