apraxia

n.
Total or partial loss of the ability to perform coordinated movements or manipulate objects in the absence of motor or sensory impairment.

[Greek aprāxiā, inaction : a-, without; see a-¹ + prāxis, action; see praxis.]

apractic a·prac'tic (ā-prăk'tĭk) or a·prax'ic (ā-prăk'sĭk) adj.

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Definition

Apraxia is a neurological disorder. In general, the diagnostic term "apraxia" can be used to classify the inability of a person to perform voluntary and skillful movements of one or more body parts, even though there is no evidence of underlying muscular paralysis, incoordination, or sensory deprivation. Additionally, motor performances in response to commands, imitation tasks, and use of familiar objects may be equally difficult but not attributable to dementia or confusion. These types of disturbances usually result from injuries, illnesses, or diseases of different regions of the brain normally responsible for regulating such abilities.

Description

The term apraxia is derived from the Greek word praxis, which refers to producing an action or movement. In 1861, Broca described in detail an 84-year-old man who suffered a sudden impairment of speech production, but preservation of oral musculature functions, overall language skills, and intelligence. Broca coined the term "aphemia" to classify the inability to articulate words in the presence of a good language foundation. In 1900, Leipmann reported a 48-year-old patient who was unable to execute various voluntary motor behaviors of the limbs and oral cavity, despite good muscle strength, intactness of certain automatic or previously well-rehearsed speech or bodily movements, and complete understanding of the intended acts. Liepmann popularized the diagnostic term "apraxia" to differentiate individuals with these types of select motor difficulties from those who struggle with movement disturbances because of weakness, paralysis, and incoordination of the muscles involved.

Demographics

There are no undisputed figures regarding the incidence of apraxia in the general population. However, because strokes are common causes, and African-American men are more susceptible to the development of this disease, by default this population may be at the greatest risk for this neurological disorder.

Causes and symptoms

Based on many additional case studies, Liepmann suggested that there are three major types of apraxia, each of which is caused by different sites of brain damage: ideational, ideo-motor, and kinetic.

Autopsy examinations and magnetic resonance imaging (MRI) scans have demonstrated that, in general, individuals with ideational, ideo-motor, and kinetic apraxias have pathologies involving either the back (parietal-occipital), middle (parietal), or front (frontal) lobes of the cerebral cortex, respectively. The individual with ideational apraxia cannot consistently produce complex serial actions, particularly with objects, due to disruptions at the conceptual stage of motor planning where the purpose and desire to perform specific movements are formulated. This individual may begin an act with a set purpose and start its performance, but then suddenly cease because the original goal is forgotten. The primary problem is failure to form concepts and/or inability to retain the conceptual plan for a sufficient period of time to allow the desired movements to be effectively programmed and executed. For example, if patients with ideational apraxia are requested to demonstrate proper use of a toothbrush, they might first brush their nails, then hesitate and brush their pants, and finally, with prompting, brush their teeth. Their actions will likely be slow and disorganized, appearing as though they have to think out each movement along the way.

Ideo-motor apraxia is characterized by derailments of bodily movement patterns, due to disturbances in the motor planning stages of a well-conceived behavioral act. Breakdowns most often occur during verbal commands to use objects rather than when the same objects are being used spontaneously. The patient with this disorder fails to translate the idea to perform specific movements into a coordinated and sequential scheme of muscle contractions to achieve the desired motor goal. If asked to demonstrate use of a pair of scissors, unlike ideational apraxics, individuals with ideo-motor apraxia will not make the mistake of using this tool as if it were a screwdriver. Rather, they might grasp the scissors with both hands and repetitively open and close the blades, or pick up the paper in one hand and the scissors in the other and rub them against one another with hesitant motions.

