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

Several lines of clinical evidence suggest that myoclonus is caused by a reduction of serotonin in the brain and hyperactivity of the inferior olive. We determined whether a change in serotonin content within the olivocerebellar system accompanied a predisposition to myoclonus and investigated the necessity of the inferior olive for a myoclonic seizure. The experiments employed the genetically epilepsy-prone rat that exhibits a profound myoclonic seizure in response to an auditory stimulus. We found that these animals demonstrated a significant reduction in the serotonergic innervation of the inferior olive without a significant change in the serotonergic innervation at any other level of the olivocerebellar circuit. The deficit in olivary serotonin was verified physiologically and pharmacologically by a reduced sensitivity of the genetically epilepsy-prone rat to the tremorogenic effect of harmaline, which is known to produce tremor through a mechanism that requires serotonergic innervation of the inferior olive. We quantified the timing of the myoclonic seizure of the genetically epilepsy-prone rat and found that its large amplitude 2-6 Hz clonus was always preceded by 9-10 Hz tremor that was synchronized among limbs. Ablation of the inferior olive by 3-acetylpyridine abolished the myoclonic seizure. The specificity of the deficit in olivary serotonin, the timing of the seizure, and the demonstration of the necessity of the inferior olive for myoclonus suggest that pathological inferior olivary activity contributes to the genesis of a myoclonic seizure.
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PMID:Removal of the inferior olive abolishes myoclonic seizures associated with a loss of olivary serotonin. 948 43

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1) is a rare, autosomal recessive disorder characterized by onset at age 6-16 years, generalized seizures, incapacitating myoclonus, and variable progression to cerebellar ataxia. The gene that causes EPM1, cystatin B, encodes a cysteine proteinase inhibitor. Only a minority of EPM1 patients carry a point mutation within the transcription unit. The majority of EPM1 alleles contain large expansions of a dodecamer repeat, CCC CGC CCC GCG, located upstream of the 5' transcription start site of the cystatin B gene; normal alleles contain two or three copies of this repeat. All EPM1 alleles with an expansion were resistant to standard PCR amplification. To precisely determine the size of the repeat in affected individuals, we developed a detection protocol involving PCR amplification and subsequent hybridization with an oligonucleotide containing the repeat. The largest detected expansion was approximately 75 copies; the smallest was approximately 30 copies. We identified affected siblings with repeat expansions, of different sizes, on the same haplotype, which confirms the repeat's instability during transmissions. Expansions were observed directly; contractions were deduced by comparison of allele sizes within a family. In a sample of 28 patients, we found no correlation between age at onset of EPM1 and the size of the expanded dodecamer. This suggests that once the dodecamer repeat expands beyond a critical threshold, cystatin B expression is reduced in certain cells, with pathological consequences.
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PMID:A PCR amplification method reveals instability of the dodecamer repeat in progressive myoclonus epilepsy (EPM1) and no correlation between the size of the repeat and age at onset. 952 56

Thyrotropin-releasing hormone (TRH) is sometimes used for the treatment of neurologic disorders such as intractable epilepsy and spinocerebellar degeneration. A 14-year-old girl with progressive myoclonus epilepsy was treated with intravenous TRH for 12 months. Clinical symptoms, such as cortical myoclonus and cerebellar signs, were improved, and P25-N33 amplitudes of somatosensory-evoked potentials decreased after TRH therapy. P100 amplitudes on flash visual-evoked potentials and photosensitivity on electroencephalograms also decreased but only temporarily. Changes in neurophysiologic findings after TRH therapy indicate that TRH inhibits hyperexcitability in the sensorimotor cortex and the visual cortex. Therefore, intravenous TRH therapy is recommended as an alternative therapy in the treatment of progressive myoclonus epilepsy.
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PMID:Successful treatment of progressive myoclonus epilepsy with TRH. 965 Jun 89

