2026 American Academy of Neurology Abstract Website

Objective:

Hypoplasia represents a congenital morphogenic error resulting in the underdevelopment of an organ or tissue, which can occur in any part of the body and may have significant clinical consequences. When involving the internal carotid artery (ICA), hypoplasia can profoundly alter cerebral hemodynamics. Congenital internal carotid artery hypoplasia (CICAH) is exceedingly rare, with an estimated incidence of 0.01%, and may be misinterpreted as an acquired ICA occlusion, potentially leading to inappropriate therapeutic decisions.

Background:

We present the case of a 66-year-old right-handed immunocompromised man with a history of kidney transplant for end-stage renal disease secondary to membranous nephropathy, maintained on cyclosporine, mycophenolate, and prednisone. His additional medical history included poorly controlled type 2 diabetes mellitus, hypertension, and atrial fibrillation managed with apixaban. He presented with acute-onset right hemiparesis (initial NIHSS = 2).

Design/Methods:

CT angiography of the head and neck demonstrated a congenitally hypoplastic left ICA with preserved flow to the left middle and anterior cerebral arteries via the right ICA and posterior circulation. Brain MRI revealed acute diffusion restriction in the left basal ganglia, consistent with a small-vessel ischemic etiology.

Results:

The patient was managed with continuation of apixaban, initiation of high-intensity statin therapy, and optimization of blood pressure control.

Conclusions:

This case underscores the importance of recognizing congenital cerebrovascular variants such as ICA hypoplasia to avoid misdiagnosis and unnecessary interventions. A thorough understanding of neurovascular anatomy and its developmental anomalies remains essential for accurate stroke evaluation and appropriate management.