Apraxic disturbances in patients with mild to moderate Alzheimer's disease

Twenty-two patients meeting the NINCDS-ADRDA diagnostic criteria for probab le AD were included in the study, along with 10 matched controls. Praxic di sturbances were investigated using eight tasks and the results were interpr eted according to the neuropsychological model of Roy and Square modified b y Rothi et al. (1988) [Aphasiology 21:381-388] which distinguishes a concep tual system concerned with knowledge of the action and function of gestures and a production system that effects gestures in the environment. Disturba nce of the production system was found only in 17 patients. Disturbance of the production system was correlated to disturbance of verbal comprehension . The patients scored lower using the left hand than the right. Disturbance of the conceptual system was found in all patients and was not significant ly correlated with other cognitive deficits. No significant difference in r esults was found according to the type of input to the conceptual system (v isual or verbal). Deficits in tasks using rear objects were correlated to d isturbances of both the production and conceptual systems. Most patients pe rformed poorly both in tasks exploring the conceptual system and in those e xploring the production system. However, two patients performed badly in pr oduction tasks but had performances in the range of controls for conceptual tasks and one patient had the opposite pattern of dissociation. This provi des evidence that the production and the conceptual system are independent. Impairment in the ability to perform everyday activities was correlated to disturbances of the conceptual system whereas poor performances in tasks e xploring the production system or in using real objects were not. (C) 2000 Elsevier Science Ltd. All rights reserved.