[Disorders of voluntary motor activity and lesions of caudate nuclei]

Three clinical cases are reported, resulting in apathy, uninterest, flattened affect and lack of initiative for usual daily activities. Intellectual performances were normal and there was no depression. This syndrome was reversible when patients were stimulated. Stereotyped behaviors resembling compulsions were frequent. One of the patients presented with prolonged akinetic episodes reversible by verbal stimulation. CT and MRI showed bilateral lesions, mainly in and around the head of the caudate nucleus. Such behavioral disorders have been termed psychic akinesia or athymhormia syndrome, suggesting that the patients suffered from a loss of drive and motivation. The lesions involved bilaterally the globus pallidus, the striatum or the frontal lobe. Recently, anatomical findings have shown several circuits through the basal ganglia additional to the motor circuit. The caudate nucleus receives inputs from the prefrontal and limbic cortex. These inputs are transmitted to the globus pallidus, then to the thalamus and ultimately return to the dorsolateral prefrontal, lateral orbitofrontal and anterior cingulate areas. Lesions in any part of these cortico-subcortical loops may be responsible for a dramatic behavioral syndrome, emphasizing their functional specificity in drive. However, a procedural learning impairment in neostriatal dysfunction could possibly explain the disorders observed in our patients.