Intradural extramedullary spinal tumors

Intradural extramedullary neoplasms are located outside the spinal cord but within the dural sheath. Schwannomas are the most common intradural extramedullary spinal lesions (30% cases), followed by meningiomas (25% cases) ².

In the pediatric population, the most common intradural extramedullary neoplasms are leptomeningeal metastases resulting from primary brain tumours.

A full list includes:

• benign tumours
  • spinal meningioma
  • spinal schwannoma
  • spinal meningioma
  • spinal neurofibroma
  • spinal paraganglioma
  • myxopapillary ependymoma
• cysts and other benign tumourlike masses
  • spinal lipoma
    • intradural spinal lipoma
  • spinal epidermoid cyst
  • spinal dermoid cyst
  • spinal neurenteric cyst
  • spinal arachnoid cyst
• malignant tumours
  • spinal leptomeningeal metastases

Clinical presentation

The most common presenting symptoms include weakness, back pain and radicular pain.

Radiographic features

Intradural extramedullary masses can have a number of general morphological features:

1. solitary vs multiple
2. may have a dural tail (especially meningiomas) 
3. may have a nerual exit foraminal (extradural) component (i.e. dumbbell appearance) ³

Plain radiograph

• may be normal
• expansion of the spinal canal or intervertebral foramina
• may show a paravertebral mass (more suggestive of a nerve sheath tumour)

CT

• purely intradural lesions may not be shown
• extradural extension
• bone erosion and sclerosis
• heavy calcification is rare in spinal meningiomas and nerve shealth tumours; a heavily calcified intraspinal mass is usually extradural extruded disc material

Myelography

• deviation of the spinal cord away from mass
• ipsilateral subarachnoid space enlargement
• contralateral subarachnoid space effacement
• intradural filling defect outlined by sharp meniscus of contrast (“meniscus sign”)
• the subarachnoid space is blocked and CSF above the block remains unopacified.

MRI

MRI is the modality of choice to fully characterise these masses, and the appearance will vary depending on the histology, and is thus discussed as part of individual articles (see above list). 

The key benefits of MRI over other modalities, is the ability to clearly define the relationship of the mass to the cord, to identify secondary lesions, to identify large feeding/draining vessels and hopefully to give a pre-operative diagnosis. 

See also

• intramedullary spinal tumours
• neoplasms of the spinal canal