Relation of anosognosia to frontal lobe dysfunction in Alzheimer's disease

Abstract

A self-rating scale of memory functions was administered to 24 non-depressed patients with probable Alzheimer's disease, divided into two groups according to the overall severity of dementia (mild, mini-mental state (MMS) > 21; moderate, MMS between 10 and 20). These groups did not significantly differ in their self-rating of memory functions. The same questionnaire was submitted to a member of each patient's family, who had to rate the patient's memory. An "anosognosia score" was defined as the difference between patient's and family's ratings. This score was highly variable, and covered, in the two groups, the full range between complete awareness of deficits and total anosognosia. Correlations between the anosognosia score and several neuropsychological data were searched for. No significant correlation was found with either the Wechsler memory scale, the MMS, or linguistic abilities and gestures. In contrast, this score was highly correlated with the "frontal score", defined as the sum of scores on the Wisconsin card sorting test (WCST), verbal fluency, Luria's graphic series, and "frontal behaviours" (prehension, utilisation, imitation behaviours, inertia, indifference). Among these tests of executive functions, the highest correlation with the anosognosia score was obtained on the WCST. This suggests that anosognosia in Alzheimer's disease is not related to the degree of cognitive deterioration but results, at least in part, from frontal dysfunction.