Neurophysiological tools are very helpful in characterizing various
movement disorders, consequently guiding etiological research and
therapy.
Movement disorders recordings are currently underutilized in neurological practice in adults and could also be extended to the pediatric population. Surface polymyography (EMG) combined with accelerometry is commonly used for the analysis of many types of
hyperkinetic movement disorders, mainly
myoclonus,
tremor,
dystonia, and sometimes
tics and
chorea. To study
myoclonus, techniques exploring cortical excitability, namely conventional EEG, EEG-jerk-locked-back-averaging (JLBA), somatosensory evoked potentials (SEP) and C-reflex studies, should necessarily complete the EMG analysis. Premovement potential recording and measures of the stimulus induced jerks latencies may help to differentiate psychogenic jerks from
myoclonus. The field of clinical usefulness of
movement disorders recordings is large. Main issues are: (1) to differentiate
tremor from
myoclonus, (2) to demonstrate and locate dystonic features, either isolated or associated to
tremor and
myoclonus, (3) to define the nature of a
tremor, (4) to assess the psychogenic nature of a
tremor or jerks, and (5) to define the neurophysiological generator of
myoclonus in the central nervous system. Neurophysiological data allow us to clearly classify
myoclonus as cortical, cortico-thalamic, and subcortical-resulting from lesions or dysfunctions of basal ganglia/reticular system-or spinal.