Apraxia

Definition

Apraxia is an impairment in the use of learned skilled movements (e.g., limb movements; speech) that occurs most often with damage affecting the left hemisphere of the brain.

Description

Apraxia is a general term for a disturbance of learned, skilled movements that cannot be attributed to sensory loss, weakness, or other cognitive impairments. To gain a processing advantage or skill each time a person attempts to enact complex, skilled movements of the limbs, mouth, and face, individuals develop memories that allow for smooth and efficient movements. The left hemisphere of the brain is integral to the ability to perform learned, skilled movements. Neurologic etiologies that affect the left cerebral cortex can lead to apraxia. Apraxia may be observed for different types of learned skilled movements leading to limb apraxia, apraxia of speech, buccofacial apraxia, and apraxic agraphia. Apraxia often is accompanied by other impairments of left hemisphere function including aphasia, dyslexia, dysarthria, and dysgraphia. Although more common in adults, apraxia can arise in children who incur brain damage or who fail to develop abilities due to left hemisphere neurologic dysfunction, sometimes termed developmental dyspraxia.

Causes and symptoms

Stroke affecting the left cerebral hemisphere is one leading cause of apraxia. Other neurologic conditions that affect the left hemisphere, such as tumor, dementia, trauma, anoxic events, and infections, may lead to apraxia. Little data exist to document the number of cases of apraxia; however, it is known that apraxia is less common than aphasia following left hemisphere damage. Although the term apraxia has been applied to other disordered movements, such as eyelid opening or dressing, it more appropriately subsumes movements related to learned skilled movements.

The patterns of apraxia vary depending upon which portion of the left cerebral hemisphere is affected:

• Limb apraxia refers to difficulty activating patterns of muscle movements when using tools and implements (e.g., unsafe use of knife or razor) and producing common pantomimes (e.g., ok, come here, drink, comb).

• Buccofacial apraxia leads to difficulty with skilled oral movements (e.g., whistle, blow out a candle).

• Apraxia of speech leads to difficulty activating the complex array of movements necessary for accurate pronunciation of sounds in words. Individuals suffering from speech apraxia struggle to utter words, mispronouncing and simplifying the sounds of speech. Some are rendered mute when the disorder is severe.

• Apraxic agraphia is impaired ability to select and sequence the series of strokes necessary for legible writing. An individual affected this way may know how to spell but cannot write.

Diagnosis

Following a clinical neurological examination, patients with apraxia are referred to rehabilitation specialists (e.g., speech-language pathologists, occupational therapists, physical therapists) trained in the examination of apraxia using standardized testing batteries for speech and limb apraxia. Specialized training is often required to recognize the error patterns in apraxia and to distinguish it from other abnormalities that may disrupt the ability to perform movements including weakness, sensory loss, or language impairments. Assessment of apraxia, which occurs in acute through chronic stages of the disorder, takes one to three hours to complete. Although some individuals may recover from apraxia, others may demonstrate chronic, significant impairments of learned skilled movements that affect communication and functioning in activities of daily living.

Treatment

Patients with apraxia may participate in rehabilitation to alleviate its consequences for communication or for safe performance of activities of daily living. A number of small group or case studies have demonstrated that behavioral treatments provided by rehabilitation professionals can be effective for improving skilled movements of the limbs or speech. Some treatment methods use drills and practice with speech or limb movements to restore skills or to engage other neural regions to mediate skilled movements. In other treatments, clinicians teach patients to compensate for the symptoms of apraxia using alternative communication modalities or methods to complete daily living activities. Patients with apraxia participate in speech-language treatment to alleviate its consequences for communication.

Prognosis

Less is known about the prognosis for recovery of apraxia than is known about other left-hemisphere cognitive disorders such as aphasia. Positive indicators may include:

• acute neurologic conditions (e.g. stroke) over degenerative conditions

• hemorrhagic over ischemic stroke

• unilateral left-hemisphere lesion

• onset within the past six to 12 months

• mild form of apraxia at onset

Health care team roles

Nursing and medical rehabilitation staff providing care for individuals with apraxia may need to implement strategies recommended by rehabilitation professionals. This will help foster communication with patients with apraxia of speech, and ensure patient safety in the hospital environment for individuals with limb apraxia. Individuals with severe limb apraxia may require close supervision when using tools and implements in daily living activities (e.g., grooming or eating).

Prevention

The way to prevent apraxia is to prevent the neurologic event that causes apraxia.

Key Terms

Aphasia

Impairment of spoken language understanding and expression associated with damage affecting the left hemisphere of the brain.

Apraxia of speech

Difficulty selecting and sequencing movements to pronounce speech sounds in the absence of weakness or incoordination.

Apraxic agraphia

Difficulty selecting and sequencing movements necessary for legible writing.

Buccofacial apraxia

Impaired ability to perform learned, skilled facial (nonspeech) movements.

Dysarthria

Speech impairment due to impaired motor (e.g., weakness, incoordination) or sensory function.

Dysgraphia

Impaired writing and spelling abilities.

Dyslexia

Impaired reading abilities.

Limb apraxia

Impaired ability to perform learned, skilled limb movements.