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

A 5-year-old boy is reported with spinal myoclonus caused by cervical astrocytoma due to neurofibromatosis. The essential clinical and electromyographical signs of spinal myoclonus are the following: (1) Continuous rhythmical appearance in muscles innervated by the affected segments of the spinal cord. (2) Synchronous myoclonus in muscles innervated by the same spinal segments of one body side, asynchronous myoclonus in muscles of different segments as well as in contralateral muscles of the same segments. (3) Usually stable frequency, which may increase to a manifold under the influence of different stimuli. (4) Accentuation of the myoclonus under mental distress, disappearance during deeper sleep. The pathophysiological basis of spinal myoclonus might be a disinhibition in the area of the spinal formatio reticularis. Supraspinal stimuli can influence the myoclonus.
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PMID:Sinal myoclonus. 9 51

This is a case of Ramsay Hunt syndrome with mental disorder. The patient had action myoclonus, grand mal seizure and severe cerebellar ataxia. Schizophrenia-like symptoms including delusion of persecution and self-reference, auditory hallucination and incoherence were characteristically observed before the neurological disturbance became manifest. Subsequently, euphoria, disinhibition, moria and mild dementia appeared with neurological symptoms. The possibility of Ramsay Hunt syndrome to accompany organic mental syndromes and the relationship between cerebellar dysfunction and psychiatric symptoms are discussed.
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PMID:Ramsay Hunt syndrome with mental disorder. 181 81

Cortical myoclonus (CM) and focal dystonia (FD) are commonly characterized by co-contraction of agonist and antagonist muscles, enhancement by intentional movement, strong influence by sensory input, and spread to adjacent muscles. On the other hand, they are different in the nature of movements, speed of muscle contraction, speed of spread, and drug effects. There are abundant data indicating that CM is due to pathological hyperexcitability of the sensorimotor cortex (S1-M1), while, in FD, no definitive evidence to suggest cortical hyperexcitability has been found. Changes in regional cerebral blood flow (rCBF) studied by positron emission tomography (PET) during movements in patients with dystonia were inconsistent with regard to S1-M1, but the frontal cortex including the rostral SMA was shown to be overactivated, suggesting the thalamocortical disinhibition based on the basal ganglia disorders.
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PMID:[Pathophysiology of involuntary movements--dystonia and myoclonus from viewpoint of brain activities]. 875 5

We have done a few physiological studies on six patients with cortical reflex myoclonus and three patients with unilateral focal dystonia caused by a discrete cerebrovascular lesion in the basal ganglia. The silent period after magnetic cortical stimulation was normal or slightly prolonged in all the patients with cortical myoclonus. In contrast, in patients with focal dystonia, it was shortened in the muscles on the contralateral side to the lesion, whereas normal in duration on the ipsilateral side. Excessive inputs from the disinhibited supplementary motor cortex to the primary motor cortex due to a lesion of the basal ganglia must cause this shortening in the dystonic hand muscles. Excitability recovery of the motor cortex after hypersynchronous activation by magnetic stimulation should be prolonged in the myoclonic patients. Cortico-cortical inhibition of the motor cortex studied with paired magnetic stimulation technique was disturbed in both the patients with myoclonus and those with dystonia. This result suggested that the disinhibition of the motor cortex is present in both disorders. Based on these results, we conclude that the motor cortex is similarly disinhibited in both disorders, but recovery function from hypersynchronous activation is different between these two groups.
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PMID:[Electromyographic analysis of cortical myoclonus and focal dystonia]. 875 6

Palatal myoclonus is usually due to a brainstem or cerebellar lesion disrupting the dentato-rubro-olivary pathway. Rarely it may be caused by a cortical lesion. The precipitating factor in 70% of all cases is an infarct. We describe an unusual case of a patient with palatal myoclonus who had an old ipsilateral cerebellar infarct and a new contralateral subcortical (corona radiata) infarct. We postulate that the new infarct caused disinhibition of the old cerebellar infarct, resulting in palatal myoclonus. Magnetic resonance imaging (MRI) of the brain did not show any hypertrophy of the inferior olivary nucleus. Her myoclonus proved refractory to clonazepam, valproate and phenytoin.
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PMID:Palatal myoclonus--a case report. 1056 80

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.
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PMID:Involvement of GABA(A) receptors in myoclonus. 1075 72