Kinetic apraxia is characterized by coarse, clumsy, groping, and mutilated movement patterns, especially on tasks that require simultaneous, sequential, and smooth contractions of separate muscle groups. These disturbances are usually proportional to the complexity of the task. The disorder does not involve ideation or concept formation, as the desired movement is almost always evident in the struggle. Typing, playing a musical instrument, and handwriting tasks are very difficult for the individual with kinetic apraxia. The problem is not with preliminary motor planning, as in ideo-motor apraxia. Instead, the kinetic apraxic suffers from disturbances in programming the motor plan into subunits of sequential muscle behaviors. Normally, such instructions are then conveyed directly to the primary motor system, which in turn initiates neural commands necessary to execute the intended act.

Apraxia of speech is a subtype of kinetic apraxia. This disorder is often observed following damage to the brain in an area named after Broca. Not infrequently, speech apraxia co-occurs with notable language disturbances, known as aphasia. Individuals with speech apraxia struggle with dysfluent articulation problems, as they grope to posture correctly sequential tongue, lip, and jaw movements during speech activities. Numerous, but variable articulatory errors occur, characterized by false starts, re-starts, sound substitutions, sound and word repetitions, and overall slow rate of speech. Multisyllabic words and complex word combinations are most vulnerable to these types of breakdowns.

Diagnosis

Testing for apraxia should employ basic screening tasks to identify individuals who do and do not require deeper testing for the differential diagnosis. Basic limb and orofacial praxis measures include the following commands:

• blow out a match
• protrude the tongue
• whistle
• salute
• wave goodbye
• brush the teeth
• flip a coin
• hammer a nail into wood
• cut paper with scissors
• tap the foot
• stand like a golfer
• jump up and down in place
• thread a needle
• tie a necktie
• recite isolated words, word sequences, and phrases

More detailed testing usually includes many additional tasks of increasing motor complexity.

Treatment team

Because the apraxias are neurological disorders, a clinical neurologist is often the team leader. A neurosurgeon may also be on the team, especially if the underlying cause requires surgical attention. Likewise, the primary medical care practitioner plays a very important role in taking care of the individual's overall health-related needs. The responsibilities of the nurse and clinical psychologist should not be underestimated, as many apraxic individuals experience the need for hospitalization, financial aid, social reintegration, and emotional and family counseling. Speech-language and occupational therapists are also key team members in those cases with clinically significant speech and/or limb-girdle movement abnormalities.

Treatment

Occupational therapists may employ exercises to rehabilitate proper use of eating utensils, health care and hygiene products, and self-dressing skills. The speech therapist focuses on retraining fluent and articulate movement patterns to improve overall speech intelligibility. Specific exercises may include tongue, lip, and jaw rate and rhythm activities, as well as combinations of complex sound and word productions.

Clinical trials

As of 2003, the National Institute of Neurological Disorders and Stroke (NINDS) sponsored two clinical trials that focused on patients with ideo-motor apraxia. These studies used different techniques to analyze brain activity as patients performed various movements and simple tasks.

The National Institute on Deafness and Other Communication Disorders (NIDCD) is also sponsoring a study. This clinical trial focuses on patients who experience speech and communication complications related to neurological illness.

Further information on these trials can be obtained by contacting the National Institutes of Health Patient Recruitment and Public Liaison Office.

Prognosis

The potential for significant improvements with treatments and self-healing (spontaneous recovery) are most likely in cases of mild apraxia with stable medical courses. For more severe cases, particularly those with progressive or unstable neurological pathologies, the prognoses for no-table gains with medical and behavioral interventions remain guarded at the outset. However, many such cases achieve sufficient gains to enable independent lifestyles.

Special concerns

People with apraxia who are elderly and/or who may also have co-morbid medical problems often require ongoing assistance with daily living activities. Nursing home facilities may be necessary for those individuals who do not have the opportunity or resources either to live by themselves or with family members, or to hire a home-based caregiver. Although apraxia most often afflicts adults, school-age children or adolescents with this disorder will require special education considerations and intensive academic and therapeutic programs.

