Imaging studies in NL. (A-B) FDG-PET imaging of a patient with neurolymphomatosis (NL). (A) Multiple sites of involvement, including the brachial and lumbosacral plexi (arrows). (B-C) Bilateral involvement of the brachial plexus in the same patient clearly detected by both FDG-PET (B) and by MRI (C) T2 short T1 inversion recovery imaging. (D-E) Enhanced MRI imaging (T1-weighted with gadolinium) of a patient with NL that affected multiple cranial nerves. (D) Bilateral abnormal enhancement of the oculomotor nerves that corresponded to the clinical presentation of bilateral ophthalmoplegia. (E) Complete resolution of abnormal enhancement after 2 cycles of treatment with intravenous high-dose methotrexate and intra-CSF treatment with cytarabine. These imaging findings matched the marked neurologic improvement observed under treatment. (F-G) FDG-PET imaging of a patient with NL who presented with severe painful sensorimotor neuropathy and bilateral brachial plexus involvement. (F) FDG-PET findings at diagnosis of NL compatible with bilateral brachial plexus involvement by lymphoma. (G) Complete resolution of abnormal tracer uptake after 2 courses of treatment with systemic high doses of methotrexate and cytarabine. The treatments lead to clear neurologic improvement and good control of the painful neuropathy.