Primate models of dystonia
Section snippets
Phenomenology and clinical models of dystonia
Dystonia is defined as a syndrome of sustained muscular contractions leading to repetitive movements and abnormal postures (Fahn, 1987). This broad definition has the advantage of including many clinical aspects of the disease, even though other frequently combined signs, such as bradykinesia (slowing of movement), myoclonia, tremor or troubles in action planning (apraxia), are not considered. From a phenomenological point of view, dystonia is the inability to select correctly the muscular
Lesions and pharmacological manipulations of the brainstem
Dystonia is characterized by muscular tonic spasms. In the early fifties, there emerged the idea that the brain stem region involved in the regulation of muscular tone could play a role in the genesis of dystonic symptoms.
Indeed, lesions of the red nucleus or the ventromedial mesencephalic tegmentum induce the onset of a spasmodic torticollis in the monkey (Battista et al., 1976, Carpenter, 1956, Foltz et al., 1959, Malouin and Bedard, 1982) (Table 1). The head turns to the side of the
Models of occupational dystonia in primates
Occupational dystonia is a particular form of focal dystonia appearing in body regions, generally the hand, and is involved in movements requiring high dexterity such as writing, playing music, professional activity, or the practice of skilled sports (Cohen and Hallett, 1988, Marsden and Sheehy, 1990). Evidence is accumulating from animal and human studies that focal hand dystonia could be the consequence of aberrant learning (Byl, 2003). A model of occupational hand dystonia has been developed
What do we learn from experimental models of dystonia?
Although we have some information about the cellular mechanisms subserving primary dystonia such as enzymatic defect (Illarioshkin et al., 1998) or the storing of non-functional protein, e.g., Torsin (Ozelius et al., 1997), in many cases the role of these biological phenomena, as well as the nature of the causal gene, remains unknown. Secondary dystonia means that a lesion in a particular region of the brain induces dystonia, although it is unknown whether this is the result of a direct effect
Acknowledgement
We wish to thank Ray Cooke for checking the English.
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