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John N Caviness - One of the best experts on this subject based on the ideXlab platform.
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Physiology-Based Treatment of Myoclonus
Neurotherapeutics, 2020Co-Authors: Ashley B. Pena, John N CavinessAbstract:Myoclonus can cause significant disability for patients. Myoclonus has a strikingly diverse array of underlying etiologies, clinical presentations, and pathophysiological mechanisms. Treatment of Myoclonus is vital to improving the quality of life of patients with these disorders. The optimal treatment strategy for Myoclonus is best determined based upon careful evaluation and consideration of the underlying etiology and neurophysiological classification. Electrophysiological testing including EEG (electroencephalogram) and EMG (electromyogram) data is helpful in determining the neurophysiological classification of Myoclonus. The neurophysiological subtypes of Myoclonus include cortical, cortical–subcortical, subcortical–nonsegmental, segmental, and peripheral. Levetiracetam, valproic acid, and clonazepam are often used to treat cortical Myoclonus. In cortical–subcortical Myoclonus, treatment of myoclonic seizures is prioritized, valproic acid being the mainstay of therapy. Subcortical–nonsegmental Myoclonus may be treated with clonazepam, though numerous agents have been used depending on the etiology. Segmental and peripheral Myoclonus are often resistant to treatment, but anticonvulsants and botulinum toxin injections may be of utility depending upon the case. Pharmacological treatments are often hampered by scarce evidence-based knowledge, adverse effects, and variable efficacy of medications.
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Myoclonus.
Continuum (Minneapolis Minn.), 2019Co-Authors: John N CavinessAbstract:This article offers clinicians a strategic approach for making sense of a symptom complex that contains Myoclonus. The article presents an evaluation strategy that highly leverages the two major classification schemes of Myoclonus. The goal of this article is to link evaluation strategy with diagnosis and treatment of Myoclonus. The growth of medical literature has helped better define Myoclonus etiologies. Physiologic study of Myoclonus types and etiologies with electrophysiologic testing has provided greater clarity to the pathophysiology of the Myoclonus in various diseases. Although studies have been limited, the role of newer treatment agents and methods has made progress. Myoclonus has hundreds of different etiologies. Classification is necessary to evaluate Myoclonus efficiently and pragmatically. The classification of Myoclonus etiology, which is grouped by different clinical presentations, helps determine the etiology and treatment of the Myoclonus. The classification of Myoclonus physiology using electrophysiologic test results helps determine the pathophysiology of the Myoclonus and can be used to strategize symptomatic treatment approaches. Both basic ancillary testing (including EEG and imaging) and more comprehensive testing may be necessary. Treatment of the underlying etiology is the ideal approach. However, if such treatment is not possible or is delayed, symptomatic treatment guided by the Myoclonus physiology should be considered. More controlled study of Myoclonus treatment is needed. Further research on Myoclonus generation mechanisms should shed light on future treatment possibilities.
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post hypoxic Myoclonus current concepts neurophysiology and treatment
Tremor and other hyperkinetic movements (New York N.Y.), 2016Co-Authors: Harsh V Gupta, John N CavinessAbstract:Background: Myoclonus may occur after hypoxia. In 1963, Lance and Adams described persistent Myoclonus with other features after hypoxia. However, Myoclonus occurring immediately after hypoxia may demonstrate different syndromic features from classic Lance–Adams syndrome (LAS). The aim of this review is to provide up-to-date information about the spectrum of Myoclonus occurring after hypoxia with emphasis on neurophysiological features. Methods: A literature search was performed on PubMed database from 1960 to 2015. The following search terms were used: “Myoclonus,” “post anoxic Myoclonus,” “post hypoxic Myoclonus,” and “Lance Adams syndrome.” The articles describing clinical features, neurophysiology, management, and prognosis of post-hypoxic Myoclonus cases were included for review. Results: Several reports in the literature were separated clinically into “acute post-hypoxic Myoclonus,” which occurred within hours of severe hypoxia, and “chronic post-hypoxic Myoclonus,” which occurred with some recovery of mental status as the LAS. Acute post-hypoxic Myoclonus was generalized in the setting of coma. Chronic post-hypoxic Myoclonus presented as multifocal cortical action Myoclonus that was significantly disabling. There was overlap of neurophysiological findings for these two syndromes but also different features. Treatment options for these two distinct clinical–neurophysiologic post-hypoxic Myoclonus syndromes were approached differently. Discussion: The review of clinical and neurophysiological findings suggests that Myoclonus after hypoxia manifests in one or a combination of distinct syndromes: acute and/or chronic Myoclonus. The mechanism of post-hypoxic Myoclonus may arise either from cortical and/or subcortical structures. More research is needed to clarify mechanisms and treatment of post-hypoxic Myoclonus.
