Contribution of imaging to the diagnosis of optic neuropathies.

Magnetic resonance imaging is the modality of choice to investigate patients with central nervous system diseases. In patients with optic neuritis, early MRI allows positive and differential diagnosis, and gives arguments for prognosis. The technique should be adapted for the exploration of visual pathways. Inflammatory optic neuritis is characterized by an early signal abnormality within the optic nerve, whereas optic nerve MRI is normal in the early phase of ischemic optic neuropathy. MRI also detects compressive and infiltrative lesions. Meningiomas are characterized by abnormalities within the peri-optical spaces, whereas a global increase in the size of the optic nerve is in favor of a glioma.