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Advanced Neurology Neurophysiology in hypokinetic disorders

ISI. Early PD patients displayed an enhanced brainstem between the dynamic and kinematic aspects of gait and
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excitability, which was found to be contralateral to the reported that the kinematic features of gait could identify
clinically affected side by R2BRRC. In contrast, APS PD features. The kinetic aspect, gait speed, and the
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patients did not exhibit any asymmetrical pattern of time up and go (TUG) scores were significantly different
brainstem excitability. Therefore, AI could be used as between PD and healthy subjects, whereas there were no
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an accurate marker of asymmetrical brainstem activity to significant differences in the dynamic features between PD
discriminate PD from PSP and MSA. In addition, AI is and healthy subjects. These findings, further, highlighted
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calculated with ease, inexpensive, and readily available for the importance of neurophysiology in discovering
daily clinical practice. 38 impaired network circuits for balance and gait, as well as
A recent exploratory study evaluated brainstem applying neurophysiology in clinical practice, especially
excitability from the AI of R2BRRC and hemisphere cortical for PD patients.
thickness (CTh) volume from the AI of MRI for early-stage 4. Discussion
differential diagnosis of drug-naïve PD and CBS patients
with asymmetrical disease onset. PD patients exhibited Based on the conducted literature search, a decline in
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increased brainstem excitability for LAS stimulation at the research and clinical interest of neurophysiology
shorter ISIs as compared to MAS, whereas no side-to-side in hypokinetic movement disorders was observed
differences were found in CBS. In particular, a significantly as compared to other more innovative techniques
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higher AI of R2BRRC at ISI of 100 ms was observed in PD exploring Parkinsonian disorders. Recent studies have
patients. The AI of MRI was computed, accounting for the investigated the pathophysiological mechanisms of both
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global mean CTh of each hemisphere, where the two sides PD and APS, using several tools and discovering new
were the means for MAS and LAS. CTh analysis of early neurophysiological features. Nonetheless, the practical
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PD and CBS patients revealed a higher AI of MRI in CBS application of neurophysiology in clinical practice remains
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due to atrophy of the hemisphere (contralateral to MAS). in its early development stage. Moreover, most of the
In summation, PD patients exhibited an asymmetrical proposed neurophysiological examinations require high-
pattern of brainstem excitability, whereas CBS patients level expertise and training, and the examinations can be
exhibited an asymmetrical pattern of cortical atrophy. The time-consuming in a clinical setting. There were only a few
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opposite neurophysiological-structural patterns relating to reported studies that focused on the use of neurophysiology
cortical and subcortical brain structures highlighted the in the differential diagnosis of hypokinetic disorders,
different pathophysiology of these diseases. Therefore, clinical follow-up of the disorders, disease progression,
the combination of the two AIs facilitates the differential and therapeutic management strategies (e.g., monitoring
diagnosis of early PD and CBS. treatment efficacy in daily clinical practice). 7,31,36-40 In this
regard, a practical approach for the use of neurophysiology
3.3.5. Neurophysiology of balance and gait disorders of hypokinetic movement disorders is proposed in
The neurophysiology of hypokinetic movement disorders Figure 1. Clinicians should utilize neurophysiological tools
also includes electrophysiological studies (e.g., balance to distinguish early PD from APS when patients exhibit
and gait disorders) that use relatively accurate devices to overlapping symptoms in the absence of reliable markers.
evaluate several kinematic parameters, such as gait speed, The application of the GTE score could be the initial step
swing time, and stride length. The conducted literature into preliminary differential diagnosis. This technique is
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search identified studies on the neurophysiology of gait easy to apply and can help clinicians recognize APS from
disorders that were focused on PD. 44-47 In particular, beta PD, despite the lack of further differentiation among APSs.
and theta activities (related to FOG) were identified during Therefore, the application of R2BRRC, with the calculation
gait analysis of PD patients with subthalamic deep brain of AI and cutoff scores to objectively quantify the presence of
stimulation through local field potential recording. 44,45 The an asymmetry in brainstem hyperexcitability, could support
balance impairment from PD and the effects of levodopa the diagnosis of early PD and also identify the precise
treatment were evaluated with wearable sensors that operate condition of APSs. 36-40 Based on the conducted literature
on dynamic posturography. The measure of reactive search, only one neurophysiological study demonstrated
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postural responses displayed an impaired axial control in the possibility of monitoring the MSA progression of MSA
PD, without any changes after levodopa administration, patients with EAS assessments. Unfortunately, this EMG
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suggesting a different pathophysiological mechanism and study necessitated a skilled neurophysiologist to conduct,
the possibility of associating other therapeutic strategies and this could be uncomfortable for patients in a clinical
for PD (i.e., rehabilitation in combination with medical setting. Recent neurophysiological examinations in PD
treatment). A recent study identified the differences also evaluated the efficacy of levodopa and neuroplastic
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Volume 3 Issue 1 (2024) 8 https://doi.org/10.36922/an.1961