Science News: Image Analysis Can Reliably Quantify Median Nerve Echogenicity and Texture Changes in Patients With Carpal Tunnel Syndrome

 Submitted by: Eman Tawfik, MD
Edited by: Pritikanta Paul, MD

Citation: Moschovos C, Tsivgoulis G, Ghika A, et al. Image analysis can reliably quantify median nerve echogenicity and texture changes in patients with carpal tunnel syndrome. Clin Neurophysiol. 2023;149:61-69. doi:10.1016/j.clinph.2023.02.171

Summary: Neuromuscular ultrasound (US) has emerged as a useful adjunct diagnostic tool in peripheral nerve disorders. The nerve cross-sectional area (CSA) is the most sensitive and reliable sonographic parameter used in clinical practice. Nevertheless, other parameters such as nerve echotexture and mobility are also important. Typical median nerve echotexture changes in carpal tunnel syndrome (CTS) are hypoechogenicity and partial or complete loss of the honeycomb fascicular pattern. These echotexture changes are usually qualitatively assessed by the sonographer depending on visual assessment. However, this method is subjective. Therefore, the authors in this study aimed to assess the reliability and diagnostic accuracy of two quantitative methods as objective methods to assess median nerve echotexture changes in patients with CTS compared to controls. 

The study was conducted on two group of participants: Group 1: < 65 years old and Group 2: > 65 years old. Group 1 included 19 healthy volunteers and 37 consecutive patients with electrodiagnostic (EDX)-proven CTS, while Group 2 included 20 healthy volunteers, 20 consecutive patients with EDX-proven CTS, and an additional 30 elderly patients with CTS from the database. Patients with secondary CTS (e.g., tenosynovitis detected in US) were excluded.

The median nerve was scanned at the level of carpal tunnel inlet and the captured image was analyzed. Median nerve brightness, gray level co-occurrence matrix (GLCM), and percentage of the hypoechoic area of the median nerve were calculated using offline software and compared with subjective assessment of the US image and CSA measurement.

In younger patients, GLCM measures were of equivalent diagnostic accuracy to nerve CSA (AUC = 0.97). In older patients, image analysis measures were equivalent or superior to subjective visual analysis and showed similar diagnostic accuracy to CSA (AUC for brightness = 0.88). Moreover, image analysis was abnormal in many older patients with normal CSA values. No difference in image analysis measures was found between groups with mild, moderate, and severe CTS. 

Comments: This study establishes the usefulness of an objective method to assess nerve echotexture in CTS. This study is in keeping with the current trend in the neuromuscular US research to quantify the sonographic parameters that are usually subjectively assessed. This study's merits encompass its broad demographic coverage, encompassing both young and elderly individuals, maintaining consistent US settings throughout measurements, and ensuring that the sonographer remained unaware of the EDX results. The limitations include the exclusion of patients with secondary CTS, the assessment of the nerve only at the carpal tunnel inlet, and the retrospective analysis of the data of some patients (30 elderly patients).