Contact Heat Evoked Potentials Amplitude Research Articles

Patterns of contact heat evoked potentials (CHEP) in neuropathy with skin denervation: Correlation of CHEP amplitude with intraepidermal nerve fiber density

ObjectiveContact heat evoked potentials (CHEPs) provide an objective approach to investigate cerebral responses to thermal stimuli mediated by Aδ fibers. Skin denervation is often associated with reduced thermal sensibilities. We aimed to investigate the influences of skin denervation on CHEPs in neuropathic patients. MethodsCHEPs were recorded at the vertex area by applying contact heat stimuli of 51°C on the distal leg of neuropathic patients with sensory symptoms and pathological evidence of skin denervation in the distal leg. Patterns and parameters of CHEPs in the neuropathic group were compared with those in the control group of age- and gender-matched subjects. ResultsThere were 25 neuropathic patients with reduced intraepidermal fiber (IENF) density (1.46±1.70fibers/mm, range: 0–5.32). In the control group, well-defined averaged tracings of CHEPs with an initial negative peak (N-wave) followed by a positive peak (P-wave) were consistently recorded in all 25 subjects. The peripheral conduction velocities of CHEPs were 9.92±4.06m/s (range: 6.06–16.60), in the range of Aδ fibers. The group of neuropathic patients had markedly reduced N–P amplitudes (p<0.0001) and prolonged N-wave latencies (p=0.049) compared to the control group. IENF density was the only neuropathic parameter correlated with N–P amplitude on multiple linear regression analysis (p=0.010) compared to large-fiber parameters. ConclusionsIn neuropathic patients with pathological evidence of skin denervation, there were reduced amplitude and prolonged latencies in CHEPs mediated by Aδ fibers. The reduction of CHEP amplitude corresponded to the degree of skin denervation. SignificanceCHEP offers electrophysiological evidence of thermal responses and provides an objective, non-invasive approach to assess the physiological counterparts of skin denervation in neuropathic patients.

Contact heat evoked potentials in normal subjects.

Laser-evoked potentials are widely used to investigate nociceptive pathways. The newly developed contact heat stimulator for evoking brain response has the advantages of obtaining reliable scalp potentials and absence of cutaneous lesions. This study aimed to identify the most appropriate stimulation site with consistent cortical responses, and to correlate several parameters of the contact heat evoked potentials (CHEPs) with age, gender, and body height in normal subjects. CHEPs were recorded at Cz with a contact heat stimulator (Medoc, Israel) in 35 normal controls. The subjects were asked to keep eyes open and remain alert. The baseline temperature was 32 degrees C, and stimulation peak heat intensity of 51 degrees C was applied to five body sites: bilateral forearm, right dorsum hand, right peroneal area, and right dorsum foot. Reproducible CHEPs were recorded more frequently when stimulated at volar forearm (62.5%) than at the lower limbs (around 40%). The first negative peak latency (N1) was 370.1 +/- 20.3 ms, first positive peak latency (P1) was 502.4 +/- 33.0 ms, and peak to peak amplitude was 10.2 +/- 4.9 microV with stimulation of the forearm. Perceived pain intensity was not correlated with the presence or amplitude of CHEPs. No gender or inter-side differences were observed for N1 latency and N1-P1 amplitude. Also, no correlation was noted between N1 and age or body height. These results support future clinical access of CHEPs as a diagnostic tool.