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Treatment of Myoclonus
Neurotherapeutics, 2014Co-Authors: John N CavinessAbstract:Myoclonus creates significant disability for patients. This symptom or sign can have many different etiologies, presentations, and pathophysiological mechanisms. A thorough evaluation for the Myoclonus etiology is critical for developing a treatment strategy. The best etiological classification scheme is a modified version from that proposed by Marsden et al. in 1982. Clinical neurophysiology, as assessed by electromyography and electroencephalography, can be used to classify the pathophysiology of the Myoclonus using a neurophysiology classification scheme. If the etiology of the Myoclonus cannot be reversed or treated, then symptomatic treatment of the Myoclonus itself may be warranted. Unfortunately, there are few controlled studies for Myoclonus treatments. The treatment strategy for the Myoclonus is best derived from the neurophysiology classification scheme categories: 1) cortical, 2) cortical–subcortical, 3) subcortical–nonsegmental, 4) segmental, and 5) peripheral. A cortical physiology classification is most common. Levetiracetam is suggested as first-line treatment for cortical Myoclonus, but valproic acid and clonazepam are commonly used. Cortical–subcortical Myoclonus is the physiology demonstrated by myoclonic seizures, such as in primary epileptic Myoclonus (e.g., juvenile myoclonic epilepsy). Valproic acid has demonstrated efficacy in such epileptic syndromes with other medications providing an adjunctive role. Clonazepam is used for subcortical–nonsegmental Myoclonus, but other treatments, depending on the syndrome, have been used for this physiological type of Myoclonus. Segmental Myoclonus is difficult to treat, but clonazepam and botulinum toxin are used. Botulinum toxin is used for focal examples of peripheral Myoclonus. Myoclonus treatment is commonly not effective and/or limited by side effects.
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Chapter 31 – Myoclonus
Handbook of clinical neurology, 2011Co-Authors: John N Caviness, Daniel D. TruongAbstract:Myoclonus can be classified as physiologic, essential, epileptic, and symptomatic. Animal models of Myoclonus include DDT and posthypoxic Myoclonus in the rat. 5-Hydrotryptophan, clonazepam, and valproic acid suppress Myoclonus induced by posthypoxia. The diagnostic evaluation of Myoclonus is complex and involves an extensive work-up including basic electrolytes, glucose, renal and hepatic function tests, paraneoplastic antibodies, drug and toxicology screens, thyroid antibody and function studies, neurophysiology testing, imaging, and tests for malabsorption disorders, assays for enzyme deficiencys, tissue biopsy, copper studies, alpha-fetoprotein, cytogenetic analysis, radiosensitivity DNA synthesis, genetic testing for inherited disorders, and mitochondrial function studies. Treatment of Myoclonus is targeted to the underlying disorder. If Myoclonus physiology cannot be demonstrated, treatment should be aimed at the common pattern of symptoms. If the diagnosis is not known, treatment could be directed empirically at cortical Myoclonus as the most common physiology. In cortical Myoclonus, the most effective drugs are sodium valproic acid, clonazepam, levetiracetam, and piracetam. For cortical–subcortical Myoclonus, valproic acid is the drug of choice. Here, lamotrigine can be used either alone or in combination with valproic acid. Ethosuximide, levetiracetam, or zonisamide can also be used as adjunct therapy with valproic acid. A ketogenic diet can be considered if everything else fails. Subcortical-nonsegmental Myoclonus may respond to clonazepam and deep-brain stimulation. Rituximab, adrenocorticotropic hormone, high-dose dexamethasone pulse, or plasmapheresis have been reported to improve opsoclonus Myoclonus syndrome. Reticular reflex Myoclonus can be treated with clonazepam, diazepam and 5-hydrotryptophan. For palatal Myoclonus, a variety of drugs have been used.
