Electroencephalographic correlates of myoclonus
Advances in Neurology
|January 1, 1986
Summary
Back-averaging EEG techniques revealed distinct patterns in myoclonus. Cortical reflex myoclonus showed a preceding cortical spike and giant somatosensory evoked potentials (SEPs), while Creutzfeldt-Jakob disease myoclonus appeared subcortical.
Area of Science:
- Neurophysiology
- Clinical Neurology
Background:
- Myoclonus, characterized by sudden muscle jerks, has diverse etiologies and complex underlying mechanisms.
- Conventional EEG-EMG polygraphy can be limited in detecting subtle EEG correlates of myoclonus.
Purpose of the Study:
- To investigate the utility of back-averaging and jerk-locked EEG-EMG techniques in characterizing myoclonus.
- To differentiate the neurophysiological origins of myoclonus in various conditions.
Main Methods:
- Fifty-five patients with myoclonus underwent EEG-EMG polygraphic recordings.
- Back-averaging and jerk-locked somatosensory evoked potential (SEP) paradigms were employed.
- Analysis focused on temporal and topographic relationships between EEG activity and myoclonus.
Main Results:
- Cortical reflex myoclonus (13/17 PME cases) exhibited a myoclonus-related cortical spike preceding the jerk by 6-22 ms and giant SEPs.
- Creutzfeldt-Jakob disease (CJD) myoclonus showed contralateral hemispheric sharp waves preceding jerks by 50-85 ms, suggesting subcortical origin.
- Essential myoclonus and oculopalatal-somatic myoclonus lacked these specific EEG correlates.
Conclusions:
- Back-averaging is valuable for identifying EEG correlates of myoclonus not seen on routine recordings.
- Distinct neurophysiological patterns differentiate cortical reflex myoclonus from subcortical forms like CJD myoclonus.
- Further investigation is needed for a subgroup of PME with vertex-maximal spikes and absent giant SEPs.
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