Abstract

Background: Multiple myeloma (MM) typically affects the bone marrow. When it spreads to the central nervous system, it usually presents as intracranial metastasis or extradural spinal lesions. Intradural spinal cord metastases are exceedingly rare.

Case Description: A 53-year-old male with immunoglobulin A kappa MM presented with a contrast-enhancing lesion at the T3-4 level, consisting of an intradural lesion and an extradural lesion extending through the foramen. The lesion’s characteristics suggested a schwannoma, but MM involvement was suspected given the patient’s history. Surgical resection and spinal stabilization were performed, and pathological examination confirmed a plasma cell neoplasm. A systematic review of the literature identified 10 cases of intradural spinal lesions associated with MM or solitary plasmacytoma. Most lesions were intradural extramedullary, located primarily in the thoracic spine. Management often included surgery, chemotherapy, and radiotherapy, but the prognosis remained poor, especially with leptomeningeal spread.

Conclusion: This case highlights the diagnostic and therapeutic challenges of intradural spinal MM involvement. While surgery can provide symptomatic relief and confirm the diagnosis, the risk of leptomeningeal dissemination requires close monitoring. A multidisciplinary approach is essential for managing these rare and complex cases, and further studies are needed to refine treatment strategies and improve patient outcomes.

Keywords: Intradural, Microsurgery, Multiple myeloma, Plasmacytoma, Spinal

INTRODUCTION

Multiple myeloma (MM) is a hematologic malignancy characterized by the proliferation of clonal plasma cells, primarily infiltrating the bone marrow. This leads to various complications, including osteolytic lesions, anemia, and renal dysfunction.[ 16 ] Although extramedullary involvement occurs in approximately 7% of cases, central nervous system (CNS) involvement remains exceedingly rare, with an incidence of only 1–2%.[ 15 , 16 ] When MM disseminates to the CNS, it typically manifests as intracranial plasmacytomas or epidural spinal lesions that result from the destruction of adjacent vertebral bones.[ 15 , 18 , 24 ] Conversely, intradural spinal cord lesions represent a distinct clinical entity, accounting for fewer than 0.1% of all complications associated with MM.[ 6 ]

The diagnosis of intradural spinal MM is challenging owing to its generalized radiographic features, which often resemble other prevalent intradural pathologies, such as schwannomas or meningiomas.[ 11 ] The imaging characteristics, which include intermediate T1-weighted signal intensity, T2 hyperintensity, and homogeneous contrast enhancement, exhibit significant overlap with benign neoplasms, thereby necessitating histopathological confirmation.[ 20 ]

The prognosis remains unfavorable, particularly in cases with leptomeningeal dissemination, with median survival ranging from 2 to 8 months, even with multimodal therapy.[ 3 , 15 , 16 ] Historical data suggest that fewer than 20% of patients survive beyond 1 year following central nervous system involvement.[ 3 ] However, recent advancements in systemic therapies, including proteasome inhibitors, immunomodulatory agents, and intrathecal chemotherapy, have yielded modest improvements in outcomes for select patient cohorts.[ 4 , 17 ] Surgical resection is instrumental in alleviating mechanical compression and procuring diagnostic tissue; nonetheless, it does not prevent subsequent leptomeningeal spread, which occurs in more than 50% of cases.[ 14 , 24 ]

This case report illustrates the diagnostic challenges and treatment complexities of intradural spinal MM lesions through a 53-year-old male patient with immunoglobulin A (IgA) kappa myeloma who developed both intradural and extradural lesions at theT3–4 vertebral levels. By combining this case with a systematic review of existing literature, we aim to improve awareness of this rare condition, assess changing treatment approaches, and emphasize the need for multidisciplinary management to enhance outcomes in this aggressive disease variant.

ILLUSTRATIVE CASE

Clinical presentation

A 53-year-old male with a history of IgA kappa MM presented with progressive right monocular vision loss, headaches, and left shoulder abduction weakness. He was treated with chemotherapy and autologous stem cell transplantation 18 months prior and is currently on the maintenance dose of lenalidomide. He was found to have right optic nerve enhancement and a partial-thickness tear of the left supraspinatus tendon with sentinel cyst formation, which explained his symptoms. However, magnetic resonance imaging (MRI) demonstrated an incidental contrast-enhancing intradural extramedullary mass at the thoracic 3–4 level with extension into the left T3-T4 foramen [ Figures 1a - e ]. While the lesion’s radiological features were suggestive of schwannoma, MM recurrence remained a differential diagnosis. Although the patient was mostly asymptomatic from this lesion, surgical resection was pursued due to the extent of spinal cord compression with back pain and the need for pathological confirmation, which was discussed at an institution-wide tumor board meeting with unanimous agreement. Instrumented fusion was also planned in anticipation of T3 pedicle removal.

