Sequential bilateral common carotid artery occlusion in protein C deficiency and patent foramen ovale: illustrative case.

backgroundCommon carotid artery occlusion (CCAO) is rare, with bilateral involvement being exceedingly uncommon. Its etiologies are heterogeneous, and sequential bilateral CCAO is exceptionally rare. Protein C deficiency is an inherited thrombophilia primarily associated with venous thromboembolism, while its role in arterial thrombosis remains unclear. In the presence of a patent foramen ovale (PFO), paradoxical embolism may contribute to arterial ischemic events. OBSERVATIONS: A 56-year-old man presented with sudden-onset motor aphasia and right hemiparesis. MR angiography demonstrated loss of flow in the left internal carotid and middle cerebral arteries. Digital subtraction angiography revealed a left CCAO proximal to the bifurcation. Emergency aspiration thrombectomy achieved recanalization, followed by carotid artery stenting for residual stenosis at the internal carotid artery origin. On postoperative day 7, he developed new neurological deficits; imaging showed occlusion of the brachiocephalic artery and right common carotid artery (CCA) with a new infarction in the right basal ganglia. Laboratory evaluation revealed protein C deficiency, and transesophageal echocardiography identified a PFO. LESSONS: Protein C deficiency in the presence of a PFO may predispose to recurrent paradoxical embolism, resulting in sequential bilateral CCAO. In cases of recurrent cryptogenic large-vessel occlusion with atypical vascular patterns, evaluation for thrombophilia and right-to-left shunt should be considered. https://thejns.org/doi/10.3171/CASE26378.