Intramedullary Spinal Cord Lesions in NF1 and NF2

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Intramedullary Spinal Cord Lesions in NF1 and NF2

• Sheila Kori

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NF1

• Most common neurocutaneous disorder, autosomal
  dominant
• Pathophysiology Mutation in or deletion of the
  NF1 gene, which encodes neurofibromin, leads to
  tissue proliferation and tumor development. The
  oligodendrocyte myelin glycoprotein is embedded
  in this gene which may be the cause of white
  matter lesions.
• Incidence 1 3,000-5,000

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NF1

• Best Imaging Tool MRI to evaluate for white
  matter lesions, visual pathway gliomas, and
  plexiform lesions
• Imaging Findings
• Hyperintense lesions on T2W1
• White Matter lesions involve dentate nuclei of
  cerebellum, globus pallidus, thalamus, pons,
  midbrain, hippocampus
• Visual pathway gliomas
• Sphenoid wing dysplasia
• Aneurysms and moyamoya
•  

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NF2

• MISME Multiple intracranial schwannomas,
  meningiomas, ependymomas
• Pathophysiology Mutations in the NF2 gene that
  encodes merlin which functions as a tumor
  suppressor. Results in decreased function or
  production of this protein causing development of
  tumors in the central and peripheral nervous
  systems. 50 of patients have NF2 as a result of
  a new gene mutation.
• Incidence 1 40,000

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NF2

• Best Imaging Tool Contrast enhanced MR
• Imaging Findings
• Bilateral vestibular schwannomas
• Meningiomas and schwannomas involving CNs
• Spinal manifestations meningiomas, ependymomas,
  and nerve sheath tumors

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Intramedullary Tumors

• Intramedullary lesions are rare, 4-10 of CNS
  tumors
• Are found more commonly in patients with
  neurofibromatosis
• NF2 associated with ependymomas
• NF1 associated with astrocytomas
• Some reports of intramedullary schwannomas

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Astrocytomas

• 75 are well-differentiated grade I, 25 are
  grade III (anaplastic) lesions
• Usually eccentrically located within the cord,
  since it arises from cord parenchyma,
  infiltrative
• Poorly defined margins, no cleavage plane
• Patchy enhancement after intravenous contrast
  material administration.
• T1WI Iso- to hypointense relative to the spinal
  cord
• T2WI hyperintense
• Average number of vertebral segments involved 7

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Astrocytomas
MR T2 (left) and post Gd T1 (right) images show
small, cystic, and enhancing astrocytoma.
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Ependymomas

• Ependymomas are slow growing, displace adjacent
  neural tissue, and arise from ependymal cells of
  central canal causing symmetric cord expansion.
• T1WI Iso- or hypointense relative to the spinal
  cord
• T2WI lesions may be isointense or hyperintense
• Most cases (60) show cord edema around the
  masses
• Average number of vertebral segments involved
  3.6
• 7884 of ependymomas have at least one cyst
• 84 enhanced after administration of intravenous
  Gd-based contrasts and (89) had well-defined
  margins on post Gd images
• NF2 patients with nonsense and frameshift
  mutations when compared with those of other types
  of mutations are more likely to have
  intramedullary tumors but not any other type of
  tumor.

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Ependymomas
MR T2 (left) and post Gd T1 (right) images show
relatively well-defined cervical ependymoma.
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Schwannomas

• Most commonly found locations extradural or
  intradural extramedullary, however there have
  been about 60 reports of intramedullary
  schwannomas.
• Pathogenesis is unknown. Some theories include
• Central inclusion of Schwann cells during
  embryological development
• Aberrant Schwann cells around intramedullary
  myelin fibers
• Extension of Schwann cells along the
  intramedullary perivascular nervous plexus
• Transformation of pial cells originating from
  neuroectoderm into Schwann cells
• Tumoral growth of Schwann cells on a dorsal root
  located in a critical area corresponding to the
  point where the dorsal root loses its cover and
  enters the pia mater

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Intramedullary Schwannomas

• Characteristics on MRI
• Well defined margins
• Uniform contrast enhancement on post Gd T1WI
• Eccentrically located on axial and coronal images
• Treatment complete resection, often likely to
  cure

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Intramedullary Schwannomas
MR sagittal (left) and axial (right) T2 images
show well-defined, eccentric schwannoma in mid
thoracic spinal cord.
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References

• Barkovich JA. Diagnostic Imaging Pediatric
  Neuroradiology. 2007 I-8-2 I-8-9
• Ozawa N, Tashiro T, et al. Subpial schwannoma of
  the cervical spinal cord mimicking an
  intramedullary tumor. Radat Med. 2006 24690-694
• Patronas NJ, Courcoutsakis N, Bromley CM, et al.
  Intramedullary and spinal canal tumors in
  patients with neurofibromatosis 2 MR imaging
  findings and correlation with genotype. Radiology
  2001 218434
• Egelhoff JC, Bates DJ, et al. Spinal MR finding
  in neurofibromatosis Types 1 and 2. AJNR. 1992
  131071-1077
• Koeller K,Rosenblum, SR, Morrison AL. Neoplasms
  of the Spinal Cord and Filum Terminale
  Radiologic-Pathologic Correlation. RadioGraphics
  2000 2017211749
• Lee M, Rezai, A, Freed D, Epstein F.
  Intramedullary Spinal Cord Tumors in
  Neurofibromatosis. Neurosurgery. 1996 3832-37