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Les effets de la consommation chronique et excessive d’alcool sur le cerveau et la mémoire sont particulièrement variables. En accord avec la théorie de la continuité proposée en 1971, il existe un gradient dans la sévérité des atteintes de mémoire épisodique et du volume des structures du circuit de Papez entre l’alcoolo-dépendance et le syndrome de Korsakoff (SK), allant des atteintes légères à modérées chez les patients alcoolo-dépendants (AD) sans complication neurologique à l’amnésie massive du SK. A contrario, il ne semble pas exister de continuité dans les atteintes exécutives et de la volumétrie des régions du circuit fronto-cérébelleux. Le gradient de sévérité des atteintes de mémoire sémantique et de mémoire procédurale observées chez les patients AD et SK serait principalement le reflet de celui existant pour la mémoire épisodique. Ainsi, le concept de continuité semble pertinent pour mieux comprendre les effets de l’alcool sur la mémoire épisodique et le circuit de Papez mais il n’est pas applicable à tous les systèmes mnésiques et à tous les circuits cérébraux. D’un point de vue clinique, la notion de continuité des effets neurotoxiques de l’alcool pourrait permettre la détection des patients AD à risque de développer des complications neurologiques graves et définitives.

Alcohol-dependence and Korsakoff’s syndrome: a continuum?There is considerable heterogeneity in the alcohol-related consequences on brain structure and function. In accordance with the continuity theory proposed in 1971, there are graded effects of episodic memory deficits and brain damage in the circuit of Papez from mild-to-moderate in “uncomplicated” alcoholics to more severe in alcoholic patients with Korsakoff’s syndrome. On the contrary, the working memory and executive functions, as well as the structures of the frontocerebellar circuit, are damaged to the same extent in the two groups of patients. A graded deterioration in semantic and procedural memory has also been reported in “uncomplicated” alcoholics and patients with Korsakoff’s syndrome. However, such impairments may principally reflect, via indirect mechanisms, those observed for episodic memory, which is required for the encoding of new semantic and procedural information. Accordingly, the relevance of the concept of continuity seems to be limited to episodic memory and its associated circuit of Papez. The continuity theory is therefore not applicable to all memory systems and to all brain circuits. The confirmation that Papez’s circuit and frontocerebellar circuits are differentially affected by chronic and excessive alcohol consumption requires further neuropsychological and neuroimaging investigations. The next step will be to compare brain metabolism and functional connectivity within those two circuits in alcoholic patients with and without Korsakoff’s syndrome. From a clinical perspective, alcoholic patients with problems of episodic memory or specific deficits in brain volume of Papez’s circuit similar to those of patients with Korsakoff’s syndrome may be considered at risk for the development of alcohol-related neuropsychiatric complications. Thus, when used in strictly defined circumstances, the continuity theory would enable the detection, prevention and treatment of the latter patients before the development of irreversible and debilitating damage such as Korsakoff’s disease.