Optic nerve meningioma

Case contributed by Mahmoud Ibrahim Mekhaimar


Left eye proptosis

Patient Data

Age: 40 years
Gender: Male

A left orbital intra-conal soft tissue mass lesion is seen replacing the retro-orbital fat and showing the following features, extension and relations:

  • it appears isodense (as compared to the extra-ocular muscles) with few calcific foci seen within. In the post-contrast series, it shows homogeneous enhancement with non-enhancing optic being circumstantially encased by the aforementioned lesion (giving tram track sign in the axial images and dot sign n the coronal images).
  • it measures about 3.3 x 2.2 x 1.8 cm along its axial and CC dimensions respectively.
  • it causes subsequent eye proptosis. 
  • it is seen abutting the left eye globe, yet no evidence of invasion.
  • it is seen extending posteriorly till the orbital apex.
  • medial bowing of the lamina papyracea and rarefaction of the superior orbital wall, yet no evidence of cortical beach.

Case Discussion

The above described features are suggestive of left optic nerve meningioma. Glioma and meningioma are the most common orbital masses. The cell of origin of optic nerve sheath meningioma is the optic nerve arachnoid sheath.

Classically, meningiomas have a “tram-track” configuration on axial images as the enhancing tumor lies on both sides of the optic nerve while the optic nerve itself does not enhance. While on coronal images, this configuration appears similar to donuts or dot sign. 

The main differential diagnosis is gliomas. It causes fusiform expansion of the optic nerve and the optic nerve could not be separated from the lesion.

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