Quality of life

Apraxia may be caused by very serious neurologic diseases or injuries. The quality of life of those afflicted with this disorder is usually influenced by its underlying cause. Many individuals have co-occurring physical, psychological, and intellectual disabilities, which complicate the differential diagnostic process and challenge the potential for meaningful rehabilitation and a fruitful quality of life. Others struggle with less intertwined functional disturbances. These individuals tend to lead more productive lives because they are not as severely impaired.

Resources

BOOKS

Hall, Penelope, Linda Jordan, and Donald Robin. Developmental Apraxia of Speech: Theory and Clinical Practice. Austin, TX: Pro Ed, 1993.

Icon Health Publishers. The Official Patient's Sourcebook on Apraxia: A Revised and Updated Directory for the Internet Age. San Diego: Icon Group International, 2002.

Vellemen, Shelley L. Childhood Apraxia of Speech. San Diego: Singular Publishing, 2002.

PERIODICALS

Geschwind, N. "The Apraxia: Neural Mechanisms of Disorders of Learned Movement." American Scientist 63 (1975): 188.

OTHER

Apraxia-Kids. Childhood Apraxia of Speech Association. December 9, 2003 (March 11, 2004). www.apraxiakids.org.

NINDS Apraxia Information Page. National Institute for Neurological Disorders and Stroke. December 17, 2001 (March 11, 2004). http://www.ninds.nih.gov/health_and_medical/disorders/apraxia.htm.

ORGANIZATIONS

National Institute of Deafness and Other Communication Disorders. 31 Center Drive, MSC 2320, Bethesda, MD 20892. (800) 411-1222. prpl@mail.cc.nih.gov. http://www.nidcd.nih.gov/.

National Institutes of Health Patient Recruitment and Public Liaison Office. 9000 Rockville Pike, Bethesda, MD 20892. (800) 411-1222. prpl@mail.cc.nih.gov. http://www.nih.gov/.

National Institute of Neurological Disorders and Stroke. P.O. Box 5801, Bethesda, MD 20824. (301) 496-5751 or (800) 352-9424. http://www.ninds.nih.gov.

Wayne State University, Department of Otolaryngology, Head and Neck Surgery. 5E-UHC, 4201 St Antoine, Detroit, MI 48201. (313) 577-0804. http://www.med.wayne.edu/otohns/index.htm.

James Paul Dworkin, Ph.D.

An impairment in the performance of voluntary actions despite intact motor power and coordination, sensation and perception, and comprehension. The apraxic person knows the act to be carried out, and has the requisite sensory-motor capacities, yet performance is defective. The abnormality is highlighted when the act must be performed on demand and out of context. Defects in performance vary from total inability to initiate the action, to incorrect serial ordering of elements, to partial approximations. A common apraxic behavior is the use of a body part as an object. Pantomiming the act of brushing the teeth, for example, a person may run the index finger across the teeth as though it were a toothbrush, while in normal performance, the hand assumes the posture of holding and moving the brush.

Apraxia is usually observed in both upper extremities. When it occurs unilaterally, it is usually the left arm and hand that are affected. This has been explained by assuming that the left cerebral hemisphere is specialized in the organization of voluntary movements, just as it is in language. The left hand is under the immediate control of the right hemisphere, but for skilled voluntary actions, the right hemisphere is dependent on information transmitted from the dominant left hemisphere over the corpus callosum. Callosal lesions produce apraxia of the left hand, because the right hemisphere is incapable of organizing the plan of movement independently. With an appropriately placed left-hemisphere lesion, a bilateral apraxia will result. When the left-hemisphere lesion also destroys the primary motor zone, the right arm is paralyzed and the apraxia is masked. The observable apraxia on the left side is referred to as sympathetic apraxia. This is seen in many individuals with right hemiplegia (unilateral paralysis of the body) and Broca's aphasia. Another apraxia often coupled with Broca's aphasia is nonspeech oral apraxia (or buccofacial apraxia). Individuals with this disorder can be observed to struggle to perform such simple acts as protruding the tongue or licking the lips on command or imitation, even though these movements are executed easily as part of the act of eating. See also Aphasia; Hemispheric laterality.

