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Temporal discrimination in patients with dystonia and tremor and patients with essential tremor

From the Department of Neurological, Psychological, Morphological and Motor Sciences (M.T., A.D.M., T.B., A.P., M.F.), University of Verona, Verona
Neurology (Impact Factor: 8.3). 12/2012; 80(1). DOI: 10.1212/WNL.0b013e31827b1a54
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ABSTRACT ABSTRACT OBJECTIVE: To investigate whether psychophysical techniques assessing temporal discrimination could help in differentiating patients who have tremor associated with dystonia or essential tremor. METHODS: We tested somatosensory temporal discrimination thresholds (TDT) and temporal discrimination movement thresholds (TDMT) in 39 patients who had tremor associated with dystonia or essential tremor presenting with upper-limb tremor of comparable severity and compared their findings with those from a group of 25 sex- and age-matched healthy control subjects. RESULTS: TDT was higher in patients who had tremor associated with dystonia than in those with essential tremor and healthy controls (110.6 ± 31.3 vs 63.1 ± 15.2 vs 62.4 ± 9.2; p < 0.001). Conversely, TDMT was higher in patients with essential tremor than in those with tremor associated with dystonia and healthy controls (113.7 ± 14.7 vs 103.4 ± 11.3 vs 100.4 ± 4.2; p < 0.001). Combining the 2 tests in a pattern for essential tremor (abnormal TDMT/normal TDT) and tremor associated with dystonia (normal TDMT/abnormal TDT) yielded a positive predictive value (PPV) of 86.7% and a negative predictive value (NPV) of 70.8% for diagnosing essential tremor and a PPV of 100.0% and NPV of 74.1% for diagnosing tremor associated with dystonia. CONCLUSIONS: TDT and TDMT testing should prove a useful tool for differentiating tremor associated with dystonia and essential tremor. Our findings imply that the pathophysiologic mechanisms underlying tremor associated with dystonia differ from those for essential tremor.

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    • "The STDT was investigated by delivering paired stimuli starting with an ISI of 0 ms (simultaneous pair), and progressively increasing the ISI in 10 ms steps, according to the experimental procedures used in previous studies (Scontrini et al., 2009, 2011; Conte et al., 2010, 2012b; Rocchi et al., 2013; Tinazzi et al., 2013). Paired tactile stimuli consisted of square-wave electrical pulses delivered with a constant current stimulator (Digitimer DS7AH) through surface skin electrodes with the anode located 0.5 cm distally to the cathode applied on the volar surface of the index finger of the left and right hand. "
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    ABSTRACT: To investigate whether theta burst stimulation (TBS) applied over primary somatosensory cortex (S1) modulates somatosensory temporal discrimination threshold (STDT) and writing performances in patients with focal hand dystonia (FHD). Twelve patients with FHD underwent STDT testing and writing tasks before and after intermittent, continuous, or sham TBS (iTBS, cTBS, sham TBS) over S1 contralateral to the affected hand. Twelve healthy subjects underwent iTBS and cTBS over S1 and STDT values were tested on the right hand before and after TBS. Baseline STDT values were higher in patients than in healthy subjects on both the affected and unaffected hand. In patients and healthy subjects iTBS decreased, whereas cTBS increased STDT values and did so to a similar extent in both groups. In patients, although STDT values decreased after iTBS, they did not normalize. S1 modulation did not improve the writing performance. In patients, S1 responds normally to protocols inducing homotopic synaptic plasticity. The inhibitory interneuron activity responsible for STDT is altered. The pathophysiological mechanisms underlying abnormal temporal discrimination differ from those responsible for motor symptoms in FHD.
    Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 09/2013; 125(3). DOI:10.1016/j.clinph.2013.08.006 · 2.98 Impact Factor
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    • "Similar approaches have been employed to detect endophenotypes among healthy relatives of patients with focal dystonias, whose genetic bases are largely unknown. For example, somatosensory spatial and temporal discrimination thresholds (TDT) have been found altered not only in focal dystonia patients (Sanger et al., 2001; Scontrini et al., 2009; Tinazzi et al., 2012) but also in some healthy family members. Interestingly in these subjects a correlation has been reported between abnormal tactile TDT and a bilateral increase in putaminal gray matter detected by Voxel Based Morphometry (Bradley et al., 2009). "
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    ABSTRACT: Dystonias are heterogeneous hyperkinetic movement disorders characterized by involuntary muscle contractions which result in twisting and repetitive movements and abnormal postures. Several causative genes have been identified, but their genetic bases still remain elusive. Primary Torsion Dystonias (PTDs), in which dystonia is the only clinical sign, can be inherited in a monogenic fashion, and many genes and loci have been identified for autosomal dominant (DYT1/TOR1A; DYT6/THAP1; DYT4/TUBB4a; DYT7; DYT13; DYT21; DYT23/CIZ1; DYT24/ANO3; DYT25/GNAL) and recessive (DYT2; DYT17) forms. However most sporadic cases, especially those with late-onset, are likely multifactorial, with genetic and environmental factors interplaying to reach a threshold of disease. At present, genetic counseling of dystonia patients remains a difficult task. Recently non-motor clinical findings in dystonias, new highlights in the pathophysiology of the disease, and the availability of high-throughput genome-wide techniques are proving useful tools to better understand the complexity of PTD genetics. We briefly review the genetic basis of the most common forms of hereditary PTDs, and discuss relevant issues related to molecular diagnosis and genetic counseling.
    Frontiers in Neurology 04/2013; 4:34. DOI:10.3389/fneur.2013.00034
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    • "Neuroimaging [3] [4] and post-mortem [5] studies in patients with ET demonstrated the presence of pathological changes mainly involving the cerebellum [6]. Otherwise, very recent studies demonstrated abnormality of sensorimotor integration circuits [7] or increased blink recovery cycle [8] in patients with DT, suggesting that this disorder might be associated with brain dysfunctions different from those detected in ET. "
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    ABSTRACT: Purpose This study is aimed at investigating the neuroanatomical patterns characterizing dystonic tremor in comparison with essential tremor. Methods Voxel-based morphometry and cortical thickness data of 12 patients with dystonic tremor, 14 patients with essential tremor and 23 age- and sex-matched healthy control subjects were analyzed. Results Patients with dystonic tremor showed a thickening and increased gray matter volume (surviving whole-brain correction for multiple comparisons) of the left sensorimotor cortex when compared to other groups. Otherwise, patients with essential tremor were characterized by a subtle atrophy of the anterior cerebellar cortex. Discussion Our multimodal structural neuroimaging study demonstrated that patients with dystonic tremor and essential tremor are characterized by different neuroanatomical abnormalities. The involvement of the sensorimotor cortex in patients with dystonic tremor suggests that this disorder may share some pathophysiological mechanisms with focal dystonia.
    Parkinsonism & Related Disorders 01/2013; 20(3). DOI:10.1016/j.parkreldis.2013.12.007 · 4.13 Impact Factor
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