Methotrexate-associated Peripheral Neuropathy on 18 F-FDG PET/CT and MRI Masquerading as Neurolymphomatosis

Area of Science:

• Neurology
• Oncology
• Toxicology

Background:

• Primary central nervous system lymphoma can present with diverse neurological complications.
• Methotrexate is a common chemotherapeutic agent with known neurotoxic potential.
• Differentiating drug-induced neuropathy from disease progression (neurolymphomatosis) is clinically challenging.

Purpose of the Study:

• To report a case of suspected neurolymphomatosis that was ultimately diagnosed as methotrexate-induced neuropathy.
• To highlight the diagnostic challenges and the importance of nerve biopsy in such cases.
• To demonstrate the efficacy of alternative therapy in managing chemotherapy-induced neurological deficits.

Main Methods:

• Clinical presentation of a 53-year-old woman with primary central nervous system lymphoma and vitreal involvement.
• Diagnostic workup including electromyography, 18F-FDG PET CT, and MRI of the forearms.
• Histopathological examination of a right ulnar nerve biopsy.
• Treatment modification from methotrexate to TEDDI-R therapy.

Main Results:

• Electromyography suggested mononeuropathies, raising suspicion for neurolymphomatosis or vasculitis.
• Imaging studies were equivocal, showing findings suspicious for neurolymphomatosis, abscesses, or infarcts.
• Nerve biopsy confirmed toxic/drug-related axonal neuropathy as the cause of symptoms.
• Discontinuation of methotrexate and initiation of TEDDI-R therapy resulted in complete pain relief.

Conclusions:

• Peripheral neuropathy following methotrexate infusion can mimic neurolymphomatosis, necessitating thorough investigation.
• Nerve biopsy is crucial for accurate diagnosis in complex neurological presentations related to chemotherapy.
• TEDDI-R therapy offers an effective alternative for managing methotrexate-induced peripheral neuropathy.