Diagnostic pitfall: optic neuritis mimicking optic nerve glioma.

We report a case of optic neuritis with enlargement of the optic nerve on MRI. This neuroradiological finding is most commonly seen in tumours of the optic nerve and led together with an inconclusive intraoperative frozen section to an incorrect tentative diagnosis of optic nerve glioma which fatally resulted in the resection of the optic nerve.