Prediction of carpal tunnel syndrome using the thenar muscle cross-sectional area by magnetic resonance imaging

Abstract

Carpal tunnel syndrome (CTS) is a common neuropathy. Although CTS progression is known to be associated with thenar muscle (TM) atrophy, the diagnostic value of TM atrophy for CTS has not been established. In this research, the thenar muscle cross-sectional area (TMCSA) was evaluated to analyze the relationship between the TMCSA and CTS. We assumed that TMCSA is a major diagnostic parameter in the CTS.Both TMCSA and thenar muscle thickness (TMT) samples were acquired from 18 CTS patients, and from 18 control subjects who underwent wrist magnetic resonance imaging with no evidence of CTS. T2-weighted transverse magnetic resonance imaging images were obtained. We measured the TMCSA and TMT at the level of first carpometacarpal joint.The average TMCSA was 296.98 ± 49.39 mm2 in the normal group and 203.36 ± 72.13 mm2 in the CTS group. The average TMT was 8.54 ± 1.45 mm in the normal group and 7.38 ± 1.14 mm in the CTS group. CTS group had significantly lower TMCSA and TMT. Receiver operator characteristics curve analysis showed that the best cutoff point for the TMCSA was 260.18 mm2, with 77.8% sensitivity, 77.8% specificity. The best cutoff point of the TMT was 7.70 mm, with 61.1% sensitivity, 66.7% specificity.Although the TMCSA and TMT were both significantly associated with CTS, the TMCSA was a much more sensitive measurement parameter. Thus, to evaluate CTS patients, the physician should more carefully inspect the TMCSA than TMT.

Analysis of the thenar muscles with ultrasound shear wave elastography: Reliability and preliminary findings

“…In particular, with respect to the crosssectional area of the muscles, the supraspinatus and rectus femoris are approximately 800 and 1200 mm 2 , respectively, 13,14 whereas the thenar muscles are only approximately 300 mm 2 in total. 15 The minimum size of the ROI in the ultrasound system used is 1 mm in diameter, and the thickness of the muscles measured is sufficiently larger than this, so the technical problem seems to be small. On the other hand, given the multiple muscle bellies involved, each with a different fiber orientation, 16 and the relative smallness especially of OPP, FPBS, and FPBD, it is understandable that there could be challenges in getting multiple examiners to identify a specific muscle exactly the same way.…”

“…Compared to these muscles, the thenar muscles are small in volume and have different tissues adjacent to each other in a small area. In particular, with respect to the cross‐sectional area of the muscles, the supraspinatus and rectus femoris are approximately 800 and 1200 mm 2 , respectively, 13,14 whereas the thenar muscles are only approximately 300 mm 2 in total 15 . The minimum size of the ROI in the ultrasound system used is 1 mm in diameter, and the thickness of the muscles measured is sufficiently larger than this, so the technical problem seems to be small.…”