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Query: UMLS:C0027066 (myoclonus)
 4,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The clinical and biological features of Alzheimer disease are not uniform in their expression; heterogeneity is evident in the disease's clinical, anatomic, and physiologic characteristics. The presence of considerable intersubject and intrasubject heterogeneity suggests that subtypes of the disease exist. We define subtypes of Alzheimer disease in regard to the behavioral features (for example, predominant right or left hemisphere, or symmetrical impairment), inheritance (familial or sporadic), dosage of chromosome 21 (presence of the Down syndrome), time course of progression, age of onset (presenile or senile), and presence or absence of motor deficit (myoclonus or signs of an extrapyramidal syndrome). Studies of regional cerebral glucose metabolism with positron emission tomography and [18-fluorine] fluorodeoxyglucose show focal alterations in glucose use, with cerebral metabolic asymmetries in patients with Alzheimer disease that are related to the nature of the cognitive deficit. Serial roentgenographic computed tomographic studies show heterogeneous rates of lateral ventricle enlargement in the disease that are related to rates of cognitive decline. Similar anatomic and physiologic abnormalities are also found in persons 45 years of age or older who have the Down syndrome. Furthermore, patients with Alzheimer disease who have extrapyramidal dysfunction or myoclonus are a distinct subgroup, with specific abnormalities of central monoamine markers of dopamine metabolism, serotonin metabolism, and the hydroxylation cofactor, biopterin. The concept of subtypes in Alzheimer disease serves as a model with which the interactions of genetic influences with environmental factors can be examined.
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PMID:NIH conference. Alzheimer disease: clinical and biological heterogeneity. 296 3

Positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (18FDG) has demonstrated the epileptogenic lesion in partial epilepsy to be hypometabolic interictally . This finding is useful for localizing the area of resection when surgical therapy is contemplated. 18FDG scans during partial seizures show increased metabolism in areas of ictal onset and spread and in other regions of decreased metabolism that could reflect postictal effects. In the generalized epilepsies, petit mal absences and generalized convulsions induced by electroconvulsive shock therapy (ECT) are associated with global hypermetabolism, while global hypometabolism is seen in the postictal period following ECT. More information about the factors that influence the interictal hypometabolic zone in partial epilepsy should improve the diagnostic value of this finding for presurgical localization and perhaps also for the evaluation of other therapeutic regimens. New techniques for more dynamic PET studies with improved resolution, combined with computerized electroencephalographic analysis, should allow more accurate interpretation of ictal, as well as interictal, phenomena. Application of PET technology to other paroxysmal disorders may provide a basis for new diagnostic classifications that have therapeutic and prognostic value and may allow clearer differentiation among epileptic phenomena, myoclonus, and movement disorders. More clinical and animal research is needed, however, before we can delineate fundamental mechanisms of human epilepsy from PET data. To this end, it is now possible to use combined multidisciplinary parallel approaches in patients and animals to define specific aspects of epileptic disorders clinically, to intensively investigate them with experimental models in the animal laboratory, and to verify the relevance of these experimental results by returning to clinical studies.
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PMID:The use of positron emission tomographic scanning in epilepsy. 643 Feb 15

Posthypoxic myoclonus and seizures precipitate as secondary neurological consequences in ischemic/hypoxic insults of the central nervous system. Neuronal hyperexcitation may be due to excessive activation of glutamatergic neurotransmission, an effect that has been shown to follow ischemic/hypoxic events. Therefore, riluzole, an anticonvulsant that inhibits the release of glutamate by stabilizing the inactivated state of activated voltage-sensitive sodium channels, was tested for its antimyoclonic and neuroprotective properties in the cardiac arrest-induced animal model of posthypoxic myoclonus. Riluzole (4-12 mg/kg i.p.) dose-dependently attenuated the audiogenic seizures and action myoclonus seen in this animal model. Histological examination using Nissl staining and the novel Fluoro-Jade histochemistry in cardiac-arrested animals showed an extensive neuronal degeneration in the hippocampus and cerebellum. Riluzole treatment almost completely prevented the neuronal degeneration in these brain areas. The neuroprotective effect was more pronounced in hippocampal pyramidal neurons and cerebellar Purkinje cells. These effects were seen at therapeutically relevant doses of riluzole, and the animals tolerated the treatment well. These findings indicate that the pathogenesis of posthypoxic myoclonus and seizure may involve excessive activation of glutamate neurotransmission, and that riluzole may serve as an effective pharmacological agent with neuroprotective potential for the treatment of neurological conditions associated with cardiac arrest in humans.
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PMID:Effect of riluzole on the neurological and neuropathological changes in an animal model of cardiac arrest-induced movement disorder. 1002 76

