How can neurophysiological studies help with movement disorders characterization in clinical practice? A review

Abstract

Background: Neurophysiological studies are ancillary tools to better understand the features and nature of movement disorders. Electromyography (EMG), together with electroencephalography (EEG) and accelerometer, can be used to evaluate a hypo and hyperkinetic spectrum of movements. Specific techniques can be applied to better characterize the phenomenology, help distinguish functional from organic origin and assess the most probable site of the movement generator in the nervous system. Objective: We intend to provide an update for clinicians on helpful neurophysiological tools to assess movement disorders in clinical practice. Methods: Non-systematic review of the literature published up to June 2019. Results: A diversity of protocols was found and described. These include EMG analyses to define dystonia, myoclonus, myokymia, myorhythmia, and painful legs moving toes pattern; EMG in combination with accelerometer to study tremor; and EEG-EMG to study myoclonus. Also, indirect measures of cortical and brainstem excitability help to describe and diagnose abnormal physiology in Parkinson's disease, atypical parkinsonism, dystonia, and myoclonus. Conclusion: These studies can be helpful for the diagnosis and are usually underutilized in neurological practice.

Diagnostic and therapeutic recommendations in adult dystonia: a joint document by the Italian Society of Neurology, the Italian Academy for the Study of Parkinson’s Disease and Movement Disorders, and the Italian Network on Botulinum Toxin

“…Surface electromyography (EMG) provides useful information about prolonged muscle activity with co-contraction of agonist and antagonist muscles or tremor activity [32]. EMG can also be useful in choosing the muscles to be treated with botulinum toxin inoculation (in order to have a better definition of the dystonic pattern, quantification of the degree of muscle activation, and a differential diagnosis between coactivation of antagonistic muscles and compensatory muscle activation) [33,34].…”

Musician’s dystonia in a percussionist – clinical video analysis and botulinum toxin intervention: a case report

“…With a handheld EMG, a characteristic dystonic signal (a tonic discharge) was detected within the 4 th finger fibres of the FDS ( Fig. S3 ) ( 13 , 14 ). It is important to note that this type of EMG device does not allow for the analysis of frequency and amplitude of the signal.…”

Minipolymyoclonus: A Critical Appraisal

“…Thus, Salazar et al [ 27 ] were uncertain of the origin of minipolymyoclonus in MSA. Grippe et al [ 36 ] have described minipolymyoclonus as “an irregular 1–20 Hz activity with muscle synchronous bursts of 25–50 ms in duration” that can arise from a peripheral or central generator. However, peripherally originating minipolymyoclonus from degenerating motor neurons generally has an EMG burst duration of < 20 ms, similar to a typical motor unit potential [ 8 , 37 ].…”