Intradural extramedullary solitary plasmacytoma originating in the cervical spine in the setting of refractory multiple myeloma: illustrative case.

Background: Multiple myeloma (MM) and plasmacytoma metastases to the spine are extremely rare, with 9 cases reported in the literature. Only 2 describe cases of solitary plasmacytoma (SP) specifically in the cervical spine, both in patients without known histories of MM. Therefore, the natural history of MM recurrence as SP in the cervical spine remains unknown.

Observations: The authors describe the case of a 67-year-old woman with a history of MM after stem cell transplant and chemotherapy in remission for a year who presented with progressive cervical myelopathy found to have an intradural extramedullary solitary lesion at C2-3 on MRI of the whole spine. The patient underwent C1-3 laminectomies for decompression and intradural biopsy of the lesion, with pathology consistent with plasmacytoma. The patient's motor examination improved significantly postoperatively.

Lessons: SP should be included in the differential diagnosis for intradural extramedullary lesions found in the spine, particularly in patients with a history of MM and tumor resistance to radiotherapy. Despite plasmacytoma's classically radiosensitive nature, it is possible to have residual tumor after radiation therapy. In these cases, patients may benefit greatly from surgical biopsy and decompression followed by adjuvant radiotherapy. https://thejns.org/doi/10.3171/CASE24731.