[Preservation of procedural memory in 18 patients operated for aneurysm of the anterior communicating artery].

Organic amnesia is typically associated with lesions in either the diencephalic or medial temporal regions of the brain. However, amnesia can result from other kinds of lesions, in particular those resulting from an aneurysm of the anterior communicating artery (ACoA). In the present study, 7 patients who became amnesic following a ruptured and operated ACoA aneurysm were comparated neuropsychologically with 11 patients with ruptures but no cognitive complaints and 18 normal control subjects. They were submitted to explicit and implicit memory tests and to tests claimed to be sensitive to frontal lobe dysfunction. The performance of the 11 ACoa patients without cognitive complaints revealed evidence for a functional frontal dysfunction (test of Stroop) and a partial deficit of explicit memory (free recall and long-term recall). The performance of the 7 ACoa amnesics revealed evidence for a functional frontal dysfunction and a deficit of explicit memory (safe in recognition). Anosognosia was also observed. The performance of all patients revealed the preservation of implicit memory in procedural tasks (serial reaction time and mirror reading) as diencephalic and temporal amnesia. The functionnal nature of the syndrome is discussed.