Peter Baxter - One of the best experts on this subject based on the ideXlab platform.
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Post-Anoxic Reticular Reflex Myoclonus in a Child and Proposed Classification of Post-Anoxic Myoclonus
Pediatric neurology, 2017Co-Authors: Min T. Ong, Ptolemaios Georgios Sarrigiannis, Peter BaxterAbstract:Abstract Objective We describe a child with post-anoxic Myoclonus of the reticular reflex type and discuss the classification of post-anoxic Myoclonus. Patient Description A nine-year-old boy with severe hypoxic-ischemic encephalopathy due to submersion developed early epileptic spasms followed by stimulus sensitive multifocal generalized Myoclonus and later dystonia. Video electromyography (EMG) polygraphy performed before treatment demonstrated that the discharges associated with the Myoclonus lasted less than 50 milliseconds. Cortical Myoclonus was excluded by jerk-locked averaging using arm muscles, which showed no cortical correlates. The recruitment order on EMG polygraphy was consistent with a brainstem generator for the Myoclonus, characteristic of reticular reflex Myoclonus. Both Myoclonus and dystonia responded to clonazepam. He remains in a persistent vegetative state. Conclusions Reticular reflex Myoclonus can be demonstrated by detailed neurophysiological assessment in children as in adults, and it has a similar poor prognosis in children. Post-anoxic Myoclonus can have several mechanisms and should not be considered synonymous with Lance-Adams Myoclonus.
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OP63 – 2453: Post-anoxic reticular reflex Myoclonus in a child
European Journal of Paediatric Neurology, 2015Co-Authors: Ptolemaios Georgios Sarrigiannis, Peter BaxterAbstract:Objective Post-hypoxic Myoclonus can be classified in various ways, including acute and chronic (Lance-Adams) forms. We present the first childhood case of post-anoxic reticular reflex Myoclonus and discuss the classification. Case A previously healthy 9 year old boy developed severe hypoxic-ischaemic encephalopathy and transient multi-organ injury following 10 minutes of cold water immersion and subsequent resuscitation. Initial GCS was 3. On day 3 he developed spasms and was treated with Phenytoin and Midazolam infusion. His EEG showed burst of spikes/polyspikes and sharp waves interspersed with relative suppression. MRI demonstrated focal signal change involving caudate nuclei and parafalcine parietal lobes bilaterally. This later evolved to volume loss with gliosis. He had multifocal and generalised Myoclonus, present from day 7, which was stimulus sensitive. On day 17 he developed dystonic spasms, evolving into status dystonicus which was treated with several medications including Clonazepam. Myoclonus stopped by day 29, 6 days following introduction of Clonazepam. By day 90 spasms resolved and Clanazepam withdrawn. Myoclonus re-emerged at 5 months. He was minimally conscious on weeks 3 and 7 but subsequent coma recovery scores were compatible with a persistent vegetative state. Results Video EMG polygraphy performed (day 22) showed the discharges associated with the Myoclonus were very short, below 50 ms. The possibility of cortical Myoclonus, assessed by jerk-locked back averaging using arm muscles, showed no cortical correlates. The recruitment order on EMG polygraphy was consistent with a brainstem generator for the Myoclonus (rostral and caudal spread from a lower brain stem lead) which is characteristic of reticular reflex Myoclonus (Hallet, 2000). Conclusion Post-anoxic Myoclonus should not be considered synonymous with Lance-Adams Myoclonus. The terms early or late are poorly defined. It is clinically more useful to classify post-anoxic Myoclonus into cortical and subcortical, and to subdivide the cortical form into acute and chronic (Lance-Adams) forms.
Steven J. Frucht - One of the best experts on this subject based on the ideXlab platform.
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Phenomenology of Myoclonus
Movement Disorders Phenomenology, 2020Co-Authors: Steven J. Frucht, Pichet TermsarasabAbstract:Myoclonus is one of the more common and least understood neurologic disorders. Myoclonus may originate anywhere within the neuraxis, and the list of disorders that can produce Myoclonus is very broad. Understanding the role of phenomenology in evaluating the Myoclonus patient is critically important to diagnosis and treatment.
