Application In Multiple Sclerosis With Contact Heat Evoked Potentials

Multiple sclerosis disease is the most common white matter demyelinating disease of CNS,whose clinical characteristic is that dissemination of the demyelinating CNS lesion in space and time.Multiple sclerosis is widely involved with white matter of CNS(e.g.cerebral hemisphere,brain stem,cerebellum,spinal cord and optic nerve) and its variation of individual is great,about 1/3 of patients have moderate functional lesion,1/3 of patients have severe functional lesion.Not only give a serious threat to the quality of life,but also make the family and the country to offer great financial burden.Therefore early diagnosis is the key point. Neurologic electrophysiologic examination plays an important role in diagnosing MS. Dissemination of demyelinating CNS lesion in space and time is supported by MRI and neurologic electrophysiologic examination.To date,VEP,BAEP,MEP and SEP are available for testing visual,auditory,corticospinal pathways and the spinal cord dorsal column,but lack of corresponding electrophysiologic examination to test spinothalamic tract function.Contact heat evoked potentials is a new neurologic electrophysiologic examination,which can excite thin myelinated A8 fibers and unmyelinated C fibers,reflect the disorder of pain and warm pathway objectively.Objective:To establish our standard of Contact heat evoked potentials,evaluate the state of nociceptive system in patients with multiple sclerosis and offer CHEP index for diagnosing MS.Methods:thirty-six definite multiple sclerosis(MS) and forty sex-,height-,and aged-matched healthy persons underwent stimulation of contact heat delivered via a circular thermode with a diameter of 27 mm(area of 573 mm~2) to excite selectively nociceptors with a rapid rising time at 70℃/s to elicit pain and contact heat evoked potential(CHEP).Thermal stimuli were sent at two intensity levels(47℃and 51℃) to three body sites:volar surface of the forearm,the skin of leg 5 cm proximal to the medial malleolus and lumbar part.The -CHEPs were recorded from Cz.The relation between the stimulus intensity and pain rating was observed,and the main components of the evoked potential were recorded.Results:1.comparison of three body sites with same intensity levels:lumbar part has the highest scores of VAS(P<0.05).2.comparison of two intensity levels with the same body sites:VAS of 51℃is higher than 47℃(P<0.05).3.there is a significant correlation between upper limb length and latency of N peak,also upper limb length and latencies of N.P peak(P<0.05).4.comparison of three body sites with same intensity levels:CHEPs of lower limb are significantly prolonged compared with upper limb and lumbar part(P< 0.05),but the amplitude is not(P>0.05).5.comparison of two intensity levels with the same body sites:there is no difference in N latency and N-P amplitude(P>0.05).6.conduction velocity of A5 fibers is 18.1±7.3m/s.7.VAS of MS(with symptom of hypesthesia) is significantly low compared with healthy subjucts(P<0.05).8.CHEPs in patients with hypesthesia are significantly delayed and reduced in amplitude compared with healthy subjucts(P<0.05).9.CHEPs in patients with no hypesthesia are significantly delayed compared with healthy subjucts(P<0.05).10.the number of relapse and segment is correlated with CHEP N peak latency.11.CHEPs abnormalitiy is observed more often in the lower than the upper limb, and the total abnormalitiy is observed more often in CHEPs than LEPs and SEPs.Conclusions:1.there is a significant correlation between upper limb length and latency of N peak,also upper limb length and latencies of N,P peak.2.comparison of two intensity levels with the same body sites:there is no difference in N latency and N-P amplitude.3.conduction velocity of A8 fibers is 18.1±7.3m/s.4.the number of relapse and segment is correlated with CHEP N peak latency, CEHPs can help to document dissemination of demyelinating CNS lesions and detect subclinical lesions thus contribute to the the diagnosis of multiple sclerosis.