Calcified Atherosclerotic Plaque Causing Near-Total Occlusion of the Middle Cerebral Artery Mimics Patent Middle Cerebral Artery on CT Angiogram and Misguided Treatment: Calcification and Pseudo-patency

Calcified cerebral emboli are an underreported but devastating cause of stroke, and may be the first manifestation of vascular or cardiac disease. These emboli are often overlooked or misinterpreted and carry a significant risk of recurrent stroke. Calcific emboli are typically hyperdense on noncontrast CT scans and CT angiography (CTA); however, they can appear isodense on iodinated contrast on CTA, creating a false sense of vessel patency (“pseudo-patency”). Similarly, calcified atherosclerotic plaques can mimic a patent artery on CTA, misdirecting potentially life-saving treatment. A 71-year-old man with a history of hypertension, dyslipidemia, ischemic heart disease, and peripheral vascular disease was admitted for right hemispheric ischemic stroke with a baseline National Institutes of Health Stroke Scale (NIHSS) score of 5. He was brought to the emergency department by his son after developing sudden-onset speech changes and left arm weakness that began 2 h before admission. The patient had been on statins and clopidogrel for the past 3 years after undergoing urgent coronary revascularization. He had been admitted to the hospital 5 years earlier with similar clinical complaints. On that occasion, he had been admitted with right hemispheric transient ischemic symptoms; however, his admission CT and CTA had been reported as unremarkable, and his cardiologic evaluation showed only minor findings. The current admission began with a head CT, which revealed microvascular brain disease and calcification of the proximal middle cerebral artery (MCA). His Alberta Stroke Program Early CT Score (ASPECTS) on noncontrast cranial CT was 10. CT perfusion (CTP) showed hypoperfusion of the right MCA, and CTA showed patent intracranial vessels. The patient had shown clinical improvement prior to the scan. Based on the CT findings, he received intravenous thrombolysis and showed complete clinical recovery (NIHSS 0) 6 h after admission. However, an MRI performed 2 days later confirmed microvascular brain disease and internal watershed lesions in the right hemisphere, and MR angiography (MRA) showed severe stenosis of the origin of the right MCA. Platelet reactivity testing using the VerifyNow assay confirmed an adequate response to clopidogrel (P2Y12 reaction units [PRU] 122). Diagnostic angiography confirmed severe, near-total occlusion of the proximal right MCA caused by a short, concentric atherosclerotic plaque lesion (Mori type A). Retrospective evaluation revealed a focal, partially calcified plaque at the origin of the right MCA on noncontrast CT 5 years earlier. During this interval, the plaque had evolved with further calcification. Although it was visible on noncontrast CT, we had failed to recognize its severity because the CTA was found to be unremarkable. CTP and a history of unexplained transient ischemic attacks (TIAs) led us to request MRA and angiography, which depicted severe stenosis. 3D rotational angiography showed a tortuous internal carotid artery (ICA) siphon with diffuse atheromatosis and severe stenosis of the origin of the right MCA, extending concentrically for 5 mm. The MCA trunk immediately following the stenosis reached a diameter of 2 mm. The patient was started on dual antiplatelet therapy with aspirin and clopidogrel and was scheduled semielectively for intracranial angioplasty. This chapter aims to raise awareness of an unusual but potentially catastrophic condition. Calcific emboli and plaques are generally hyperdense on noncontrast CT and CTA; however, they may appear isodense to iodinated contrast on CTA, giving a false sense of vessel patency (“pseudo-patency”). This will likely lead to conservative management of patients requiring urgent revascularization. In cases where the clinical presentation suggests a large vessel occlusion not seen on conventional CT angiography, we recommend alternative modalities such as multiphase CTA, CTP and MRI/MRA, and verification with catheter angiography.