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Improvement of Isolated Myoclonus Phenotype in Myoclonus Dystonia after Pallidal Deep Brain Stimulation.
Tremor and other hyperkinetic movements (New York N.Y.), 2016Co-Authors: Ritesh A. Ramdhani, Anousheh Behnegar, Steven J. Frucht, Brian H KopellAbstract:Background: Myoclonus–dystonia is a condition that manifests predominantly as myoclonic jerks with focal dystonia. It is genetically heterogeneous with most mutations in the epsilon sarcoglycan gene ( SGCE ). In medically refractory cases, deep brain stimulation (DBS) has been shown to provide marked sustainable clinical improvement, especially in SGCE -positive patients. We present two patients with Myoclonus–dystonia (one SGCE positive and the other SGCE negative) who have the isolated Myoclonus phenotype and had DBS leads implanted in the bilateral globus pallidus internus (GPi). Methods: We review their longitudinal Unified Myoclonus Rating Scale scores along with their DBS programming parameters and compare them with published cases in the literature. Results: Both patients demonstrated complete amelioration of all aspects of Myoclonus within 6–12 months after surgery. The patient with the SGCE -negative mutation responded just as well as the patient who was SGCE positive. High-frequency stimulation (130 Hz) with amplitudes greater than 2.5 V provided therapeutic benefit. Discussion: This case series demonstrates that high frequency GPi-DBS is effective in treating isolated Myoclonus in Myoclonus–dystonia, regardless of the presence of SGCE mutation.
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Myoclonus
Current Treatment Options in Neurology, 2008Co-Authors: Victoria C. Chang, Steven J. FruchtAbstract:Myoclonus is a hyperkinetic movement disorder characterized by quick, involuntary jerks. It encompasses a vast range of etiologies and widespread anatomic locations. Treatment frequently requires multiple agents and is often only partially beneficial. These patients pose a considerable challenge for the clinician, further complicated by the fact that many of the treatment choices lack evidence-based support. In the past few years, publications regarding therapy have been largely observational case reports or series. Although the literature on treatment of cortical Myoclonus appears to be growing, evidence regarding Myoclonus of noncortical origin is less well established. Investigation of more satisfactory treatments is needed, as this condition can be disturbing, debilitating, and sometimes harmful for patients. Continuing investigations are using various animal models (mostly of posthypoxic Myoclonus), electrophysiologic studies, new imaging techniques such as diffusion tensor imaging, and genetic studies. Meanwhile, the clinical approach to diagnosing and classifying Myoclonus remains largely unchanged. This review updates readers on current investigations and suggests guidelines for diagnosing and treating Myoclonus.
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Myoclonus.
Current opinion in neurology, 2003Co-Authors: Pinky Agarwal, Steven J. FruchtAbstract:Myoclonus, one of the most common involuntary movement disorders, poses particular challenges for the treating physician. The evaluation of a patient with Myoclonus depends completely on the clinical history and examination, supported when necessary by electrophysiology, neuroimaging and selected genetic and laboratory testing. The sudden, shock-like jerks which define Myoclonus may be highly disabling, and when they persist, often require treatment. In a paper published in this journal, we reviewed the published trials of antimyoclonic agents, and formulated a treatment algorithm based on the available evidence. In the current paper, we present our approach for evaluating patients with Myoclonus, and suggest practical guidelines for treating patients based on the pre-2000 literature and on studies published in the last 2 years. The newer medications which are being used in management of Myoclonus are levetiracetam and gamma-hydroxybutyric acid. Levetiracetam is especially useful for posthypoxic Myoclonus and gamma-hydroxybutyric acid for alcohol-sensitive Myoclonus. A combination of medications is often needed to obtain adequate control of symptoms. Botulinum toxin is also being introduced for focal Myoclonus with encouraging results. There are no approved medications for Myoclonus, and most therapies are borrowed from the antiepileptic and psychiatric armamentarium. Nonetheless, there is a logic to the choice and dosing of antimyoclonic drugs, and we hope that by applying a few simple principles, neurologists will approach the care of these patients with confidence.
