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

Action myoclonus, reviewed in this chapter, is the term applied to arrhythmic muscular jerking induced by voluntary movement. It is made worse by attempts at precise or coordinated movement (intention myoclonus) and may also be provoked by certain sensory stimuli. The effective stimuli for action myoclonus is probably feedback from muscle afferents, although it may be initiated by corollary discharge from motor cortex to reticular formation before or at the onset of voluntary movement. The condition is usually associated with diffuse neuronal disease such as post-hypoxic encephalopathy, uremia, and the various forms of PME, although action myoclonus may be limited to one limb in some cases of focal cerebral damage. It is caused by hyperexcitability of the sensorimotor cortex (cortical reflex myoclonus) or reticular formation (reticular reflex myoclonus), or both. No consistent pathological change has been reported in autopsied cases of action myoclonus. The underlying disorder appears to be a loss of inhibitory mechanisms involving serotonin and possibly GABA as transmitter agents. The term PME is used for the association of myoclonus with degenerative changes in the nervous system which are commonly diffuse but may predominate in certain systems. There may or may not be associated tonic-clonic seizures, other manifestations of epilepsy, or dementia. Those cases of PME associated with Lafora inclusion bodies and cerebral storage diseases can be distinguished from the system degenerations. Systems which may be involved in the latter group include cerebellodentatorubral, pyramidal, extrapyramidal, optic, auditory, posterior columns and gracile and cuneate nuclei, spinocerebellar pathways, motor neurons of cranial nerves and anterior horns, and muscle fibers. Confronted with this diversity of pathological change, it seems unnecessary to make any clinical distinction between Ramsay Hunt syndrome and Unverricht-Lundborg syndrome (Baltic myoclonus) because cerebellar signs are found in patients described under both headings. Additional systems may be involved in individuals or families who are otherwise typical. All three names could well be joined in an eponymous title (Unverricht-Lundborg-Hunt disease) or the condition simply known as the systems degeneration type of PME, as Halliday (43) suggested. The cause of the condition (or spectrum of conditions) is at present unknown. Action myoclonus usually responds to sodium valproate or clonazepam, and some individuals, particularly those with posthypoxic myoclonus, improve with the administration of serotonin precursors.
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PMID:Action myoclonus, Ramsay Hunt syndrome, and other cerebellar myoclonic syndromes. 308 Aug 51

The baboon Papio papio is naturally predisposed to present several types of myoclonus, the study of which can help in understanding the various human myoclonic symptomatologies. The three types of myoclonus which are studied have been called A, B and C. Myoclonus A, which is induced by intermittent photic stimulation in photosensitive animals, is of epileptic nature: It is always preceded by spikes-waves predominating in the fronto-rolandic cortex (areas 4 and 6) and can be followed by secondarily generalized tonic-clonic seizures. Myoclonus B, which occurs when the animal is agitated, is facilitated by somatic stimulations. Since it is never preceded or accompanied by spikes-waves and since it is never associated with epileptic seizures, myoclonus B is considered as non-epileptic. Myoclonus C occurs during wave-sleep. They are associated with spikes-waves during the slow but not during paradoxical sleep. Myoclonus A, B and C can co-exist in the same animal when it is photosensitive. Myoclonus B and C can co-exist in the same animal when it is non-photosensitive. Clinically, the three types of myoclonus have different symptomatologies. Myoclonus A is bilateral and synchronous. It always involves initially the eyelids and face. It can secondarily become generalized to the whole body. Myoclonus B, which is also bilateral and synchronous, is limited to the truncular musculature and to the proximal part of limbs. It never involves the eyelids and face. It never becomes generalized. Myoclonus C has a variable symptomatology and can be parcellar. The nervous structures originating the three types of myoclonus in the baboon are not identical. Myoclonus A is originated in the fronto-rolandic cortex, where a neuronal generator is triggered by visual inputs induced by photic stimulation. It appears mainly due to a dysfunction of the GABA system, because it is suppressed by GABA agonists and by benzodiazepines. On the contrary, it is facilitated by GABA antagonists. Myoclonus B has probably its origin in the lower brain stem (ponto-bulbar reticular formation) and is favored by cerebellar lesions. It appears mainly due to a dysfunction of the cholinergic system and is considerably facilitated by atropine. Myoclonus C can also have its origin in the lower brain stem but, contrary to myoclonus B, it can involve the cortex and thus can be accompanied by spikes-waves. The 3 types of myoclonus which are distinguished in the baboon have different relationships with epilepsy.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[Myoclonia. From the myoclonia of Papio papio to various human myoclonias]. 351 16

