Brachial plexitis or neuritis? MRI features of lesion distribution in Parsonage–Turner syndrome

Introduction: This study seeks to characterize lesion distribution in Parsonage–Turner Syndrome (PTS) using high-resolution MRI. Methods: MRIs of 27 patients with clinically confirmed PTS were reviewed. Two radiologists independently evaluated the brachial plexus proper, side and terminal plexus branches, and more distal, upper extremity nerves. Results: All patients had at least 1 clinically involved nerve. MRI revealed that the plexus appeared normal in 24 of 27 patients; in 3 other patients, signal hyperintensity was seen immediately proximal to the take-off of abnormal side or terminal branch nerves. Focal intrinsic constrictions were detected in 32 of 38 nerves. MRI interobserver agreement was high (Cohen's κ = 0.839). Discussion: MRI findings, corroborated by electrodiagnostic testing, localized abnormalities to plexus branches and peripheral nerves, suggesting that PTS is characterized by 1 or more mononeuropathies rather than changes involving a portion of or the complete plexus proper. These results may improve diagnosis, prognostication, and management. Muscle Nerve 58: 359–366, 2018.