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a pilot tolerability and efficacy study of levetiracetam in patients with chronic Myoclonus
Neurology, 2001Co-Authors: Steven J. Frucht, Elan D Louis, Cathy Chuang, Stanley FahnAbstract:Levetiracetam was recently approved as adjunctive therapy for partial onset seizures. The authors conducted an open-label trial of levetiracetam in eight patients with chronic Myoclonus. Patients were assessed by using the Unified Myoclonus Rating Scale. Levetiracetam was well tolerated. Three of five patients with cortical Myoclonus experienced reductions in their Myoclonus scores, providing support for a larger, placebo-controlled trial in cortical Myoclonus.
Daniel D. Truong - One of the best experts on this subject based on the ideXlab platform.
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Post-Hypoxic Myoclonus in Rodents
Movement Disorders, 2015Co-Authors: Kwok-keung Tai, Daniel D. TruongAbstract:Abstract Myoclonus, or brief, very rapid, sudden, shock-like involuntary jerking movements that involve small muscles or the whole body, is manifested in a wide variety of neuropathological conditions affecting the central nervous system. Myoclonus can be classified based on anatomic distribution, pattern of contractions, pathophysiology, or etiology. One of the most disabling forms of Myoclonus is known as post-hypoxic Myoclonus, which is caused by brain damage resulting from prolonged oxygen deprivation during cardiac arrest or anesthesia accidents during surgery. Asthma attacks, airway obstruction, and drug intoxication can also trigger post-hypoxic Myoclonus. Animal models may be useful in elucidating the mechanism of post-hypoxic Myoclonus. This chapter provides an overview of a rat model, highlighting the behavioral, pharmacological, and neuroanatomical features that parallel those observed in humans.
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Chapter 31 – Myoclonus
Handbook of clinical neurology, 2011Co-Authors: John N Caviness, Daniel D. TruongAbstract:Myoclonus can be classified as physiologic, essential, epileptic, and symptomatic. Animal models of Myoclonus include DDT and posthypoxic Myoclonus in the rat. 5-Hydrotryptophan, clonazepam, and valproic acid suppress Myoclonus induced by posthypoxia. The diagnostic evaluation of Myoclonus is complex and involves an extensive work-up including basic electrolytes, glucose, renal and hepatic function tests, paraneoplastic antibodies, drug and toxicology screens, thyroid antibody and function studies, neurophysiology testing, imaging, and tests for malabsorption disorders, assays for enzyme deficiencys, tissue biopsy, copper studies, alpha-fetoprotein, cytogenetic analysis, radiosensitivity DNA synthesis, genetic testing for inherited disorders, and mitochondrial function studies. Treatment of Myoclonus is targeted to the underlying disorder. If Myoclonus physiology cannot be demonstrated, treatment should be aimed at the common pattern of symptoms. If the diagnosis is not known, treatment could be directed empirically at cortical Myoclonus as the most common physiology. In cortical Myoclonus, the most effective drugs are sodium valproic acid, clonazepam, levetiracetam, and piracetam. For cortical–subcortical Myoclonus, valproic acid is the drug of choice. Here, lamotrigine can be used either alone or in combination with valproic acid. Ethosuximide, levetiracetam, or zonisamide can also be used as adjunct therapy with valproic acid. A ketogenic diet can be considered if everything else fails. Subcortical-nonsegmental Myoclonus may respond to clonazepam and deep-brain stimulation. Rituximab, adrenocorticotropic hormone, high-dose dexamethasone pulse, or plasmapheresis have been reported to improve opsoclonus Myoclonus syndrome. Reticular reflex Myoclonus can be treated with clonazepam, diazepam and 5-hydrotryptophan. For palatal Myoclonus, a variety of drugs have been used.
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Myoclonus and parkinsonism.
