Apraxia

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Definition

Apraxia is a motor disorder caused by damage to the brain (specifically the posterior parietal cortex or corpus callosum. Apraxia is inability to carry out learned purposeful movement despite the presence of a good motor, sensory, or coordination function. Both the desire and the capacity to move are present but the person simply cannot execute the act.

Causes

Lesions of the premotor frontal cortex of either hemisphere, left inferior parietal lobe, and corpus callosum can produce apraxia. Apraxia is more evident with left hemisphere damage than right and is commonly seen with aphasia.

Apraxia has a neurologic cause that localizes fairly well to the left inferior parietal lobule, the frontal lobes (especially the premotor cortex, supplementary motor area, and convexity), or the 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

Signs and symptoms

There are two main types of apraxia-

Ideational apraxia

It is an inability of the patient to produce movement either on command or automatically and represents a complete breakdown in the conceptualization of the task. It is an impaired performance of skilled motor acts despite intact sensory, motor, and language function. . Ideational apraxia is often seen in patients with extensive left hemisphere damage, dementia, or delirium.

Ideomotor apraxia

In this type, the patient is unable to produce a movement on command but is able to move automatically. Thus, the patient can perform habitual tasks when not commanded to do so and often perseverates, repeating the activity over and over. It is an impaired performance of skilled motor acts despite intact sensory, motor, and language function.

Patients with ideomotor apraxia show temporal and spatial errors affecting timing, sequencing, amplitude, configuration, and limb position in space. They frequently use their limb as an object rather than demonstrating how to use the object. Patients are often able to perform the same acts without difficulty in their daily lives. This phenomenon has been called the “voluntary-automatic dissociation”

Performance may differ depending on gesture type: transitive (involving an object; eg, using a hammer) versus intransitive (eg, waving goodbye); meaningful (eg, mimicking a familiar gesture such as rubbing one’s chin) versus meaningless (eg, mimicking a novel gesture such as placing the dorsum of the hand against the contralateral cheek).

Lesion area - Most frequently from lesions in the left, dominant hemisphere. here is evidence that both frontal lesions and posterior parietal lesions can result in apraxia.

Eg. The patient may fail to walk if requested to in a traditional manner. However, if a cup of coffee is placed on a table at the other end of the room and the patient is told, “Please have coffee,” the patient is likely to traverse the room to get it

Buccofacial Apraxia

It is actually a type of ideomotor apraxia and is characterized by difficulties with performing the purposeful movements that involve facial muscles related to the mouth. It involves difficulty in responding to the commands like “pretend to blow out a candle,” or producing an orderly sequence of phonemes to produce speech.

Conceptual Apraxia

Patients with conceptual apraxia show impairment of object or action knowledge. They may misuse objects, have difficulty matching objects and actions, be unaware of the mechanical advantage afforded by tools, or be unable to judge whether a gesture is well- or ill-formed. It can be seen in patients with dementia and have been associated with lesions of posterior regions of the left hemisphere.

Orofacial Apraxia

Orofacial apraxia is characterized by an impairment of skilled movements involving the face, mouth, tongue, larynx, and pharynx (eg, blowing a kiss). Orofacial apraxia has been associated with inferior frontal, deep frontal white matter, insula, and basal ganglia lesions. Moreover, orofacial apraxia frequently coexists with limb apraxia. Based on these observations, orofacial apraxia has been considered a subtype of ideomotor apraxia. However, orofacial and limb apraxia can be dissociated, suggesting that the neural systems underlying these disorders are at least partially separable

Limb Kinetic Apraxia

The term limb-kinetic apraxia has been used to describe inaccurate or clumsy distal limb movements. It is often seen in the limb contralateral to the affected hemisphere, regardless of side.. The nature of limb-kinetic apraxia has been controversial. This disorder has been associated with frontal lesions and can be difficult to differentiate from concurrent limb weakness. Limb-kinetic apraxia has also been observed in patients with neurodegenerative conditions such as CBD, progressive supranuclear palsy, and Parkinson’s disease. Limb-kinetic apraxia tends to be independent of modality (eg, verbal command versus imitation), and there is typically no voluntary-automatic dissociation.

Diagnosis

Many patients with apraxia present with aphasia and it may be sometimes difficult to distinguish.

Outcome measures

Goodglass and Kaplan test for apraxia is composed of universally known movements, such as blowing, brushing teeth, hammering, shaving, and so forth. It is based on what the authors consider a hierarchy of difficulty for patients with apraxia

Additional apraxia tests may be found in Butler and the work of van Heugten et al,171 who have adapted the Arnadottir OT-ADL Neurobehavioural Evaluation (A-ONE) as an observational method of testing for apraxia.