Clinical History
A 46-year-old female presented with a headache. Cerebral non-enhanced computed tomography and angiography were performed.
Imaging Findings
A 46-year-old female presented with a severe headache that began suddenly. Non-enhanced computed tomography (CT) and complete cerebral angiography were performed. The CT results showed a subarachnoid
hemorrhage more prominent in the anterior interhemispheric fissure. There was a loculation suggesting anterior cerebral artery (ACA) aneurysm (Fig. 1a). On the right and left carotid angiograms, a
small lobulated, narrow-based aneurysm was identified at the distal A2 segment of the ACA. In addition, there was only one ACA which supplied both ACA territories and no anterior communicating artery
(Fig. 2a, b).
Discussion
Azygous ACA may be observed as an incidental finding with little clinical significance, and has a prevalence of between 0.2% and 4%. An azygous ACA supplying both ACA territories is a single,
unpaired vessel arising from the confluence of the right and left horizontal (A1) ACA segments. The anterior communicating artery is absent. If the embryonic median artery of the corpus callosum
persists, an azygous ACA is formed. Associated anomalies may include, as in our patient, an increased risk of intracranial aneurysm, holoprosencephaly and neuronal migration anomalies.
Differential Diagnosis List
Azygous anterior cerebral artery.
Final Diagnosis
Azygous anterior cerebral artery.