The role of neurplasticity in dystonia

Herman Oppenheim first coined the term “dystonia” in 1911 to describe a generalised form of the condition with childhood onset, which he called “dystonia musculorum deformans”.1,2 In more recent years, dystonia is now recognised as a spectrum of neurological movement disorders characterised by patterned and sustained muscle contractions, resulting in abnormal postures and involuntary twisting movements. 1 

In epidemiological studies, it is estimated that the prevalence of early-onset primary torsion dystonia is as high as 50 per million.3 In the UK alone, it is estimated over 70,000 people are affected by the condition. However, despite the prevalence of this debilitating disorder, the mechanisms underlying dystonia are poorly understood. Although dystonia can arise in the context of cerebral damage, patients with primary dystonia show no overt signs of neurological lesions or neurodegeneration.4 

However, imaging studies in these patients have uncovered functional abnormalities in several brain structures and subtle microstructural defects.5–7 Rather than implicating any particular gene, protein or brain region critical to pathogenesis, these studies suggest that dystonia may result from abnormalities in the motor circuitry. It is hypothesised that aberrant neuroplasticity underlies these functional changes. In this essay I will discuss the experimental evidence surrounding this paradigm and the implications of these findings in the clinical setting. 

Although there is a myriad of studies implicating numerous genes and molecules, I will limit my discussion to the sensorimotor circuitry itself and the potential mechanisms that may facilitate derangement of these neuronal networks. Classification of Dystonia Before I discuss the pathophysiology of dystonia, I must first consider the diversity of this disorder. Indeed, dystonia manifests in a variety of forms and there are three modes of classification: aetiology (i.e. primary dystonia, secondary dystonia, dystonia-plus syndromes and paroxysmal dystonia); age of onset; or anatomical distribution (i.e. generalised, focal, segmental and hemi-dystonia).1,

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