Intramedullary spinal cord metastasis

Metastatic deposit within the spinal cord parenchyma causing acute/subacute myelopathy; uncommon but high-stakes because treatment is time-sensitive.

Clinical

• Rapidly progressive limb weakness, sensory level, sphincter symptoms
• Often known systemic malignancy, but can be first presentation
• Primary sites commonly lung, breast, melanoma, renal; also lymphoma/leukaemia

Imaging features

MRI (primary tool)

• Short segment intramedullary enhancing nodule or mass, often eccentric
• Marked surrounding T2 hyperintense oedema that can be long-segment and disproportionate to lesion size
• Variable cord expansion
• Specific enhancement patterns:
  • Rim sign: thin peripheral rim of more intense enhancement
  • Flame sign: ill-defined tapering enhancement at superior/inferior margin
• Look for accompanying leptomeningeal disease or other spine/brain metastases

Top differentials

• Ependymoma:
  • Central, smoother expansion
  • May have cyst/syrinx
  • Haemorrhage can occur
• Astrocytoma: longer segment infiltrative expansion, less discrete nodule
• Demyelination (MS/NMOSD/MOGAD):
  • Clinical context
  • Lesions often longer or multifocal
  • Enhancement less nodular
• Intramedullary abscess: diffusion restriction, infection context