Contact heat evoked potential:the method,normative reference data and it's application in cerebral infarction / 中华物理医学与康复杂志

ABSTRACT

Objective To establish the method of contact heat evoked potential(CHEP)and to explore the value of this evoked potential in pain testing of patients with cerebral infarction.Methods A total of 100 healthy volunteers and 30 patients were examined.The healthy volunteers were divided into 3 groups according to the length of their arms(Group A56.0～65.0 cm ;Group B65.5～74.0 cm ;Group C74.5～83.0 cm).A recently de- veloped heat-foil technique with a rapid temperature rising rate at 70℃/s was used to elicit pain and contact heat e- voked potentials.Contact heat was delivered via one circular thermode(diameter 27 mm,area 573 mm~2)and set at two intensity levels(49.5℃and 54.5℃)to three body sitesthe thenar eminence,the dorsum of hand and proximal volar forearm.The subjects were asked to rate the pain with numerical rating scale after each stimulus and CHEP was recorded from Cz and Pz.The association between stimulus intensities and pain rating was explored,the main compo- nents of the evuked potential were watched.CHEP,sensory conduction velocity(SCV)and somatosensory evoked potentials(SEP)were performed in patients with hemi-anesthesia caused by cerebral infarction.Results The pain intensity ratings were 3.2?0.3 and 4.4?0.5 at thenar eminence,5.0?0.7 and 6.3?0.8 at the dorsum of hand and 5.3?0.6 and 7.2?0.5 at the proximal volar forearm when the temperature of 49.5℃and 54.5℃was applied, respectively;Three components,Cz/N550,Cz/P750 and Pz/P1000,were identified in the evoked potentials.Cz/ N550 and Cz/P750 appeared when the dorsum of hand and proximal volar forearm were stimulated.In contrast,Pz/ P1000 could be identified when nociceptors of thenar eminence and proximal volar fbrearm were excited.In the pa- tients with cerebral infarction,CHEP disappeared or became abnormal on one side,while SCV and SEP were normal on that side.Conclusion It was suggested that CHEP could be elicited reliably in the controls.CHEP is helpful in the assessment of analgesia in patients with cerebral infarction.