Quantitative T2‐mapping magnetic resonance imaging for assessment of muscle motor unit recruitment patterns. Issue 5 (12th February 2021)

• Record Type: Journal Article
• Authors: Argentieri, Erin C.; Tan, Ek Tsoon; Whang, Jeremy S.; Queler, Sophie C.; Feinberg, Joseph H.; Lin, Bin; Sneag, Darryl B.
• Is Part Of: Muscle & nerve. Volume 63:Issue 5(2021)
• Page Start: 703
• Page End: 709
• Publication Date: 2021-02-12
• Subjects: electromyography -- MRI -- muscle -- musculoskeletal -- T2 mapping; Neuromuscular diseases -- Periodicals; Muscles -- Periodicals; Nerves -- Periodicals; 616.74
• DOI: 10.1002/mus.27186
• Languages: English
• ISSNs: 0148-639X

Abstract

Abstract: Introduction: In this study, we aimed to determine whether muscle transverse relaxation time (T2 ) magnetic resonance (MR) mapping results correlate with motor unit loss, as defined by motor unit recruitment patterns on electromyography (EMG). Methods: EMG and 3‐Tesla MRI exams were acquired no more than 31 days apart in subjects referred for peripheral nerve MRI. Two musculoskeletal radiologists qualitatively graded T2 ‐weighted, fat‐suppressed sequences for severity of muscle edema‐like patterns and manually placed regions of interest within muscles to obtain T2 values from T2 ‐mapping sequences. Concordance was calculated between qualitative and quantitative MR grades and EMG recruitment categories (none, discrete, decreased) as well as interobserver agreement for both MR grades. Results: Thirty‐four muscles (21 abnormal, 13 control) were assessed in 13 subjects (5 females and 8 males; mean age, 46 years) with 14 EMG‐MRI pairs. T2 ‐relaxation times were significantly ( P < .001) increased in all EMG recruitment categories compared with control muscles. T2 differences were not significant between EMG grades of motor unit recruitment ( P = .151‐.702). T2 and EMG score concordance was acceptable (Harrellʼs concordance index [c index]: rater A, 0.71; 95% confidence interval [CI], 0.51‐0.87; rater B, 0.77; 95% CI, 0.57‐0.91). Qualitative MRI and EMG score concordance was poor to acceptable (c index: rater A, 0.60; 95% CI, 0.50‐0.79; rater B, 0.72; 95% CI, 0.55‐0.89). T2 values had moderate‐to‐substantial ability to distinguish between absent vs incomplete (ie, decreased or discrete) motor unit recruitment (c index: rater A, 0.78; 95% CI, 0.50‐1.00; rater B, 0.86; 95% CI, 0.57‐1.00). Discussion: Quantitative T2 MR muscle mapping is a promising tool for noninvasive evaluation of the degree of motor unit recruitment loss.