Approach to Apraxia

Apraxia is the inability to perform a previously learned, purposeful motor task – despite having the desire and physical ability to do so. Apraxia can commonly affect the performance of activities of daily living such as brushing teeth and dressing.

Different types of praxis include:

• Ideomotor praxis: ability to perform intentional, learned motor movements or simple gestures.
  • Bihemispheric lesions of the deep white matter, commissural tracts, or the basal ganglia may be a cause of ideomotor apraxia.^[1]
• Ideational praxis: ability to sequence and plan complex motor acts, which requires knowledge of the object's function, and knowledge of the sequence of steps required. If an individual has ideational apraxia, some clinicians consider this to be a more severe form of ideomotor apraxia.^[2]
• Visuoconstructional (Constructional) praxis: ability to plan and carry out movements to organize, draw, and copy figures and shapes.
  • Thus, constructional apraxia refers to the inability to draw. Constructional apraxia localizes to the right hemisphere (right parietal lobe) or to the frontal lobes.
• Facial praxis: ability to perform intentional movements using different parts of the face (e.g. - forehead, lips, eyes, eyebrows, tongue, cheeks)

• Stroke and dementia are the most common causes, but other causes can include metabolic or neurological disorders.
• In typical right-handed patients, apraxia (and also aphasia) are caused by lesions to the left hemisphere.^[3]
• Lesions can affect the inferior parietal lobule, frontal lobes (premotor cortex, supplementary motor area), or the corpus callosum.
  • These areas all contains the memory of learned patterns of movement, and thus any lesion will result in apraxia.
• For example, the engram (i.e. - stored knowledge) for skilled limb movements is located in the left inferior parietal lobule in most right-handed people, but the engrams are translated into motor programs by the premotor cortices.
  • Thus, left frontal lesions, especially near supplementary motor and premotor cortices, can cause limb apraxia.

In neurodegnerative diseases (e.g. - Alzheimer's) that cause apraxia, sophisticated motor skills that require extensive learning, such as job-related skills, are the first functions that become impaired. More instinctive functions like chewing, swallowing and walking are lost in the last stages of the disease. 

In order to thoroughly examine for apraxia, the following assessments should be done:

1. Imitation of gestures: Both meaningful (e.g. - wave, salute, hitch-hiking sign) and meaningless gestures (body and non-body oriented hand positions) should be imitated by the patient
2. Use of imagined object: Tell the patient to do common daily tasks such as “comb your hair,” “brush your teeth,” “show me how you hammer a nail,” or “carve a loaf of bread.” A common error is to use a body part as a tool, such as a finger for a toothbrush. Actual use of the object (i.e. - holding a real toothbrush in the hand) generally elicits better performance than when it is mimed. When this is seen, it is called ideomotor apraxia.
3. Orobuccal movements: Ask patient to blow out a candle, show how to whistle, stick out their tongue, cough, or lick their lips
4. A sequencing task: The Luria test (fist-edge-palm “test”), or the Go-No-Go Test can be used.

• NeuroExam.com - Apraxia (Video)
• YouTube: Oculomotor Apraxia