Tumor spread in unilateral optic glioma. Study report No. 2. North American Study Group for Optic Glioma

We describe 106 cases with unilateral optic nerve gliomas confined initially to the orbit. Thirty-four have been observed without biopsy or excision, 28 had a biopsy and 44 had complete excision of the glioma. Data on these cases were collected from 21 academic centers and comprise the second report by a recently formed study group. Some of the cases have been previously reported, but the present study extends their follow-up. The cases have been analyzed with regard to the certainty of diagnosis, the basis for unilaterality, the type of excision, duration of follow-up and growth of the tumor. We addressed three related questions. Can even the most sophisticated neuroimaging and histological techniques reliably detect the cranial extent of an optic glioma? Is the tumor often enough unifocal in one nerve so that excision has a reasonable chance to effect a cure? What percentage of untreated unilateral optic gliomas eventually spread to the chiasm? While this is an ongoing study, data collected to date seem to indicate that most tumors are unicentric and that only infrequently do they invade the chiasm (4 of 106 cases).