A clinicopathologic study of optic neuropathies associated with intracranial mass lesions with quantification of remaining axons.

We examined three patients with intracranial mass lesions that damaged the anterior visual pathway and studied this damage histologically after the patients died. Estimation of the number of surviving axons in the six optic nerves generally showed the greatest atrophy to be in the temporal sector in cross sections immediately behind the globe. More posterior to the globe, atrophy appeared greatest in the center of several nerves. This pattern of damage may result from particular vulnerability of macular axons to damage along the anterior visual pathway. Optic disk pallor was present in two eyes that had less than 40% of the normal number of axons remaining, while one optic disk appeared to be normal with 70% of the axons intact. Afferent pupillary defects were observed in two patients who had two to three times as many remaining axons in the contralateral optic nerve as in the nerve on the side of the defect.