The purpose of this paper is to provide the rationale for therapeutic silencing of the alpha-synuclein gene (SNCA) in Parkinson’s disease (PD). The paper reviews the public health significance of PD; the causal links between rare SNCA variants and familial PD; the association of common SNCA variants and PD susceptibility; the association of SNCA variants also with age at onset and motor and cognitive outcomes in PD; therapeutic strategies targeting SNCA in PD; and preliminary findings and considerations on small interfering RNA-based therapies and PD.
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During the last two decades, the many developments in the treatment of movement disorders such as Parkinson disease and dystonia have enhanced our understanding on organization of the basal ganglia, and this knowledge has led to other advances in the field. According to many electrophysiological and anatomical findings, it is considered that motor information from different cortical areas is processed through several cortico-basal ganglia loops principally in a parallel fashion and somatotopy from each cortical area is also well preserved in each loop. Moreover, recent studies suggest that not only the parallel processing but also some convergence of information occur through the basal ganglia. Information from cortical areas whose functions are close to each other tends to converge in the basal ganglia. The cortico-basal ganglia loops should be comprehended more as a network rather than as separated subdivisions. However, the functions of this convergence still remain unknown. It is important even for clinical doctors to be well informed about this kind of current knowledge because some symptoms of movement disorders may be explained by disorganization of the information network in the basal ganglia.
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Deep Brain Stimulation (DBS), arguably, is the most dramatic development in movement disorders since the levodopa for Parkinson’s disease. Yet, its mechanisms of action of DBS are unknown. However, DBS related research already has demonstrated that current concepts of basal ganglia pathophysiology are wrong. Specifically, the notion that over-activity of the globus pallidus interna causes parkinsonism, the basis for the most current theories, is no longer tenable. The development of any new theory will be aided by an understanding of how current theories are wrong and why have these flawed theories persist. Many of the problems of current theories are more matters of inference, assumptions, presumptions, and the accepted level of ambiguity than they are of fact. Consequently, it is imperative that these issues be addressed. Just as the inappropriate use of a tool or method is grounds for criticism, methods of reasoning are tools that can be used inappropriately and should be subject to discussion just as misuse of any other tool. Thorough criticism can provide very important lesions though the process could be mistaken as harsh or personal; neither is the case here. At the least, such analyzes can point to potential pitfalls that could be avoided in the development of new theories. As will be discussed, theories are important for the development of therapies but perhaps most important, for the acceptance of new therapies, as was the case for the recent resurgence of interest in surgical therapies.
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Psychogenic movement disorders (PMD) are a group of disorders which are in the border zone between neurology and psychiatry. All necessary laboratory investigations should be done to rule out an underlying organic disorder. While clinical acumen of a trained movement disorder specialist may be sufficient to diagnose most PMD, there are clinical situations where electrophysiological tests are required either to rule out an organic movement disorder or even diagnose a PMD. Current electrophysiological test are most useful for tremor, followed by jerks and least for spasms or dystonia. Commonly used electrophysiologic tests include multichannel surface electromyography (EMG), accelerometry, electroencephalography time locked with EMG, premovement potential (Bereitschaftspotential), and somatosensory evoked potentials. Psychogenic tremor is a low frequency tremor with variable frequency and duration of EMG bursts, entrainable, has a high coherence with voluntary movements, and presence of coactivation sign. Patients with psychogenic jerks have well organized triphasic pattern of activation of agonist and antagonist muscles. The jerks are associated with EMG bursts of long duration (usually > 70 ms), long and variable latencies in stimulus induced jerks, absence of craniocaudal pattern of muscle recruitment in apparent startle response, and often a Breitschaftspotential (premovement potential) precedes the jerk. Electrophysiological characterization of psychogenic dystonia is difficult and the tests are usually performed to rule out organic dystonia with characteristic findings. Finally, caution should be exerted in interpreting the electrophysiological tests as both false positive and false negative diagnosis of PMD may still occur.
