Apraxia

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Parul Pahal, M.B.B.S[2] Norina Usman, M.B.B.S[3]

Synonyms and keywords: Dyspraxia

Overview

'Praxis', a Greek work, is the ability to perform the learned movements. It usually comprises of three components, namely, ideation, motor planning, and execution that results in purposeful movements. Apraxia, however, is the inability to perform these skilled and learned movements when there is a breakdown in any component of praxis. This disorder makes it difficult to perform daily tasks and negatively impact the quality of life. Apraxia is a complex neurological disease with cognitive-motor dysfunction. It can occur as a result of brain trauma/disease, and higher motor functional neuronal pathways damage in the setting of preserved comprehension, coordination, elementary sensory and motor systems. The most common types of apraxia are Ideational and Ideomotor.

Historical Perspective

• Steinthal introduced the term 'apraxia' in 1971. However, a German physician, Hugo Lipmann first established the conceptual knowledge and published complete description of apraxia after studying the gestures in a 48-year old stroke patient who had a left hemispheric stroke.
• Lipmann noticed that, despite of resolution of the paresis, the patient was unable to perform tasks such as buttoning the shirt, with no affect on spontaneous movements, and doing simple tasks on command. He observed this phenomenon specifically in patients with left hemispheric lesions. He also concluded that the planning of the motor movements occurs in the motor area of the left side of the brain.Lipmann further proposed that the 'praxis' information flows from the posterior brain areas (parietal and occipital lobes) to the anterior (motor cortex).
• The major subtypes classified by Lipmann were ideational, ideomotor, and limb-kinetic apraxia.
• One of the behavioral neurologist, Norman Geschwind, presented that the superior longitudinal fasciculus involvement disconnects the Wernike's are from the left premotor cortex, leading to 'apraxia'.

Classification

• The most common types of apraxia are-
  • Ideational apraxia, like the name depicts, problem in conceptualization of the task. The person may be able to name the objects correctly but fails to coceptualize how that object is used.
  • Ideomotor apraxia can be seen more frequently in neurodegenerative disorders and stroke patients. In this disorder, there is difficulty or inability to execute familiar or learned movements on command despite of understanding the command and willingness to perform that action. The characteristic of this type of apraxia is the inability to a transitive movement. For example, the person can describe how a tool such as comb is used, but, when asked to use that tool, he is unable to perform the task (i.e. combing the hair) using the comb
  • Limb-kinetic apraxia

• Certain task-specific apraxiahave been identified, and these include-
  • Sitting apraxia
  • Dressing apraxia
  • Eyelid opening apraxia
  • Gait apraxia

• Other types of apraxia, include-
  • Buccofacial apraxia
  • Classic apraxia
  • Constructional apraxia
  • Ideokinetic apraxia
  • Motor apraxia
  • Oculomotor apraxia

Pathophysiology

'Praxis' comprises three components, which include ideation, motor planning, and execution to carry out the purposeful movement. There are particular regions of the brain that represent specific component functions, and these regions together work as a ‘praxis system’ to process and execute a purposeful movement. Dysfunction in any of these regions, namely, frontal and parietal cortex, basal ganglia, and the white matter which connects theses areas, leads to apraxia.

The movements which requires tools are transitive movements, and the ones which do not require tools are intransitive. The intransitive movements are gestural which can be meaningful (communicative), or meaningless movements (not representational). In apraxia, it is more

types can be largely classified into transitive movements (i.e., those requiring tools), and intransitive movements which are gestural, which can further be divided into meaningful and meaningless movements. Meaningful movements are those that are communicative, such as waving goodbye, whereas meaningless movements are those that are not representational, such as touching one's chin. Patients are often more impaired in the performance of transitive movements, than intransitive ones.21,22 As a result, the majority of efforts to probe the neural basis of praxis has been conducted in subjects pantomiming and using tools.

Treatment

• No standardized treatment is available for apraxia. The frequency of limb apraxia in left hemispheric stroke patients is reported to be nearly 51%and, hence, the therapeutic efforts are so far mostly concentrated towards stroke patients (left hemispheric stroke patients). Based on the studies, following treatment modalities have been considered so far-
  • Rehabilitative treatment- 30 sessions, each lasting 50 minutes, 3 times weekly have been tried.
  • Behavioral training Program-These include gesture-production exercises.

