Sonographic Findings Are Associated With Carpal Tunnel Symptom Severity.

PURPOSE: The purpose of this study was to identify associations between the clinical manifestations of carpal tunnel syndrome (CTS) and the sonographic measurements of the median nerve in the carpal tunnel. We hypothesized that sonographic changes in the median nerve from proximal to distal along the carpal tunnel would be associated with symptom severity scores.

METHODS: We report on 38 patients with clinical signs and symptoms of CTS in a prospective investigation. Subjects underwent sonographic evaluation with measurement of median nerve cross-sectional area (CSA) at 3 locations: the level of the pronator quadratus, pisiform, and hamate. In addition, we measured dimensions of the carpal tunnel at the levels of the pisiform (inlet) and hamate (outlet). Finally, we recorded maximal thickness of the transverse carpal ligament (TCL). Patients underwent routine clinical evaluation and 31 patients had electrodiagnostic examination. Patients completed the Levine Katz Questionnaire (LKQ) to characterize severity of clinical symptoms. Each clinician was blinded to symptom severity scores. Pearson correlation coefficients were calculated to measure the relationship between LKQ score and sonographic measures.

RESULTS: Median nerve CSA decreased over the course of the carpal tunnel from proximal to distal in 30 of 38 wrists. A greater absolute change in CSA of the median nerve over the course of the carpal tunnel between the pisiform and the hamate as well as between the pronator quadratus and the hamate correlated with increased severity of clinical symptoms. Increased thickening of the TCL also correlated with greater symptom severity scores.

CONCLUSIONS: Changes in CSA of the median nerve as well as thickening of the TCL correlate with CTS severity.

TYPE OF STUDY/LEVEL OF EVIDENCE: Diagnostic II.