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Orthostatic hypotension (OH) is known to be present even in patients with early Parkinson’s disease (PD). To affirm the presence of OH and find correlation between OH and other dysautonomic symptoms in PD, this study has done in newly-diagnosed PD patients.
Forty-five non-demented patients with no prior history of treatment for PD were recruited (17 men, 63.8 ± 10.1 years of age). All the patients were evaluated for OH before starting medications. Autonomic symptoms were evaluated with structured questionnaires. Clinical characteristics of PD were evaluated (median Hoehn and Yahr stage 2.0 (1–3), 1.3 ± 1.1 years of disease duration), and comorbid medical conditions that could affect blood pressure were also recorded.
OH was prevalent, and eighteen patients (40%) showed orthostatic hypotension, and twenty-seven (60%) did not (normotensive group). There was no significant difference in demographic and clinical characteristics between groups. The presence or severity of symptoms of autonomic dysfunction in the OH group also not differed from those of the normotensive group.
OH was prevalent even in the early stage of PD, and was not related to presence or severity of any other symptoms of autonomic dysfunction. Our findings suggest that clinicians should pay attention to OH from the early stage of disease.
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The sequence effect (SE) in Parkinson’s disease (PD) denotes progressive slowness in speed or progressive decrease in amplitude of repetitive movements. It is a well-known feature of bradykinesia and is considered unique in PD. Until now, it was well-documented in advanced PD, but not in drug-naïve PD. The aim of this study is to know whether the SE can also be measured in drug-naïve PD.
We measured the SE with a computer-based, modified Purdue pegboard in 4 drug-naïve PD patients, which matched our previous study with advanced PD patients.
We observed progressive slowness during movement, that is, SE. Statistical analysis showed a strong statistical trend toward the SE with the right hand, but no significance with the left hand. There was no statistical significance of SE with either the more or less affected hands.
These results indicate that the SE can be identified in drug-naïve PD, as well as in advanced PD, with objective measurements and support the idea that the SE is a feature in PD observed during the early stage of the disease without medication.
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We investigated the cognitive profiles in a large sample of patients with multiple system atrophy-cerebellar ataxia (MSA-C) and compared directly them in patients with clinical diagnosis of probable MSA-C without dementia and control subjects with intact cognition.
We prospectively enrolled 26 patients with clinical diagnosis of probable MSA-C. All patients underwent a standardized neuropsychological test of the Seoul Neuropsychological Screening Battery.
The score of Korean version of the Mini- Mental State Examination was significantly lower in patients with MSA-C (27.2 ± 2.5) than in control subjects (28.9 ± 1.0,
Patients with MSA-C show more severe and more widespread cognitive dysfunctions than controls. Our results also indicate that cognitive dysfunction in patients with MCA-C is suggestive of disruption of the cerebellocortical circuits.
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Various neurologic manifestations of herpes simplex virus (HSV) encephalitis have been reported on the literatures. Chorea, ballism, choreoathetosis and myoclonus were reported as movement disorders which might be related with brain lesion by HSV encephalitis, but negative myoclonus (NM) has never been reported before. NM can be characterized as a shock-like involuntary jerky movement caused by a sudden, brief interruption of muscle activity. We experienced a case of HSV encephalitis with NM in unilateral arm and leg. In polygraphic monitoring, electroencephalography (EMG) silent periods are 50–250 ms in duration with no detectable EMG correlate.
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Zolpidem is usually used for the treatment of insomnia as a hypnotic drug. It was also suggested to be effective in the treatment of dystonia in some studies. A 74-year-old woman had been suffering from frequent and intense bilateral spasms of the eyelids for 20 years. She has been treated with botulinum toxin injection and taken some medications. But, she experienced a little effect and was not satisfied with those treatments. Her symptom was improved after taking Zolpidem which had been prescribed for insomnia by her primary physician. She did not show any improvement after placebo injection and neostigmine test. This is the first report which shows improvement of isolated blepharospasm by Zolpidem in Korea. Zolpidem can be one of useful alternative pharmacological treatments for blepharospasm. Further randomized, blinded, placebo-controlled studies are needed to validate this finding.
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