Electrophysiological features of myoclonus‐dystonia |
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Authors: | Jie‐Yuan Li MD Danny I. Cunic PhD Guillermo Paradiso MD Carolyn Gunraj MHSc Pramod K. Pal MD Anthony E. Lang MD FRCPC Robert Chen MBBChir MSc FRCPC |
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Affiliation: | 1. Division of Neurology, Department of Medicine and Toronto Western Research Institute, University of Toronto, Toronto, Ontario, Canada;2. Division of Neurology, Department of Internal Medicine, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan;3. Faculty of Medicine, School of Medicine, National Yang‐Ming University, Taipei, Taiwan |
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Abstract: | Inherited myoclonus‐dystonia (M‐D) is an autosomal dominant disorder characterized by myoclonus and dystonia that often improves with alcohol. To examine the electrophysiologic characteristics of M‐D, we studied 6 patients from 4 different families and 9 age‐matched healthy subjects. Neurophysiological studies performed include electromyography (EMG)‐electroencephalography (EEG) polygraphy, jerk‐locked back‐averaged EEG, somatosensory evoked potentials (SEP), long‐latency reflex (LLR) to median and digital nerve stimulation, and transcranial magnetic stimulation studies with short‐interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long‐interval intracortical inhibition (LICI). All 6 patients showed myoclonus and dystonia on clinical examination and EMG testing. The EMG burst durations ranged from 30.4 to 750.6 milliseconds (mean, 101.5 milliseconds). Jerk‐locked back‐averaged EEG failed to reveal any preceding cortical correlates. Median nerve SEP revealed no giant potential. No patients had exaggerated LLR to median or digital nerve stimulation. There was no significant difference in SICI, ICF, and LICI between M‐D patients and normal subjects. Myoclonus in inherited M‐D is likely of subcortical origin. Normal intracortical inhibition and facilitation suggest that the GABAergic circuits in the motor cortex are largely intact and that the mechanisms of myoclonus and dystonia are different from those for cortical myoclonus and other dystonic disorders. © 2008 Movement Disorder Society |
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Keywords: | myoclonus dystonia physiology transcranial magnetic stimulation cortical inhibition |
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