Figure 1:

(a) Preoperative T2-weighted sagittal magnetic resonance imaging (MRI) showing the intradural lesion located posterior to the T3 vertebral body. (b and c) Preoperative axial T2-weighted MRI sections illustrating the intradural solid tumor compressing the spinal cord, (c) also demonstrate the T3-4 foraminal extension of the tumor. (d and e) Preoperative axial T1-weighted MRI sections demonstrating spinal cord compression and extent of intradural lesion. (f) Intraoperative microscopic image illustrates the identification of an extradural tumor at the T3 to T4 level. (g) The T3 pedicle was removed to expose the entirety of the extradural tumor, which was then resected, isolating the nerve root. (h) The dura was opened to expose the intradural part of the tumor, which was well-defined and removed with meticulous dissection. (i) Surgical field after complete tumor removal. (j) Watertight dural closure. (k and l) Postoperative anterior-posterior and lateral upper thoracic X-rays demonstrating T1-5 stabilization.

Management

After obtaining preposition neuromonitoring recordings, the patient was positioned prone on the surgical bed. T1 to T5 levels were exposed using standard surgical techniques. Pedicle screws were placed at T1-T5 levels on the right side and at T1, T2, and T5 on the left side. The extradural tumor was identified at the T3-T4 level. The left T3 pedicle was subsequently removed to expose the entirety of the tumor. The extradural tumor was carefully resected, isolating the left T3 nerve root [ Figure 1f ]. The dura was opened at midline, revealing a well-defined extramedullary tumor, which was carefully dissected and completely resected [ Figures 1g - i ]. The dura was then closed with 5-0 Prolene in a watertight fashion [ Figure 1j ]. Finally, left T4 pedicle screw was placed, followed by permanent rod placement and fusion.

Postoperative outcomes

The patient recovered well from the surgery without complications, and postoperative upright X-ray films demonstrated good alignment without evidence of hardware failure [ Figures 1k and l ]. Histopathological examination revealed plasma cell neoplasm with abundant necrosis and focal plasmablastic change. Fluorescence in situ hybridization analysis reported translocation of IGHG1 and FGFR3 genes, deletion of the normal IGHG1 gene, and monosomy of chromosome 13, which confirmed the diagnosis of relapsed MM. Postoperatively, the patient recovered well with no acute complications. No new neurological deficits were appreciated. Unfortunately, the patient later developed leptomeningeal dissemination with altered mental status. The patient was initially placed with an intrathecal drug delivery system to manage the leptomeningeal disease. Leptomeningeal disease is currently controlled by triple chemotherapy (methotrexate/hydrocortisone/cytarabine) using an Ommaya reservoir.

DISCUSSION

Extramedullary hematopoietic MM often heralds a poor prognosis and rarely involves the CNS.[ 1 , 6 ] However, when CNS involvement does occur, MM typically presents as intracranial metastases. These lesions are thought to arise from hematogenous dissemination or contiguous seeding from local lytic bone lesions.[ 23 , 24 ] Intradural spinal cord MM lesions are exceedingly rare, with only a few cases reported in the literature.

We conducted a systematic literature review to identify reported cases of spinal intradural lesions associated with MM or solitary plasmacytoma to characterize this manifestation further. A PubMed search was performed from January 1950 to February 2025 using the keywords “multiple myeloma,” “plasmacytoma,” “spine,” “spinal,” and “intradural.” Studies were included if they described at least one human case of MM or solitary plasmacytoma involving an intradural spinal lesion. Exclusion criteria included cases of spinal bony metastases with secondary extradural compression, diffuse leptomeningeal dissemination without a discrete intradural lesion, and non-English publications. Two authors independently screened titles and abstracts, and data extracted included publication details, patient demographics, clinical presentation, lesion location, MRI findings, and treatment strategies [ Table 1 ]. Level of evidence was evaluated for each study using the 2011 Oxford Centre for Evidence-Based Medicine, and the risk of bias was assessed by applying the Joanna Briggs Institute checklists for case reports. As all studies included in the review were case reports, inherent biases, such as publication and selection biases, must be taken into account.

Table 1:

Review of the reported cases of intradural plasmacytoma and MM in the literature.

Intradural involvement of the spinal canal in MM or solitary plasmacytoma is a rare but clinically significant manifestation, with only 10 cases reported in the literature.[ 3 , 6 , 8 , 10 , 13 , 14 , 20 , 26 , 21 , 25 ] Patients presented across a wide age range, from 25 to 67 years (mean age: 50), with an equal gender distribution (5 females, 5 males). Clinical symptoms varied, primarily reflecting the lesion’s location and degree of neurological involvement. Radiculopathy (4/10) and paraparesis (4/10) were the most common presentations, while progressive ataxia (1/10) and quadriparesis (1/10) were also observed.

The MRI findings of intradural plasmacytoma and MM cases demonstrate variable patterns across T1-weighted, T2-weighted, and postcontrast sequences. On T1-weighted imaging, lesions typically exhibited homogeneous isointense signals relative to the spinal cord or adjacent tissues.[ 10 , 20 ] T2-weighted sequences showed greater variability, with hyperintense signals observed in most cases.[ 10 , 11 ] Postcontrast enhancement patterns were predominantly homogeneous, as evidenced in seven cases. Heterogeneous enhancement occurred in Glasser and Glasser,[ 11 ] while Hans et al.[ 13 ] described irregular nodular enhancement. Adjacent bony changes were inconsistently observed. Singh et al.[ 20 ] and the present case documented hyperostotic vertebral reactions, while Faddoul et al.[ 8 ] and Zazpe et al.[ 25 ]reported no associated bone alterations. Leptomeningeal spread with neural foramen involvement was uniquely noted in Hsu et al.[ 14 ] These imaging features align with broader literature describing plasmacytomas as solid tumors with nonspecific but enhancing characteristics on MRI, often requiring differentiation from more common intradural pathologies such as meningioma or neurofibroma.