The behavioral and electrographic effects of chronic (7 days), localized infusion of GABA (100 micrograms/microliter) into the somatomotor cortex of fully amygdala-kindled rats is reported. The animals were stimulated once daily until a stage 5 (generalized clonic seizure) was obtained for five consecutive days. After determination of a stable seizure triggering threshold, the rats were implanted with osmotic minipumps (1 microliter/h for 7 days) connected to previously implanted bilateral cannulae. Amygdala stimulation was continued for 14 successive days. GABA infusion reduced the motor seizure without significantly modifying the limbic afterdischarge. This effect lasted until termination of drug application, with recovery of stage 5 convulsions on the following 3 to 5 days. No effects were observed in saline-infused animals or in rats with unilateral GABA treatment. Upon cessation of GABA treatment (removal of the osmotic devices by day 7 postimplantation), spontaneous epileptic discharges localized to the infusion sites appeared. In some animals, the abnormal activity was accompanied by behavioral signs of myoclonus. This cortical hyperexcitability lasted 2 to 24 h, with complete recovery afterward. These data indicate that two types of focal epilepsy may coexist independently in the same animal and provide confirmation of previous observations in the monkey on the existence of a "GABA-withdrawal syndrome" after chronic, focal infusion of the amino acid.
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PMID:Anticonvulsant effect of intracortical, chronic infusion of GABA in kindled rats: focal seizures upon withdrawal. 365 26

The effects of DL-allylglycine, an inhibitor of GABA synthesis, on the responses to photic stimulation were studied in the cat kindled in the lateral geniculate body (GL). For 3 to 8 h after the injection of DL-allylglycine at a subconvulsant dose (30 or 40 mg/kg, i.v.), the kindled cat showed a stable level of photosensitivity without any toxic effects and responded with various degrees of myoclonus or a generalized tonic-clonic convulsion when photic stimulation was repeated at hourly intervals. The incidence of photically induced myoclonus reached its plateau during this period. Our results suggest that photosensitivity of the lateral geniculate-kindled cat is related to the modification of GABAergic mechanisms, and that when the GL-kindled cat is pretreated with DL-allylglycine it is a reliable model of photosensitive epilepsy.
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PMID:Effects of allylglycine on photosensitivity in the lateral geniculate-kindled cat. 375 82

The ability of the selective GABA-receptor agonist, progabide, to suppress abnormal involuntary movements was evaluated in a preliminary open pilot study. 17 patients, 10 males and 7 females, aged 10-78 years, with hyperkinetic movement disorders were included in the study. Daily doses of progabide ranged from 900 to 3600 mg (median 2400 mg) corresponding to 14-45 mg/kg (median 45 mg/kg), while the duration of treatment varied from 2 to 52 weeks. Improvement, with a reduction of involuntary movements exceeding 25%, occurred in two of four patients with Gilles de la Tourette's syndrome, and in two of three patients with postanoxic intention myoclonus, while no consistent beneficial effects were registered in ten patients with Huntington's chorea, postanoxic choreoathetosis, torsion dystonia, tardive dyskinesia, action tremor, essential myoclonus, or oro-branchio-respiratory myoclonus.
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PMID:Progabide in the treatment of hyperkinetic extrapyramidal movement disorders. 386 33

GABAergic agents have been evaluated for acute anticonvulsant activity in baboons, Papio papio with photosensitive epilepsy. The potent GABAA agonists muscimol and THIP are proconvulsant. (-)Baclofen, 2 mg/kg suppresses myoclonic responses; higher doses facilitate EEG paroxysmal activity. (S) gamma-vinyl GABA, 100-200 mg/kg, suppresses myoclonic responses for more than 24 h. Some derivatives of esters of beta-carboline-3-carboxylate that bind to the benzodiazepine receptor, e.g. ZK 91296 and ZK 93423, suppress myoclonus with a potency at least as great as diazepam.
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PMID:GABAergic agents as anticonvulsants in baboons with photosensitive epilepsy. 608 55

Papio papio may show two different kinds of myoclonus. A first type corresponds to myoclonus induced by photic stimulation (25 Hz). This type is always preceded by paroxysmal discharges. Another type of myoclonus may be induced, or at least facilitated, by some benzodiazepines, especially lorazepam and, to a lesser extent, diazepam. This type is neither preceded nor accompanied by paroxysmal discharges. A single injection of lorazepam (1 mg/kg i.v.) blocks the first type of myoclonus but favors the appearance of the second. However, these effects do not follow the same evolution; while myoclonus induced by photic stimulation disappears immediately after the injection, benzodiazepine-induced myoclonus appears only 10-15 min. Furthermore, whereas the former reappears after 150-210 min, the latter may persist for a longer time (up to 1 h). A preliminary pharmacologic study of benzodiazepine-induced myoclonus indicates that drugs increasing brain GABA level block this type of myoclonus. The possible reticular origin of benzodiazepine-induced myoclonus is suggested.
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PMID:[Myoclonus induced by some benzodiazepines in the Papio papio. Comparison with myoclonus induced by intermittent light stimulation (author's transl)]. 612

