Orbital imaging v


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Orbital imaging v

  2. 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. 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. 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. 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. 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. 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. 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. 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. 10. Optic Nerve Glioma:
  11. 11. Optic Nerve Glioma:
  12. 12. Optic Nerve Glioma:
  13. 13. Optic Nerve Glioma:
  14. 14. Optic Nerve Glioma:
  15. 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. 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. 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. 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.
  19. 19. 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.
  20. 20. 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.
  21. 21. Optic Nerve Sheath Meningioma:
  22. 22. Thank you