Apraxia
Apraxia
Apraxia or dyspraxia is a disorder of movement characterized by the inability to perform a voluntary motor act despite an intact motor system (i.e., no ataxia, weakness) and without impairment in level of consciousness. Automatic/reflex actions are preserved, hence there is a voluntary-automatic dissociation; some authors see this as critical to the definition of apraxia.
Different types of apraxia have been delineated, the standard classification being that of Liepmann (1900):
- Ideational apraxia, conceptual apraxia:
- A deficit in the conception of a movement; this frequently interferes with daily motor activities and is not facilitated by the use of objects. There is often an associated aphasia.
- Ideomotor apraxia (IMA):
- A disturbance in the selection of elements that constitute a movement (e.g., pantomiming the use of tools); in contrast to ideational apraxia, this is a "clinical" disorder inasmuch as it does not greatly interfere with everyday activities; moreover, use of objects may facilitate movement; it may often be manifest as the phenomenon of using body parts as objects (e.g., in demonstrating how to use a toothbrush or how to hammer a nail), a body part is used to represent the object (finger used as toothbrush, fist as hammer).
- Limb-kinetic, or melokinetic, apraxia:
- Slowness, clumsiness, awkwardness in using a limb, with a temporal decomposition of movement; difficult to disentangle from pure motor deficits associated with corticospinal tract lesions.
Apraxia may also be defined anatomically:
- Slowness, clumsiness, awkwardness in using a limb, with a temporal decomposition of movement; difficult to disentangle from pure motor deficits associated with corticospinal tract lesions.
- Parietal (posterior):
- Ideational and ideomotor apraxia are seen with unilateral lesions of the inferior parietal lobule (most usually of the left hemisphere), or premotor area of the frontal lobe (Brodmann areas 6 and 8)
- Frontal (anterior):
- Unilateral lesions of the supplementary motor area are associated with impairment in tasks requiring bimanual coordination, leading to difficulties with alternating hand movements, drawing alternating patterns (e.g., m n m n in joined up writing: alternating sequences test, Luria figures). This may be associated with the presence of a grasp reflex and alien limb phenomena (limb-kinetic type of apraxia).
Apraxia is more common and severe with left hemisphere lesions.
Difficulties with the clinical definition of apraxia persist, as for the agnosias. For example, "dressing apraxia" and "constructional apraxia" are now considered visuospatial problems rather than true apraxias. Likewise, some cases labeled as eyelid apraxia or gait apraxia are not true ideational apraxias. The exact nosological status of speech apraxia also remains tendentious.
References
Crutch S. Apraxia. Advances in Clinical Neuroscience & Rehabilitation
2005; 5(1): 16,18
Freund H-J. The apraxias. In: C Kennard (ed.). Recent advances in clinical neurology 8. Edinburgh, Churchill Livingstone, 1995: 29-49 Grafton S. Apraxia: a disorder of motor control. In: D’Esposito M (ed.). Neurological foundations of cognitive neuroscience. Cambridge: MIT Press, 2003: 239-258
Heilman KM, Gonzalez Rothi LG. Apraxia. In: Heilman KM, Valenstein E (eds.). Clinical neuropsychology (4th edition). Oxford: OUP, 2003: 215-235
Leiguarda RC, Marsden CD. Limb apraxias. Higher-order disorders of sensorimotor integration. Brain 2000; 123: 860-879
Pramstaller PP, Marsden CD. The basal ganglia and apraxia. Brain
1996; 119: 319-340
Cross References
Alien hand, Alien limb; Body part as object; Crossed apraxia; Eyelid apraxia; Forced groping; Frontal lobe syndromes; Gait apraxia; Grasp reflex; Optic ataxia; Speech apraxia
