The Korsakoff syndrome

Pathology correlations: The Korsakoff syndrome results from cerebral lesion s due to thiamine depletion, usually of alcoholic etiology. Other nutrition al, or genetic factors, could be implicated. Exceptionally, it results from thalamic disease or a tumor of the third ventricle floor. Pathophysiological considerations: Anterograde and retrograde aspects of ep isodic memory are principally impaired, contrasting with the preservation o f semantic and procedural memory. Opposition between explicit (impaired) an d implicit (unimpaired) memory is one of the main cognitive features of thi s syndrome. Several cerebral structures, components of Various memory syste ms, are simultaneously damaged. Critical lesion sites for anterograde amnes ia involve the memillary bodies, the mamillotalamic tract and the anterior thalamus. Retrograde amnesia is dependent on function abnormalities of a ci rcuit between the dorso-median thalamus and the prefrontal cortex. Impairme nt of retrieval and chronological disorganization of memories contribute to this extensive retrograde amnesia, probably because of frontal dysfunction . Confabulations and false recognitions are produced in the initial stage o f the disease. They are, in the same way, interpreted as the consequence of frontal desafferentation due to dorso-median thalamus damage. The impact o f diencephalic destruction on the frontal lobes is evidenced clinically by behavioral changes and dysexecutive syndrome. Neuroimaging studies of the b rain show a decreased regional metabolic ration in the frontal areas. Prognosis: Korsakoff syndrome is a serious disorder, responsible for cognit ive handicap. There is no curative treatment Preventive measures, consistin g in systematic prescription of thiamine in alcoholics, is the main effecti ve measure. (C) 2000, Masson, Paris.