Optic nerve glioma (pilocytic astrocytoma) - neurofibromatosis type 1
Presentation
2 months history of headache and progressive bilateral vision impairment.
Patient Data
A lobulated ill-defined space-occupying lesion is noted in the suprasellar region, involving the optic chiasm and both optic nerves and extends to the right hypothalamus, causing fusiform enlargement of both optic nerves, and extending into the optic canals, and the left hypothalamus, compressing the foramina of Monro and the 3rd ventricle and causing biventricular hydrocephalus, more on right side with periventricular edema.
The lesion abuts the leACA.
It's iso-intense on T1, hyper-intense on T2, with heterogeneous enhancement on post-contrast T1.
Areas of high intensity on T1, T2 and flair, with no enhancement on post-contrast T1 are noted in the basal ganglia bilaterally and brainstem, mostly representing focal areas of signal intensity (FASI).
The findings correlate with optic nerve glioma (Dodge stage 3) within the context of neurofibromatosis type 1.
Café au lait spots are noted on the right shoulder, this is one of the cutaneous manifestations of NF1.
Histology:
Sections show neoplastic glial cell proliferation. The tumor background is focally loose myxoid-containing stellate-shaped glial cells, and focally dense containing spindle-shaped (pilocytic) glial cells. several Rosenthal fibers are noted. There is no evidence of increased mitotic activity, vascular endothelial hyperplasia, or necrosis.
Diagnosis:
Brain tumor, optic nerve, and chiasm
Consistent with pilocytic astrocytoma, WHO grade I.
Case Discussion
Neurofibromatosis type 1 (NF1), also known as von Recklinghausen disease is an autosomal dominant disorder, caused by a mutation in the NF1 gene.
It is a multisystem disease, affecting the nervous, musculoskeletal, cardiopulmonary, integumentary, and other systems.
Focal areas of signal intensity (FASI), also known as unidentified bright objects (UBO) is the most common intracranial finding in patients with neurofibromatosis type 1 1.
Optic nerve gliomas may affect the optic nerves, the optic chiasm and optic tracts, so it is called optic pathway gliomas (OPG). It is usually unilateral and commonly shows fusiform enlargement of the optic pathway.
On MRI: the optic nerve glioma is:
iso to hypointense onT1
iso to hyperintense on T2
the enhancement is variable on T1C+ (from absent to intense)
The diagnosis was confirmed by pathology (pilocytic astrocytoma, WHO grade I).
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