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.

Differences between episodic and chronic tension-type headaches in nociceptive-specific trigeminal pathways

Background The trigeminal nociceptive system plays a pivotal role in the pathophysiology of tension-type headaches (TTH). Objective This study investigated and compared nociceptive-specific trigeminal pathways in patients with episodic and chronic TTH (ETTH and CTTH, respectively) using the nociceptive blink reflex (nBR) and nociceptive trigeminocervical reflex (nTCR). Methods We recorded nBR and nTCR in patients with ETTH and CTTH, and healthy controls using concentric electrodes and subsequently compared the threshold (i.e. sensory, pain) and parameters of reflex (i.e. the R2 component of the nBR and the late responses of the nTCR). Results Women with ETTH ( n = 40) and CTTH ( n = 32) and age-matched controls ( n = 40) were recruited. CTTH patients displayed significantly lower amplitude and area under the curve (AUC) values of the R2 component for the nBR compared with those displayed by ETTH patients and controls ( p < 0.05). Moreover, the amplitude and AUC of the R2 component was negatively correlated with the frequency of headaches, whereas the latency of the R2 component for the nBR was positively correlated with the frequency and duration of headaches in the TTH groups ( p < 0.05). However, no significant differences in the late response parameters (i.e. latency, duration, amplitude, or AUC) were noted between the groups in terms of the nTCR. Conclusions R2 suppression associated with CTTH suggests decreased brainstem excitability. This may be the result of excessive descending inhibitory influences.