Movement disorders : official journal of the Movement Disorder Society
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Review
The identification of Parkinson's disease subtypes using cluster analysis: a systematic review.
The clinical variability between patients with Parkinson's disease (PD) may point at the existence of subtypes of the disease. Identification of subtypes is important, since a focus on homogeneous groups may enhance the chance of success of research on mechanisms of disease and may also lead to tailored treatment strategies. Cluster analysis (CA) is an objective method to classify patients into subtypes. ⋯ The cluster profiles "old age-at-onset and rapid disease progression" and "young age-at-onset and slow disease progression" emerged from the majority of studies. Other cluster profiles were less consistent across studies. Future studies with a rigorous study design that is standardized with respect to the included variables, data processing, and CA technique may advance the knowledge on subtypes in PD.
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Fixed dystonia is an uncommon but severely disabling condition typically affecting young women following a minor peripheral injury. There is no evidence of any structural lesions of the central nervous system nor any clear peripheral nerve or root damage. Electrophysiological techniques such as short intracortical inhibition, cortical silent period and a plasticity inducing protocol have revealed similarities but also differences compared to classical mobile dystonia. ⋯ In accordance with previous studies patients with mobile dystonia were abnormal in mental rotation and temporal discrimination, whereas patients with fixed dystonia were only impaired in mental rotation. Possible explanations for this deficit may include the influence of the abnormal body posture itself, a shared predisposing pathophysiology for mobile and fixed dystonia, or a body image disturbance. These findings add information to the developing pathophysiological picture of fixed dystonia.