Sometimes a Biopsy is Best

A 30 -year-old pregnant woman without significant medical or ocular history presented with decreased right eye vision. In her 2nd trimester, she was diagnosed with Lyme disease with a bulls-eye rash and positive Lyme antibodies; she was treated with two weeks of amoxicillin. At 33 weeks pregnant she developed a right periorbital headache and decreased brightness with the right eye. The eye was sore but she had no pain with eye movements. Six days later an outside eye provider documented right optic nerve edema with 20/400 vision. An MRI/MRV without contrast at an outside ER reportedly showed right optic neuritis. She received 5 days of IV methylprednisolone (1000mg/day). She reported brighter colors but no objective improvement in vision. Lyme IgM was negative and IgG was positive but no other imaging or serologic workup was performed. Over the next 3 weeks, her vision worsened to no light perception (NLP). At 40 weeks pregnant she presented to our institution with NLP vision in the right eye with an rAPD. The left eye vision and exam was normal. The right eye fundus exam showed mild disc edema with temporal pallor and optociliary shunt vessels. She was admitted and a healthy baby was delivered. A contrast enhanced MRI brain/orbits showed diffuse enhancement, STIR hyperintensity, and restricted diffusion of an enlarged right optic nerve; this was favored to represent right optic neuritis. AQP4-IgG and MOG-IgG were checked twice and negative; lumbar puncture CSF studies were normal. She was treated with IV methylprednisolone (1000mg/day for 5 days), plasmapheresis every other day for 5 sessions, and rituximab weekly for 5 infusions. Her vision briefly improved to light perception but then returned to NLP. A repeat MRI showed stable diffuse enhancement and enlargement of the right optic nerve. A biopsy of the optic nerve was performed