Apraxia is a disorder caused by damage to specific areas of the cerebrum. Apraxia is characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements. It is a disorder of motor planning, which may be acquired or developmental, but may not be caused by incoordination, sensory loss, or failure to comprehend simple commands (which can be tested by asking the person to recognize the correct movement from a series). Apraxia should not be confused with ataxia, a lack of coordination of movements, aphasia, an inability to produce and/or comprehend language; abulia, the lack of desire to carry out an action; or allochiria, in which patients perceive stimuli to one side of the body as occurring on the other.
The root word of apraxia is praxis, Greek for an act, work, or deed. It is preceded by a privative a, meaning without.
There are several types of apraxia including:
* ideomotor (inability to carry out a motor command; for example, "act as if you are brushing your teeth" or "salute") - the form most frequently encountered by physicians. The ability to spontaneously execute the task may remain, however.
o limb apraxia when movements of the arms and legs are involved;
o nonverbal-oral or buccofacial (inability to carry out facial movements on command; e.g., lick lips, whistle, cough, or wink);
* ideational (inability to perform a task on command or automatically ; for example, "pick up this pen and write down your name")
* limb-kinetic (inability to make fine, precise movements with a limb);
* verbal (difficulty planning the movements necessary for speech), also known as Apraxia of Speech (see below);
* constructional (inability to draw or construct simple configurations), such as intersecting pentagons;
* oculomotor (difficulty moving the eye, especially with saccade movements). This is one of the 3 major components of Balint's syndrome.
* gait apraxia
Each type may be tested at decreasing levels of complexity; if the person tested fails to execute the commands, you can make the movement yourself and ask that the person mimic it, or you can even give them a real object (like a toothbrush) and ask them to use it.
Apraxia may be accompanied by a language disorder called aphasia.
Symptoms of Acquired Apraxia of speech (AOS) and Childhood Apraxia of Speech (CAS) include inconsistent articulatory errors, groping oral movements to locate the correct articulatory position, and increasing errors with increasing word and phrase length. AOS often co-occurs with Oral Apraxia (during both speech and non-speech movements) and Limb Apraxia.
Childhood Apraxia of Speech (CAS) presents in children who have no evidence of difficulty with strength or range of motion of the articulators, but are unable to execute speech movements because of motor planning and coordination problems. This is not to be confused with phonological impairments in children with normal coordination of the articulators during speech.
Acquired apraxia of speech involves the loss of previously acquired speech levels. It occurs in both children and adults who have (prior to the onset of apraxia) acquired some level of speaking ability. Unlike Childhood Apraxia of Speech, AOS is typically the result of a stroke, tumor, or other known neurological illness or injury.
Ideomotor apraxia is almost always caused by lesions in the language-dominant (usually left) hemisphere of the brain; and, as such, these patients often have concomitant aphasia, especially of the Broca or conduction type. Left-side ideomotor apraxia may be caused by a lesion of the anterior corpus callosum.
Ideational apraxia is commonly associated with confusion states and dementia.
Constructional apraxia is associated with hepatic encephalopathy due to cerebral edema.