Handbook of clinical neurology, 2007Co-Authors: Daniel D. Truong, Roongroj BhidayasiriAbstract:Publisher Summary Myoclonus refers to symptoms or signs that are non-specific in relation to their neuroanatomical source and pathogenesis. It is characterized as sudden, brief, shock-like, involuntary movements caused by muscular contractions (positive Myoclonus) or inhibitions (negative Myoclonus). Etiological classification distinguishes Myoclonus into four categories that include: (1) physiological Myoclonus, (2) essential Myoclonus, (3) epileptic Myoclonus, and (4) symptomatic Myoclonus. Myoclonus is a recognized feature of many basal ganglia disorders where parkinsonian signs predominate. Essentially, Myoclonus and Parkinsonism can occur simultaneously in three conditions: (1) Parkinson's disease (PD) where patients are treated chronically with levodopa, (2) von Economo's encephalitis, and (3) acutely in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication. The association between Myoclonus and Parkinsonism has also been described in other Parkinsonian disorders, including multiple system atrophy (MSA), corticobasal degeneration (CBD), diffuse Lewy body disease (DLB), postencephalitic Parkinsonism, and frontotemporal dementia with Parkinsonism (FTD). Electrophysiological studies play a crucial role in the evaluation of Myoclonus in various parkinsonian disorders, not only for differential diagnosis, but also for better understanding of the physiological mechanism underlying each type of Myoclonus.
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Involvement of GABAA receptors in Myoclonus
Movement Disorders, 2000Co-Authors: Rae R. Matsumoto, Daniel D. Truong, Kevin D. Nguyen, A. Terri Dang, Tin T. Hoang, Paola SandroniAbstract:Alterations in multiple neurochemical systems have been reported in animal and human studies of posthypoxic Myoclonus. It is impossible, however, to establish causative relationships between the observed changes and the myoclonic movements from these studies. Therefore, to establish causative links between neurochemical changes and Myoclonus, ligands that target neurotransmitter systems that are altered in posthypoxic Myoclonus were microinjected into the lateral ventricles of normal rats to identify the changes that can produce Myoclonus. Of the ligands that were tested, only the GABA A antagonists produced Myoclonus after intracerebroventricular administration, suggesting the importance of disinhibition of GABAergic systems in Myoclonus, To further examine the role of GABA in Myoclonus, GABAergic antagonists were microinjected into the nucleus reticularis of the thalamus (NRT), an area of the brain in which extensive pathologic changes are seen in posthypoxic animals. GABA A , but not GABA B , antagonists produced Myoclonus after microinjection into the NRT. Earlier investigators have further reported the ability of GABA A antagonists to produce Myoclonus after microinjection into the caudate. The data therefore suggest that disruption of activity at GABA A receptors at any one of a number of levels in the neural axis can produce Myoclonus.
Peter Brown - One of the best experts on this subject based on the ideXlab platform.
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Myoclonus current concepts and recent advances
Lancet Neurology, 2004Co-Authors: John N Caviness, Peter BrownAbstract:Myoclonus presents as a sudden brief jerk caused by involuntary muscle activity. An organisational framework is crucial for determining the medical significance of the Myoclonus as well as for its treatment. Clinical presentations of Myoclonus are divided into physiological, essential, epileptic, and symptomatic. Most causes of Myoclonus are symptomatic and include posthypoxia, toxic-metabolic disorders, reactions to drugs, storage disease, and neurodegenerative disorders. The assessment of Myoclonus includes an initial screening for those causes that are common or easily corrected. If needed, further testing may include clinical neurophysiological techniques, enzyme activities, tissue biopsy, and genetic testing. The motor cortex is the most commonly shown Myoclonus source, but origins from subcortical areas, brainstem, spinal, and peripheral nervous system also occur. If treatment of the underlying disorder is not possible, treatment of symptoms is worthwhile, although limited by side-effects and a lack of controlled evidence.