Progressive myoclonus epilepsy of the Unverricht-Lundborg type is the most common cause of progressive myoclonus epilepsy worldwide. Typical features include onset at the age of 6-15 years, stimulus-sensitive myoclonus, tonic-clonic seizures, a progressive course and characteristic electroencephalographic findings with an exceptionally high sensitivity to photic stimulation. With modern anticonvulsive therapy the symptoms are relatively well controlled, and the disease may not always progress. Previously, no biochemical or pathological marker existed for the diagnosis of Unverricht-Lundborg disease. The positional cloning strategy was applied to identify the genetic defects that are responsible for this disease. The underlying gene encodes cystatin B, a cysteine protease inhibitor. The major mutation worldwide is an unstable expansion of a dodecamer minisatellite repeat unit in the promoter region of the cystatin B gene. In addition, five 'minor' mutations have been described. In the majority of patients, a reduced level of the cystatin B gene product seems to be the primary mechanism in the pathology, but the pathogenetic mechanisms are yet unknown. The molecular genetic findings have made a specific diagnosis possible and are the basis for understanding the molecular pathogenesis of the disease. This understanding may lead to the development of specific therapies for Unverricht-Lundborg disease.
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PMID:Clinical features and genetics of progressive myoclonus epilepsy of the Univerricht-Lundborg type. 981 34

Progressive myoclonus epilepsy of the Lafora type or Lafora disease (EPM2; McKusick no. 254780) is an autosomal recessive disorder characterized by epilepsy, myoclonus, progressive neurological deterioration and glycogen-like intracellular inclusion bodies (Lafora bodies). A gene for EPM2 previously has been mapped to chromosome 6q23-q25 using linkage analysis and homozygosity mapping. Here we report the positional cloning of the 6q EPM2 gene. A microdeletion within the EPM2 critical region, present inhomozygosis in an affected individual, was found to disrupt a novel gene encoding a putative protein tyrosine phosphatase (PTPase). The gene, denoted EPM2, presents alternative splicing in the 5' and 3' end regions. Mutational analysis revealed that EPM2 patients are homozygous for loss-of-function mutations in EPM2. These findings suggest that Lafora disease results from the mutational inactivation of a PTPase activity that may be important in the control of glycogen metabolism.
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PMID:A novel protein tyrosine phosphatase gene is mutated in progressive myoclonus epilepsy of the Lafora type (EPM2). 993 43

This paper reviews existing publications on the use of piracetam for the treatment of cortical myoclonus of various etiologies and includes the personal experience of the authors in progressive myoclonus epilepsy. Two double-blind comparisons with placebo provided results which allow recommendations for the dosage and usage of piracetam in cortical myoclonus. Wide individual variation (7-24g daily) exists in dosage requirements but responses are dose-related so that dosage should be increased until an optimum effect is obtained. Tolerability after long-term use of piracetam in high dosage has been very good and without toxicity or serious adverse effects. Side effects have been occasional, mild and transient. The authors present their experience of 12 patients with progressive myoclonus epilepsy in whom the administration of up to 45 g piracetam daily, when added to existing anti-epileptic treatment, caused marked and sometimes spectacular improvement and was without significant adverse effects. Improvement was maintained for up to 7 years. The use of piracetam for disabling cortical myoclonus of any etiology, either as an addition to existing antimyoclonic drugs or as monotherapy, may bring about profound improvement in disability and quality of life. Piracetam should be considered a first-line drug for the treatment of cortical myoclonus.
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PMID:Piracetam in the treatment of cortical myoclonus. 1033 9

A 20-year-old Japanese woman was diagnosed as suffering from adult type A neuronal ceroid lipofuscinosis (NCL) by rectal biopsy in the first year of manifestation. Her sister was in good health, and her parents were non-consanguineous. She had graduated from a public high school and then went to a typist school, when she developed action myoclonus and dystonia. On admission, she was of short stature and her clinical features included high arched palate, cataracta, and accentuated deep tendon reflexes. Her IQ was 50. Visual failure was not observed. Brain MRI showed no abnormalities. Together with myoclonus and the abnormalities in EEG which included poly spike and wave complex, progressive myoclonus epilepsy was considered as differential diagnoses. Ultrastructurally, lipopigments of granular matrix and curvilinear profile were found in Schwann cells in rectal biopsy. Adult NCL, known as Kufs' disease, is classified into two clinical types; progressive myoclonus epilepsy (type A) and dementia with motor disturbance (type B). Adult NCL is very rare in Japan, and this is the first report of adult NCL type A in Japan.
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PMID:[A case of adult neuronal ceroid lipofuscinosis type A]. 1039 79

