APRAXIA

disturbance, caused by cerebral lesion, in the ability to carry out useful or skilled acts; motor power and mental capacity remain intact. Kinetic, or motor, apraxia results in one upper extremity's being affected so that the individual, even though there is no muscle weakness, cannot carry out fine motor acts, such as turning a key in a lock. Ideational apraxia is the ultimate in absent-mindedness, the loss of capability to formulate a plan of action. The plan is never wholly organized, and even that part that is organized cannot be maintained sufficiently long to be carried out. Portions of the act may be completed but not in proper sequence. The individual may strike a match, for example, to light a campfire but then will hold the match until it burns his fingers. This type of apraxia is usually caused by diffuse lesions or toxemia in the cerebral cortex. Ideokinetic apraxia is a condition brought about by an interruption of the association tracts, in which there is no coordination between ideation and motor activity. An affected individual will complain, for example, that he cannot use his hand, but then he will slap a mosquito with it. He is unable to perform certain acts (e.g., whistling or making a fist) upon command but is able to do so automatically. The cortical lesion responsible for ideokinetic apraxia is usually in the supramarginal gyrus and may be on one or both sides. Constructional apraxia, caused more often by a lesion in the right cerebral hemisphere than in the left, is the inability to put together elements in the correct fashion to form a meaningful wholee.g., being unable to build a structure with blocks or to copy a design.