Visual Sensory Processing is Altered in Myoclonus Dystonia

Abstract

Background Abnormal sensory processing, including temporal discrimination threshold, has been described in various dystonic syndromes. Objective To investigate visual sensory processing in DYT‐SGCE and identify its structural correlates. Methods DYT‐SGCE patients without DBS (DYT‐SGCE‐non‐DBS) and with DBS (DYT‐SGCE‐DBS) were compared to healthy volunteers in three tasks: a temporal discrimination threshold, a movement orientation discrimination, and movement speed discrimination. Response times attributed to accumulation of sensory visual information were computationally modelized, with μ parameter indicating sensory mean growth rate. We also identified the structural correlates of behavioral performance for temporal discrimination threshold. Results Twenty‐four DYT‐SGCE‐non‐DBS, 13 DYT‐SGCE‐DBS, and 25 healthy volunteers were included in the study. In DYT‐SGCE‐DBS, the discrimination threshold was higher in the temporal discrimination threshold (P = 0.024), with no difference among the groups in other tasks. The sensory mean growth rate (μ) was lower in DYT‐SGCE in all three tasks (P < 0.01), reflecting a slower rate of sensory accumulation for the visual information in these patients independent of DBS. Structural imaging analysis showed a thicker left primary visual cortex (P = 0.001) in DYT‐SGCE‐non‐DBS compared to healthy volunteers, which also correlated with lower μ in temporal discrimination threshold (P = 0.029). In DYT‐SGCE‐non‐DBS, myoclonus severity also correlated with a lower μ in the temporal discrimination threshold task (P = 0.048) and with thicker V1 on the left (P = 0.022). Conclusion In DYT‐SGCE, we showed an alteration of the visual sensory processing in the temporal discrimination threshold that correlated with myoclonus severity and structural changes in the primary visual cortex. © 2019 International Parkinson and Movement Disorder Society

Tactile Temporal Discrimination Is Impaired in Myoclonus‐Dystonia

“…In conjunction with previous results on visual TDT, 3 our results suggest a widespread disturbance of the sensory information processing for DYT-SGCE patients. Basal ganglia and sensori-motor cortex are known to be involved in tactile TDT processing.…”

“…Myoclonus-dystonia, caused by mutation of the epsilonsarcoglycan gene (DYT-SGCE), is clinically characterized by myoclonus associated with mild dystonia, likely underpinned by a dysfunction of the cerebello-thalamo-cortical and striatopallido-thalamo-cortical pathway. 2 We showed abnormal threshold for the visual TDT in the most severe DYT-SGCE 3 patients treated with deep brain stimulation of the internal globus pallidus. The existence of abnormalities in another sensory modality remains unclear.…”

Cognitive and Neuropsychiatric Impairment in Dystonia

“…Although once again the cohort examined was small, this study benefited from the genetic homogeneity of the SGCEpositive cohort with sensory mean growth rate, a measure of sensory accumulation in the processing of visual information, significantly lower in this group compared to controls across all three measures (p < 0.01). In those without DBS, the sensory mean growth rate in the temporal discrimination threshold was also negatively correlated with the thickness of the primary visual cortex, which itself was significantly thicker compared to unaffected controls (p = 0.001), collectively supporting the key role that sensory processing, likely in its multiple formats, plays in giving rise to, or propagating dystonia pathogenesis [53].…”

ε-sarcoglycan myoclonus-dystonia—overview of neurophysiological, behavioral, and imaging characteristics

“…In this regard, in addition to motor learning and motor inhibition difficulties, M-D patients have also shown sensory abnormalities in the visual and tactile domain [58,59].…”