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Advanced Neurology Neurophysiology in hypokinetic disorders

Table 1. Summary of the neurophysiological insights of studies reported from 2019 to 2023 on PD
Neurophysiological assessment Neurophysiological insights Studies
EMG
Polymyography and (i). Rest tremor assessment: the most specific hand position is the complete (i) Wilken et al. 8
accelerometric analysis prone position. (ii) Wilken et al. 9
(ii). Re-emergent tremor assessment: avoids provocation maneuvers (iii) Wilken et al. 10
(iii). Re-emergent tremor assessment: pause duration is amplitude-related
Acoustic myography A reliable indicator of abnormal motor activity at the early stage of PD Celicanin et al. 11
TMS (i) Tremor versus akinetic PD: Decreased RMT and AMT (i) Khedr et al. 13
(ii) Rest tremor versus re-emergent tremor: similar CMC and tremor (ii) Leodori et al. 14
resetting, but increased frequency (iii) Leodori et al. 15
(iii) PD with tremor suppression: Increased CMC at tremor frequency during (iv) Ammann et al. 16
both rest and postural tremor (v) Shirota et al. 17
(iv) Decreased SICI on the LAS at an early stage of PD (vi) Saravanamuttu et al. 19
(v) Increased SICF at an early stage of PD (vii) Moriyasu et al. 20
(vi) No SICF facilitation in advanced PD patients and PD patients in the OFF- (viii) Ginanneschi et al. 21
medication state
(vii) Levodopa treatment influenced LTP
(viii) Exercise influenced the I-O curves
EEG (i) Upper limb freezing: use of different cortical pathways when re-initiating (i) Zang et al. 23
movement after freezing or voluntary stops (ii) Karimi et al.
24
(ii) Freezing of gait: theta band synchrony over the Cz and contralateral (iii) Betrouni et al. 25
supplementary motor areas (iv) Waninger et al. 26
(iii) Resting-state EEG and spectral power analysis within seven bands (v) Farashi et al. 27
frequency determined the severity of cognitive impairment in PD (vi) Barcelon et al. 36
(iv) Resting-state EEG data and dopamine transporter PET imaging displayed
excessive EEG beta coherence, correlating with severity and dopamine
transporter activity
(v) A combination of EEG data and graph theory displayed an increase in the
gamma bands and a decrease in beta bands after levodopa treatment
(vi) A modified total EEG score of ≤9 distinguished PD from APS
Cortical potentials (i) Decreased CNV amplitude over the central vertex correlating with the (i) Tzvetanov et al. 22
severity of the disease. (ii) Sciacca et al. 7
(ii) Long-duration response to levodopa in synergy with motor exercise
acted on surrogate markers of neuroplasticity (P300, MEPs, and BP) with
prevalent latency improvement, inducing cortical adaptive changes
R2BRRC Increased brainstem excitability contralateral to the MAS and increased AI Sciacca et al. 38
Abbreviations: AI: Asymmetry index; AMT: Active motor threshold; APS: Atypical Parkinsonian syndrome; BP: Bereitschaftspotential;
CMC: Corticomuscular coherence; CNV: Contingent negative variation; EEG: Electroencephalography; EMG: Electromyography; I-O: Input-output;
LAS: Less affected side; LTP: Long-term potentiation; MAS: More affected side; MEP: Motor evoked potential; P300: Auditory evoked cognitive
potential; PD: Parkinson’s disease; PET: Positron emission tomography; R2BRRC: R2 blink reflex recovery cycle; RMT: Resting motor threshold;
SICF: Short-interval intracortical facilitation; SICI: Short-interval intracortical inhibition; TMS: Transcranial magnetic stimulation.

The effects of tremor-provocation tasks on re-emergent pause duration of re-emergent tremors was amplitude-
tremor latency and variability were assessed by the related, as it was observed that a decrease in the levodopa-
accelerometric analysis of hand movements in the OFF induced amplitude indirectly prolonged the pause duration
state with and without the provocation maneuver of before a re-emergent tremor. Acoustic myography
10
backward counting. Pause duration, peak frequencies, (AMG) was recently employed to evaluate abnormal
9
and slope of tremor return were measured during motor activity in early PD patients and the efficacy of anti-
the provocation task, and it was reported that tremor Parkinsonian medications. PD patients were subjected
11
provocation reduced the latency of re-emergent tremor. to AMG of the upper limb muscles of the more affected
9
However, provocation maneuvers could make it harder side (MAS) during active and passive movements, in
for pause identification before re-emergent tremors. the OFF-medication (non-medicated) state, and 1 and
9
In another study, tremor activity was measured in PD 3 h after an oral intake of 200 mg levodopa. Motor
11
patients during the OFF and ON states with bilateral efficiency (E-score), temporal muscle fiber recruitment
accelerometers. Correlation analysis suggested that the (T-score), spatial summation (S-score), and S/T ratio were
10
Volume 3 Issue 1 (2024) 3 https://doi.org/10.36922/an.1961