AANEM News Express

AANEM News Express

Science News: Utility of Shear Wave Elastography and High-Definition Color for Diagnosing Carpal Tunnel Syndrome

Submitted by: Eman Tawfik, MD
Edited by: Vishwajit Hegde, MD

Sung JH, Kwon YJ, Baek SH, Son MH, Lee JH, Kim BJ. Utility of shear wave elastography and high-definition color for diagnosing carpal tunnel syndrome. Clin Neurophysiol. 2022;135:179-187. doi:10.1016/j.clinph.2021.10.020

Summary: This prospective study investigated shear wave elastography and high definition color in carpal tunnel syndrome (CTS) patients with variable degrees of severity. The authors recruited patients with clinical evidence of CTS and healthy volunteers as a control group. The patients underwent EDX testing, and the severity of CTS was determined using Canterbury grading (6 grades). The patients were subsequently classified into nerve conduction study (NCS)-negative (normal NCS), mild-to-moderate CTS (grades 1–3), and severe CTS (grades 4–6).
Neuromuscular ultrasound (US) performed on the same day as EDX included measurement of:

1. Median nerve (MN) cross-sectional area at the tunnel inlet and outlet
2. MN stiffness at the tunnel inlet and mid-forearm with calculation of wrist/forearm MN stiffness
3. Abductor pollicis brevis (APB), abductor digiti minmi (ADM) muscle stiffness with calculation of APB/ADM stiffness ratio.
4. Median nerve intraneural vascularity using HD color with grading of blood flow from 0 to 3 based on the richness of the blood flow signal within the nerve.   
There were 123 wrists from 70 patients were included in the study. MN stiffness and wrist/mid-forearm stiffness ratio were significantly greater in the three CTS groups compared to controls. The nerve stiffness and the score of blood flow increased with increased severity of CTS which means that the degree of nerve stiffness and intraneural hypervascularity reflect the severity of entrapment. The results also showed excellent diagnostic ability of nerve stiffness and stiffness ratio to differentiate EDX-proven CTS from healthy individuals.
Moreover, nerve stiffness can differentiate between mild-to-moderate CTS and severe CTS. The significant increase in nerve stiffness in NCS-negative group compared to controls suggest a potential role of shear wave elastography in the detection of subclinical CTS or in the diagnosis of patients with clinically suspected CTS but their EDX tests are normal.

Comments: Although advanced US techniques are currently confined to research, there use clinically is rapidly progressing and soon will become a routine practice as the evidence of their value accumulates. This study adds to our understanding of the structural nerve changes that occurs in CTS and reports increased nerve stiffness and vascularity. The nerve stiffness increases with increase in CTS severity. Thus, shear wave elastography could help in grading CTS severity and subsequently determine the prognosis and the proper management.

Articles of Similar Interest:

Nam K, Peterson SM, Wessner CE, Machado P, Forsberg F. Diagnosis of Carpal Tunnel Syndrome using Shear Wave Elastography and High-frequency Ultrasound Imaging. Acad Radiol. 2021;28(9):e278-e287. doi:10.1016/j.acra.2020.08.011

Mohammadi A, Afshar A, Mirza-Aghazadeh-Attari M, Mokhtari SAS. Application of shear wave elastography and median nerve cross-section area in the diagnosis and staging of carpal tunnel syndrome: a case-control study. Pol J Radiol. 2021;86:e638-e643. Published 2021 Nov 26. doi:10.5114/pjr.2021.111437

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