Increased baseline temperature improves the acquisition of contact heat evoked potentials after spinal cord injury

ObjectiveTo investigate the effect of increasing the skin surface baseline temperature for contact heat evoked potentials (CHEPs).MethodsCHEPs were studied in healthy subjects and subjects with chronic cervical spinal cord injury (SCI) using a conventional 35 °C (condition 1) or increased 42–45 °C baseline temperature (condition 2). A third condition was used to standardize the contact heat stimulus duration from the different baseline temperatures. Changes in peak latency and N2P2 amplitude of the CHEPs and rating of perceived intensity were examined between conditions.ResultsIn healthy subjects, increasing the baseline temperature for contact heat stimulation significantly increased the rating of perceived intensity (conditions 2 and 3), as well as the amplitude of CHEPs (condition 2 only). Following SCI, an increased baseline temperature facilitated perception of contact heat stimulation and evoked potentials could be recorded from dermatomes that were insensitive to contact heat from a conventional baseline temperature.ConclusionsEnhancing the acquisition of CHEPs can be achieved by increasing the baseline temperature. This effect can be attributed, in part, to shortening the stimulation duration.SignificanceAfter SCI, increasing the baseline temperature for CHEPs in dermatomes with absent or diminished sensation improved the neurophysiological resolution of afferent sparing.

► Increased skin surface baseline temperature increases the N2P2 amplitude of contact heat evoked potentials.
► The effect of an increased baseline on N2P2 amplitude can be attributed in part to shortening the stimulus duration and improving the synchronization of the afferent volley.
► After spinal cord injury, varying the baseline temperature improved the perception of noxious stimuli and acquisition of evoked potentials in dermatomes with absent or diminished sensation according to conventional sensory testing methods (i.e. pinprick testing and 35 °C baseline contact heat evoked potentials).