Pain Phenotyping in Carpal Tunnel Syndrome Based on IASP Criteria: A Cross-Sectional Study

The primary aim of this study is to determine the pain phenotype in carpal tunnel sydrome (CTS) using an algorithm to support clinical reasoning processes. A secondary aim entails examining whether symptom severity, functional status, health related quality of life (HRQoL) and electrodiagnostic findings differs between the pain phenotypes in CTS.

This cross-sectional study included 113 patients with CTS. Following the electrodiagnostic assessments, participants completed the Margolis pain diagram, Numeric Pain Rating Scale, Boston Carpal Tunnel Questionnaire, and Short Form-36 (SF-36). Clinical sensory examinations were performed, and pain phenotypes were classified using an IASP-aligned clinical phenotyping approach. Between-group differences were analyzed using covariate-adjusted multivariate models (MANCOVA), controlling for age, sex, pain intensity, and symptom duration.

Of the participants, 53 (46.9%) were classified as having a neuropathic pain phenotype and 60 (53.1%) as having a mixed pain phenotype. Significant differences were observed between groups in symptom severity (P=0.035), functional status (P=0.0001), selected SF-36 domains (P=0.043-0.002), and electrodiagnostic parameters, including motor latency (P<0.001), motor amplitude (P=0.019), sensory amplitude (P<0.001) and sensory conduction velocity (P=0.001). The neuropathic pain group demonstrated more favorable electrophysiological findings, as well as better symptom severity, functional status and HRQoL scores.

In this study, approximately half of the patients were classified as neuropathic pain phenotype and the other half as mixed pain phenotype. Patients with a mixed pain phenotype exhibited worse clinical, functional, and electrodiagnostic profiles compared to those with neuropathic pain. Pain phenotyping may support improved clinical characterization and patient stratification in CTS.