Intramedullary spinal tumors

Intramedullary spinal tumors are rare, representing 4-10% of all CNS tumors and less than 10% of all pediatric CNS neoplasms . They account for 20% of all intraspinal tumors in adults and 35% of all intraspinal tumors in children .

A long duration of symptoms prior to diagnosis is typical.

Pathology

Classification

They can be classified according to many ways:

Associations

Intramedullary spinal neoplasms are more common in patients with neurofibromatosis:

  • ependymomas occur more often in patients with NF2
  • astrocytomas occur more often in patients with NF1

Approximately 70% of intramedullary tumors are associated with cysts . Two types of cysts are recognized:

  • tumoral (or intratumoral) cysts
    • contained within the tumor itself
    • typically demonstrate peripheral enhancement
    • may result from necrosis, fluid secretion, or degeneration of the neoplasm
    • need to be resected along with the solid portion of the tumor because there is a high likelihood of neoplastic cells within the cyst wall
    • occurs in association with the following proportion of tumors
      • spinal ganglioglioma: in 46%
      • spinal ependymoma: in 22%
      • spinal astrocytoma: in 21%
      • spinal hemangioblastoma: in 2-4%
  • non-tumoral (or reactive) cysts
    • occur rostral or caudal to the solid portion of the tumor
    • occur due to dilatation of the central canal
    • do not enhance
    • present in 60% of all intramedullary spinal tumors
    • may resolve once the neoplasm is resected

Syringomyelia occurs in approximately 50% of all intramedullary tumors but is most frequently associated with hemangioblastomas .

Clinical presentation

The presentation of intramedullary tumors depends on their size and location. The most common presenting symptoms include back/neck pain, radicular pain, weakness, paresthesia, gait disturbance and bowel and bladder dysfunction. Brown-Sequard syndrome may occur. An uncommon presentation is acute headache due to subarachnoid hemorrhage .

In children, progressive scoliosis may be seen. Motor regression and frequent falls may be the presenting features in young children .

Symptoms are usually slowly progressive. Due to their non-specific nature, the diagnosis is often delayed. An exception is intramedullary metastastases, which are diagnosed within one month of symptom onset in up to 75% of cases .

Radiographic features

Plain film

Widening of the interpedicular distance may be seen in less than 10% of cases

CT

Generally not useful because bony changes are relatively rare.

Myelography
  • the spinal cord can be enlarged
  • gradual subarachnoid space effacement
MRI

3 general characteristics of intramedullary neoplasms are recognized on MRI:

  • they cause either focal or diffuse spinal cord expansion
  • they produce high signal intensity on proton density and T2 weighted images
  • the vast majority show at least some contrast enhancement, in contrast to intracranial neoplasms, even low-grade intramedullary tumors enhance to some degree; however, the absence of enhancement does not exclude an intramedullary neoplasm in the presence of cord expansion
  • Differential diagnosis

    Various lesions may mimic intramedullary tumors. The differential diagnosis of intramedullary tumors includes:

    • vascular lesions
      • cavernous malformation (cavernoma)
        • rounded regions of heterogeneous signal intensity on T1 and T2 weighted images due to blood
        • products of varying ages (“popcorn appearance”)
        • low signal intensity rim on T2 weighted images (hemosiderin)
        • hypointense “blooming” on gradient echo sequences (hemosiderin)
        • may demonstrate minimal enhancement on post-contrast images
        • minimal cord expansion or edema unless there has been recent hemorrhage
      • dural arteriovenous fistula (DAVF)-(type I AVM) 
        • spinal cord may be normal size or enlarged
        • hyperintense on T2 weighted images (due to edema)
        • prominent vessels (flow voids) are usually present on the posterior aspect of the cord
        • variable enhancement on post-contrast images
        • typically located in the dorsal aspect of the lower thoracic cord and conus medullaris
      • spinal cord infarction 
        • spinal cord is usually enlarged
        • hyperintense on T2 weighted images and DWI
        • post-contrast enhancement may or may not be present (enhancement is usually present in the subacute stage)
        • signal intensity abnormality may be limited to the central grey matter or may involve most of the cross sectional area of the cord
        • signal abnormality typically extends over multiple vertebral body segments
        • can occur at any location in the cord but has a propensity for the upper thoracic or thoracolumbar regions
        • vertebral body T2 hyperintensity may occasionally be seen (due to concomitant infarction)
    • inflammatory lesions
      • demyelination (e.g. multiple sclerosis)
        • usually no spinal cord enlargement (enlargement is seen in 6-14% cases)
        • plaques are generally shorter than two vertebral body segments in length and involve less than half the cross-sectional area of the cord
        • characteristically peripherally located in the dorsal and lateral columns
        • isointense to hypointense on T1 weighted images (unlike brain plaques, cord plaques may not be visible as areas of hypointensity on T1 weighted imaegs)
        • hyperintense on T2 weighted images
        • signal abnormality is typically poorly marginated
        • plaque enhancement correlates with acute lesion activity (usually lasts less than two months)
        • in most patients additional lesions of variable enhancement are present in the brain and spinal cord (MS is solely confined to the spinal cord in 5-24% of patients )
      • transverse myelitis
        • variable enlargement of the spinal cord
        • hyperintense on T2 weighted images and iso- or hypointense on T1 weighted images
        • variable enhancement patterns (none, diffuse, patchy, peripheral)
        • lesions commonly extend for 3-4 spinal segments
        • lesions typically occupy greater than two thirds of the cross-sectional area of the cord
        • acute clinical course
      • spinal cord abscess 
        • core is hypointense on T1 weighted images and hyperintense on T2 weighted images
        • rim enhancement
        • cord expansion
        • may show restricted diffusion on DWI
        • may have adjacent vertebral or disc abnormalities
    • spinal cord contusion (acute)
      • isointense to hypointense on T1 weighted images, hyperintense on T2 weighted images
      • cord swelling
      • usually associated with other spinal injuries (osseous, disc, vascular)

    See also