• With treatment, an improvement in praxis and daily living activities is seen in apraxia patients, based on some studies. The communicative gestures training has led to significant improvement of the gestures which were practiced during the training sessions, with some unpracticed gestures also showing some improvement. However, the sustainability of these positive results is not clear. Although rehabilitative training has been reported to benefit, but, for sustained benefit, training alone is not sufficient.

• Noninvasive brain stimulation- This method had been used widely for many neurological disorders, but there is very limited data for its use in cognitive disorders. However, some studies have shown that this technique has been tried for therapeutic and investigational purpose for this complex neurological disorder and may show some positive results. This technique when used with rehabilitative training, may be useful. Through this technique and different stimulation settings, inhibitory or excitatory influences are exerted on cortical excitability or plasticity. The synergistic approach using this technique prior to rehabilitative training, not only increases the efficacy, but it also increases the sustainability of the improvement seen. Some examples of non-invasive brain stimulation techniques which have been used in some neurological conditions with some improvement in the cognitive function components of the disease can be tried-
  • Transcranial direct current stimulation (tDCS)-low-level continuous electric current is delivered to influence plasticity and excitabililty of the cortex. In this, anodal tDCS works in excitatory ways, and cathodal tDCS in inhibitory ways.
  • single-pulse or rTMS- It can be delivered in either low frequency (0.2–1 Hz) for inhibitory mode, or in high frequency (≥5 Hz) for excitatory mode.
  • theta-burst stimulation (TBS)-It is also a magnetic stimulation method like rTMS, but it shows equal efficacy even with shorter stimulation period.
  • paired associative stimulation (PAS)- This stimulation technique can be used to tackle physiological mechanisms underlying memory using long-term depression (LTD), and long-term potentiation (LTP)

Overview

Apraxia is a neurological disorder characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire and the physical ability to perform the movements. It is a disorder of motor planning which may be acquired or developmental, but may not be caused by incoordination, sensory loss, or failure to comprehend simple commands (which can be tested by asking the person tested to recognize the correct movement from a series). The root word of Apraxia is praxis, Greek for an act, work, or deed. It is preceded by a privative a, meaning 'without'.

Types

There are several types of apraxia including:

• ideomotor (inability to carry out a motor command, for example, "act as if you are brushing your teeth" or "salute") - the form most frequently encountered by physicians,
  • limb apraxia when movements of the arms and legs are involved,
  • nonverbal-oral or buccofacial (inability to carry out facial movements on command, e.g., lick lips, whistle, cough, or wink),
• ideational (inability to create a plan for or idea of a specific movement, for example, "pick up this pen and write down your name"),
• limb-kinetic (inability to make fine, precise movements with a limb),
• verbal (difficulty planning the movements necessary for speech), also known as Apraxia of Speech (see below)
• constructional (inability to draw or construct simple configurations),
• oculomotor (difficulty moving the eye)

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 tooth brush) and ask them to use it.

Apraxia may be accompanied by a language disorder called aphasia.

Apraxia of speech

Developmental Apraxia of Speech (DAS) 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. This is not to be confused with phonological impairments in children with normal coordination of the articulators during speech.

Symptoms of Acquired Apraxia of Speech (AOS) and Developmental Apraxia of Speech (DAS) 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.

Causes

Ideomotor apraxia is almost always caused by lesions in the language-dominant (usually left) hemisphere of the brain, and as such these patients often have concomitant aphasia, especially of the Broca or conduction type. Left-side ideomotor apraxia may be caused by a lesion of the anterior corpus callosum.

Ideational apraxia is commonly associated with confusion states and dementia.

Treatment

Generally, treatment for individuals with apraxia includes physical therapy, occupational therapy or speech therapy, or Oral Motor Therapy and IVIG. If apraxia is a symptom of another disorder (usually a neurologic disorder), the underlying disorder should be treated.

Prognosis

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.

Related Chapters

• Dyspraxia

References

• Epstein, O. (2003). Clinical Examination. London: Mosby. p. 294. ISBN 0-7234-3229-5.
• Kasper DL, Braunwald E, Fauci AS, Hauser SL, Longo DL, Jameson JL. Harrison's Principles of Internal Medicine. New York: McGraw-Hill, 2005. ISBN 0-07-139140-1.