Diagnostic Significance of Ultrasonographic Measurements and Median-Ulnar Ratio in Carpal Tunnel Syndrome: Correlation with Nerve Conduction Studies.

BACKGROUND AND PURPOSE: We determined the reliability of ultrasonography (US) measurements for diagnosing carpal tunnel syndrome (CTS) and their correlation with symptom duration and electrophysiology findings. We determined whether the ratio of the median-to-ulnar cross-sectional areas (CSAs) can support CTS diagnoses.

METHODS: The pisiform CSA (CSA(pisiform)), swelling ratio (SR), palmar bowing, and CSA(pisiform)/ulnar CSA (CSA(ulnar)) measurements made in two subgroups of CTS patients (having sensory affection alone or having both sensory and motor affection) were compared with controls. CSA(ulnar) was measured in Guyon's canal at the level of most-protuberant portion of the pisiform bone.

RESULTS: The values of all of the measured US parameters were higher in patients with CTS (n=50) than in controls (n=62). CSA(pisiform) could be used to diagnose CTS of mild severity. All of the parameters were positively correlated with the distal latency of the compound muscle action potential, and all of them except for SR were negatively correlated with the sensory nerve conduction velocity. A CSA(pisiform)/CSA(ulnar) ratio of ≥1.79 had a sensitivity of 70% and a specificity of 76% for diagnosing CTS.

CONCLUSIONS: Only CSA(pisiform) measurements were reliable for diagnosing early stages of CTS, and CSA(pisiform)/CSA(ulnar) had a lower diagnostic value for diagnosing CTS.