Anterior circulation acute ischemic stroke due to vertebral artery ostial stenosis in a patient with congenital internal carotid artery agenesis: a case report.

Background: Congenital agenesis of internal carotid artery (ICA) is a rare cerebrovascular variation entity. Most cases of congenital ICA agenesis are asymptomatic and discovered incidentally. Congenital ICA agenesis presenting as ischemic stroke is even rare. Case presentation: An 80-year-old male patient was admitted to our hospital due to sudden dysarthria and left limb weakness for 3.5 h. Based on emergency physical examination and head computed tomography (CT) scan results, acute ischemic stroke (AIS) of right cerebral hemisphere was suspected. Following intravenous thrombolysis with recombinant tissue plasminogen activator, right congenital agenesis of ICA was confirmed by CT and digital subtraction angiography. Additionally, there was a severe right vertebral artery ostial (VAO) stenosis. After ruling out common causes of AIS such as haematological diseases, arterial dissection, organic heart disease, immunological abnormality and underlying possible malignancies, we hypothesize that the severe stenosis of the right VAO may have contributed to the development of AIS in this case. Conclusions: We present a case of right congenital ICA agenesis in which severe stenosis of the right VAO may have played a role in the development of AIS. This case underscores a rare scenario where a lesion in the posterior circulation leads to an infarction in the anterior circulation in the setting of congenital ICA agenesis. [ABSTRACT FROM AUTHOR]