We report a 36-year-old woman whose first MRI after developing symptoms of cervical nerve root irritation was normal. Eight months later, after progression to tetraparesis and demonstration of an extensive contrast-enhancing intramedullary lesion giving high signal on T2-weighted images, the diagnosis of lymphoblastic non-Hodgkin's lymphoma was made by biopsy. The lesion responded for a short time to corticosteroid medication, but later rapidly extended to the epidural soft tissues, probably due to a cerebrospinal fluid fistula. Despite radio-and chemotherapy, the patient survived only 7 months from histological diagnosis and 15 months from the onset of symptoms.