Apraxia and Related Syndromes:

Author: Jasvinder Chawla, MBBS, MD, MBA, Associate Professor of Neurology, Director of Neurology Residency Training Program, Director of Clinical Neurophysiology Laboratory, Assistant Director of Neurology Clerkship Program, Department of Neurology, Loyola University Medical Center
Coauthor(s): Daniel H Jacobs, MD, Associate Professor of Neurology, University of Central Florida College of Medicine

Introduction
Background
Apraxia is one of the most important and least understood major behavioral neurology syndromes. It is one of the best localizing signs of the mental status examination and also predicts disability in patients with stroke or dementia (unlike aphasia). Patients with apraxia cannot use tools; therefore, they are unlikely to perform activities of daily living well. Patients with aphasia, without coexisting apraxia, can live independently, take the bus or subway, and lead a relatively normal life; a patient with significant limb apraxia is likely to remain dependent.

Heilman defined apraxia in negative terms, "Apraxia is defined as a disorder of skilled movement not caused by weakness, akinesia, deafferentation, abnormal tone or posture, movement disorders such as tremors or chorea, intellectual deterioration, poor comprehension, or uncooperativeness."1 To simplify matters, apraxia can be considered a form of a motor agnosia. Patients are not paretic but have lost information about how to perform skilled movements.



There is no consensus on how to divide and organize the many different syndromes known as apraxias. Authors have divided apraxias based on the following:

•Body part affected (eg, limb apraxia or buccofacial apraxia)
•Dysfunctional sensory area (left inferior parietal) or motor areas (left premotor and left supplementary motor)
•If use of tools is affected (transitive vs intransitive)
•If knowledge about the use of tools is preserved (conceptual)
•Deficits in pantomiming tool use and gesture (ideomotor)
The term apraxia is used to describe a variety of syndromes, including the following, which are not considered true apraxias by some.

•Dressing apraxia - Usually associated with right parietal lesions and part of a neglect syndrome
•Constructional apraxia - Inability to copy 2-dimensional drawings or 3-dimensional assemblies (may be associated with right or left parietal and left frontal among other brain regions)
•Gait apraxia - Part of the triad of symptoms of normal pressure hydrocephalus
•Gaze apraxia - Part of Balint syndrome
•Apraxia of eyelid opening
•Magnetic apraxia

Pathophysiology
Apraxia is a syndrome reflecting motor system dysfunction at the cortical level, exclusive of primary motor cortex. In planning movements, previously learned, stored complex representations of skilled movements are used. These 3-dimensional, supramodal codes, also called representations or movement formulae, are stored in the inferior parietal lobule of the left hemisphere. Diseases that involve this part of the brain, including strokes, dementias, and tumors, can cause loss of knowledge about how to perform skilled movements.

Apraxia can occur with lesions in other locations as well. Information contained in praxis representations is transcoded into innervatory patterns by the premotor cortices, including the supplementary motor area (SMA) and possibly the convexity of the premotor cortex; the information is then transmitted to the primary motor cortex and a movement is performed. Lesions of the SMA or other premotor cortices also can cause apraxia; in this case, knowledge about movement is still present, but the ability to perform movement is absent.

Apraxia also occurs with lesions of the corpus callosum, such as tumors or anterior cerebral artery strokes. Although the corpus callosum is not known to be involved directly in the performance of skilled movements, it contains crossing fibers from the right hemisphere to the premotor cortex. This type of apraxia represents a classic disconnection syndrome; patients with callosal apraxia typically are apractic only with the left hand.

Frequency
United States
Few data are available regarding the frequency of apraxia; however, it commonly occurs after stroke and in dementia—2 of the most frequent neurological illnesses.

International
Few data are available regarding the frequency of apraxia.

Mortality/Morbidity
Apraxia is not a disease but a syndrome; consequently, it has no attributable morbidity or mortality.

Race
No data are available.

Sex
No good data are available.

Age
No good data exist concerning the occurrence of apraxia in different age groups. However, it is more common in older age groups, as they typically have higher frequencies of stroke and dementia.

Clinical
History
Frequently, patients with apraxia are unaware of their deficits. Accordingly, history of a patient's ability to perform skilled movements should be obtained from both the patient and caregivers. Caregivers should be asked about the ability of patients to perform activities of daily living, especially those that involve household tools (eg, using a knife, fork, and toothbrush correctly; using kitchen utensils safely and correctly to prepare a meal; using tools such as a hammer or scissors correctly). Caregivers should also be queried about the overall activity level of the patient and whether reductions in their total activities have occurred. The patient may simply sit on the couch and watch television, uninterested in previously important activities. This apathy can be associated with many different kinds of brain dysfunction, but occasionally occurs because the patient is not able to perform his or her usual activities.



