Persistent post-surgical pain and signs of nerve injury: the Tromsø Study.

Abstract

The contribution of nerve lesions and neuropathic pain to persistent post-surgical pain (PPSP) is poorly established. The aim of this study was to assess the association between PPSP and symptoms and signs of possible nerve injury in an unselected surgical sample. Eighty-one individuals with and without persistent pain after surgical procedures, were recruited from a cross-sectional study. Follow-up examination with questionnaires and quantitative sensory testing was performed 15-32 months later (21-64 months after surgery). The median rating of maximum pain intensity among individuals with PPSP decreased from numerical rating scale 4/10 at baseline to 2/10 at follow-up, but considerable changes occurred in both directions. Individuals with PPSP at follow-up were significantly more likely to self-report sensory abnormalities than those without PPSP; however, results from sensory testing did not differ significantly between the groups. Self-report of sensory disturbances at the site of surgery was associated with increased warm detection thresholds and tactile pain thresholds. Among individuals with PPSP, 61% had positive findings on sensory testing, suggesting probable neuropathic pain. In this study, associations between self-reported symptoms and PPSP were stronger than associations between self-reported symptoms and results of psychophysical tests. Fluctuations in pain intensity together with wide ranges for normal variability in sensory functions, hampers detection of significant group differences. Methodological aspects of quantitative sensory testing applied in a mixed clinical sample are discussed.