Of the 10 cases, four were isolated intradural plasmacytomas, while the remaining six occurred in the setting of MM. Lesions were predominantly intradural extramedullary (8/10), with only two cases of intramedullary involvement, both of which were solitary plasmacytomas. Lesions were distributed throughout the spinal axis, with a predilection for the thoracic region (6/8), followed by the cervical (3/8) and lumbar (2/8) regions. One patient had multiple intradural lesions spanning the cervical and thoracic levels. Among the four patients with solitary plasmacytomas, it remains unclear whether any developed MM during follow-up, warranting further investigation to establish the progression risk from plasmacytoma to MM.

Management strategies varied based on lesion type and systemic disease status. Surgical resection was frequently performed (8/10), primarily for symptomatic relief and diagnostic confirmation. A multimodal approach combining surgery, radiotherapy, and chemotherapy was the most common treatment strategy. Two patients received only chemoradiotherapy.[ 13 , 22 ] Among these, one experienced significant neurological deterioration at 10 months, while another died 6 months post-treatment.[ 13 , 22 ] Both cases also likely represented poor surgical candidates due to either disease stage or severe preoperative neurological deficits, such as quadriparesis.

Surgical intervention is crucial in cases presenting with severe neurological symptoms.[ 6 , 11 ] Tumor debulking or complete resection can provide substantial relief by decompressing nerve roots, leading to immediate symptom resolution and an improved quality of life.[ 8 , 20 , 25 ] This is particularly important given the poor prognosis of extramedullary MM, which has a median survival of 2–8 months.[ 2 , 12 , 19 , 22 ] In spinal MM cases, survival times range from 1 to 11 months according to the reported literature, though small sample sizes limit these findings.[ 13 , 14 , 22 ] Adjuvant local radiotherapy is frequently utilized regardless of the extent of surgical resection, as plasmacytomas exhibit radiosensitivity. Radiotherapy has been shown to enhance local cure rates.[ 5 , 19 , 22 ] However, due to the rarity of intradural lesions, there is no established consensus on the optimal RT dose.[ 5 , 6 , 19 , 22 ] In some cases of complete resection, observation and follow-up may suffice, although additional data are required to confirm this approach.[ 10 , 14 , 21 ]

Intrathecal chemotherapy is a critical component of multimodal therapy for leptomeningeal dissemination in MM, though outcomes remain poor overall. In the presented case, the patient developed leptomeningeal disease postoperatively and was managed with triple intrathecal chemotherapy (methotrexate/hydrocortisone/cytarabine) through an Ommaya reservoir, which controlled disease progression. A multi-institutional study of 37 MM patients with CNS involvement reported a median survival of 4.6 months, but long-term survival (median 17.1 months) was achieved in a subset receiving intrathecal chemotherapy combined with radiotherapy and immunomodulatory agents like lenalidomide.[ 3 ] The current guidelines recommend combining intrathecal chemotherapy with systemic therapies and radiation, mirroring approaches used for CNS lymphomas, though no standardized protocols exist due to limited data.[ 7 ] While intrathecal chemotherapy helps reduce cerebrospinal fluid tumor burden and may prolong survival in select cases, its efficacy remains constrained by the blood–brain barrier’s limitation on systemic drug penetration.[ 3 ]

While the treatment of CNS MM remains poorly defined, there is a critical need for systemic therapies that can effectively cross the blood–brain barrier and target the disease.[ 12 , 15 , 16 ] A recent multi-institutional cohort study showed survival improvement for CNS MM patients beyond 2016, but the current approaches have yet to address the dismal prognosis of the condition sufficiently.[ 9 , 16 ] Although T-cell redirecting therapies have demonstrated durable response rates for MM patients, these therapies have not shown similar efficacy in extramedullary disease.[ 16 ] Therefore, optimizing the detection of extramedullary disease, along with the development of future clinical trials and targeted therapies, is essential to improving outcomes for CNS MM patients.

CONCLUSION

This case enhances the understanding of spinal intradural involvement in MM, highlighting the diagnostic and therapeutic challenges associated with this rare condition. While limited by sample size, the literature review provided insights into the clinical management of this rare manifestation. Chemotherapy and radiotherapy are crucial in treating MM, but they may not provide the immediate symptom resolution that surgery offers, especially in intradural spinal cases where most patients present with neurological deficits. When severe neurological symptoms are present, surgical intervention is highly effective in alleviating pain and deficits. This underscores the importance of a multidisciplinary approach tailored to the lesion’s characteristics and the patient’s overall clinical context. Given the rarity of intradural MM, further studies are needed to refine treatment protocols and identify prognostic factors for these patients.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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