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ARTICLES: K. Quencer, M. S. Okun, G. Crucian, H. H. Fernandez, F. Skidmore, and K. M. Heilman Limb-kinetic apraxia in Parkinson disease Neurology 2007; 68: 150-151 [Abstract] [Full text] [PDF]

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Limb-kinetic apraxia in Parkinson disease

Michael Swash   (24 April 2007)

Reply from the Editorialists

William M. Landau, Jonathan W. Mink, Rochester, NY   (24 April 2007)

Limb-kinetic apraxia in Parkinson disease 24 April 2007
Michael Swash, Royal London Hospital Dept of Neurology, Royal London Hospital, London E1 1BB UK Send Correspondence to journal: Re: Limb-kinetic apraxia in Parkinson disease mswash{at}btinternet.com Michael Swash	Quencer et al describe that limb-kinetic apraxia may be a feature of the Parkinson Disease (PD) which is a conceptual change in the nosology of apraxia. [1] However, the strictly linguistic approach taken by Landau and Mink [2] in their accompanying editorial does not illuminate a pathway that will allow further exploration. Since Liepmann and Kleist recognized apraxias as higher levels of movement disorders without signs of a primary motor or sensory pathway disorder, [3] the definition of apraxia has subtly expanded to include higher-order functional disorders resulting from cortical or cortico-striatal dysfunction in both focal and degenerative CNS disease. [4,5] Corticobasal degeneration and PD are two such degenerative diseases. The "lack of deftness" [1] noted in the first description by James Parkinson has usually been ascribed to the extrapyramidal syndrome. However, the observations reported by Quencer et al [1] raise the intriguing possibility that the motor disorder is more properly ascribed to a form of higher-order motor disorder that includes apraxia due to the inability to perform learned motor tasks. The term 'apraxia' has conventionally been reserved for higher-order motor disorders not attributable to lower-level motor dysfunction, a definition that has always been unsatisfactory because the intention is unclear. In this sense, Landau and Mink's reliance on their dictionary [2] is understandable but, nonetheless, the term apraxia is beginning to be used more broadly. A number of different subtypes of apraxia have long been recognized [3,5] but the concept is expanding to include motor deficits accompanying various primary motor disorders which vary considerably and may involve lack of finger/hand deftness, among other deficits. This change in usage of the concept of apraxia will lead to a much more precise understanding of the various components of motor dysfunction underlying these clinical phenomena. Apraxia, therefore, can be recognized in patients with major primary motor or sensory system dysfunction in a range of different brain disorders and it underlies much of the functional disability experienced by these patients. References 1. Quencer K, Okun MS, Crucian G, Fernandez HH, Skidmore F, Heilman KM. Limb-kinetic apraxia in ParkinsonÕs disease. Neurology 2007;68:150-151 2. Landau WM, Mink JW. Is decreased dexterity in Parkinson disease due to apraxia? Neurology 2007;68:90-91 3. Leiguarda R, Marsden CD. Limb apraxias: higher-order disorders of sensorimotor integration. Brain 2000;123:860-879 4. Leiguarda R. Apraxias as traditionally defined. In: Freund H-J, Jeannerod M, Hallett M, Leiguarda R, eds. HigherÐorder motor disorders. Oxford: Oxford University Press. 2000:303-338 5. Zadikoff C, Lang AE. Apraxia in movement disorders. Brain 2005;128:1480-1497. Disclosure: The author reports no conflicts of interest. The authors of the article were asked to respond but declined.
Reply from the Editorialists 24 April 2007
William M. Landau, St. Louis, MO , Jonathan W. Mink, Rochester, NY Send Correspondence to journal: Re: Reply from the Editorialists landauw{at}neuro.wustl.edu William M. Landau, et al.	We are gratified to see that our editorial has provoked debate concerning the concept of apraxia. [2] However, we must disagree with Dr. Swash. Simply expanding the concept of apraxia is unlikely to "lead to a much more precise understanding" of motor dysfunction. In the past two decades, there has been substantial progress in understanding the richness of complex motor processing in the forebrain. However, to lump any manifestations of disturbed complex (higher-order) motor processing under the rubric of apraxia does not provide higher-order understanding. Fastening the mindful apraxia label does not provide insight into which and how neural circuits are disrupted. The authors report no conflicts of interest.