Lesions of the optic nerve.

As experts on the central nervous system, neurologists are expected to be familiar with the many conditions that can result in visual loss arising from lesions of the optic nerve. The optic nerves are unique central nervous system structures in terms of surrounding anatomy, size, location, and blood supply; therefore, they are uniquely vulnerable to every pathological process that can affect the central and peripheral nervous systems, including inflammation, ischemia, compression, infiltration, toxic or hereditary metabolic dysfunction, trauma, and mechanical damage. This chapter highlights the importance of being able to identify the historical and clinical features that will enable neurologists to narrow down the broad differential diagnosis of optic nerve lesions. Distinguishing an optic neuropathy on the basis of history and clinical examination alone, however, can be difficult, especially when bilateral optic neuropathies are present. Specific ancillary tests, especially new imaging modalities, help further localization and differential diagnosis.