[An unusual case of anterior communicating artery syndrome].

We describe the case of a 51-year-old man who developed acute partial anterior communicating artery syndrome (ACoAS) due to a nonruptured aneurysm of that artery. The patient presented with anterograde memory deficits, particularly impaired delayed recall, whereas his declarative learning and retrograde memory were relatively spared. Full ACoAS is usually associated with confabulations and personality change, which did not present in the case reported here. However, the patient presented with the flat affect and reduced drive typical of frontal lobe disorder. Clinical and neuropsychological assessment largely ruled out other causal factors involved in the symptomatology. Upon follow-up 2 years after onset of the AcoAS, the patient's neuropsychological performance had remained stable, yet his affective resonance and, in part, his spatial orientation had improved. We conclude that malformations of the intracranial arterial system ought to be taken into account as differential diagnosis of acute memory disorders.