Teaching NeuroImages: Median nerve MRI changes over time in neuralgic amyotrophy

A 40-year-old woman presented with 2 weeks of left arm pain followed by hand weakness and numbness. Electrodiagnostic testing revealed an isolated median sensorimotor axonopathy localizing proximal to the pronator teres. The working diagnosis of a forme fruste of neuralgic amyotrophy was made. MRI of the left arm was performed to exclude rare structural causes of proximal median neuropathy. The median nerve showed inflammatory features with a diffusely increased signal on short tau inversion recovery sequences that enhanced with gadolinium (figure, A). Two years after onset, symptoms had resolved. Repeat MRI showed resolution of the abnormal findings (figure, B).