Central post-stroke pain--somatosensory evoked potentials in relation to location of the lesion and sensory signs.

Somatosensory evoked potentials (SEPs) were studied in 27 patients with central post-stroke pain and in 19 controls. A scoring system for SEP was used, in which increasing abnormalities rendered increasing scores. SEPs evoked by electrical stimulation of the median and tibial nerves were compared to perception thresholds for touch, vibration, innocuous and noxious temperature. All patients had reduced temperature sensibility, while the threshold for touch and vibration was abnormal in only 52% and 41%, respectively. Decreased touch and vibration sensibility had a high correlation with high SEP scores, while no correlation was found between reduced temperature sensibility and SEP. The patients with thalamic lesions had the most severely affected SEPs, the ones with lower brain-stem lesions were the least affected. The results support the notion that the SEP is dependent on the lemniscal pathways and that lesions of the spinothalamic pathways are crucial for the development of CPS.