There are several disorders that are controversial with regard to their interpretation as forms of apraxia. The nonfluent speech pattern of Broca's aphasia, often riddled with speech-sound errors, is considered as apraxia of speech by some authorities, while others view it as an integral part of the linguistic deficit of the aphasia. In dressing apraxia and in some types of constructional apraxia, the defect appears to be perceptually based. Limb-kinetic apraxia is widely interpreted today as a mild spastic paresis, while ideational apraxia, commonly associated with dementia, is likely due to conceptual confusion rather than to a disturbance of motor organization. See also Agnosia.

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(əprak′sēə)
n

A loss of ability to execute a purposeful, goal-oriented, or skilled act resulting from selective damage to certain high-level brain centers, either sensory, motor, or both.

Disorder of the cerebral cortex, which results in an inability to make precise skilled movements.

The inability to make purposeful skilled movements. Like the aphasias, the apraxias are classical syndromes in human neuropsychology. Animals do not develop apraxia as a consequence of brain lesions, no matter where the lesion is located. In man, apraxia occurs, as a rule, after a lesion in the hemisphere dominant for language, usually the left hemisphere. In those rare instances where language is processed in the right hemisphere, apraxia might be expected after right-sided brain damage.

This observation might suggest that apraxia should be considered among those neuropsychological symptoms that are language dependent. An inherent relationship between the two syndromes, however, has not been demonstrated. Both aphasia and apraxia vary independently. After left-sided brain damage there can be recovery of language functions in the presence of persisting apraxia, and vice versa.

There are two varieties of apraxia, traditionally termed ideomotor apraxia and ideational apraxia. These terms reflect late 19th-century views on the organization of psychological processes in the brain; in particular, they imply a two-stage model of motor processing, similar to the traditional two-stage model of sensory processing (perception and apperception) developed during the same period. Although these models have been abandoned in favour of a multi-step, multi-modal integration model of processing, it is still convenient to adopt the terms ideomotor and ideational in modern research provided they are used as neutral denominators and do not confer a priori theoretical implications.

1. Ideomotor apraxia
2. Ideational apraxia

1. Ideomotor apraxia

This is a common syndrome in which the execution of simple or complex, meaningful (or symbolic), or meaningless (or non-symbolic) movements with the oro-facial musculature and/or with the limbs is impaired in a characteristic way. The paramount feature is not clumsiness of movement or absence of execution, but rather a distortion of movements, which Hugo Liepmann termed parapraxia. Parapraxias are brought about by inadequate selection of the elements that contribute to a motor sequence and/or by impairment in the sequential combination of these elements. Both aspects, impaired selection and sequencing of elements, are of equal importance. In order to arrive at the diagnosis of ideomotor apraxia, one has to make sure that the motor disorder is not explained by paresis, sensory impairment, disturbances in the coordination of movements, or problems in understanding a specified task because of either language disturbance or impaired intellectual performance.

A striking feature of ideomotor apraxia is that the execution of movements is impaired only when they are required out of their natural context. Traditionally, the examination is done by making the patient perform certain movements, like whistling, sticking out his tongue, blowing out his cheeks, performing the sign of the cross or a military salute, or placing the back of his hand on his front. These and similar movements are required either on verbal command or by imitation after demonstration by the examiner. It is important to note that a patient with ideomotor apraxia is perfectly able to brush his teeth in the morning, in a natural setting, whereas he performs the same movement in a rather parapraxic way when required to do so in the doctor's examination room. A convincing explanation for this well-recognized feature has not yet been put forward. One could be tempted to entertain a disconnection model, specifying that movements are impaired when they are elicited by input from the language system or from the visual system, but not when the input is generated in the limbic system. The reliance of spontaneous, context-dependent actions on limbic input to the motor system, however, still has to be demonstrated in both physiological and anatomical terms.

