Apraxia

Apraxia is a neurological disorder characterized by the inability to perform learned (familiar) movements on command, even though the command is understood and there is a willingness to perform the movement. Both the desire and the capacity to move are present but the person simply cannot execute the act.

Patients with apraxia cannot use tools or perform such acts as tying shoelaces or button shirts etc. The requirements of daily living are difficult to meet. Patients whose ability to speak is interrupted (aphasia) but who are unaffected by apraxia are able to live a relatively normal life; those with significant apraxia are almost invariably dependent.
Apraxia comes in several different forms:

Limb-kinetic apraxia is the inability to make precise or exact movements with a finger, an arm or a leg. An example is the inability to use a screwdriver notwithstanding that the person affected understands what is to be done and has done it in the past.

Ideomotor apraxia is the inability to carry out a command from the brain to mimic limb or head movements performed or suggested by others.

Conceptual apraxia is much like ideomotor ataxia but infers a more profound malfunctioning in which the function of tools is no longer understood.

Ideational apraxia is the inability to create a plan for a specific movement.

Buccofacial apraxia, (sometimes called facial-oral apraxia) is the inability to coordinate and carry out facial and lip movements such as whistling, winking, coughing etc on command. This form includes verbal or speech developmental apraxia, perhaps the most common form of the disorder.

Constructional apraxia affects the person’s ability to draw or copy simple diagrams or to construct simple figures.

Oculomotor apraxia is a condition in which patients find it difficult to move their eyes.

Apraxia is believed to be caused by a lesion in the neural pathways of the brain that contain the learned patterns of movement. It is often a symptom of neurological, metabolic, or other disorders that can involve the brain.

Credit to - www.rarediseases.org