This document discusses imaging findings of optic nerve enlargement. It focuses on optic nerve glioma and optic nerve sheath meningioma. For optic nerve glioma, CT can evaluate the optic nerve but MR imaging is more sensitive for intracranial extension. Findings include fusiform nerve enlargement that may enhance variably. For optic nerve sheath meningioma, CT can show tram-track or donut appearances, while MRI is best to assess intra-cranial spread, showing segmental nerve thickening and enhancement. Differential diagnosis includes tumors, increased intracranial pressure, and other non-neoplastic causes.

1. HEAD AND NECK IMAGING
EHAB ABOU ELFOTOUH. MD.

2. Optic Nerve Enlargement D.D:
 Neoplasms:
 Optic nerve glioma.
 Meningioma.
 Hemangioblastoa.
 Schwannoma.
 Ganglioglioma.
 Medulloepitheliomas.
 Metastasis.
 Leukemia.
 Nonneoplastic:
 Increased intracranial
pressure.
 Optic neuritis.
 Graves disease.
 Orbital pseudotumor.
 Toxoplasmosis.
 Tuberculosis.
 Sarcoidosis.
 Central retinal vein
occlusion.
 Traumatic hematoma of
the optic nerve.

3. Optic Nerve Glioma:
 Optic nerve gliomas are histologically juvenile pilocytic
astrocytomas, WHO grade I.
 May involve any portion of the optic pathways as well
as the hypothalamus.
 Representing 4% of orbital tumors.
 Usually manifested in the first decade of life.
 The most common intraconal tumor of childhood.
 More than half of patients have neurofibromatosis type
1 (NF1).

4. Optic Nerve Glioma:
 CT Imaging
Findings:
 Imaging depends on the
macroscopic growth
pattern of the tumor.
 Allows good evaluation of
the optic nerve due to the
intrinsic contrast between
the nerve and the conal
fat.
 But is less sensitive
than MR imaging for
intracranial extension.

5. Optic Nerve Glioma:
 Fusiform enlarged
optic nerve.
 kinking or tortuosity of
its course.
 Iso- to slightly hypo
attenuation.
 May be eccentric or a
discrete mass seen
from the nerve.

6. Optic Nerve Glioma:
 High attenuation or
calcification are rare.
 Enlargement of the optic
canal.
 Enhancement is
variable.
 Cystic tumors show
enhancement of its
wall.

7. Optic Nerve Glioma:
 MR imaging:
 Better shows intracranial
extent.
 Coronal and axial thin-
section of T1, T2 and fat
suppression.
 Screening examination of
the brain.
 Post contrast T1 and fat
supp. images.

8. Optic Nerve Glioma:
 Fusiform or less commonly
eccentric globoid,
enlargement of optic
pathway.
 iso- to hypointense to
the optic pathway on
TIWIs.
 slightly hyperintense on
T2WIs.
 Areas of hemorrhage or
calcification are rare.

9. Optic Nerve Glioma:
 Enhancement with IV
gadolinium is variable.
 Posterior extension may
at seen only at post IV
contrast imaging.
 Isolated optic nerve
glioma more common in
patients with NF1.
 Optic pathways
extension more
common in children
without NF1.

10. Optic Nerve Glioma:

11. Optic Nerve Glioma:

12. Optic Nerve Glioma:

13. Optic Nerve Glioma:

14. Optic Nerve Glioma:

15. Optic Nerve Sheath
Meningioma:
 Meningiomas primarily in the optic nerve sheath are
even rarer than glioma.
 Mostly often in middleaged women.
 Bilateral optic nerve sheath meningiomas are rarely
and association with neurofibromatosis.
 Predominant early feature is visual loss.
 Proptosis occurs later.
 Physical examination reveals an abnormal optic
disk, which may be swollen or atrophic.
 Visual field revealed usually a central scotoma.
 Restriction of eye movement.

16. Optic Nerve Sheath
Meningioma:
 CT findings:
 Segmental or diffuse
thickening of the optic
nerve.
 Fusiform but uniform
thickening of nerve
sheath more common.
 Normal optic nerve
running through the
tumor, have „ „tram-
track‟ „ appearance on
axial images.

17. Optic Nerve Sheath
Meningioma:
 In coronal views a
“donut” configuration,
with a ring of high
density around nerve.
 Low-density normal
nerve surrounded by the
higher density tumor.
 This finding can
differentiating
meningioma from
glioma.

18. Optic Nerve Sheath
Meningioma:
 Calcification is
uncommon but more
frequent than in
gliomas.
 Enhanced on post
contrast imaging.
 Optic canal widening
may be demonstrated.
 Typical hyperostosis of
adjacent bones.

20. Optic Nerve Sheath
Meningioma:
 MRI findings:
 Better for assessment of
intra-cranial extension.
 Segmental or diffuse
enlargement.
 Fusiform thickening.
 On T1WIs, iso-signal with
gray matter.
 On T2WIs, iso to slight
bright signals.

21. Optic Nerve Sheath
Meningioma:
 O post contrast, intense
enhancing criteria.
 „tram-track‟ on axial
imaging.
 “doughnut” configuration
on coronal scan.
 Intra-cranial extension
better detected on post
contrast scan.

22. Optic Nerve Sheath
Meningioma:

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