Aggressive Low-Grade Optic Nerve Glioma in Adults

Primary optic nerve gliomas are most commonly benign pilocytic astrocytomas (World Health Organization [WHO] Grade I) occurring in childhood and following an indolent course. Malignant optic gliomas occur in adulthood and follow an extremely aggressive course, with rapid infiltration of the chiasm, blindness, and death typically within months. A third category of optic glioma, occurring in adulthood, histopathologically benign (WHO Grade I-II) but following an aggressive course, has been rarely reported. The authors describe clinical and histopathologic features of clinically aggressive but histopathologically benign optic nerve gliomas of adulthood. Retrospective review of cases of biopsy-proven optic nerve glioma in the neuro-ophthalmology division of the Jules Stein Eye Institute from 1990 to 2011 was carried out. Cases following an aggressive course were selected for review of clinical, neuroradiologic, and histopathologic features. Three cases were selected for detailed study. Ages ranged from 31 to 45 years. All were initially diagnosed with optic nerve inflammation or benign neoplasm based on clinical and neuroradiologic features, but all suffered neuroradiologic extension and rapid deterioration of vision in the affected eye to no light perception over 3-8 weeks. Optic nerve biopsies were undertaken for the suspicion of malignancy. Features ranged from WHO Grade I (pilocytic astrocytoma, ganglioglioma) in two cases, to WHO Grade II in one case (diffuse astrocytoma, histopathologically benign, but associated with aggressive features such as high p53 [13-21%] and Ki-67 [40%]). The diffuse astrocytoma case subsequently developed extensive intracranial extension suspicious for malignant transformation. These findings indicate that benign optic nerve glioma in adults may be initially misdiagnosed as inflammation, be clinically aggressive, and require excision to prevent further intracranial involvement.