Detection of Brachial Plexus and Extraplexal Involvement in Neuralgic Amyotrophy Using MR Neurography: a Single-Center Retrospective Study.

PURPOSE: Neuralgic amyotrophy (NA) is an underrecognized idiopathic inflammatory disorder and MR Neurography (MRN) has become an essential tool for depicting nerve lesions and muscle edema. Imaging is frequently restricted to the brachial plexus and shoulder. However, involvement of distal arm nerves and muscles is common. This study aims to explore imaging findings in patients with NA by utilizing MRN of both the plexus and the associated limb.

METHODS

Patients with NA who underwent MRN of the upper extremity between January 2017 and February 2026 were retrospectively identified. A total of 35 consecutive patients were enrolled, and their clinical features were reviewed. Two experienced neuroradiologists assessed the MRN images for the presence of nerve lesions and muscle edema. Associations between nerve lesions and muscle edema were analyzed.

RESULTS

In 35 patients (median age 46 years, 12 female; median onset-to-MRN 141 days), MRN revealed plexus (n = 28) and terminal branch-level (n = 20) abnormalities. Muscle edema was observed in 26 patients. Correlation analysis revealed significant associations between nerve lesions and edema; specifically, suprascapular lesions were associated with edema in the corresponding muscles. Further significant correlations were identified for the median, radial, musculocutaneous, and axillary nerves.

CONCLUSION

NA is a multifocal neuropathy involving the brachial plexus and distal peripheral nerves. Limiting imaging to the plexus alone carries the risk of missing pathological findings. This study presents a single-center experience with an MRN approach that is sensitive in detecting both nerve lesions and muscle edema of the plexus and the associated limb.