Changes in electrical perceptual threshold in the first 6 months following spinal cord injury.

OBJECTIVES: To investigate the use of electrical perceptual threshold (EPT) testing to follow the natural history of sensory progression after complete and incomplete acute spinal cord injury (SCI) and to compare EPT changes with the American Spinal Injuries Association (ASIA) Impairment Scale (AIS). STUDY DESIGN: Prospective descriptive study. METHODS: ASIA examination and EPT testing was performed on 17 patients (7 AIS A, 10 AIS B-D), within 1, 3, and 6 months after acute SCI. EPT assessment was carried out bilaterally at ASIA sensory points from 2 levels above the neurological level to all levels below, including the sacral segments. Comparisons of EPT values above, at, and below the SCI were made at the three time points as well as comparisons of EPT data to ASIA assessment. RESULTS: There was poor agreement between lowest normal level on EPT and ASIA assessment. Over time, EPTs tended to deteriorate above and at the ASIA level in AIS A patients with modest changes below the neurological level of injury (NLI), mainly where EPTs correlated with the zone of partial preservation. Sacral sparing was detected in one patient with EPT testing, but not with ASIA assessment. AIS B-D patients showed improvement at the ASIA level and extensive changes, both improvement and deterioration, below the NLI. CONCLUSION: EPT testing has sufficient sensitivity to detect subclinical changes in sensory function as early as the first month post-SCI, which is not apparent in ASIA examination. In particular, the testing is able to show abnormalities at and around the injury site for both complete and incomplete SCI. In addition, EPT allows for the detection and monitoring of alterations, both improvements and deterioration, in the abnormal range of sensation.

Electrical perceptual threshold testing: a validation study.

BACKGROUND/OBJECTIVE: To investigate inter-rater and intra-rater reliability of electrical perceptual threshold (EPT) testing in assessing somatosensory function in healthy volunteers. STUDY DESIGN: Prospective experimental. SETTING: Hospital-based spinal cord injuries unit. METHODS: Cutaneous electrical stimulation of 4 dermatomes at ASIA sensory key points (C3, T1, L3, and S2) was performed on 40 control subjects. The lowest ascending stimulus intensity at which sensation was perceived was recorded as the EPT. Mean EPT values for each dermatome, as determined by 2 testers at 2 time points, were examined and plotted against a normative template. Differences and associations between intra- and inter-rater measurements and left-right measurements were studied. EPT results for 2 people with spinal cord injuries were also examined. RESULTS: EPT measurements from left and right sides, obtained from the 2 time points and 2 testers, were found to be strongly associated, with the exception of left and right side measurements at the S2 dermatome. No significant differences in the mean EPT for tester or time period were found. The intra- and inter-rater reliability was good for all dermatomes tested. Mean EPT measurements fell within the range of a normative template at each of the 4 dermatomes tested. CONCLUSION: EPT is an objective, reproducible, and quantifiable method of assessing sensation in a control group. However, caution should be applied in certain dermatomes such as S2, where there was large variation between left and right side measurements.