A 51-year-old man presented under stroke protocol with left-sided weakness, evolving over hours, and 3 weeks of radicular pain. He had multiple myeloma (MM), treated 7 years earlier with autologous stem cell transplant, maintained thereafter on lenalidomide and bortezomib. Gadolinium-enhanced magnetic resonance imaging (MRI) revealed leptomeningeal enhancement throughout the lower spinal cord, conus medullaris, and cauda equina (Figure 1A, arrows). Cerebrospinal fluid (CSF) contained 326 × 106 nucleated cells/liter, 2 × 106 erythrocytes/liter, 95.5 milligrams/deciliter of protein (normal range, 20-40), and normal glucose. Papanicolaou-stained CSF cytology showed abnormal plasma cells (Figure 1B) with monoclonal Kappa light chain expression. Systemic staging investigations were unremarkable. He was diagnosed with isolated leptomeningeal recurrence of MM. He underwent craniospinal radiation after induction intrathecal chemotherapy, and later received selinexor and pomalidomide. On 7-month follow-up, his weakness resolved but pain persisted.
Figure 1.
A, Pre-gadolinium axial view of bulky leptomeningeal disease in the spine. B, A nodular lesion (arrowhead) is apparent at the same level seen in (A) following the administration of gadolinium. C, Diffuse leptomeningeal enhancement is demonstrated on a sagittal view MRI of the spine (arrows). D, Cerebrospinal fluid cytology depicting the presence of immature plasma cells. MRI indicates magnetic resonance imaging.
Neurohospitalists know that many cancers can have meningeal spread. Leptomeningeal myelomatosis (LMM) is rare and less well known. It is diagnosed by confirming malignant plasma cells in CSF. While the incidence remains unclear, 23 of approximately 2000 patients with MM had LMM, with a median survival of 3 months from diagnosis.1 The median onset from MM diagnosis to LMM is approximately 390 to 434 days.1,2 Our patient is atypical because LMM was diagnosed 7 years after his MM diagnosis. This prolonged latency is rare.
Workup includes lumbar puncture, systemic staging, and brain and spine MRI. Neuroimaging may be negative in 30% of cases.2 Although the optimal therapy is unestablished, treatment typically involves intrathecal chemotherapy and sometimes craniospinal radiotherapy.3
Acknowledgements
The authors thank the patient for providing consent to publish his case.
Authors’ Note: Signed, informed patient consent was obtained. Given the nature of our paper, ethics approval was not sought.
Declaration of Conflicting Interests: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.
Funding: The authors received no financial support for the research, authorship, and/or publication of this article.
ORCID iD: Amit K. Sharma, MD 
https://orcid.org/0000-0002-2616-0884
Seth A. Climans, MD
https://orcid.org/0000-0002-4961-237X
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