apraxia

n. Apraxia is the loss of the ability to produce purposeful, skilled movements as the result of brain pathology. This impairment in the production of learned (or skilled) movements is not caused by weakness, paralysis, lack of coordination, or sensory loss. Three subtypes of motor apraxia are described: (1) limb kinetic apraxia, (2) ideokinetic or ideomotor apraxia, and (3) ideational apraxia. Limb kinetic apraxia is a loss of the kinetic components of engrams resulting in coarse or unrefined movements. Ideokinetic or ideomotor apraxia is a loss of the voluntary ability to perform learned movements. Ideational apraxia is an impairment of ideational (conceptual) knowledge resulting in loss of the conceptual linkage between tools and their respective actions as well as the ability to sequence correctly produced movements. Ideomotor apraxia can be divided according to the body segment where apraxia is observed: face apraxia (ocular and oral apraxia), limb apraxia (upper limb apraxia and gait apraxia), and axial apraxia (body trunk apraxia). Sometimes a further distinction between motor apraxias (limb kinetic apraxia, ideokinetic or ideomotor apraxia, and ideational apraxia) and spatial apraxias, associated with an inability to manipulate objects (constructional apraxia and dressing apraxia), is introduced. Some authors, however, argue that so-called spatial apraxias should not be considered apraxias, but simply interpreted as visuoconstructive/ visuospatial defects. - AA