Accuracy of MRI in defining tumor-free margin in optic nerve glioma surgery.

PURPOSE: To determine the value of preoperative MRI in predicting the histopathologic margin of optic nerve glioma undergoing surgical resection.

METHODS: Retrospective, noncomparative, multicenter case series of patients diagnosed with prechiasmal optic nerve glioma, using MRI, who underwent surgical resection. Clinical data were abstracted from patient medical records at 6 medical centers through a survey vehicle. Preoperative MRI findings were compared with intraoperative findings and postoperative histopathologic interpretations of the posterior margins of 13 surgically resected optic nerve gliomas.

RESULTS: A total of 13 patient submissions qualified for study entry based on preoperative MRI having identified a unilateral optic glioma anterior to the optic chiasm. Of these, 2 cases (15%) demonstrated an abnormal macroscopic appearance of the chiasm intraoperatively and were surgically debulked rather than resected as planned preoperatively. The remaining 11 patients underwent resection posterior to the margins indicated by preoperative MRI. Of these, 3 (27%) demonstrated evidence of microscopically positive margins on histopathologic examination. Follow up ranged from 3 months to 21 years. One patient with involvement of the chiasm manifested tumor growth; no other recurrences or evidence of growth occurred in the remaining patients, including 1 other case with involvement of the chiasm and 3 cases with positive surgical margins.

CONCLUSIONS: Unilateral optic nerve gliomas limited to the prechiasmatic nerve on MRI not infrequently extend beyond the MRI borders. This finding is of significance when considering management options, particularly surgical resection.