spinal meningioma

Meningiomas arising from the coverings of the spinal cord are one of the two most common intradural extramedullary spinal tumors, representing 25-30% of all such tumors .

This article specifically relates to spinal meningiomas. For a discussion on intracranial meningiomas and a general discussion of the pathology refer to the main article: meningioma.

Epidemiology

Spinal meningiomas represent a minority of all meningiomas (approximately 12%) . They have a peak incidence in the sixth through eighth decades .

Spinal meningiomas have a strong sex predilection in adults, stronger than that seen with intracranial meningiomas, with females accounting for 75-90% of cases . In children, there does not appear to be a sex predilection.

Risk factors

The best recognized environmental risk factor is exposure to high dose ionizing radiation, especially in childhood . Prior trauma is another risk factor .

Associations

There is an increased incidence of spinal meningiomas in patients with neurofibromatosis type 2 (NF2). In fact, in the pediatric population, meningiomas uncommonly occur outside of the setting of NF2.

Clinical presentation

Despite usually being small, due to the confines of the spinal canal, spinal meningiomas can result in significant neurologic dysfunction. The majority of patients present with motor deficits as a result of compression of the spinal cord. Less common presentations include sensory deficits, pain and sphincter dysfunction.

Pathology

Most spinal meningiomas are benign, with 70-90% being classified as WHO grade I lesions . Less common are tumors with more aggressive features consistent with WHO grade II (5-25%) or grade III (1-5%).

There are many histomorphometric variants of meningioma recognized in the WHO classification. The most common spinal meningioma histology is WHO grade I meningothelial meningioma (80%) . WHO grade II clear cell meningiomas have a predilection for the spine and are believed to originate from the denticulate ligaments .

For a discussion of the pathology of meningiomas, refer to the general meningioma article.

Radiographic features

The vast majority (90%) of spinal meningiomas are intradural extramedullary in location. Occasionally (5%), purely extradural tumors are found. The remainder (5%) have both intradural and extradural components taking on a dumbbell appearance.

Spinal meningiomas are not distributed evenly along the canal :

  • cervical spine: 15%
  • thoracic spine: 80%
  • lumbosacral spine: 5%

Meningiomas are most often located lateral to the spinal cord (60-70%) . Those in the cervical spine are more likely to be located anteriorly compared to those in the thoracic spine .

Most meningiomas are solitary lesions (98%). Multiple meningiomas are most often associated with NF2 .

Plain radiograph
  • usually normal
  • rarely bone erosion or calcification
CT 
  • isodense or moderately hyperdense mass
  • hyperostosis may be seen but is not as common as in the intracranial forms
  • calcification may be present but are uncommon (5%) 
CT myelography
  • arachnoid isolation sign: intradural tumor separated from spinal cord by contrast in subarachnoid space
MRI
  • well-circumscribed
  • broad-based dural attachment
  • dural tail sign (60-70%)
  • ginkgo leaf sign in meningiomas arising lateral or ventrolateral to the spinal cord

They share similar signal characteristics to typical intracranial meningiomas:

  • T1: isointense to slightly hypointense, possibly heterogeneous
  • T2: isointense to slightly hyperintense
  • T1 C+ (Gd): moderate homogeneous enhancement

Occasionally, densely calcified meningiomas are hypointense on T1 and T2 and show only minimal contrast enhancement.

Treatment and prognosis

Spinal meningiomas are typically slow growing. Surgery is the treatment of choice and complete tumor removal is achieved in the vast majority of patients. Less than 10% experience recurrence .

Differential diagnosis

The primary differential consists of nerve sheath tumors (spinal schwannoma and spinal neurofibroma):

  • typically located anteriorly (compared to meningiomas that are usually located posterolaterally)
  • tendency for multiplicity
  • may have low-intensity central regions on post-contrast T1 and T2 weighted images
  • not associated with a broad dural base
  • neural exit foraminal widening is more commonly seen with nerve sheath tumors