Temporal discrimination thresholds in adult-onset primary torsion dystonia: an analysis by task type and by dystonia phenotype

Abstract

Adult-onset primary torsion dystonia (AOPTD) is an autosomal dominant disorder with markedly reduced penetrance. Sensory abnormalities are present in AOPTD and also in unaffected relatives, possibly indicating nonmanifesting gene carriage (acting as an endophenotype). The temporal discrimination threshold (TDT) is the shortest time interval at which two stimuli are detected to be asynchronous. We aimed to compare the sensitivity and specificity of three different TDT tasks (visual, tactile and mixed/visual-tactile). We also aimed to examine the sensitivity of TDTs in different AOPTD phenotypes. To examine tasks, we tested TDT in 41 patients and 51 controls using visual (2 lights), tactile (non-painful electrical stimulation) and mixed (1 light, 1 electrical) stimuli. To investigate phenotypes, we examined 71 AOPTD patients (37 cervical dystonia, 14 writer's cramp, 9 blepharospasm, 11 spasmodic dysphonia) and 8 musician's dystonia patients. The upper limit of normal was defined as control mean ?2.5 SD. In dystonia patients, the visual task detected abnormalities in 35/41 (85%), the tactile task in 35/41 (85%) and the mixed task in 26/41 (63%); the mixed task was less sensitive than the other two (p = 0.04).Specificity was 100% for the visual and tactile tasks. Abnormal TDTs were found in 36 of 37 (97.3%) cervical dystonia, 12 of 14 (85.7%) writer's cramp, 8 of 9 (88.8%) blepharospasm, 10 of 11 (90.1%) spasmodic dysphonia patients and 5 of 8 (62.5%) musicians. The visual and tactile tasks were found to be more sensitive than the mixed task. Temporal discrimination threshold results were comparable across common adult-onset primary torsion dystonia phenotypes, with lower sensitivity in the musicians.

Inferior Parietal Lobule Encodes Visual Temporal Resolution Processes Contributing to the Critical Flicker Frequency Threshold in Humans

“…Moreover, we demonstrated that CFFt is sensitive to manipulation by TMS plasticity inducing protocols. This new information may be useful for future studies in patients with movement disorders including dystonia [80]–[83] in which altered multimodal sensory temporal processing has been demonstrated.…”

Sensory-motor integration in focal dystonia

“…The pervasive sensory deficits described in different forms of adult-onset focal dystonia and the fact that tactile deficits are present even in the absence of motor symptoms led to the hypothesis of a sensory endophenotype in focal dystonia (Bradley et al, 2012;Fiorio et al, 2003;Hutchinson et al, 2013), that could be a useful biological marker of genetic status. This hypothesis is mainly supported by the observation that deficits in somatosensory SDT and TDT are present also in some patients' unaffected relatives, who could carry a mutated known (e.g.…”

Temporal discrimination threshold with healthy aging

“…Even higher TDTs, sufficient to differentiate from Parkinson patients, were reported in multiple system atrophy (Rocchi et al, 2013). In dystonia, increased TDT (Conte et al, 2014b, Bradley et al, 2012, Scontrini et al, 2009, Fiorio et al, 2008a, Fiorio et al, 2003, Sanger, et al, 2001, Bara-Jimenez, et al, 2000, Tinazzi et al, 1999) is not only prevalent, but considered to be an endophenotype in autosomal dominant primary torsion dystonia, seen even in unaffected carriers (Kimmich et al, 2011, Bradley et al, 2009, Fiorio et al, 2007). That TDT is highly associated with particular gene mutations has led to interest in developing TDT as a useful tool in performing genetic studies.…”