Page 84 - AN-3-1

Advanced Neurology Neurophysiology in hypokinetic disorders

drug-induced Parkinsonism). In contrast, hyperkinetic 2019 and August 2023. The literature search included
movement disorders commonly include tremors, peer-reviewed articles written in English and excluded
dystonias, myoclonus, choreas, and tics. In this regard, review articles. The search was conducted in the PubMed
a conventional clinical examination (e.g., differential database using the following keywords: “neurophysiology
diagnosis) of phenotypically similar movement disorders and hypokinetic disorders,” “neurophysiology and
may not result in an accurate diagnosis of the condition. In Parkinson’s disease,” “neurophysiology and atypical
2
particular, hypokinetic disorders often exhibit overlapping parkinsonism,” “neurophysiology and Multiple system
clinical features, making them indistinguishable. The atrophy,” “neurophysiology and Progressive supranuclear
primary symptom of PD is bradykinesia in combination palsy,” and “neurophysiology and corticobasal syndrome.”
with either rest tremor, rigidity, or both with an The most relevant studies (i.e., utilized neurophysiology in
asymmetrical distribution. In contrast, APSs have a hypokinetic movement disorders in clinical practice) were
3,4
more rapid progression, disabling functional prognosis, reviewed and discussed. The recent neurophysiological
and poor response to dopaminergic treatment, thereby approaches to PD, MSA, PSP, and CBS are summarized in
limiting the effectiveness of differential diagnosis at the Tables 1 and 2. In addition, a neurophysiological diagnostic
early stages of APS. Likewise, only postmortem pathology algorithm for the differential diagnosis of hypokinetic
can definitively diagnose Parkinsonian syndromes. Above movement disorders in clinical practice is proposed in
5
all, alpha-synucleinopathies (e.g., PD and MSA) and Figure 1 according to observed neurophysiological features
tauopathies (e.g., PSP and CBS) are often misdiagnosed at in hypokinetic movement disorders.
their respective clinical onset. In this regard, an effective
diagnostic tool for movement disorders should be able to 3. Results
precisely and accurately distinguish the disorders for better
treatment outcomes. 3.1. Neurophysiology of hypokinetic movement
disorders
Neurophysiological tools could be decisive in defining
the type of movement disorders, thereby facilitating better The recent neurophysiological applications in hypokinetic
decision-making related to pharmacological and surgical movement disorders are summarized according to PD and
treatments. For example, neurophysiological assessments APS in Tables 1 and 2, respectively. While only a handful
6
of PD and APS may subsequently result in better decision- of neurophysiological insights into hypokinetic movement
making for effective treatment approaches, such as reducing disorders were reported from 2019 to 2023, the findings of
therapy-related motor complications, promoting motor these studies (e.g., differential diagnosis and treatment of
learning, and even assessing the efficacy of new therapeutic hypokinetic movement disorders in clinical practice) were
trials. Surface EMG combined with accelerometry, motor reviewed and described herein.
evoked potentials (MEPs), electroencephalography 3.2. Neurophysiological assessments of PD
(EEG) recording, auditory-evoked potential (P300),
Bereitschaftspotential (BP), blink reflex (BR), and R2 blink From the conducted literature search, it was noted that most
reflex recovery cycle (R2BRRC) are the most common of the articles disclosed electrophysiological techniques for
neurophysiological tools used in the characterization of managing PD and studied the specific electrophysiological
movement disorders, albeit the current underutilization features and pathophysiological mechanisms of PD. 8-27
in clinical practice. Despite the advancement of more However, there was only one study that suggested
accurate diagnostic techniques, especially in the field neurophysiological examinations for managing PD and its
of neuroimaging, recent evidence (relating to the early onset. 7
clinical management and treatment of hypokinetic
disorders) has convinced clinicians to consider applying 3.2.1. Polymyography and accelerometric analysis
electrophysiological assessments for diagnosing different Video and accelerometric recordings were recently used
disorders. This study aimed to establish neurophysiology in the standardization of hand positions for rest tremor
6,7
insights into hypokinetic movement disorders for assessment in PD, whereby different daily tasks were
evaluating the potential application of neurophysiological performed to evaluate rest tremor. Neurophysiological
8
assessments in clinical practice. examinations revealed that the prone position had the
highest specificity for detecting rest tremors in PD,
2. Methods whereas the tremor amplitude was better observed when
8
A non-systematic review was conducted, focusing on the hands were in a hanging position. Contrariwise, the
literatures related to the neurophysiology of hypokinetic evaluation of re-emergent tremor requires a different
movement disorders and published between January clinical approach as compared to that for resting tremor.

Volume 3 Issue 1 (2024) 2 https://doi.org/10.36922/an.1961