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: 8.29). 12/2012; 80(1). DOI: 10.1212/WNL.0b013e31827b1a54
Source: PubMed


To investigate whether psychophysical techniques assessing temporal discrimination could help in differentiating patients who have tremor associated with dystonia or essential tremor.

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.

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.

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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Available from: Antonella Conte, Oct 07, 2015
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    • "Another measure for assessing somatosensory processing is the proprioceptive temporal discrimination motor threshold (TDMT), defined as the shortest interval at which the subject perceives two externally-induced passive movements as separate in time.[17] The TDMT is normal in patients with focal dystonia and abnormal in those with essential tremor (ET).[18], [19] Because ET probably involves the cerebellar and brainstem oscillating loops,[20] an abnormal TDMT could depend on cerebellar dysfunction. "
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    ABSTRACT: Background and Methods In order to obtain further information on the pathophysiology of functional tremor, we assessed tactile discrimination threshold and proprioceptive temporal discrimination motor threshold values in 11 patients with functional tremor, 11 age- and sex-matched patients with essential tremor and 13 healthy controls. Results Tactile discrimination threshold in both the right and left side was significantly higher in patients with functional tremor than in the other groups. Proprioceptive temporal discrimination threshold for both right and left side was significantly higher in patients with functional and essential tremor than in healthy controls. No significant correlation between discrimination thresholds and duration or severity of tremor was found. Conclusions Temporal processing of tactile and proprioceptive stimuli is impaired in patients with functional tremor. The mechanisms underlying this impaired somatosensory processing and possible ways to apply these findings clinically merit further research.
    PLoS ONE 07/2014; 9(7):e102328. DOI:10.1371/journal.pone.0102328 · 3.23 Impact Factor
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    • "Tremor may be classified either as dystonic tremor or tremor associated with dystonia (TAWD) according to the Movement Disorder Society Consensus Statement (Deuschl et al., 1998). Similarities in phenotypic features of dystonic tremor and TAWD predominate over differences, suggesting that the two forms of tremor may be manifestations of the same disease (Defazio et al., 2013; Tinazzi et al., 2013). Differences in gender, body distribution and temporal thresholds of tremor between patients with dystonia and tremor and those of patients with essential tremor also indicate that tremor in dystonia and essential tremor are different entities (Defazio et al., 2013; Tinazzi et al., 2013). "
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    ABSTRACT: The [123I]ioflupane - a dopamine transporter radioligand - SPECT (DaT-SPECT) has proven to be useful in the differential diagnosis of tremor. Here, we investigate the diagnoses behind patients with hard-to-classify tremor and normal DaT-SPECT. Therefore, 30 patients with tremor and normal DaT-SPECT were followed up for 2 years. In 18 cases we were able to make a diagnosis. The residual 12 patients underwent a second DaT-SPECT, were then followed for additional 12 months and thereafter the diagnosis was reconsidered again. The final diagnoses included cases of essential tremor, dystonic tremor, multisystem atrophy, vascular parkinsonism, progressive supranuclear palsy, corticobasal degeneration, fragile X–associated tremor ataxia syndrome, psychogenic parkinsonism, iatrogenic parkinsonism and Parkinson’s disease. However, for 6 patients the diagnosis remained uncertain. Larger series are needed to better establish the relative frequency of the different conditions behind these cases.
    Frontiers in Aging Neuroscience 03/2014; 8:56. DOI:10.3389/fnagi.2014.00056 · 4.00 Impact Factor
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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 · 3.10 Impact Factor
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