Apraxias

Abstract

Apraxia is defined as the difficulty or inability to perform learned skilled actions. We describe the various motor impairments classified as apraxia. The neuroanatomic network thought to underlie praxis encompasses frontal and parietal cortices and the basal ganglia. As corticobasal syndrome is characterised by frontal, parietal and basal ganglia disease, we highlight the frequent occurrence of apraxia in this disorder. We also discuss several current models of praxis to explain the findings seen in apraxic patients, focussing on the neuroanatomical networks described in the literature. Understanding the alterations in the networks underlying praxis during learning and as a result of injury will help guide the development of novel rehabilitative and therapeutic interventions. Key Concepts: Apraxia is the difficulty in performing acquired actions. Apraxia is not caused by a sensory or motor disorder, and is independent of other symbol‐mediated disorders such as aphasia as these have been dissociated in multiple reported patients. There are several different forms of apraxia such as ideomotor apraxia, and each is characterised by the specific manner in which action is compromised. The network of anatomical structures underlying praxis includes the frontal and parietal cortices, basal ganglia and white matter tracts projecting between these areas. Interruption of this frontal–parietal–basal ganglia network results in apraxia. Unilateral apraxia may be the first presenting sign of a neurodegenerative condition known as corticobasal syndrome, which is characterised by frontal, parietal and basal ganglia dysfunction. Apraxia also may be due to other conditions such as stroke and head trauma.