Non-arteritic anterior ischemic optic neuropathy secondary to idiopathic intracranial hypertension

Purpose: Patients with increased intracranial pressure and underlying hypertensive emergency may present with optic disc edema. Papilledema in this setting may be a predisposing risk factor for superimposed non-arteritic anterior ischemic optic neuropathy (NAION). We highlight the role of neuroimaging including diffusion-weighted imaging in magnetic resonance imaging that can help to differentiate visual loss from NAION versus papilledema in fulminant IIH with and without hypertension. Observations: A 46-year-old female presented with acute vision loss in the right eye and transient right hemiparesis. Neuro-ophthalmic examination revealed optic disc edema in both eyes. Magnetic resonance imaging (MRI) of the brain with diffusion-weighted imaging (DWI) sequences showed restricted diffusion in the optic nerve head of the affected eye. Lumbar puncture revealed an elevated opening pressure of 34.8 cm H2O confirming increased intracranial pressure. Additionally, literature searches were conducted in the PubMed, Google Scholar and Embase databases to uncover previous cases of patients with ischemic optic neuropathy and restricted diffusion on MRI. Conclusions and importance: We highlight the shared pathophysiology between optic disc edema related visual loss in NAION and papilledema in IIH. We review the overlapping clinical and radiographic findings in these two conditions which may occur simultaneously. The presence of restricted diffusion in the optic nerve head versus in the optic nerve parenchyma may support a diagnosis of superimposed NAION and might influence the decision to perform surgery in cases of IIH with fulminant visual loss. Although restricted diffusion on MRI DWI sequences is often used to define cytotoxic edema related to ischemic infarction in the brain, this radiographic finding alone should not be used to determine the indication for surgery for papilledema related visual loss in fulminant IIH.