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

Abstract

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.

Nerve Imaging in the Wrist

“…Studies presented mixed results with one study showing 2 mm of palmar bowing to have a 44% sensitivity and 85% specificity in identifying patients with CTS. 31,32 Other studies showed palmar bowing at the carpal tunnel inlet (between the scaphoid and pisiform) to be a specific sign of CTS with a threshold of 1 mm demonstrating a specificity of 97%. 28 Median nerve hypervascularity on Doppler US is a specific although insensitive sign of CTS, with one study demonstrating a sensitivity of 69% and specificity of 95%.…”

“…Cutoffs of 2.5 and 3 have been used, and in general, flattening ratio is not a sensitive or specific sign for identifying cases of CTS. 28,31,32 Median nerve CSA can also be measured just distal to the carpal tunnel outlet with one study showing a CSA > 14 mm 2 to have a sensitivity of 64% and specificity of 100% in identifying cases of CTS. 28 MRI is less commonly performed for suspected CTS and has been less extensively studied than US.…”

Ultrasound-guided carpal tunnel injections

“…5,6 US-based morphological parameters for detecting CTS are an increased cross-section area (CSA) of the MN at the carpal tunnel inlet or outlet, flattening of the MN, and bowing of the transverse carpal ligament (TCL) at the level of the carpal tunnel outlet. [7][8][9] Elastography has been proven as a useful adjunct US method in CTS evaluation. 10 Therapeutic recommendations for CTS depend on disease severity and may include anything from a conservative approach to surgical intervention.…”

Ultrasonographical Evaluation of the Median Nerve Mobility in Carpal Tunnel Syndrome: A Systematic Review and Meta-Analysis

“…Elsaman, et al [ 10 ] introduced a diagnostic criterion for CTS—the depth of the carpal tunnel (DCT), which is defined by the distance from the surface of the flexor retinaculum to the highest point of the capitate bone. To accommodate individual anthropometric variability, the wrist:forearm ratio (WFR), wrist–forearm difference (WFD), median-to-ulnar nerve ratio (MUR) and median-to-ulnar nerve difference (MUD) were also suggested as diagnostic criteria for CTS [ 11 , 12 , 13 , 14 , 15 ]. In addition, increased intraneural vascularity of the MN was also reported in patients with CTS [ 16 , 17 ].…”

“…In addition, increased intraneural vascularity of the MN was also reported in patients with CTS [ 16 , 17 ]. Gonzalez-Suarez et al [ 11 ] revealed that combining the WFD obtained by grayscale sonography and intraneural hypervascularity obtained by color Doppler could provide better sensitivity of up to 98.1%. Some researchers [ 18 , 19 ] further utilized elastography to observe the changes in the nerve environment and tissue elasticity.…”