The degenerative type of progressive myoclonus epilepsy (PME) is a hereditary disease with grand mal seizures, stimulus sensitive myoclonus, characteristic EEG and mental deterioration in the late stage. GABAergic antiepileptic drugs are the most effective ones in this disease, with an unknown etiology. In this study, the GABA concentration in the CSF of 15 PME patients was measured and compared with values of sex- and age-matched epileptic controls. It was correlated with the concentrations of 5HIAA and HVA in the CSF, which were determined earlier from the same patients. The GABA concentration in the PME patients was statistically significantly decreased, to about 75% of that of the epileptic controls. It correlated with HVA and 5HIAA concentrations in the PME patients, but not in the epileptic controls. It is unknown whether these findings are related to the primary cause of PME or whether they are only secondary, owing to a loss of respective neurons or synapses.
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PMID:Decrease of GABA in the cerebrospinal fluid of patients with progressive myoclonus epilepsy and its correlation with the decrease of 5HIAA and HVA. 618 74

In eight monkeys (Cercopithecus aethiops), previously treated with haloperidol for 4-14 months, we have examined the behavioral effect of: (1) methylphenidate vs apomorphine; (2) 4,5,6,7-tetrahydroisoxazolo-(5,4-c)-pyridin-3-ol(THIP, a GABA agonist) vs diazepam; and (3) THIP and diazepam in methylphenidate-induced behavior. Methylphenidate (0.5-5.0 mg/kg) and apomorphine (0.1-0.5 mg/kg) both increased locomotion, but otherwise exhibited different behavioral profiles. Methylphenidate induced repetitive movements of head, limbs, and trunk, and hallucinatory-like behavior, but not oral hyperkinesia (licking and gnawing), whereas apomorphine preferentially caused oral hyperkinesia. THIP produced a syndrome of bradykinesia, dystonia, ataxia, myoclonus, sedation, and decreased responsiveness, whereas diazepam produced only bradykinesia, ataxia, sedation, and decreased responsiveness, but not dystonia and myoclonus. Methylphenidate-induced locomotion and repetitive movements were reduced by THIP and diazepam, whereas hallucinatory-like behavior was markedly aggravated by THIP, but not by diazepam.
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PMID:Methylphenidate, apomorphine, THIP, and diazepam in monkeys: dopamine-GABA behavior related to psychoses and tardive dyskinesia. 642 Aug 23

The activity of compounds inhibiting neuronal or glial GABA uptake has been assessed following intracerebroventricular (i.c.v.) or intraperitoneal (i.p.) administration in DBA/2 mice (sound-induced seizures) or Swiss S mice (pentylenetetrazol-induced seizures). Sound-induced seizures are suppressed by the i.c.v. injection of (+/-)-nipecotic acid, 3.2 mumol, or (+/-)-cis-4-hydroxynipecotic acid, 2 mumol, but not by i.p. injection of (+/-)-nipecotic acid, 3.2 mmol/kg or (+/-)-cis-4-hydroxynipecotic acid 4 mmol/kg. Pentylenetetrazol-induced seizures are not suppressed by i.c.v. injection of (+/-)-nipecotic acid 1-4 mumol, or (+/-)-cis-4-hydroxynipecotic acid, 2-4 mumol. THPO (4,5,6,7-tetrahydroisoxazolo[4.5-c]pyridin-3-ol), 1-5 mumol i.c.v. or 1-4 mmol/kg i.p., protects against sound-induced seizures. There is no protection against pentylenetetrazol seizures after i.c.v. THPO injection, but THPO, 2-8 mmol/kg i.p., is protective. Among prodrugs, (+/-)-nipecotic acid pivaloyloxymethyl ester protects against sound-induced seizures, when given i.c.v. (3.2 mumol) or i.p. (1.6-3.2 mmol/kg) and against pentylenetetrazol seizures when given i.p. (0.5-4 mmol/kg). (+/-)-cis-4-hydroxynipecotic acid methyl ester protects against sound-induced seizures when given i.p. (3.2 mmol/kg), but is only partially protective against pentylenetetrazol seizures, when given i.p. (4 mmol/kg). Some prodrugs induce myoclonus following either i.c.v. or i.p. administration.
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PMID:Anticonvulsant activity of GABA uptake inhibitors and their prodrugs following central or systemic administration. 687 58


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