Successful treatment of central nervous system myeloma manifesting as cauda equina nodules with intrathecal chemotherapy, lenalidomide and dexamethasone

We report a case of central nervous system myeloma manifesting as cauda equina nodules, successfully treated with triple intrathecal (IT) chemotherapy, lenalidomide and dexamethasone. After presenting with multiple plasmacytomas which led to a diagnosis of non-secretory myeloma at age 56, the patient underwent multiple episodes of treatment for relapsing myeloma over a 7-year period. In March 2017, he presented with declining gait over a month with bilateral hip flexion weakness, absent lower limb reflexes and dorsal column loss. MRI of the spine revealed multiple enhancing cauda equina nodules at L1-L3. Cerebrospinal fluid (CSF) examination confirmed a clonal plasma cell population and disease was not found elsewhere. He was treated with radiotherapy, IT and intravenous methotrexate and cytarabine. However, repeat lumbar puncture revealed persistent disease. Clearance of CSF plasma cells was achieved with two times a week IT cytarabine, methotrexate and dexamethasone. He was started on lenalidomide and dexamethasone with no evidence of disease progression at 12 months.