Transcript Intramedullary Lesions in NF1 and NF2 (NXPowerLite)

INTRAMEDULLARY SPINAL
CORD LESIONS IN NF1 AND
NF2
Sheila Kori
NF1
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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
NF1
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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
NF2
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“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
NF2
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Best Imaging Tool: Contrast enhanced MR
Imaging Findings:
 Bilateral vestibular schwannomas
 Meningiomas and schwannomas involving CNs
 Spinal manifestations: meningiomas, ependymomas, and
nerve sheath tumors
Intramedullary Tumors
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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
Astrocytomas
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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
Astrocytomas
MR T2 (left) and post Gd T1
(right) images show small,
cystic, and enhancing
astrocytoma.
Ependymomas
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Ependymomas are slow growing, displace adjacent neural tissue, and arise from
ependymal cells of central canal causing symmetric cord expansion.
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T1WI: Iso- or hypointense relative to the spinal cord
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T2WI: lesions may be isointense or hyperintense
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Most cases (60%) show cord edema around the masses
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Average number of vertebral segments involved = 3.6
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78%–84% of ependymomas have at least one cyst
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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.
Ependymomas
MR T2 (left) and post Gd T1
(right) images show relatively
well-defined cervical
ependymoma.
Schwannomas
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Most commonly found locations: extradural or intradural extramedullary,
however there have been about 60 reports of intramedullary schwannomas.
Pathogenesis is unknown. Some theories include:
1.
Central inclusion of Schwann cells during embryological development
2.
Aberrant Schwann cells around intramedullary myelin fibers
3.
Extension of Schwann cells along the intramedullary perivascular
nervous plexus
4.
Transformation of pial cells originating from neuroectoderm into
Schwann cells
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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
Intramedullary Schwannomas
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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
Intramedullary Schwannomas
MR sagittal (left) and axial
(right) T2 images show welldefined, eccentric schwannoma
in mid thoracic spinal cord.
References
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Ozawa N, Tashiro T, et al. Subpial schwannoma of the cervical spinal cord mimicking an
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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; 218:434
Egelhoff JC, Bates DJ, et al. Spinal MR finding in neurofibromatosis Types 1 and 2. AJNR.
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