Diagnostic Accuracy of Ultrasound Parameters in Carpal Tunnel Syndrome: Additional Criteria for Diagnosis.

OBJECTIVES: To determine the diagnostic capacity of ultrasound (US) in detecting carpal tunnel syndrome (CTS). METHODS: Volunteer adults with and without CTS symptoms were recruited from offices in metropolitan Manila, where employees' work was hand/wrist intensive. Carpal tunnel syndrome was independently diagnosed by a reference standard (positive findings on a physical examination and nerve conduction studies). Blinded US measurements were taken of the median nerve (cross-sectional area, hypervascularity, wrist-to-forearm ratio, wrist-forearm difference, swelling ratio, flattening ratio, and palmar bowing of the flexor retinaculum) at the carpal tunnel inlet and carpal tunnel outlet (CTO). RESULTS: A total of 117 eligible consenting participants (234 hands) were included, with 54 hands (23.1%) with a diagnosis of CTS. There were no anthropometric differences between arms with and without CTS. Men and women older than 33 years were 5 times more likely to report CTS than younger people. A CTO wrist-forearm difference of greater than 0.03 cm had the strongest association with CTS (odds ratio, 4.7; 95% confidence interval, 1.4-15.9), with an area under the curve of 0.58 (sensitivity, 94.4%; specificity, 21.7%). The area under the curve increased to 0.59 when the next strongest measurement (CTO hypervascularity of 1+: odds ratio, 3.8; 95% confidence interval, 1.8-8.1) was included (sensitivity, 98.1%; specificity, 27.7%). Adding further US parameters did not improve the diagnostic capacity of US for CTS. Diagnostic capacity was independent of age and the duration of CTS symptoms. CONCLUSIONS: Combining US findings for the CTO wrist-forearm difference and hypervascularity provides a sensitive, alternative diagnostic tool for CTS.

Inter-Rater and Intra-Rater Reliability of Sonographic Median Nerve and Wrist Measurements.

BACKGROUND: Electrophysiologic studies have been considered the "gold standard" in diagnosing carpal tunnel syndrome (CTS); however, reports of false-negative results, as well as discomfort for the patient during the procedure has paved the use of ultrasound, being a painless and cost-efficient tool, as an alternative means for its diagnosis. Various ultrasound parameters assessing the median nerve and wrist dimensions have been described, but description of landmarks to assess these in a reliable manner has been lacking. METHODOLOGY: A systematic search of different databases yielded data regarding ultrasound parameters for CTS diagnosis, the landmarks used, and presence of reliability testing. Based on this, three sonologists discussed the external and sonographic landmarks that will be used in measuring the median nerve measurements, bowing of the flexor retinaculum and the carpal tunnel dimensions. A pilot test with two consecutive healthy participants using the discussed ultrasound parameters was carried out, and results were subjected to inter- and intra-rater reliability testing. Modifications were accordingly made on the acquisition of ultrasound image using external landmarks. The reliability testing proper was done with ten consecutive healthy participants. RESULTS: Based on the systematic review and the pilot study, external landmarks were used to locate the median nerve in the forearm, carpal tunnel inlet and outlet. For the forearm measurement, it was taken 10 cm proximal from the distal palmar crease. The distal palmar crease was the external landmark used for the carpal tunnel inlet, while for the carpal tunnel outlet; it was measured 1 cm distal to the distal palmar crease. Instead of using the inner edge of the hook of hamate and trapezium, the apices of these bones were used as the landmarks in measuring the carpal tunnel outlet dimensions. There was excellent intra-rater reliability (mid-forearm, carpal tunnel inlet and outlet) except for the following: cross-sectional area (CSA) of the median nerve at the carpal tunnel inlet and outlet; and bowing of the flexor retinaculum. All the parameters had an excellent inter-rater reliability measured at the three levels (intraclass correlation [ICC]: Of 0.77-0.99) except for CSA of the median nerve at the levels of the forearm (fair-to-good with ICC of 0.71) and the carpal tunnel inlet (fair-to-good reliability of ICC: 0.43). CONCLUSION: There was an improved inter- and intra-rater reliability when external landmarks were used instead of sonographic landmarks.