The structure of apraxia has been investigated on the basis of qualitative analysis of the parapraxic errors. This analysis was based on studies by David Efron, who was the first to apply sophisticated methods for the description of expressive movements in a study of gestural behaviour. He used the term 'linguistic' to denote the referential aspect of symbolic movements. While his analysis was focused only on movements as a whole, single components of movements were systematically studied by Birdwhistel (1970), who applied the methods of structural linguistics to the study of normal movements. He recognized posture and movement as patterned behaviour, and he developed a notation system which permitted a description of a hierarchy of motor elements similar to the description of speech elements in a linguistic hierarchy.

Stimulated by this research, K. Poeck and M. Kerschensteiner have developed a method permitting the quantitative and qualitative assessment of single components constituting the apraxic movements. A code has been elaborated which enables one to transcribe the characteristics of the single components of the motor sequence. Error analysis showed that the most characteristic behaviour in apraxia is perseveration (the inappropriate repetition of parts of speech or movement). In apraxia it occurs not only as the repetition of a whole movement or motor sequence but also, much more importantly, as the intrusion of motor elements that were part of a movement correctly or incorrectly performed many tasks before. To give an example, the patients not only repeated the military salute when they were asked to touch their chin but they perseverated on the rhythmic elements of the movement 'to show that somebody is crazy' when they performed the static movement of the military salute — i.e. they tapped their temple while their hand was in correct military salute position. The perseveratory tendency is so strong that when asked to imitate a movement, the patients were likely to repeat a movement or an element of a movement carried out earlier in spite of the visual evidence of the correct execution by the examiner.

In a systematic study with 200 apraxia tasks given to 88 patients with left-sided brain damage, 10 patients with right-sided brain damage, and 10 control subjects, no differences between the right and left limbs were found. Meaningful (i.e. practised, easily verbalized) and meaningless (i.e. unpractised and difficult to verbalize) tasks were equally impaired. The aphasic language disturbance did not explain errors on verbal command. No qualitative relation between aphasia and apraxia was detected, nor any subtypes of apraxia characterized by certain patterns of error.

Therapy is not necessary because ideomotor apraxia occurs only under the conditions of examination and does not impair the patient's spontaneous actions.

2. Ideational apraxia

A rare condition, this is observed in patients with lesions in the language-dominant hemisphere. There is only one case on record where the syndrome was the consequence of a right-sided brain lesion. This patient was left-handed and had right-sided or at least bilateral representation of language functions.

Patients with ideational apraxia are seriously impaired when they are about to carry out sequences of actions requiring the use of various objects in the correct way and order necessary to achieve an intended goal. These patients are conspicuous in everyday behaviour because they have problems in, for example, preparing or even eating a meal, or doing some professional routine they have performed for years. The behavioural disturbance of these patients is most frequently misinterpreted as indicating mental confusion — and all the more so since, in addition to ideational apraxia, they are regularly aphasic.

Patients do not fail these tasks because they have problems in the recognition of objects. In spite of their aphasia they frequently give pertinent verbal comments on the task, indicating that the language problem cannot be the determinant factor. Ideational apraxia is not a very severe degree of ideomotor apraxia; although both syndromes may occur in the same patient, they vary independently of each other. On the basis of a small number of observations it is suggested that the ideational apraxia syndrome is due to a disturbance in the associative elaboration of various inputs with motor programmes. This would be in line with modern concepts of the hierarchical organization of the motor system. Ideational apraxia is a great handicap for the patient, and therefore it is necessary to develop appropriate lines of treatment. Such treatment should first attempt to teach the patient to avoid perseverative behaviour.

(Published 1987)

— Klaus Poeck

Bibliography
• Birdwhistel, R. L. (1970). Kinesics and Context.
• Geschwind, N. (1974). Selected Papers on Language and the Brain.
• Poeck, K. (1984). 'Clues to the disruptions to limb praxis: Qualitative studies'. In Roy, E. A. (ed.), Disruptions to the Sequencing of Actions: Advances in Psychology.
• Rothi, L. J., and Heilman, K. M. (1997). Apraxia: The Neuropsychology of Action.

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