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Apraxia (from Greek praxis, an act, work, or deed) is the inability to execute learned purposeful movements, despite having the desire and the physical capacity to perform the movements. Apraxia is an acquired disorder of motor planning, but is not caused by incoordination, sensory loss, or failure to comprehend simple commands (which can be tested by asking the person to recognize the correct movement from a series). It is caused by damage to specific areas of the cerebrum. Apraxia should not be confused with ataxia, a lack of coordination of movements; aphasia, an inability to produce and/or comprehend language; abulia, the lack of desire to carry out an action; or allochiria, in which patients perceive stimuli to one side of the body as occurring on the other. Developmental coordination disorder (DCD) is the developmental disorder of motor planning.
There are several types of apraxia including:
- Ideomotor apraxia: These patients have deficits in their ability to plan or complete motor actions that rely on semantic memory. They are able to explain how to perform an action, but unable to "imagine" or act out a movement such as "pretend to brush your teeth" or "pucker as though you bit into a sour lemon." The ability to perform an action automatically when cued, however, remains intact. This is known as automatic-voluntary dissociation. For example they may not be able to pick up a phone when asked to do so, but can perform the action without thinking when the phone rings.
- Ideational/conceptual apraxia: Patients have an inability to conceptualize a task and impaired ability to complete multistep actions. Consists of an inability to select and carry out an appropriate motor program. For example, the patient may complete actions in incorrect orders, such as buttering bread before putting it in the toaster, or putting on shoes before putting on socks. There is also a loss of ability to voluntarily perform a learned task when given the necessary objects or tools. For instance, if given a screwdriver, the patient may try to write with it as if it were a pen, or try to comb one's hair with a toothbrush.
- Buccofacial or orofacial apraxia: Non-verbal oral or buccofacial ideomotor apraxia resulting in difficulty carrying out movements of the face on demand. For example, an inability to lick one's lips or whistle.
- Constructional apraxia: The inability to draw or construct simple configurations, such as intersecting pentagons.
- Gait apraxia: The loss of ability to have normal function of the lower limbs such as walking. This is not due to loss of motor or sensory functions.
- Limb-kinetic apraxia: Difficulty making precise movements with an arm or leg.
- Oculomotor apraxia: Difficulty moving the eye, especially with saccade movements that direct the gaze to targets. This is one of the 3 major components of Balint's syndrome.
Each type may be tested at decreasing levels of complexity; if the person tested fails to execute the commands, you can make the movement yourself and ask that the person mimic it, or you can even give them a real object (like a toothbrush) and ask them to use it.
Apraxia of speech
Apraxia of speech (AOS) involves the loss of previously acquired speech levels. It occurs in both children and adults who have (prior to the onset of apraxia) acquired some level of speaking ability. AOS is typically the result of a stroke, tumor, or other known neurological illness or injury. Apraxia may be accompanied by a language disorder called aphasia.
Symptoms of AOS include inconsistent articulatory errors, groping oral movements to locate the correct articulatory position, and increasing errors with increasing word and phrase length. AOS often co-occurs with Oral Apraxia (during both speech and non-speech movements) and Limb Apraxia.
Developmental verbal dyspraxia presents in children who have no evidence of difficulty with strength or range of motion of the articulators, but are unable to execute speech movements because of motor planning and coordination problems.
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Apraxia is most often due to a lesion located in the left hemisphere of the brain, typically in the frontal and parietal lobes. Lesions may be due to stroke, acquired brain injuries, or neurodegenerative diseases such as Alzheimer’s disease or other dementias, Parkinson’s disease, or Huntington’s disease. It is also possible for apraxia to be caused by lesions in other areas of the brain including the right hemisphere. 
Ideomotor apraxia is typically due to a decrease in blood flow to the left hemisphere of the brain and particularly the parietal and premotor areas. It is frequently seen in patients with corticobasal degeneration. 
Ideational apraxia often results in functional impairments in activities of daily living (ADLs) similar to those seen with late stage dementia. More recently, it has been observed in patients with lesions in the left hemisphere near areas associated with aphasia, however more research is needed on ideational apraxia due to brain lesions. The localization of lesions in areas of the frontal and temporal lobes would provide explanation for the difficulty in motor planning seen in ideational apraxia as well as its difficulty to distinguish it from certain aphasias.
Constructional apraxia is often caused by lesions of the inferior right parietal lobe, and can be caused by brain injury, illness, tumor or other condition that can result in a brain lesion. 
Although qualitative and quantitative studies exist, there is little consensus on the proper method to assess for apraxia. The criticisms of past methods include failure to meet standard psychometric properties as well as research-specific designs that translate poorly to non-research use.
The Test to Measure Upper Limb Apraxia (TULIA) is one method of determining upper limb apraxia through the qualitative and quantitative assessment of gesture production. In contrast to previous publications on apraxic assessment, the reliability and validity of TULIA was thoroughly investigated. The TULIA consists of subtests for the imitation and pantomime of non-symbolic (“put your index finger on top of your nose”), intransitive (“wave goodbye”) and transitive (“show me how to use a hammer”) gestures. Discrimination (differentiating between well- and poorly-performed tasks) and recognition (indicating which object corresponds to a pantomimed gesture) tasks are also often tested for a full apraxia evaluation.
However, there may not be a strong correlation between formal test results and actual performance in everyday functioning or activities of daily living (ADLs). A comprehensive assessment of apraxia should include formal testing, standardized measurements of ADLs, observation of daily routines, self-report questionnaires and targeted interviews with the patients and their relatives.
Treatment for individuals with apraxia includes speech therapy, occupational therapy, and physical therapy. Yet, treatments for apraxia have received little attention for several reasons, including the tendency for the condition to resolve spontaneously in acute cases. Additionally, the very nature of the automatic-voluntary dissociation of motor abilities that defines apraxia means that patients may still be able to automatically perform activities if cued to do so in daily life. Nevertheless, research shows that patients experiencing apraxia have less functional independence in their daily lives, and that evidence for the treatment of apraxia is scarce. However, a literature review of apraxia treatment to date reveals that although the field is in its early stages of treatment design, certain aspects can be included to treat apraxia. One method is through rehabilitative treatment, which has been found to positively impact apraxia, as well as activities of daily living. In this review, rehabilitative treatment consisted of 12 different contextual cues, which were used in order to teach patients how to produce the same gesture under different contextual situations. Additional studies have also recommended varying forms of gesture therapy, whereby the patient is instructed to make gestures (either using objects or symbolically meaningful and non-meaningful gestures) with progressively less cuing from the therapist. No single type of therapy or approach has been proven as the best way to treat a patient with apraxia, since each patient's case varies. However, one-on-one sessions usually work the best, with the support of family members and friends. Since everyone responds to therapy differently, some patients will make significant improvements, while others will make less progress.
The prognosis for individuals with apraxia varies. With therapy, some patients improve significantly, while others may show very little improvement. Some individuals with apraxia may benefit from the use of a communication aid. However, many people with apraxia are no longer able to be independent. They should avoid activities in which they might injure themselves or others.
Occupational therapy and counseling and play therapy may help both patients and their caregivers learn ways to deal with the apraxia. However, because people with limb apraxia may have trouble directing their motor movements, occupational therapy for stroke or other brain injury can be difficult.
No drug has been shown useful for treating apraxia.
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