Application In Guillain-Barrè Syndrome With Contact Heat Evoked Potentials

Objective:to establish a new method of contact heat evoked potential by stimulating nociceptive fibers,,and study the representation of contact heat evoked potential when we applicated it on normal subjects,and assesse the application of contact heat evoked potential in Guillain-Barr(?) syndrome.Data and method:we collected 60 patients of Guillain-Barr(?) syndrome participating in the study,whom accepted the cure in hospital from January in 2007 to September in 2008,average age 38.10±15.81years old,male 33,female 27.we also maked a normal control group,which contain 50 healthy volunteers participated in the study,,average age 36.20±13.29 years old,male 30,female 20.None of the patients had objective sensory disability,parts of the Guillain-Barr(?) syndrome had subjective sensory disability,so we divided the patients into two groups according to sensory disability, as existing sensory abnormal group and normal subjective sensory group.The former contained 21 patients,man 10,women 11.And the latter included 39 patients,man 23,women 16.All of people underwent stimulation of contact heat evoked potential stimulator,delivered via a circular thermode to excite selectively nocieeptors with a rapid rising time at 70℃/s to elicit pain and contact heat evoked potential(CHEP).The intensity level of temperature we choosed for stimulating was 47℃,then we sent it to two sites of body of entire subjects:skin of leg above internal malleolus and skin of waist at the anterior superior iliac spine level.The way we selected for stimulating was single pulse stimulation,the interval time between two consecutive stimulation was 10s,and we would consecutive stimulate 10 times on every sites at 47℃.Recording electrodes were put in Cz and Pz and reference electrode was put in forehead according to the international eletroencephalogram 10-20 systerm.,at where we could obtain the wave form of contact heat evoked potential.We used Keypoint.net equipment for recording the representation of contact heat evoked potential when we stimulated on 60 Guillain-Barr(?) syndrome and 50 healthy volunteers.After the first stimulation 3～5s on evey body sites we selected,all of subjects would assessed the stimulus intensity on oral according to visual analog scale(VAS).In this study,we need record the relationship between stimulus intensity and pain ranking,the main components of contact heat evoked potential and nerve conduction velocity of peripheral nerve.The nerve conduction velocity was calculated from the latency difference of the CHEP and center to center distance from leg above internal malleolus to waist at the anterior superior iliac spine level. Result:When we stimulated skin of leg above internal malleolus and skin of waist at the anterior superior iliac spine level at 47℃,we could record the wave form of contact heat evoked potential at corona from all of person whom participated in this study.The evoked potential mainly contained two parts,they were normal phase wave N1 and negative phase wave P1,very few people we could record negative phase wave P2.The average latency of N1 wave was 402.50±23.14 ms,the average amplitude of N1-P1 inter-peak was 44.68±17.68μV,and the average pain raking was 6.25±0.92,when we stimulated the skin of leg above internal malleolus on normal control group.Then we stimulated the skin of waist at the anterior superior iliac spine level,recorded the average latency of N1 wave was 352.03±20.38 ms,the average amplitude of N1-P1 inter-peak was 49.92±19.69μV,and the average pain raking was 6.82±0.97.the average peripheral nerve conduction velocity of normal subjects was 13.28±2.31m/s.The relation ship between stimulus intensity and pain raking when we stimulated skin at 47℃was:the pain raking of existing sensory abnormal group was significantly reduced(P＜0.01),comparing to normal control group when we stimulated the skin of leg above internal malleolus and of waist at the anterior superior iliac spine level at 47℃,but the difference of pain raking between normal subjective sensory group and normal control group,and between existing sensory abnormal grouP and normal subjective sensory group were not statistically significant(P＞0.05).When we stimulated the leg skin,the N1 latency we obtained of existing sensory abnormal group was highly prolonged comparing to that of normal control group(P＜0.05),the N1-P1 inter-peak amplitude of existing sensory abnormal groupalso highly reduced comparing to that of normal control group(P＜0.05),the peripheral nerve conduction velocity of existing sensory abnormal group was significantly slowed down comparing to that of normal control group(P＜0.01).But the difference of N1 latency and N1-P1 inter-peak amplitude and the peripheral nerve conduction velocity between normal subjective sensory group and normal control group,and between existing sensory abnormal group and normal subjective sensory group were not statistically significant(P＞0.05).when choosed the skin of waist at the anterior superior iliac spine level as stimulus,the difference of N1 latency and N1-P1 inter-peak amplitude between this three groups was not statistically significant(P＞0.05).Conclusion:Our study show that contact heat evoked potential could electively excite the pain nociceptor,which maked it has the capability to assess the functional ststus of conduction tract of pain perception mediated by AS-fiber and C-fiber.So,when contact heat evoked potential was applicated on Guillain-Barr(?) syndrome,we could find the functional disturbance of Aδ-fiber according the N1 latency and N1 -P1 inter-peak and nerve conduction velocity.Furthermore,it was operated convenient,stable wave form,easy tolerance.Therefore contact heat evoked potential can provide a practical,rapid and non-invasive additional clinical tool of potential utility in the evaluation of small fibre neuropathy and neuropathic pain states.