Congenital Hypoplasia of Bilateral Internal Carotid Artery with Migraine-Like Headache with Aura

To the Editor: A 36‐year‐old man with intermittent migraine‐like headache with aura for 20 years underwent cerebrovascular computed tomography angiography (CTA) revealing very small calibers of bilateral internal carotid arteries (ICAs) in other hospital. He was admitted to our hospital for further examination several days later. He had no vascular risk factors, and no family history of atherosclerotic or cerebrovascular diseases. On admission, general physical and neurological examinations were normal and vascular systolic murmur was not detected in the neck. Blood tests, including items relevant to diabetes, dyslipidemia, and vasculitis, were unremarkable. Carotid ultrasound [Figures 1a and 1b] showed small diameters of the bilateral extracranial carotid arteries without arterial wall thickening or atherosclerotic plaque, consistent with CTA findings. Transcranial doppler examination showed increased mean flow velocities (MFVs) in the bilateral posterior cerebral arteries (right, 75.5 ± 1.3 cm/s; left, 73.5 ± 1.3 cm/s) compared with the bilateral middle cerebral arteries in the headache‐free period (right, 54.5 ± 2.4 cm/s; left, 57.2 ± 1.9 cm/s) and during the attacks (right, 43.8 ± 1.5 cm/s; left, 46.5 ± 1.3 cm/s). Catheter angiography [Figure 1c‐1e] revealed symmetrical hypoplasia along the entire course of bilateral ICAs and development of collateral circulation by the bilateral posterior communicating arteries (PCOMAs). CT of skull base [Figure 1f] revealed hypoplasia of bilateral carotid canals (CCs). Cranial MRI, electroencephalogram, and aortic, renal, and lower extremity angiography were normal.