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This was a child with bilateral visual loss.

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We have the FLAIR scan on the left and the

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post-gadolinium T1-weighted scan

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through the brain on the right.

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As we scroll through,

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we immediately identify an abnormality in the left orbit

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which is intraconal and is inseparable

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from the optic nerve. So once again,

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we are considering optic nerve glioma versus

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optic nerve meningioma.

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In children, optic nerve gliomas are much more common

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than optic nerve meningiomas,

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which are a tumor generally of middle age.

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In this case,

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as we scroll further superiorly, we see that there is a

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large lesion which is affecting the optic chiasm,

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as well as the prechiasmal optic nerves.

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On post-gadolinium enhanced post-gadolinium-enhanced scan,

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we see the prechiasmal portion,

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the optic chiasmal portion and we're starting to see

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some elements of enhancement extending more posteriorly.

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This lesion infiltrates the interpeduncular cistern,

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as well as the left temporal lobe.

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I mentioned previously that these tumors generally are

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pilocytic astrocytomas,

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and therefore, the presence of cystic portions

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should not be unexpected.

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Here we have, on the T1 post-gadolinium enhanced scan,

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an area of cyst formation that has similar signal

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intensities to cerebrospinal fluid on the FLAIR scan,

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and this would be a cystic component

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of this pilocytic astrocytoma.

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Remember that pilocytic astrocytomas are

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World Health Organization grade one tumors,

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and therefore considered benign tumors.

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Nonetheless, the large size of this lesion and the infiltration of

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the optic nerves, as well as the optic chiasm,

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leads to symptoms that are quite extreme

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with regard to blindness in this child.

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In the adult, one can have optic nerve gliomas, as well.

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When they occur in the adult,

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they are more likely to be glioblastomas,

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and therefore have malignant potential.

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In this case, we see contrast enhancement along the

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ependymal surface of the ventricle.

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On the post-gadolinium enhanced scan,

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you're seeing portions of the ventricle

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showing contrast enhancement.

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This would suggest the potential for malignant

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degeneration of this pilocytic astrocytoma.

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The patient also has enlarged ventricles.

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And this is likely because of the obstruction of the cerebrospinal

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fluid transmission through the foramen of Monro,

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with secondary enlargement of the lateral ventricles.

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So, this is an unusual case of optic nerve glioma

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that has subarachnoid seeding into the interpeduncular cistern,

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along the ependyma of the lateral ventricle,

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leading to obstruction at the foramen of Monro

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and secondary hydrocephalus.

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The fact that this lesion is bilateral also suggests that this is

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likely of a congenital variation.