Arterial Spin Labeling Magnetic Resonance Imaging to Diagnose Contrast-Induced Vasospasm After Intracranial Stent Embolization.

Background: Contrast-induced encephalopathy (CIE) is a rare and misdiagnosed complication of intravascular injection of contrast, responsible for arterial vasospasm and neurologic effects. Conventional radiologic findings are not in themselves specific for cerebral vasospasm diagnosis. We present a case in which arterial spin labeling (ASL) perfusion magnetic resonance imaging (MRI) was useful in early diagnosis of CIE.
Case Description: A 56-year-old woman was admitted for elective flow-diverter embolization of a recanalized left supra-ophthalmic internal carotid artery aneurysm; at 4 hours postprocedure, she acutely developed sensitive aphasia and right arm paresis. Although no-contrast computed tomography and MRI with fluid-attenuated inversion recovery and diffusion-weighted imaging sequences did not demonstrate acute ischemic/hemorrhagic cerebral foci or cortical edema, ASL showed decreased cerebral blood flow (CBF) in the insular-temporal-parietal anterior lobe, suspected for hypoperfusion due to vasospasm, which was not confirmed by subsequent emergent digital subtraction angiography. At 16 hours, because of worsening symptoms, patient underwent an additional MRI, which showed slight insular cortical edema on fluid-attenuated inversion recovery and corresponding slight restricted diffusion-weighted imaging with a severe reduction in CBF value; at this time, emergent digital subtraction angiography demonstrated distal arterial vasospasm of left middle cerebral artery, and vasospasm therapy was started. Within 48 hours of symptom onset, the patient gradually improved to a complete neurologic recovery, with normalization of CBF values in the concerning cerebral region.
Conclusions: CIE should always be considered in patients with focal neurologic deficits after iodinate contrast exposure. ASL perfusion MRI with CBF maps could be a promising tool for prompt, early confirmation of underlying vasospasm, as cortical edema and distal vasospasm could not be detected on conventional radiologic imaging.
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