The experiments strongly suggested that the reason why Purkinje cells die so easily after global brain ischemia relates to deficiencies in aldolase C and EAAT4 that allow them to survive pathologically intense synaptic input from the inferior olive after the restoration of blood flow. This conclusion is based on: (a) the remarkably tight correspondence between the regional absence of aldolase C and EAAT4 in Purkinje cells and the patterned loss of Purkinje cells after a bout of global brain ischemia; (b) the necessity of the olivocerebellar pathway for the ischemic death of Purkinje cells; and (c) the build-up of pathologically synchronous and high-frequency burst activity within the inferior olive during recovery from ischemia. Indeed, the correspondence between the absence of aldolase C and EAAT4 to sensitivity to ischemia could be demonstrated for zones of Purkinje cells as small as two neurons. A second finding was that Purkinje cells are not uniformly sensitive to transient ischemia, since they die most frequently in zones where aldolase C and EAAT4 are absent. One implication of the experiment is that factors beyond the unique synaptic and membrane properties of Purkinje cells play an important role in determining this neuron's high sensitivity to ischemia. The data strongly imply that two properties of Purkinje cells that make them susceptible to ischemic death are their reduced capability to sequester glutamate and reduced ability to generate energy during anoxia. The patterned death of Purkinje cells is sufficient to induce a form of audiogenic myoclonus, as determined with a neurotoxic dose of ibogaine. Ibogaine-induced myoclonus is recognized behaviorally as a reduced ability to habituate to a startle stimulus and resembles the myoclonic jerk of rats during recovery from a prolonged bout of global brain ischemia. Commonalities of ischemia and ibogaine-induced neurodegeneration are the intricately striped Purkinje cell loss in the posterior lobe and a nearly complete deafferentation of the lateral aspect of the fastigial nucleus from the cerebellar cortex, in particular the dorsolateral protuberance. Thus, the data point strongly to a cerebellar contribution to audiogenic myoclonus. Single-neuron electrophysiology experiments in monkeys have demonstrated that the evoked activity in the deep cerebellar nuclei occurs too late to initiate the startle response (60) and electromyography of the postischemic myoclonus of rats corroborates this view (see Chapter 31) (20). However, the nearly complete loss of GABAergic terminals in the dorsolateral protuberance after Purkinje cell death would be expected to dramatically increase its tonic firing and the background excitation of the brain-stem structures that it innervates. The fastigial nucleus innervates a large number of autonomic and motor structures in the brainstem and diencephalon, including the ventrolateral nucleus of the thalamus and the gigantocellular reticular nucleus in the medulla--structures that have been implicated in human posthypoxic myoclonus (6, 7). We propose that the posthypoxic myoclonic jerk of rats is, at least in part, due to disinhibition of the fastigial nucleus produced by patterned Purkinje cell death in the vermis. The argument is as follows: the loss of GABAergic inhibition in the fastigial nucleus after ischemia leads to diaschisis of the motor thalamus and reticular formation which, in turn, is responsible for enhanced motor excitability and myoclonus. That the audiogenic myoclonus after global brain ischemia in the rat gradually resolves over a period of 2 to 3 weeks is consistent with this view, as restoration of background excitability after CNS damage in rats has been documented to occur within this time-frame (61). Our view brings together the physiologic finding that posthypoxic myoclonus appears to originate in the sensory-motor cortices and/or reticular formation with the consistent anatomical finding of Purkinje cell loss after ischemia, and explains the puzzle of Marsden's unique cases of myoclonus associated with coeliac disease (1). Moreover, our argument is consistent with findings both in rats (62, 63) and humans (64) that damage to the vermis impairs the long-term habituation of the startle reflex. It remains to be determined whether the pathologically enhanced startle responses after vermal damage resemble brain-stem reticular or cortical myoclonus at the electrophysiologic level of analysis. What is the purpose of the regional expression of aldolase C and EAAT4 in Purkinje cells? The close correspondence between the spatial distribution of aldolase C and the parasagittal anatomy of the cerebellum (48) has led to the view that aldolase C may help specify connectivity during development. While the present experiments do not address this issue, they underscore the fact that aldolase plays a fundamental role in metabolism. Because Purkinje cells have a repressed expression of aldolase A (31), whatever role the absence of aldolase C may play during development comes at the price of metabolic frailty later in adulthood. From another point of view, aldolase C and EAAT4 appear to confer upon Purkinje cells the ability to survive their own climbing fiber. Indeed, climbing fibers form a distributed synapse that synchronously releases glutamate (or aspartate) at all levels of the dendritic tree simultaneously (65, 66). Such synchronous activation triggers calcium influx throughout the Purkinje cell dendrites at a magnitude that is unparalleled in the nervous system (12), and, thus, places an extraordinarily high metabolic demand on the Purkinje cell. The apparently reduced level of aldolase in a subpopulation of Purkinje cells provides the condition for energy failure and death during anoxia so long as the climbing fibers are intact or when climbing fiber activation is pharmacologically enhanced under normoxic conditions, such as after ibogaine (53-56). Lastly, the argument that diaschisis produced by patterned cerebellar degeneration leads to thalamo-cortical and reticular hyperexcitability agrees with C. David Marsden and his colleagues' bold demonstration of an inhibitory influence of cerebellar cortex on motor cortex in humans (67). Our anatomic data indicate that the spatially distinct zones of Purkinje cells, which are killed by global brain ischemia, may be the origin of such inhibition.
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PMID:Why do Purkinje cells die so easily after global brain ischemia? Aldolase C, EAAT4, and the cerebellar contribution to posthypoxic myoclonus. 1196 59

