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"Shave" biopsy of the optic nerve in isolated neurosarcoidosis.

We report a case of isolated central nervous system sarcoidosis, limited to the optic nerve, characterized by negative systemic work up and neuroradiological features consistent with both optic sheath meningioma and optic nerve glioma. A magnetic resonance imaging examination revealed a dural tail sign associated with a diffuse enhancement and enlargement of the optic nerve. Both positive laboratory findings and systemic manifestation of sarcoidosis or autoimmune diseases were absent. Because of progressive visual loss, tissue confirmation was sought and the optic nerve itself biopsied after non-diagnostic dural samplings. The approach to this was to perform a "shave" biopsy of the optic nerve within its intracranial compartment. This procedure spared the central macular fibers and was not associated with loss of vision. The use of the fiber-sparing "shave" biopsy provided diagnostic samples containing non-caseating granulomas, without compromising the patient's preoperative central visual field. The authors advocate the use of this simple and safe technique when a definitive diagnosis among optic nerve meningioma, optic nerve glioma and isolated neurosarcoidosis cannot be reached by means of less invasive procedures.