d-Fenfluramine is a potent serotonin (5-HT) reuptake inhibitor/releaser and, until its recent recall, was prescribed as an anoretic agent. This study demonstrates that 10 mg/kg d-fenfluramine i.p., when administered to rats in a warm (27 degrees C) environment, produces neuronal degeneration within select brain regions. Degeneration was detected and localized using a recently developed fluorescent marker of neuronal degeneration, Fluoro-Jade. The most extensive cortical damage was in the anterior cingulate region. In the medial thalamus, degeneration was frequently seen within the intralaminar nuclei, and somewhat less frequently observed within the paraventricular nucleus, the mediodorsal nucleus, and the gelatinosis nucleus. Cerebellar damage occurred primarily in medial Purkinje cells and occasionally in granule cells or basket cells. Degeneration was not observed in either saline-injected control animals or in rats given even higher doses of 25 mg/kg d-fenfluramine but kept in a cooler environment (23 degrees C). The degeneration was clearly most prominent in animals with body temperatures of 41 degrees to 42 degrees C, but this degeneration was not seen in animals given saline that became extremely hyperthermic in a 37 degrees C environment. Behavioral signs such as tremors, myoclonus, rigidity, and splayed legs were seen in all animals with extensive neurodegeneration. The areas damaged by d-fenfluramine, when hyperthermia occurs, could play a role in the expression of the serotonin syndrome. Elevated extracellular 5-HT levels alone are probably not sufficient for neurotoxicity, and additional factors such as hyperthermia, regional specificity of 5-HT receptor subtypes, blood flow, and/or neuronal networks may be involved.
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PMID:d-Fenfluramine produces neuronal degeneration in localized regions of the cortex, thalamus, and cerebellum of the rat. 1033 Jun 89

We report a 70-year-old right handed man with a 5-year history of slowly progressive clumsiness of his left hand. A neurological examination disclosed mild rigidity and myoclonus in his left hand. He showed limb-kinetic apraxia, but neither ideational apraxia nor ideomotor apraxia was present. Aphasia and agnosia were also absent. He was thought to have the primary progressive limb-kinetic apraxia clinically. Brain CT and MRI revealed focal atrophy in the right postcentral gyrus and the supplementary motor area. A positron emission tomography (PET) study showed diffuse decrement of cerebral blood flow, predominantly in the right hemisphere. The decrease in the uptake of [18F]-Fluoro-deoxyglucose also revealed glucose hypo-metabolism, especially in the right frontal and parietal lobe. Striatal [11C]NMSP and [18F]FDOPA uptake were also reduced in an asymmetric pattern. These findings suggest that our patient is likely to have corticobasal degeneration. Transcranial magnetic stimulation using double pulse paradigm revealed a decrease in the level of cortico-cortical inhibition in the motor cortex on the affected side. Our results indicate increase in the excitability of motor cortical neurons in primary progressive limb-kinetic apraxia, likely due to a decreased excitability of cortico-cortical inhibitory mechanism as a result of focal degeneration of cortical neurons.
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PMID:[Progressive limb-kinetic apraxia with myoclonus focal atrophy in the postcentral gyrus and the supplementary motor area]. 1107 Sep 25

A major consequence of severe cardiac arrest is impairment of neurological functions. Posthypoxic myoclonus and seizures are two of the major neurological problems following ischemic and hypoxic insults. This condition affects motor function to different degrees of severity ranging from mild to serious debilitation. The pathophysiological mechanism(s) associated with these neurological conditions remain elusive. Glutamate-mediated neuronal overexcitation is thought to play a major role in the neuronal damage and in the neurological consequences of the posthypoxic state. Therefore, lamotrigine, a new anticonvulsant that indirectly modulates glutamatergic neurotransmission by interfering with voltage-dependent sodium channels, was tested for its effectiveness in controlling the neurological and histopathological changes in the animal model of cardiac arrest-induced myoclonus. Lamotrigine dose-dependently attenuated the audiogenic seizures and action myoclonus seen in this rat model. Histological analysis using Nissl staining and the novel Fluoro-Jade histochemistry in cardiac-arrested rats showed an extensive neuronal degeneration in the hippocampus and cerebellum. Lamotrigine treatment significantly attenuated the neuronal degeneration in these brain areas. The neuroprotective effect was more pronounced in hippocampal pyramidal and cerebellar Purkinje neurons. The therapeutic window of lamotrigine in this model was 8 hours. These results suggest that lamotrigine can be viewed as a potential antimyoclonic and neuroprotective agent for the treatment of posthypoxic myoclonus and seizures. The study also suggests that neuronal hyperexcitability may play a role in the etiology of posthypoxic myoclonus and seizure.
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PMID:Antimyoclonic and neuroprotective effects of lamotrigine in an animal model of cardiac arrest. 1267 Dec 43

The mechanism of cerebral hypoxia-induced myoclonic jerks is not known. Some studies have suggested that glutaminergic NMDA receptor activation in the inferior olive resulting in excitotoxic neuronal injury in the cerebellum is the underlying cause of posthypoxic myoclonus. To test this hypothesis, the effect of memantine, an NMDA receptor antagonist, on the intensity of myoclonic jerks and the extent of cerebral ischemia-induced neurodegeneration in the cerebellum were evaluated in a rat model of posthypoxic myoclonus. The myoclonus scores for the posthypoxic rats treated with memantine were significantly higher than those treated with saline. The myoclonic scores for the posthypoxic rats injected with 100mg/kg memantine are higher than those posthypoxic rats injected with 30 mg/kg memantine. In contrast, the number of Fluoro-Jade B positive degenerating neurons in the Purkinje cell layer of the cerebellum did not differ significantly between the memantine-treated and the saline-treated posthypoxic rats. This pattern of results suggests that glutaminergic NMDA receptor activation in the cerebellum does not play a significant role in the generation of myoclonus in a rat model of posthypoxic myoclonus. Further, these results also suggest that NMDA receptor antagonists would exacerbate posthypoxic myoclonus in this animal model.
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PMID:Memantine exacerbates myoclonic jerks in a rat model of posthypoxic myoclonus. 2043 35