Cavernous malformation of the optic nerve mimicking optic neuritis.

A 30-year-old woman developed acute visual loss and optic disc elevation in the left eye after breastfeeding her second son. The initial diagnosis was optic neuritis. However, MRI showed a lesion in left intraorbital and intracanalicular optic nerve and several cerebral lesions with imaging features of cerebral cavernous malformations (CCMs). Genetic testing was positive for abnormalities known to predispose to CCMs in the patient and her father, who also showed MRI evidence of CCMs. During a 44-month follow-up period in which no intervention took place, the patient's vision in the affected eye fluctuated but eventually became extinguished. Serial MRIs did not always show lesion changes that explained the visual deterioration. In familial CCM, pregnancy might be a "second hit" to genetically predisposed tissue.