Specific Mechanical Pain Hypersensitivity Over Peripheral Nerve Trunks in Women With Either Unilateral Epicondylalgia or Carpal Tunnel Syndrome

Abstract

Case-control study with blinded examiner. To investigate if pressure pain sensitivity is related to specific nerve trunks in the upper extremity of patients with either unilateral lateral epicondylalgia (LE) or carpal tunnel syndrome (CTS). In the clinical setting, patients with LE tend to exhibit radial nerve trunk tenderness, whereas patients with CTS exhibit median nerve tenderness. No studies have investigated if specific nerve pressure pain hypersensitivity exists in patients with either LE or CTS. Sixteen women with unilateral LE (mean±SD age, 43±7 years), 17 women with unilateral CTS (43±6 years), and 17 healthy women (43±6 years) were included in this study. Pressure pain thresholds (PPT) were bilaterally assessed over the median, ulnar, and radial nerve trunks, as well as over the C5-6 zygapophyseal joints, by an examiner blinded to the subjectsí condition. A mixed-model analysis of variance was used to evaluate differences in PPT among groups (LE, CTS, or controls) and between sides (affected/nonaffected or dominant/nondominant). The individuals in both the LE and CTS groups demonstrated lower PPT bilaterally over the median (group, P<.001; side, P=.437), radial (group, P<.001; side, P=.556), and ulnar (group, P<.001; side, P=.938) nerve trunks as compared to controls. Additionally, radial (P<.001) and ulnar (P=.005) nerves were more sensitive bilaterally in patients with LE than in patients with CTS. The median nerve was more sensitive bilaterally in patients with CTS than patients with LE (P=.002). Lower PPT over the cervical spine (group, P<.001; side, P=.233) were found bilaterally in both the LE and CTS groups. Further, patients with CTS exhibited lower cervical PPT than patients with LE (P<.001). PPT was negatively correlated with both pain intensity and duration of symptoms in both the LE and CTS groups (P<.001). Bilateral mechanical nerve pain hypersensitivity is related to specific and particular nerve trunks in women with either unilateral LE or CTS. Our results suggest the presence of central and peripheral sensitization mechanisms in individuals with either LE or CTS.