Bicaudate infarcts in the setting of congenital absence of A1 segment

A 51-year-old woman with a history of hypertension and smoking presented with sudden onset of confabulation, delusions, and blunted affect. She was oriented to time, place, and person with intact language, strength coordination, and sensation. Gait was slow and wide-based. Serum and CSF yielded no abnormalities. Brain MRI showed bilateral caudate infarcts (figure 1). Cerebral angiography did not provide evidence of dissection or stenosis of the internal carotid artery or major atherosclerosis intracranially or involving the aortic arch. However, it showed an embolus in the right A1, with congenital absence of the left A1 segment; there was a thrombus at the origin of the right internal carotid artery (figure 2). No source of thromboembolism was identified on transthoracic echocardiography. Infarction spared the more distal cortical branches of anterior cerebral artery territories because these benefited from a retrograde filling through middle cerebral artery and posterior cerebral artery pial collaterals, more developed on the left. This congenital vascular variant, one that clinicians should be cognizant of, leads to the bilateral nature of the infarcts.^1,2