Delirious after undergoing workup for stroke

Typical CT scan findings in CIE include abnormal cortical contrast enhancement and edema, subarachnoid contrast enhancement, and striatal contrast enhancement (Figure 1, Figure 2, and Figure 3). Since the first clinical description, reports of 39 CT-/MRI-confirmed cases of CIE have been published in English language medical literature, with documented clinical follow-up³ and a median recovery time of 2.5 days. In a case report by Ito et al,⁴ there were no supportive radiographic findings. Ours is the second documented case that showed no radiologic signs of CIE. With a paucity of other etiologic evidence, negative lab tests for other causes of delirium, and the rapid resolution of Ms. L’s AMS after providing IV fluids as supportive treatment, a temporal correlation can be deduced, which implicates iodine-based contrast as the inciting factor.

Iodine-based contrast agents have been used since the 1920s. Today, >75 million procedures requiring iodine dyes are performed annually worldwide.⁵ This level of routine iodine contrast usage compels a mention of risk factors and complications from using such dyes. As a general rule, contrast agent reactions can be categorized as immediate (<1 day) or delayed (1 to 7 days after contrast administration). Immediate reactions are immunoglobulin E (IgE)-mediated anaphylactic reactions. Delayed reactions involve a T-cell mediated response that ranges from pruritus and urticaria (approximately 70%) to cardiac complications such as cardiovascular shock, arrhythmia, arrest, and Kounis syndrome. Other less prevalent complications include hypotension, bronchospasm, and CIN. Patients with the following factors may be at higher risk for contrast-induced reactions:

• asthma
• cardiac arrhythmias
• central myasthenia gravis
• >70 years of age
• pheochromocytoma
• sickle cell anemia
• hyperthyroidism
• dehydration
• hypotension.

Although some older literature reported correlations between seafood and shellfish allergies and iodine contrast reactions, more recent reports suggest there may not be a direct correlation, or any correlation at all.^5,6

Iodinated CIE is a rare complication of contrast angiography. It was first reported in 1970 as transient cortical blindness after coronary angiography.⁷ Clinical manifestations include encephalopathy evidenced by AMS, affected orientation, and acute psychotic changes, including paranoia and hallucinations, seizures, cortical blindness, and focal neurologic deficits. Neuroimaging has been pivotal in confirming the diagnosis and in excluding thromboembolic and hemorrhagic complications of angiography.⁸

Encephalopathy has been documented after administration of iopromide,^9,10iohexol,¹¹ioxilan,⁴ and metrizamide. The mechanism of neurotoxicity is unclear, but several theories have been formulated. The contrast agent may disturb the blood-brain barrier and enter the brain. This may be a primary mechanism leading to encephalopathy when the hypertonic contrast agent draws water out of the endothelial cells of brain capillaries, arterioles, and venules. This may cause the endothelial cells to shrink and to separate at tight junctions directly affecting the blood-brain barrier. Alternatively, the increase in intraluminal pressure caused by injection of the contrast agent, in concert with contrast agent-induced cerebral vasodilatation, might contribute to increasing vascular wall tension, further separating tight junctions. A third theory suggests that vesicular transport may be a mechanism of osmotic barrier opening. Further studies would be required to investigate these mechanisms.

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