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A 32-year-old female with multiple sclerosis (MS) was admitted following an episode resembling a flare of MS. Sixteen days before the presentation she had a conventional angiogram with 259 ml of non-ionic iodine contrast iohexol 300. Two days after the procedure she developed left eye vision change and a headache. Two weeks later she developed a gait imbalance and right-sided weakness. She was admitted to a hospital where an MRI showed numerous small ring-enhancing lesions on MPRAGE, primarily in the vascular territory subjected to the angiography. There was no restricted diffusion within the lesions. A significant amount of surrounding edema was present. The patient was treated with methylprednisolone 1000mg for 5 days for what was considered acute disseminated encephalomyelitis (ADEM) with resolution of her symptoms. Follow-up imaging across the next 15 months showed gradual improvement in the edema and resolution of the contrast-enhancing lesions

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Contrast-induced encephalopathy (CIE) is a rare complication of angiographic procedures. Pathophysiology is hypothesized to be related to brain-blood barrier permeability and extravasation of contrast. Most of the reported cases describe confusion, visual and speech impairment, seizures, and hemiparesis manifesting soon after the contrast infusion with symptoms resolution within 48 hours. Imaging findings of CIE are linked to edema with corresponding T2 FLAIR hyperintensity without DWI-restricted diffusion. Previous reports considered age, hypertension, diabetes, and kidney impairment as risk factors for CIE, although most of the evidence came from coronary angiography cases. In some cases, there was a predilection to posterior circulation raising concerns about PRES overlap.

The reported case is unique in terms of delayed presentation, extensive lesion burden, and the patient’s comorbid multiple sclerosis. The last aspect raises the question of whether altered immune reactivity played a role in this presentation.