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.
There are two main types of apraxia of speech:
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.
· Verbal apraxia: People with verbal or oral apraxia find it challenging to make the movements necessary for speech. They may have problems producing sounds and understanding rhythms of speech.
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.
The major symptom of Apraxia is a person’s inability to perform movement in the absence of any physical paralysis. Commands to move are understood, but cannot be executed. When movement is initiated, it is usually very clumsy, uncontrolled and inappropriate. In some cases, movement may occur unintentionally. Apraxia is sometimes accompanied by a person’s loss of ability to comprehend or use words (Aphasia).
Specific types of Apraxia are characterized by an inability to perform particular movements on command. For example, in Buccofacial Apraxia, an affected individual is unable to cough, whistle, lick one’s lips, or wink when asked. In Constructional Apraxia, an individual is unable to reproduce simple patterns or copy simple drawings.
Apraxia is caused by a defect in the brain pathways that contain memory of learned patterns of movement. The lesion may be the result of certain metabolic, neurological or other disorders that involve the brain, particularly the frontal lobe (inferior parietal lobule) of the left hemisphere of the brain. In this region, complex, 3-dimensional representations of previously learned patterns and movements are stored. Patients with apraxia cannot retrieve these models of stored skilled movements.
Oculomotor apraxia is a dominant genetic trait. The gene for this condition has been mapped to chromosome 2p13. Each chromosome has a short arm designated “p” and a long arm designated “q”. Chromosomes are further sub-divided into many bands that are numbered. For example, “chromosome 2p13” refers to band 13 on the short arm of chromosome 2. The numbered bands specify the location of the thousands of genes that are present on each chromosome.
Genetic diseases are determined by two genes, one received from the father and one from the mother.
Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary for the appearance of the disease. The abnormal gene can be inherited from either parent, or can be the result of a new mutation (gene change) in the affected individual. The risk of passing the abnormal gene from affected parent to offspring is 50% for each pregnancy regardless of the sex of the resulting child.
Tissue or cellular damage (lesions) to other specific parts of the brain, whether as a result of stroke or wounds, tumors, or dementias, may also cause apraxia. These other locations include the so-called supplementary motor area (premotor cortex) or corpus callosum.
If apraxia is the result of a stroke it usually abates within weeks. Some cases of apraxia are congenital. When a child is born with apraxia it is usually the result of malformations of the central nervous system. At the other extreme, individuals with deteriorating intellectual functioning (degenerative dementia) may also develop apraxia.
Individuals with a condition of deteriorating intellectual functioning (degenerative dementia) may also develop Apraxia.