PAIN-RELATED SOMATOSENSORY-EVOKED POTENTIALS CAN QUANTITATIVELY EVALUATE HYPALGESIA IN WALLENBERGS SYNDROME

In 6 patients with Wallenberg's syndrome who showed a dissociated loss of pain sense, we recorded pain-related somatosensory evoked potentia ls following CO2 laser stimulation of the hand dorsum (pain SEPs). Two components, N2 and P2, were recorded by stimulation of the unaffected hand, whereas on the affected side they were absent or decreased in p roportion to the severity of hypalgesia which was evaluated by both ne edle test and CO2 laser stimulation. Latency of either component, if a ppeared, was longer in the affected hand stimulation than that in the unaffected one. In contrast, N20 of the conventional electrically-stim ulated SEPs (electric SEPs) showed no difference between the two sides . It is concluded that, unlike other electrophysiological methods, pai n SEPs following CO2 laser stimulation can quantitatively evaluate fun ctional impairment of the spinothalamic tract in Wallenberg's syndrome .