Reliability of cutaneous electrical perceptual threshold in the assessment of sensory perception in patients with spinal cord injury

The electrical perceptual threshold (EPT) test complements the American Spinal Injury Association (ASIA) assessment of cutaneous sensory function by providing a quantitative assessment for each dermatome. The aim here was to establish the reliability of the EPT by examining inter- and intra-rater repeatability of test results in spinal cord injury (SCI). Twelve persons with incomplete spinal cord injury (iSCI; two stable at20 months and 10 sub-acute at9 months post-injury) and 12 control subjects took part. EPT was established at the ASIA sensory key points. A pulse of 0.5 ms in duration was applied three times per second. Threshold was determined by the method of limits. The strength of stimulation was augmented (0.1 mA.s(-1)) until the recipient reported sensation, then reduced until sensation was lost. EPT was taken as the lowest strength at which the subject reported sensation. Threshold was determined by two raters to establish intra- and inter-rater reliability. There were no significant differences in mean intra- or inter-rater EPT values at, above, or below the level of lesion (ASIA sensory level) for iSCI subjects. The intra-class correlation coefficient (ICC) was 0.56-0.80 for intra-rater and 0.52-0.91 for inter-rater classes, depending on the level tested. There was a significant correlation (Pearson's r = 0.93) between EPTs for four different dermatomes of control subjects assessed using two different types of stimulator. EPT provides an objective and quantitative measure of threshold for cutaneous sensory function. The method has good inter- and intra-rater reliability, and can be assessed using different stimulators.