Case report: Diffusion-weighted imaging may be useful in patients with vision loss

The authors present a case report of a 67-year-old African American male with untreated hypertension, hyperlipidemia and diabetes mellitus who presented with light perception only in his left eye after sudden visual deterioration in a waxing and waning manner over the previous eight days. Ophthalmologic and fluorescein angiography (FA) exams confirmed central retinal artery occlusion (CRAO) but revealed no embolus. Similarly, magnetic resonance imaging (MRI) revealed restricted diffusion within the distal left optic nerve, suggesting a more proximal occlusion causing distal optic nerve as well as retinal ischemia. After extensive workup revealed no embolic source, the occlusion was postulated to be a vascular consequence of the patient's hypertension and diabetes.

The patient presented in a faltering manner, rather than with more typical abrupt total vision loss. Ophthalmic examination showed a cherry-red spot in the left macula with associated retinal pallor consistent with CRAO. FA showed delayed filling of the superior retinal arcades, as well as choroidal hypoperfusion, suggesting not just a retinal artery occlusion but a more proximal occlusion involving the distal ophthalmic artery and short posterior ciliary arteries. MRI and intracranial magnetic resonance angiography performed during work-up for intracranial ischemia revealed small-vessel disease appropriate for his age and comorbidities without significant stenosis. However, the optic nerve just behind the globe showed restricted diffusion on diffusion-weighted imaging (DWI), reduced apparent diffusion coefficient and gadolinium enhancement on dedicated orbital imaging.

The authors say that the findings of restricted diffusion within the optic nerve along with a normal brain MRI, which led to the diagnosis of optic nerve ischemia, suggest that focused review of the orbits on DWI in patients with a history of vision loss is prudent. They conclude that higher resolution DWI evaluation of the orbits may be of value in patients with suspected CRAO for whom therapy is being considered, although this requires further study.