Quantitative sensory testing in the diagnosis of carpal tunnel syndrome

ABSTRACT

Quantitative sensory testing [QST] is a reliable way of assessing large and small sensory nerve fiber function. Sensory and pain thresholds are among the used procedures. Sensory deficits may be quantified and the data can be used in parametric statistical analysis in research studies and drug trials. Sensory and pain thresholds were measured in 20 patients with clinical features of Carpal Tunnel syndrome [CTS] and positive routine electrophysiological studies [group 1] and 20 similar patients with negative routine electrophysiological studies [group 2]. Twenty apparently normal controls [group 3] were enrolled for comparison. There was a positive correlation between the quantitative perceptive tests [sensory and pain thresholds] with routine electrophysiological studies. Comparing groups 1 and 3 p=0.000 and p=0.001 for sensory and pain thresholds respectively. Pain threshold only showed a statistically significant difference [p=0.003] on comparing groups 2 and 3. Sensory and pain thresholds showed a statistically significant difference on comparing groups 1 and 2 [p=0.000, p=0.04 respectively]. Rapidly conducting fibers were less involved in group 2, explaining the negative results obtained in this group with routine electrophysiological studies. A painful stimulus was used to excite group C fibers that are mostly not tested with routine electrophysiological studies. It seems that type la fibers are primarily tested with routine electrophysiological studies. Quantitative sensory testing is a successful method for evaluation of large populations of patients where routine electrophysiological studies would be impractical. Pain threshold can be a preliminary adjuvant technique in screening CTS patients with negative routine electrophysiological studies