Abstract: Objective To evaluate the diagnostic value of somatosensory evoked potential(SEP) in lumbosacral disc herniation(LDH). Methods Posterior tibial nerve somatosensory evoked potential(PTNSEP) and dermatomal somatosensory evoked potential(DSEP) were recorded from 60 patients with radiculopathy caused by LDH and 30 healthy subjects. Results DSEP was abnormal in 56 cases(93.3%) and PTNSEP was abnormal in 26 cases(43.3%).The significant difference was observed(P<0.001).The abnormality of DSEP from L4 dermatome was detected mainly in patients with L3-4 LDH, the abnormality of DSEP from L5 dermatome was detected mainly in patients with L4-5 LDH, the abnormality of DSEP from L5S1 dermatome was detected mainly in patients with S1 LDH.DSEP can reflect the compressed extent of nerve root. Conclusions There was a good correlation of DSEP with lumbosacral nerve root injury,which supplement the information that can not be provided by imaging examingation.DSEP is a sensitive electrophysic method that not only is used to evaluate single nerve root function,but also is helpful in the location of the lesion.

Key words: somatosensory evoked potential, lumbosacral disc herniation, forensic clinicology