Radiation
myelopathy is a rare, late-stage adverse event that develops following irradiation at or above 50 Gy. Here, we report a case of irreversible
paraplegia caused by palliative radiation (20 Gy in 5 fractions) to the spinal cord combined with intrathecal
methotrexate (IT-MTX). A 69-year-old man presented with
back pain, prompting a diagnosis of
acute myeloid leukemia. At the first visit, he complained of
muscle weakness and
hypoesthesia in both legs; spinal magnetic resonance imaging (MRI) revealed an epidural mass compressing the spinal cord at the fifth to seventh level of the thoracic vertebrae. This was considered to be an extramedullary lesion of
leukemia, and he received
remission induction therapy including IT-MTX; palliative radiation (20 Gy in 5 fractions) of the epidural mass was initiated the following day. Then, during the course of consolidation
therapy, a second IT-MTX was performed after 1 month and a third after 3 months. While the consolidation
therapy was complete, yielding remission, he developed sudden
paraplegia, as well as bladder and bowel dysfunction (BBD), 10 months later. Spinal MRI showed extensive intramedullary high signal intensity on T2-weighted image, including the irradiation field. It was thought
myelopathy was due to irradiation of the spinal cord combined with IT-MTX. He immediately received
steroid pulse
therapy; however, the
paraplegia and BBD did not improve. It is extremely rare for irreversible radiation
myelopathy to occur with IT-MTX and palliative radiation to the spinal cord. We believe that even with low-dose palliative radiation, caution is required for combined use with IT-MTX.