Heightened pain sensitivity in individuals with signs and symptoms of carpal tunnel syndrome and the relationship to clinical outcomes following a manual therapy intervention

Abstract

Neurophysiological responses related to lessening of pain sensitivity are a suggested mechanism of manual therapy. Prior studies have observed generalized lower pain thresholds associated with carpal tunnel syndrome (CTS) in comparison to healthy controls. The present study sought to determine whether similar findings were present in suprathreshold measures and measures specific to central integration of pain (temporal summation and after sensations). Additionally, we wished to determine whether measures of pain sensitivity were related to clinical outcomes in participants with signs and symptoms of CTS receiving a manual therapy intervention. Individuals with signs and symptoms of CTS reported greater pain sensitivity to suprathreshold measures of mechanical pain, temporal summation, and after sensation in comparison to healthy controls. Immediate lessening of mechanical pain sensitivity and after sensations in response to a manual therapy intervention and 3-week attenuation of temporal summation following a 3-week course of manual therapy were associated with 3-week changes in clinical pain intensity in participants with signs and symptoms of CTS. These findings suggest heightened pain sensitivity across several parameters may be associated with CTS. Furthermore, changes in mechanical pain, after sensation, and temporal summation may be related to improvements in clinical outcomes.

Figure 1

Association Between Immediate Change In Mechanical Pain Sensitivity At The Brachioradialis And 3- Week Change In Clinical Pain (r= 0.52) Positive numbers on the y- axis indicate greater improvement in clinical pain related to carpal tunnel syndrome over a 3- week period. Positive numbers on the x- axis indicate lessening of mechanical pain sensitivity at the brachioradialis over a 3- week period. Individuals in the top right quadrant and lower left quadrant demonstrated a positive association between immediate changes in mechanical pain sensitivity at the brachioradialis and 3- week changes in clinical pain.

Figure 2

Association Between 3- Week Change in Temporal Summation and 3- Week Change in Clinical Pain (r= 0.41) Positive numbers on the y- axis indicate greater improvement in clinical pain related to carpal tunnel syndrome over a 3- week period. Positive numbers on the x- axis indicate lessening of temporal summation of thermal pain over a 3- week period. Individuals in the top right quadrant and lower left quadrant demonstrated a positive association between 3- week changes in temporal summation and clinical pain.