The Mental and Cognitive Syndrome of Patients with Focal Lesions of Basal Ganglia

Abstract

In 1981, the first modern case of mental manifestations of bilateral lesions of the basal ganglia was reported (Laplane et al; 1981). Two years ago, in the preceding IBAGS meeting, 12 similar cases were presented confirming the initial description. Whatever the nature of the basal ganglia lesions (wasp sting, anoxia, carbon oxide poisoning, disulfiram intoxication and trauma), the same mental syndrome was observed that associated in variable proportions 1) a loss of psychic self activation and 2) obsessive compulsive behaviours or motor stereotypies. Loss of psychic self activation is characterised by a behavioural inertia that is reversed by an environmental demand: the patient may remain without any activity for hours but he feels no impression of boring himself. In the most complete cases, the patient describes a sensation of mental emptiness, without loss of consciousness. This motor and mental akinesia contrasts with a normal or near normal behaviour when the patient is stimulated. An affective reactivity is also present but the reaction does not last and the patient returns quickly to his usual indifference. Obsessive compulsive behaviours may be purely mental, very similar to these occurring in OCT or remain limited to elementary mental counting. They may be motor, including movements of snapping or licking the fingers or mixed, the repetitive movement pacing the mental counting. Since the first publication, several papers have described the same troubles following pallidal (Ali cherif et al. 1984; Strub et al. 1989) and also frontal (Laplane et al. 1988), striatal (Habib et Poncet 1988) and thalamic lesions (Bogousslavsky et al. 1991), demonstrating the involvement in mental auto-activation and in control and inhibition of motor or purely mental programs of a fronto-frontal loop passing through the basal ganglia and thalamus.