Intramedullary spinal tumors

Intramedullary spinal tumors are rare, representing 4-10% of all CNS tumors and <10% of all pediatric CNS neoplasms ⁵. They account for 20% of all intraspinal tumors in adults and 35% of all intraspinal tumors in children ⁸.

A long duration of symptoms prior to diagnosis is typical.

Pathology

Classification

They can be classified according to many ways:

• intramedullary neoplastic lesion

  • glial neoplasms: 90-95% of all intramedullary tumors ⁵

    • spinal ependymoma: 60% of all glial spinal cord tumors ⁵  

    • spinal astrocytoma: 33% of all glial spinal cord tumors ⁵

    • spinal ganglioglioma: 1% of all glial spinal cord tumors ⁵

    • spinal glioblastoma (primary): 7.5% of all intramedullary gliomas and only 1.5% of all spinal cord tumors ¹¹

  • non-glial neoplasms

    • highly vascular lesions

      • spinal hemangioblastoma

      • spinal paraganglioma

    • other rare lesions

      • intramedullary metastasis

      • primary lymphoma of the spinal cord

      • spinal primitive neuroectodermal tumor

      • solitary fibrous tumor

• intramedullary benign masses

  • spinal canal epidermoid cyst

  • spinal canal lipoma

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 ³. 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 ^5,6,9

    • 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 ³.

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 ⁸.

In children, progressive scoliosis may be seen. Motor regression and frequent falls may be the presenting features in young children ⁷.

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 ⁶.

Radiographic features

Plain radiograph

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

Three 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 ^8,12

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) ⁴

    • 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 ⁴)

  • 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 tuberculoma

• 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

• neoplasms of the spinal canal

• intradural extramedullary spinal tumors