Physical
•Testing for ideomotor apraxia can be performed at the bedside with simple tests for the ability to use tools. The examiner asks patients to perform 3 pantomimes of activities. The author of this article asks patients to pantomime hammering a nail into the (imaginary) wall in front of them, screwing a screw into the wall, and using a pair of scissors to cut a piece of paper. Nevertheless, many other pantomimes could be performed, including brushing teeth, cutting with a saw, whipping eggs with an eggbeater, or peeling a potato.
◦A healthy response to any of these commands is to perform a crisp, well-planned movement. Patients should perform the movement with the hand oriented correctly to hold an imaginary tool, with the tool held at the correct orientation and distance from the target (wall, screw, paper, respectively), and with the motion performed in such a way that the action gets performed. In other words, the author would like to see an action that would successfully cut a piece of paper, as if scissors and paper were really there.
◦Any type of error in performing the above activities (in the absence of aphasia or lack of comprehension of the command or lack of motor deficit) implies a loss of knowledge about the movement to be performed. If the hand is not oriented to hold the tool correctly, if the action is performed in the wrong plane, if the target (eg, wall) is not located correctly, or if movement is performed incorrectly, the response is scored as an error.
•Buccofacial apraxia implies a completely different process and lesion; it is tested separately. Unlike limb apraxia, in which a patient cannot perform skilled movements with the limbs, in buccofacial apraxia (also called oral apraxia), patients cannot perform skilled actions involving the lips, mouth, and tongue in the absence of paresis. Localization too is unique.
◦In buccofacial apraxia, the lesion is usually in or near area 44 (ie, the Broca area). To test for buccofacial apraxia, the patient should be asked to perform tasks with his mouth, like blow out a match, kiss, or brush his teeth.
◦Neighborhood signs also should be checked. Buccofacial apraxia usually occurs with Broca aphasia, whereas limb apraxia due to a parietal lesion may co-occur with Wernicke aphasia if the temporal lobe also is involved, or conduction aphasia or features of Gerstmann syndrome (ie, acalculia, right-left confusion, alexia with agraphia) if the angular gyrus also is involved.
•The nature of the response is also important. Additional tests of apraxia might include the ability to imitate commands (in aphasic patients), ability to select by choice correct and incorrect movements, or the ability to perform commands with each hand. Patients may be asked to actually use a tool or to perform an act when viewing a tool.
•Conceptual apraxia is defined as the loss of knowledge about tools and movements associated with their use. Patients with parietal lesions may have conceptual apraxia. These patients may be contrasted with patients with SMA lesions or other lesions of the premotor cortex. The latter type of patient would have normal knowledge about how to move, yet be unable to perform the movement correctly because of faulty transcoding of the "innervatory patterns" in the motor cortex.
•In a report published in 2008, Goldenberg hypothesized that “imitation of meaningless gestures and use of tool and objects depend on left parietal lobe integrity because of their demands on categorical apprehension of spatial relationships between multiple objects or between multiple parts of objects.”18 •Sometimes, testing the patient in a more practical setting may be necessary. For example, a patient may perform well by imitating movements, without the use of tools. However, if a dinner tray with a fork, a pencil, and a toothbrush are presented, selection of the wrong tool may be more obvious and evident.
•Magnetic apraxia is a type of forced grasp response, which often may be associated with frontal lesions and a degenerative disease known as corticobasal degeneration with neuronal achromasia (Rebeiz syndrome) or related conditions such as Alzheimer disease and progressive supranuclear palsy. This apraxia may be unilateral (affecting either side) and may resemble utilization behaviors or the alien hand syndrome. Patients may be unable to disengage from objects in front of them.
•Unilateral apraxia may be the presenting sign of corticobasal degeneration; memory is typically unaffected early. (Rarely, Alzheimer disease, progressive supranuclear palsy, Pick disease, and nonspecific degenerative dementia can present with that phenotype.) In addition to apraxia, patients may develop a truly useless limb and bizarre behaviors with the limb, including magnetic responses, forced grasping, and levitation of the limb. These clinical features are common but not absolutely necessary for the diagnosis. The pathology described in this condition, balloon cells with neuronal achromasia, is unique.
•Rothi has described a number of apraxia error types. These include errors of orientation of the hand around the object, errors of external spatial orientation, and movement errors. Other error types include perseverative errors (ie, repeating a previously made movement), body part as tool errors (ie, using the hand as the hammer rather than holding a hammer), and body part as object errors (ie, hand as the object of the action). While these errors can confirm that apraxia is present, no correlation can be made between lesion site and error type.
•Other (non)apraxia types
◦Dressing apraxia refers to inattention to the left side when dressing; it signifies a feature of the neglect syndrome rather than the loss of the ability to use tools. Typically, a right hemisphere lesion is implicated. It has no relationship with ideomotor apraxia.
◦Limb-kinetic apraxia (as distinct from limb apraxia) means a clumsy hand. Typically, it refers to the inability to make precise movements with the limb, especially the fingers contralateral to a brain injury. For example, patients may not be able to make rapid finger movements, to grasp objects in a pincer fashion, or to perform tapping movements.
◦Constructional apraxia refers to the inability to draw or copy quality pictures such as interlocking pentagons or complex figures such as the Rey-Osterreith figure. Constructional apraxia can localize damage to several brain areas, including frontal or left or right parietal. Patients with frontal damage tend to perseverate on or repeat elements of the figure, or to transform elements into familiar elements, such as transforming the circle with 3 dots into a face. Patients with right hemisphere damage (especially parietal) on the whole do worse than patients with left hemisphere damage at integrating the basic elements of the diagram, although left hemisphere-damaged patients also made many errors. Error types were described by Lezak.2 •Gait apraxia (also called Bruns ataxia) is observed in patients with normal pressure hydrocephalus. It has no relationship to ideomotor apraxia.
•Gaze apraxia, seen in Balint syndrome, has no relationship to ideomotor apraxia. Apraxia of eyelid opening has no relationship to ideomotor apraxia.
Causes
As discussed in the introduction, apraxia has a neurological cause that localizes fairly well to the left inferior parietal lobule, frontal lobes (especially the premotor cortex, supplementary motor area, and convexity), or corpus callosum. Any disease of these areas can cause apraxia, although stroke and dementia are the most common causes. Interestingly, callosal apraxia is rare after callosotomy and is much more common with anterior cerebral artery strokes or tumors.