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Background Movement execution in healthy individuals increases the somatosensory temporal discrimination threshold. These changes are a result of mechanisms of sensory gating at the subcortical level. Although the somatosensory temporal discrimination threshold is abnormally increased in patients with focal dystonias, the effect of movement execution on somatosensory temporal discrimination in dystonic patients is unknown. Objectives The objective of this study was to determine whether somatosensory temporal discrimination threshold modulation induced by voluntary movement is normal in different forms of focal dystonia. Methods We enrolled 71 dystonic patients (24 with blepharospasm, 31 with cervical dystonia, and 16 with focal hand dystonia) and 39 age-matched healthy participants. Paired stimuli for the somatosensory temporal discrimination threshold were triggered by movement execution at movement onset and at various time intervals thereafter. We analyzed the kinematic features of the motor task to ascertain whether tactile input induces changes in movement parameters. Results Movement execution led to greater and longer lasting increases in somatosensory temporal discrimination threshold values, both upon movement onset and at various time intervals thereafter, in patients with cervical dystonia and focal hand dystonia than in those with blepharospasm or the healthy participants. Somatosensory temporal discrimination testing did not induce any changes in the mean velocity of index finger movements in either patients or healthy participants. Conclusions Somatosensory temporal discrimination threshold changes induced by movement execution are abnormal in focal dystonias. This abnormality is related to the type of dystonia. Abnormal gating of sensory information is likely involved in movement-induced triggering or worsening of different forms focal dystonia. © 2018 International Parkinson and Movement Disorder Society.

Existing scales for rating the severity of blepharospasm (BSP) are limited by a number of potential drawbacks. We therefore developed and validated a novel scale for rating the severity of BSP. The development of the scale started with careful examination of the clinical spectrum of the condition by a panel of experts who selected phenomenological aspects thought to be relevant to disease severity. Thereafter, selected items were first checked for reliability, then reliable items were combined to generate the scale, and clinimetric properties of the scale were evaluated. Finally, the confidence with which the scale could be used by people without high levels of movement disorders skill was assessed. The new scale, based on objective criteria, yielded moderate to almost perfect reliability, acceptable internal consistency, satisfactory scaling assumptions, lack of floor and ceiling effects, partial correlations with a prior severity scale and with a quality of life scale, and good sensitivity to change. Despite a few limitations, the foregoing features make the novel scale more suitable than existing scales to assess the severity of BSP in natural history and pathophysiologic studies as well as in clinical trials.

The aim of this study was to investigate the somatosensory temporal discrimination threshold in patients with essential tremor (sporadic and familial) and to evaluate whether somatosensory temporal discrimination threshold values differ depending on the body parts involved by tremor. We also investigated the somatosensory temporal discrimination in patients with isolated voice tremor. We enrolled 61 patients with tremor: 48 patients with essential tremor (31 patients with upper limb tremor alone, nine patients with head tremor alone, and eight patients with upper limb plus head tremor; 22 patients with familial vs. 26 sporadic essential tremor), 13 patients with isolated voice tremor, and 45 healthy subjects. Somatosensory temporal discrimination threshold values were normal in patients with familial essential tremor, whereas they were higher in patients with sporadic essential tremor. When we classified patients according to tremor distribution, somatosensory temporal discrimination threshold values were normal in patients with upper limb tremor and abnormal only in patients with isolated head tremor. Temporal discrimination threshold values were also abnormal in patients with isolated voice tremor. Somatosensory temporal discrimination processing is normal in patients with familial as well as in patients with sporadic essential tremor involving the upper limbs. By contrast, somatosensory temporal discrimination is altered in patients with isolated head tremor and voice tremor. This study with somatosensory temporal discrimination suggests that isolated head and voice tremors might possibly be considered as separate clinical entities from essential tremor.

We designed this study to find out more about the relationship between the sensory effects of Botulinum toxin type A (BTX) and the clinical benefits of BTX therapy in patients with cervical dystonia (CD). In 24 patients with CD, we tested sensory temporal discrimination (STD) in the affected and two unaffected body regions (neck, hand, and eye) before and 1 month after BTX injection. In 8 out of the 24 patients with CD, STDT values were tested bilaterally in the three body regions before, 1 and 2 months after BTX injection. As expected, STD testing disclosed altered STD threshold values in all three body regions tested (affected and unaffected by dystonic spasms) in patients with CD. STD threshold values remained unchanged at all time points of the follow-up in all CD patients. The lack of BTX-induced effects on STD thresholds suggests that STD recruits neural structures uninvolved in muscle spindle afferent activation.