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Myoclonus
CNS Drugs, 1995Co-Authors: Peter BrownAbstract:Several different types of Myoclonus can be distinguished on physiological grounds. Cortical Myoclonus arises from an abnormal discharge in the sensori-motor cortex and corticospinal pathways. Brainstem reticular reflex Myoclonus and hyperekplexia are forms of generalised Myoclonus arising in the brainstem, and palatal Myoclonus is a segmental form of brainstem Myoclonus. Ballistic overflow Myoclonus occurs in hereditary essential Myoclonus. Propriospinal Myoclonus consists of axial jerks of spinal origin, while segmental spinal Myoclonus is thought to arise as a result of the isolation of spinal motoneurons from inhibitory influences or from direct cellular injury. Treatments of first choice for cortical Myoclonus are valproic acid (sodium valproate) and clonazepam. Primidone and phenobarbital (phenobarbitone) may also be useful. However, most patients require polypharmacy for adequate symptomatic improvement. Piracetam has advantages in these circumstances, as its addition to existing treatments is rarely accompanied by sedation. 5-Hydroxytryptophan in combination with carbidopa is now rarely used because of gastrointestinal adverse effects. In patients with brainstem reticular reflex Myoclonus, valproic acid and clonazepam are the most useful agents. In hyperekplexia, treatment is directed against the disabling tonic spasms, rather than jerks. Carbamazepine, phenytoin and clonazepam are useful agents in this respect. Ballistic overflow Myoclonus may improve with anticholinergic drugs, such as benzatropine (benztropine) or trihexyphenidyl (benzhexol). Antiepileptic drugs are disappointingly ineffective in this condition. Treatment of palatal Myoclonus is often unsuccessful, but phenytoin, carbamazepine, clonazepam, trihexyphenidyl and baclofen have been effective in some patients. Clonazepam is effective in over half of patients with propriospinal Myoclonus, but other anticonvulsants are usually unhelpful. Segmental spinal Myoclonus is often resistant to drug treatment, but diazepam, carbamazepine, tetrabenazine and, particularly, clonazepam are sometimes effective.
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the Myoclonus in corticobasal degeneration evidence for two forms of cortical reflex Myoclonus
Brain, 1994Co-Authors: P. D. Thompson, T. C. Britton, J C Rothwell, Peter Brown, C. D. MarsdenAbstract:: The clinical and physiological characteristics of Myoclonus in 14 patients with corticobasal degeneration are described. The Myoclonus was focal, confined to one limb (usually the arm) and was most prominent on voluntary action or in response to sensory stimulation. On clinical inspection, the Myoclonus appeared to occur at rest but EMG recordings revealed that apparently spontaneous Myoclonus occurred only on a background of more or less continuous muscle activity (responsible for the rigidity and dystonia). The jerks consisted of hypersynchronous short duration bursts of EMG activity coincident in agonists and antagonists. Reflex Myoclonus in hand muscles, to stimulation of the median nerve at the wrist, had a latency of approximately 40 ms. In 13 of the 14 patients reflex Myoclonus was not associated with enlargement of the cortical sensory evoked potentials (SEPs); the later components of the parietal SEP were poorly formed and dominated by a broad positive wave with a peak latency approximately 45 ms. Prefrontal components of the SEP were relatively preserved, but there were no significant differences between the SEPs evoked from myoclonic and non-myoclonic limbs. Action Myoclonus was not preceded by an identifiable cortical wave in the electroencephalogram back-averaged before each jerk. Magnetic, but not electric, brain stimulation evoked repetitive bursts of Myoclonus suggesting enhanced cortical excitability. The combination of focal, predominantly distal, hypersynchronous jerks, evidence of enhanced cortical excitability, together with the known cortical pathology in corticobasal degeneration suggests that the Myoclonus in these patients may be cortical in origin. Since the latency of reflex Myoclonus in corticobasal degeneration is only 1-2 ms longer than the sum of the afferent and efferent times to and from the cortex, we propose the reflex Myoclonus is mediated by direct sensory input to motor cortical areas that activate corticospinal tract output. Such Myoclonus differs from the typical form of cortical reflex Myoclonus in which reflex jerks have a longer latency (50 ms in hand muscles), cortical SEPs are enlarged and action Myoclonus is preceded by a cortical discharge. It is proposed that these various forms of cortical Myoclonus can be explained by the presence of different cortical relays of sensory information to cortical motor areas. The Myoclonus of corticobasal degeneration may represent enhancement of a direct sensory input to the motor cortex. In contrast, the more widely recognized variety of cortical reflex Myoclonus may involve abnormal relays through sensory cortex to motor cortex, either directly or via cerebellar-thalamo-cortical projections.
