Bilateral infarction in the anterior cerebral artery vascular territory due to an unusual anomaly of the circle of Willis.

BACKGROUND Bilateral infarction in the anterior cerebral artery vascular territory is rare and usually results from rupture of an aneurysm of the anterior communicating artery. In the case of an anomaly of the anterior part of the circle of Willis, thrombosis also may lead to bilateral infarction. CASE DESCRIPTION A 73-year-old right-handed man presented with a complete loss of communicative behavior and an almost complete quadriplegia. 99mTc-hexamethylpropyleneamine oxime single-photon emission-computed tomography (HMPAO SPECT) of the brain showed a "horseshoe" image, reflecting bilateral perfusion defects in areas supplied by the anterior cerebral arteries. Postmortem examination of the brain revealed an unusual anomaly of the circle of Willis in which the postcommunicating part of the right anterior cerebral artery was absent. CONCLUSIONS In our patient a unique developmental anomaly of the circle of Willis indirectly contributed to bilateral infarction in the territory of the anterior cerebral artery. The patient's neuropsychological profile, dominated by akinetic mutism, was highly suggestive of involvement of the receptive language modalities. For the first time, 99mTc-HMPAO SPECT of the brain revealed a horseshoe image in bilateral infarction in the territory of the anterior cerebral artery.