Contact heat evoked potential:a method of detection / 中华神经科杂志

ABSTRACT

Objective To evoke cerebral potentials by stimulating nociceptive fibers with contact heat evoked potentials stimulator (CHEPS)and estimate the nerve conduction velocities of peripheral nerve fibers mediating these responses.Methods Subjects were set in supine position.A heat-foil technology with a rapid rising speed at 70 ℃/s was used to elicit pain and contact heat evoked potentials(CHEP).Contact heat was delivered via one circular thermode (diameter 27 mm,area 573 mm~2).Thermal stimuli were sent at two intensity levels (49.5 ℃ and 54.5 ℃) to three body sitesthenar eminence,the dorsum of hand and proximal volar forarm.Contact heat evoked potentials were recorded from Cz and Pz.A systemic effect between stimulus intensities and pain rating were observed,the main components of this evoked potential were observed.Nerve conduction velocity was calculated from latency difference of CHEP and center to center distance of distal and proximal stimulus arrays.Results The pain intensity rating was 3.2?0.3 and 4.4?0.5 when thenar eminence was stimulated at the temperature of 49.5 ℃ and 54.5 ℃ respectively;the rating was 6.3?0.8 and 7.2?0.5 when the dorsum of hand and proximal volar forarm were stimulated at the temperature of 54.5 ℃ respectively.Three components,Cz/N550,Cz/P750 and Pz/P1000,were found in the evoked potentials.Nerve conduction velocities of the fibers were (12.9?7.5) and (1.7?0.4) m/s respectively,which were corresponding to those of A8 fiber and C fiber.Conclusions CHEPs can be elicited reliably and stably.Velocities of peripheral nerve fibers demonstrate that A8 fiber and C fiber mediate the response.