Use sensory sparing, myokymia, and the pain pattern to distinguish radiation plexopathy from neoplastic plexopathy, because the management pathway changes immediately once the localization is clear. The goal is to localize the lesion correctly before chasing the wrong cause.

Radiation-induced lower motor neuron syndrome causes weakness and areflexia without sensory loss; Radiation plexopathy is typically painless and can show myokymia on EMG; Tumor plexopathy is usually painful; Spinal cord radiation toxicity can be progressive or remitting; Consolidative therapy in primary CNS lymphoma may include whole-brain radiation or high-dose chemotherapy