Magnetic resonance imaging in detection of extracranial internal carotid artery dissection

This 28-year-old woman presented with a 4-week history of bilateral visual loss. She had a known history of multiple sclerosis. Her vision was 20/60 OD and 20/40 OS, with an RAPD OS and optic pallor OU. Her fields and MRI are shown. Optic tract lesions usually result in an incongruous homonymous hemianopsia. In the absence of an ipsilateral optic neuropathy a contralateral afferent pupillary defect in the setting of a homonymous hemianopsia localizes the lesion to the optic tract. Likewise, band, or ""bow-tie,"" atrophy (nasal fibers) of the optic nerve may occur in the contralateral eye (eye with the temporal visual field loss) in patients with optic tract lesions and a homonymous hemianopsia. Pair with Image 91_25.