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.

Figure 1

Carotid ultrasound (a, b) showed thin calibers of bilateral carotid arteries [right common carotid artery (CCA), 3.9 mm; Left CCA, 4.1 mm; right internal carotid artery (ICA), 1.6 mm; Left ICA, 1.5 mm]. Catheter angiography (c-e) revealed symmetrical hypoplasia of bilateral internal carotid arteries (arrows) along the entire course and the collateral circulation established from posterior circulation into anterior one by development of bilateral posterior communicating arteries (arrows). Computerized tomography of skull base (f) showed hypoplasia of bilateral carotid canals (arrows).

Hypoplasia of the ICA is a rare arterial anomaly with an incidence below 0.01%,[1] whose exact cause of is not known. The probable cause is due to some insult sustained by the growing embryo during the 4th–8th weeks of gestational life.[1] The CC is closely linked to the development of the ICA during embryonic life. Thus the CC is small and not well developed in cases of hypoplasia. The diagnosis of our patient, congenital hypoplasia of the bilateral ICAs is based on its characteristic angiographic findings and the presence of hypoplastic CCs by CT of the skull base. Most patients with this anomaly are asymptomatic, and it is identified only incidentally due to sufficient cerebral collateral circulation, commonly through the bilateral PCOMAs. Symptomatic patients often present with ischemic or hemorrhagic stroke.[1] However, to our knowledge migraine-like headache with aura has not been reported as a symptom of the hypoplasia.

The migraine-like headache in our patient may be associated with hypoplastic ICAs. Lovrenciζ et al.,[2] suggested that cerebral hypoperfusion in the posterior circulation due to vertebral artery hypoplasia may induce a migraine aura. Agostoni et al.,[3] noted that migraine with aura may be the outcome rather than the cause of cerebral ischemia, and cerebral hypoperfusion could reduce the threshold for developing spreading depression preceding a migraine aura.[4] An association between decreased cerebral blood flow and migraine or migraine-like headache had been reported.[5] MFVs in the anterior circulation of our patient were obviously decreased owing to hypoplasia of bilateral ICAs, which were lower during the attacks, and therefore we speculated that this might have induced his migraine-like headache with aura.

In conclusion, bilateral ICA hypoplasia is a very rare condition. Many cases are probably asymptomatic, being identified only incidentally. However, migraine-like headache with aura may be the sole clinical symptom because of seriously reduced cerebral blood flows.