The Diagnostic Value Of SEP In LDH And Its Forensic Significance

The identification of clinical forensic medicine often includes the evaluation of the function of lumbosacral disc herniation ( LDH ). For their benefit, people under going identification sometimes tend to pretend to be disable or exaggerate the degrees of the functional disturbance , which make the subjective clinical examination more unBclievable. As a means of objective examination, imaging studies only provide the morphological changes. Because the variations of the a-dapt and compensation of human body are greater, there may be structural changes, but not abnormal in the function. Thereforce, it is important to find an objective way in determining the function of the nerve root injuried in clinical forensic medicine.The electric neurophysiology can provide reliable information about nerve root function that would supplement the structural information provided by the imaging study. Electromyography and nerve conduction velocity, as traditional means,can not provide enough useful diagnostic information about nerve root function. In recent years, somatosensory evoked potential(SEP)has been applied to determining nerve root function in LDH. SEP is a kind of bioelectric reaction which is characterized by time - locked and special response. The response can be reorded at the any part of special somatosensory system including from derma-tomes to peripheral nerve, spinal posterior root, et al, when stimulated in a proper style. At the base of special anatomy,SEP is a sensitive,reliable tool for determining the function, which can reflect the dysfunction of the sensory system. For nerve root is one of the part of conduction passway, the changes of SEP could reflect the nerve root function in some extent. Since 1980s,studies about the evaluation on the nerve root function with SEP have been begun at abroad. There have been few clinical reports and no any reports in forensic medicine at internal since1990s. At present,there are doubts about the applications of SEP at the diagnose of LDH. For this, in this study, we perform the examination of PTNSEP and DSEP on 60 patients with LDH and 30 healthy subjects in order to find the objective, dependable index,and evaluate its usefulness for estimating the location and extent of nerve root dysfunction, and provide the clinical forensic medicine with objective evidence.Subjects and methodsThere are 60 patients with unilateral radiculopathy due to LDH in test group. All patients have clinical signs and symptoms of LDH. Among the patients, there are 8 patients for L3 -4 intervertebral disc herniation, 28 patients for L4 -5,24 patients for L5S1. There are 30 healthy subjects as control group.The examination is performed with keypoint evoked potential equipment. The nerve is stimulated using constant current square wave pulses of 0.2ms duration delivered at a frequency of 2. 3Hz. The stimulus intensity is above the level which induce a visible muscle twitch without producing discomfort, or three times of the sensory threshold. The electrode impedance is kept under 5Kohm. The ground electrode is a conducting band placed around the leg of the stimulated limb. We use the system bandpass of 500 -2000Hz. A total of 240 trials are averaged for each trace and two or more traces are superimposed to ensure repro-ducibility. All records are obtained with the subjects lying supine in a quiet room,where the temperature is kept at 22 ~24癈. Examination of DSEP:Stimulations are delivered at the above the medial malleolus for L4 dermatome,at the thirth metararsophalangeal joint for L5 dermatome , at the lateral malleolus for S1 dermatome. Recording electrode is placed at the Cz', referred to Fz. Observed index: if N1 ,P1 and peak latency and interside latency difference(ILD) of N1 ,P1 is disappear or not. Abnormal standard; ( 1) Disappear or flat of N1 or P1; (2) More than the upper limit of peak latency of N1 or P1 from the control by calculating the means plus 3 standard deviations; ( 3 ) More than the upper limit of ILD of N1 or P1 from the control by calculating the means p...