Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027066 (myoclonus)
 4,275 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Clonazepam (5-(2-chlorophenyl)-1,3-dihydro-7-nitro 2H-1,4 benzodiazepin-2-one) (2 mg/kg) reduced a p,p'-DDT-induced myoclonus in mice by 50%. This antimyoclonic action of clonazepam was counteracted by the serotonin (5-HT) receptor blockers methysergide, metergoline and cinnanserin and potentiated by the 5-HT uptake inhibitors fluoxetine and chlorimipramine. Clonazepam (4 mg/kg) reduced plasma tryptophan by 27%, but had no effect on brain tryptopham, 5-HT, 5-hydroxyindoleacetic acid, 5-HT synthesis and 3H-5-HT receptor binding. Clonazepam (10(-5) M) inhibited brain synaptosomal 3H-5-HT uptake by 23% and increased 3H-5-HT release by 24%. However, 2-8 mg/kg of clonazepam administered intraperitoneally had no effect on 5-HT uptake or release. gamma-Aminobutyric acid (GABA) agonists (muscimol, acetylenic GABA, amino-oxyacetic acid) and the GABA antagonists bicuculline and isoniazid had no effect on p,p'-DDT-induced myoclonus. Furthermore, bicuculline did not counteract the antimyoclonic effect of clonazepam. We suggest that the antimyoclonic action of clonazepam is mediated by enhancement of serotonergic rather than GABAergic neurotransmission.
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PMID:Antimyoclonic action of clonazepam: the role of serotonin. 52 Apr 16

A case of rhythmic myoclonus of the quadriceps related to involvement of the crural nerve by a schwann-cell sarcoma of the thigh is reported. The rhythm of involuntary contractions varies between 35 and 300 per minute. The myoclonic jerks occur rhythmically in the quadriceps only during full extension of the knee. The jerks are inhibited during lengthening of the quadriceps by active or passive flexion of the knee. Clonazepam is very effective in controlling the myoclonus. It is suggested that the myoclonus is the consequence of a response of alpha-motoneurons of the spinal cord to the excitation of Ia fibers of the crural nerve by the tumor. This activation appears to be enhanced by descending excitation pathway and inhibited by activation of Golgi tendon organs of the quadriceps.
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PMID:[Rhythmic quadriceps myoclonia related to sarcomatous involvement of the crural nerve]. 91 62

Clonazepam, a new benzodiazepine derivative, was used in the treatment of intention myoclonus with excellent results. Five patients, three with postanoxic encephalopathy and two with degenerative central nervous system disorders, all refractory to other therapy, responded with marked decrease in myoclonus. The effective dosage was 7 to 12 mg a day in divided doses. One patient has been treated for over 4 years with no toxicity or breakthrough of symptoms. Except for transient sedation, there have been no untoward side effects. Clonazepam is an important addition to the therapy of intention myoclonus.
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PMID:Intention myoclonus: successful treatment with clonazepam. 94 66

In contrast to juvenile rigid form of Huntington's disease (HD) in which myoclonus is often seen, only 5 patients with myoclonus complicating adult HD have been reported. We herein described an adult HD patient who suffered from severe action myoclonus leading to physical disability. To our knowledge, this is the first case report in Japan. The patient, a 32-year-old female with a family history of chorea, developed choreiform movements and mental changes since the age of 24. Subsequently her motor disability has been aggravated by distinctively different involuntary movements characterized by sudden, violent, continuous muscular contractions of four extremities on any attempts at movement. Examination revealed moderate dementia and chorea complicated by frequent myoclonic jerks involving upper and lower extremities in posture or during movement. A head CT scan and MRI revealed caudate atrophy. The myoclonus, as recorded by surface electromyography over the right arm consisted of 40-60 msec-synchronous semirhythmic bursts. The cortical component of SEP was enlarged and C reflex was also observed. Clonazepam (4 mg a day) was instituted with a pronounced reduction in myoclonus and a return to her previous level of daily life activity. Although myoclonic jerks are often recognized in juvenile patients with rigid form of HD, they have been considered to exert a minor influence on physical disability. By contrast, our present observation and review of literature suggest that myoclonus may lead to severe motor impairment in adult HD.
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PMID:[Action myoclonus in adult Huntington's disease]. 129 Nov 67

A 50-year-old woman was admitted to our hospital because of abnormal involuntary movement of upper abdomen. Three months before admission, she had suffered from left lateral chest pain without skin lesions for one week. The neurological examination on admission revealed myoclonus of upper abdomen, and hyperalgesia and thermohyperesthesia from T4 to T9. There was no weakness, the tendon reflexes were symmetrical and the plantar responses were flexor. The surface EMG disclosed the symmetrical, synchronous contractions of m. rectus abdominis and m. obliques externus abdominis. This spinal myoclonus reduced during sleep. The EEG, CT and MRI showed no abnormalities. Serum varicella-zoster virus (VZV) titers increased significantly on follow-up examinations. Clonazepam, 1.5 mg daily was effective in this patient. The myoclonus spontaneously disappeared without clonazepam in six weeks after onset, and at the same time the sensory disturbance also improved. From the neurological findings and clinical course, we consider this spinal myoclonus was probably elicited by involvement of the inhibitory interneurons of the dorsal horns, due to immune response to latent VZV infection but not to direct neuronal destruction by VZV. Spinal myoclonus should be recognized as the spectrum of neurological disease associated with VZV even in the absence of skin lesions.
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PMID:[Varicella-zoster virus-associated spinal myoclonus without skin lesions]. 139 36

