Technical advances in ultrasound and MR imaging of carpal tunnel syndrome

Abstract

The aim of this study was to compare the latest ultrasound-array technology to a conventional "high-resolution" transducer, modified MRI technique, and nerve conduction studies (NCS), in the diagnosis of carpal tunnel syndrome (CTS). In 19 normal wrists and 15 wrists with CTS, US with two different transducers was performed: a conventional linear-array transducer (LA) and a newly developed Multi-D linear-array transducer (MDA) were used. The US images were evaluated determining the swelling and the flattening ratios of the median nerve and correlated to respective findings in MRI (1.5 T) and to NCS. The NCS confirmed CTS in all 15 wrists. Measures of median nerve compression (swelling and flattening ratios) were significantly different in patients with CTS and controls (p < 0.01) with both types of US transducers and MRI. The MDA yielded higher correlation to MRI than the LA. Using critical values of 1.3 for the swelling and 3.4 for the flattening ratio, MRI, and US with the MDA yielded a sensitivity of 100% each. Modern imaging modalities allow for an exact diagnosis of CTS even in cases with only slight median nerve pathology.

Use of Sonography in Carpal Tunnel Syndrome Surgery-A Prospective Study-

“…7,8,11,34) The most consistent indicator seems to be the cross-sectional area of the nerve at the level of pisiform bone and hook of hamate, at the wrist crease (proximal tunnel). 7,8,11,17,21,34) Increase in the swelling ratio, or the cross-sectional area at the level of the pisiform bone compared to the area at the level of distal radius, is another sonographic indicator. 7,8,37) The changes in the cross-sectional area values between pre-and postoperative studies for each level are also meaningful.…”

“…Recently, sonography has been evaluated for the evaluation of patients with CTS, 3,11,[16][17][18][19]21,25,28,31,32,34,35,37) and may be a useful alternative to the nerve conduction study, 7,11,20,21,23,31,34,38) with high sensitivity and specificity. 3,11,25,31,32,34,37) Most studies used nerve conduction as the gold standard.…”

The role of diagnostic radiology in compressive and entrapment neuropathies

“…Quantitative analysis has been performed for the median nerve at the carpal tunnel: The "swelling ratio" -the ratio of the mean cross-sectional area of the nerve at the levels of the pisiform and distal radioulnar joint -is abnormal over 1.3, and the "flattening ratio" of the nerve's major to minor axis at the level of the hamate is abnormal over 3.4 [31,44]. Although initial reports had suggested that the "flattening ratio" of the median nerve had a poor predictive value [45], the recent study by Keberle et al utilised angle-corrected measurements for diagnosis of carpal tunnel syndrome (CTS) [44].…”

Carpal tunnel syndrome: elastosonographic strain ratio andcross-sectional area evaluation for the diagnosis and disease severity.

“…The most commonly used US method is the measurement of the cross-sectional area (CSA) of the median nerve at various levels within the carpal tunnel mostly at inlet, mid tunnel, and at outlet [5][6][7][8][9]. To reduce the discrepancies in the CSA measurements, comparison of the CSA of the median nerve within the carpal tunnel to an unaffected site such as the forearm has been proposed and the swelling ratio has been suggested as a promising method [10][11][12].…”