2026 American Academy of Neurology Abstract Website

Objective:

To describe a case of atypical optic neuritis with secondary posterior ischemic optic neuropathy (PION) leading to the diagnosis of neuromyelitis optica spectrum disorder (NMOSD).

Background:

PION describes a vascular insult to the optic nerve posterior to the optic nerve head. Typically, non-arteritic PION is secondary to arterial thrombotic or watershed ischemic injury particularly in perioperative patients. We describe an atypical case of PION secondary to severe edema associated with optic neuritis later confirmed to be aquaporin-4-positive NMOSD.

Design/Methods:

N/A

Results:

A 73-year-old woman presented with sudden-onset painless central vision loss in the left eye upon awakening. She denied scalp tenderness, jaw claudication, pain with eye movements, or dyschromatopsia. Methylprednisolone 1000mg IV was started for concern for giant cell arteritis. Neuro-ophthalmologic examination showed left relative afferent pupillary defect, decreased visual acuity (20/200 OS), and dyschromatopsia. Funduscopic examination was unrevealing for disc edema or evidence of retinal ischemia. MRI of the brain and orbits demonstrated restricted diffusion in the posterior half of the intraconal optic nerve with longitudinally extensive enhancement extending posteriorly to the optic chiasm. MRI of the cervical spine did not show any lesions. Bilateral temporal artery biopsy was negative. Inflammatory markers, MOG-IgG, Lyme, ANA, and paraneoplastic antibodies were negative. Lumbar puncture showed elevated protein and normal WBC. Serum aquaporin-4 antibodies were positive (titer 1:1000). She was diagnosed with NMOSD. Mycophenolate mofetil was initiated, as the patient refused infusion treatment. Visual acuity improved to 20/40 at follow-up. She returned nine months later with a second episode of optic neuritis in the right eye and agreed to IV treatment with inebelizumab.

Conclusions:

Painless monocular vision loss without optic disc edema is concerning for PION in older patients. Evidence of ischemia/restricted diffusion on neuroimaging should not mislead clinicians from completing the work-up for causes of atypical optic neuritis such as NMOSD.