Dual-Energy CT to Diagnose Pseudoedema in Contrast-Induced Encephalopathy Following Cerebral Angiography

Background: Contrast-induced encephalopathy (CIE) is a syndrome that may be clinically unrecognized and misdiagnosed as cerebral edema. Methods: Case report and review. Results: A 72-year-old woman was admitted for elective endovascular embolization of a 10-mm left anterior communicating artery aneurysm. One hour post-procedure, she acutely developed global aphasia. Emergent head computed tomography (CT) and computed tomography-angiography (CTA) showed high attenuation of the left hemispheric subarachnoid spaces interpreted as hemispheric edema; emergent magnetic resonance imaging revealed left hemispheric punctate infarcts. At 12 h, she developed right hemiparesis and encephalopathy. Repeat CTA and CT perfusion revealed decreased left hemisphere cerebral blood flow and diminutive caliber of distal left middle cerebral artery territory vasculature. Repeated angiography with intra-arterial verapamil and systemic blood pressure augmentation were performed for presumed vasospasm. At 20 h, head CT was concerning for worsening left hemispheric edema, but dual-energy, iodine-subtracting sequences revealed significant contrast extravasation contributing to the appearance of sulcal effacement but without actual edema. Out of concern for blood–brain barrier breakdown from CIE, pressor augmentation was discontinued and the patient gradually improved to full neurological recovery within 72 h of symptom onset. Conclusions: Our case is the first known to report the use of dual-energy, iodine-subtracting CT as a diagnostic tool in differentiating between cerebral edema and pseudoedema in CIE.