A patient with myoclonus epilepsy had 2 types of negative myoclonus as well as positive myoclonus at rest. One type followed a large EMG discharge at the end of continuous contraction and the other did not. Both types of negative myoclonus and positive myoclonus were preceded by EEG activity, predominantly distributed in the contralateral central region. It is suggested that an abnormal activity around the motor cortex suppresses a voluntary contraction as well as induces myoclonus. Clonazepam was markedly effective on both positive and negative myoclonus.
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PMID:Cortical activity-associated negative myoclonus. 140 1

A 23-year-old man suffered from palatal myoclonus for 2 years. It had appeared one week after a minor head trauma. MRI and basal cisternography revealed a localized atrophy of the left paramedian part of the medulla, encroached upon the left vertebral artery. Clonazepam treatment was beneficial. This particular case is discussed in relation to etiopathogenesis and other causes of palatal myoclonus.
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PMID:Unusual CT and MRI findings in palatal myoclonus. 157 91

Postural myoclonus associated with long-term administration of neuroleptics was demonstrated in schizophrenic patients. Sixty patients who had been taking neuroleptics for more than 3 months were investigated for myoclonus and the relationships between postural myoclonus and age, duration of illness, duration of medication, current daily dose, cumulative dose, occurrence of abnormal finger movement, parkinsonism, and tardive dyskinesia were evaluated. Twenty-three patients (38%) showed postural myoclonus when holding the hands forward with the elbow joints flexed at about 90%. Male patients showed a higher incidence of myoclonus than female patients. Patients with myoclonus had been given significantly higher doses of neuroleptics than those without myoclonus. There was a significant correlation between the occurrence of myoclonus and abnormal finger movement. Electromyographic recordings in 7 patients with prominent myoclonus revealed that arrhythmic jerks occurred in the extensor carpi radialis and posterior deltoid muscles and that the jerks on the left and right side were not synchronized. Clonazepam reduced the frequency of the myoclonic activity.
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PMID:Postural myoclonus associated with long-term administration of neuroleptics in schizophrenic patients. 197 Nov 87

Clonazepam is a potent anticonvulsant 1,4-benzodiazepine that controls some types of myoclonus. Its primary mode of action is to facilitate GABAergic transmission in the brain by a direct effect on benzodiazepine receptors. GABA receptors lie on the cell bodies of dorsal raphe neurons, and GABA acts to inhibit raphe cell firing, an action potentiated by benzodiazepines. Clonazepam does not alter 5-HT synthesis but decreases 5-HT utilization in brain and blocks the egress of 5-HIAA from the brain. It is not known whether the actions of clonazepam in altering 5-HT function are responsible for its antimyoclonic action, since these are observed only after large doses. Also, the effects of clonazepam are the exact opposite of those predicted from the beneficial effects of 5-HTP in human myoclonic disorders. Finally, why clonazepam, more than other benzodiazepines, is of benefit in the treatment of myoclonus is not clear. This may be due to some pharmacokinetic feature of the drug in conjunction with its potency at benzodiazepine receptors.
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PMID:Mechanism of action of clonazepam in myoclonus in relation to effects on GABA and 5-HT. 241 52

The present study investigates whether clonazepam exerts its antimyoclonic action through a GABA independent mechanism. We have studied the antimyoclonic effect of clonazepam and compared it with that of aminooxyacetic acid (AOAA), a GABA transaminase inhibitor, against myoclonus induced by picrotoxin, a GABA receptor antagonist and allylglycine, a drug which inhibits synthesis and release of GABA. We have also investigated the effect of clonazepam against picrotoxin-induced myoclonus in rats pretreated with either AOAA or submyoclonic dose of allylgylycine. Clonazepam pretreatment inhibited both picrotoxin and allylglycine-induced myoelonus whereas AOAA was effective in inhibiting only picrotoxin-induced myoclonus. The protective effect of clonazepam against picrotoxin-induced myoclonus was potentiated by AOAA pretreatment. Moreover, clonazepam afforded protection against picrotoxin-induced myoclonus in rats pretreated with a submyoclonic GABA reducing dose of allylglycine. These findings indicate that a GABA independent mechanism may also be involved in the antimyoclonic action of clonazepam.
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PMID:The antimyoclonic action of clonazepam through a GABA--independent mechanism. 262 Sep 67


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