The authors report a case of area-specific stimulus-sensitive postanoxic myoclonus and discuss possible pathophysiology. A 71-year-old man sustained cardiorespiratory arrest that lasted 10 minutes and remained unresponsive. On the first EEG obtained 8 hours after the arrest there was no cerebral electrical activity before stimulation of the trigeminal-innervated areas. Periorbital stimulation was associated with bursts of spike-wave activity and generalized myoclonic jerks, whereas other types of stimulation did not elicit any response. A second EEG obtained 32 hours later showed a nonreactive alpha coma pattern. The patient died 7 days after the arrest. Area-specific stimulus-sensitive postanoxic myoclonus is very rare. The regularity of generalized bursts of spike-wave activity (cortical response) in response to stimulation of trigeminal-innervated areas suggests that the resting EEG electrocerebral silence may have been a result of cortical suppression with disinhibition of stimulus-sensitive brainstem-generated myoclonus.
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PMID:A case of area-specific stimulus-sensitive postanoxic myoclonus. 1276 83

We report a case of serotonin syndrome in a patient being treated with paroxetine for depression. Despite prompt discontinuation of medication, his serotonin syndrome continued for 10 days before full consciousness was restored. The patient was a 48-year-old male with chief complaints of hypobulia and suicidal thoughts. He consulted as a psychiatric outpatient, and oral paroxetine 20 mg/day, etizolam 1.0 mg/day, and brotizolam 0.25 mg/day were immediately started. Upsurge of feeling and disinhibition state were noted the following day, then on treatment day 6 his condition deteriorated to substupor state and he was admitted for further treatment. On admission, change of mental condition (consciousness disturbance), perspiration, hyperreflexia, myoclonus and tremor were seen, and serotonin syndrome caused by paroxetine was suspected. Paroxetine was thus discontinued, and under intravenous drip his condition gradually improved. However, it was not until the 10th hospital day that he became fully alert. In examinations, no infectious, metabolic or organic diseases were detected. The patient's condition often improves with in 24 hours of discontinuation of the causative medication in serotonin syndrome. Symptoms continued for 10 days in this patient, however, perhaps because paroxetine was administered for 6 days before discontinuation. In addition, interaction with other medications may have occurred. Therefore, when serotonin syndrome is suspected, prompt discontinuation of the suspected causative medication, followed by close monitoring of the pharmacokinetics is warranted.
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PMID:[Case of prolonged recovery from serotonin syndrome caused by paroxetine]. 1502 11

The question whether general tetanus arises from the independent sum of multiple local tetani or results from the actions of the transynaptic tetanus neurotoxin (TeNT) in higher brain centres remains unresolved. Despite the blood-borne dissemination of TeNT from an infected wound, the access to the central nervous system is probably prevented by the blood-brain barrier. However, several long-term sequelae (e.g. autonomic dysfunction, seizures, myoclonus, and sleep disturbances) present after the subsidence of muscle spasms might be indicative of central actions that occur farther away from lower motoneurons. Subsequently, the obvious entry route is the peripheral neurons followed by the transynaptic passage to the brain. We aimed at describing the pathophysiological correlates of TeNT translocation using the oculomotor system as a comprehensive model of cell connectivity and neuronal firing properties. In this study, we report that injection of TeNT into the medial rectus muscle of one eye resulted in bilateral gaze palsy attributed to firing alterations found in the contralaterally projecting abducens internuclear neurons. Functional alterations in the abducens-to-oculomotor internuclear pathway resembled in part the classically described TeNT disinhibition. We confirmed the transynaptic targeted action of TeNT by analysing vesicle-associated membrane protein2 (VAMP2) immunoreactivity (the SNARE protein cleaved by TeNT). VAMP2 immunoreactivity decreased by 94.4% in the oculomotor nucleus (the first synaptic relay) and by 62.1% presynaptic to abducens neurons (the second synaptic relay). These results are the first demonstration of physiological changes in chains of connected neurons that are best explained by the transynaptic action of TeNT on premotor neurons as shown with VAMP2 immunoreactivity which serves as an indicator of TeNT activity.
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PMID:Transynaptic effects of tetanus neurotoxin in the oculomotor system. 1598 57


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