Progressive myoclonus epilepsy of the Unverricht-Lundborg type (EPM1; MIM 254800) is an autosomal recessive disorder characterized by seizures, myoclonus and progression to cerebellar ataxia. EPM1 arises due to mutations in the cystatin B (CSTB) gene which encodes a cysteine proteinase inhibitor. Only a minority of EPM1 alleles carry point mutations, while the majority contain large expansions of the dodecamer CCCCGCCCCGCG repeat which is present at two to three copies in normal individuals. The dodecamer repeat is located in the 5' flanking region of the CSTB gene, presumably in its promoter. The pathological repeat expansion results in a reduction in CSTB mRNA, which may be cell specific. To elucidate the mechanism of this reduction of gene expression, we have studied the putative CSTB promoter in vitro. A 3.8 kb fragment, containing the putative promoter with a 600 bp repeat expansion, showed a 2- to 4-fold reduction in luciferase activity compared with an identical fragment with a normal repeat; this reduction was observed only in certain cell types. Introduction of heterologous DNA fragments of 730 and 1000 bp into the normal promoter, instead of the repeat expansion, showed similarly reduced activity. Terminal deletions of the promoter implicate a putative AP-1 binding site, upstream of the repeat, in CSTB transcription activation. We propose that a novel mechanism of pathogenesis, the altering of the spacing of transcription factor binding sites from each other and/or the transcription initiation site due to repeat expansion, is among the causes of reduction in CSTB expression and thus EPM1.
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PMID:Altered spacing of promoter elements due to the dodecamer repeat expansion contributes to reduced expression of the cystatin B gene in EPM1. 1044 45

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is characterized by onset at age 6-15 years, stimulus-sensitive myoclonus, tonic-clonic seizures, and typical EEG findings, with marked sensitivity to photic stimulation. Previously the course of the disease was progressive throughout the life, and no biochemical or pathologic marker existed for the diagnosis of EPM1. With modern anticonvulsive therapy, the prognosis has improved significantly, the symptoms are nowadays relatively well controlled, and the disease may not always progress. Moreover, the molecular genetic findings have now made possible an etiologic diagnosis of EPM1. The positional cloning strategy was applied to identify the gene whose defects are responsible for EPM1. The underlying gene encodes cystatin B, a cysteine protease inhibitor. The major mutation worldwide is an unstable expansion of a dodecamer minisatellite repeat unit in the promoter region of the cystatin B gene. In addition, five "minor" mutations have been described. Cystatin B mutations are now known to account for both Mediterranean myoclonus and for "Baltic" myoclonus, described mainly from Finland, thus solving a long-term controversy and proving that these two disorders are one single disease entity. The pathogenetic mechanisms in EPM1 are yet unknown, but in the majority of patients, a reduced level of the cystatin B gene product seems to be the primary mechanism in the pathology. Understanding the molecular pathogenesis of EPM1 may lead to the development of specific therapies for the disease.
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PMID:Progressive myoclonus epilepsy of Unverricht-Lundborg type. 1044 47

A 7-year-old female with benign childhood epilepsy with centrotemporal spikes developed epileptic negative myoclonus (ENM) seizures during carbamazepine (CBZ) treatment. She had experienced nocturnal partial seizures since 5 years of age. Interictal electroencephalography demonstrated typical rolandic discharges. Valproate was first initiated at 6 years of age, but the seizures were uncontrollable. Carbamazepine was added and valproate withdrawn. The frequency of partial seizures did not decrease. Moreover, she had brief episodes of tone loss in each or both arms and eye blinking several weeks after CBZ introduction. Unilateral loss of arm tone corresponded to spike-and-wave discharges in the contralateral centrotemporal region, and a loss of tone in arms was associated with bilateral synchronous discharges. Eye blinking was also related to bilateral synchronous discharges and classified as a myoclonic seizure. The ENM and myoclonic seizures disappeared soon after CBZ withdrawal. Therefore the authors concluded that CBZ induced the ENM and myoclonic seizures in this patient. CBZ sometimes induces generalized seizures in the treatment of partial epilepsy and generalized epilepsy. CBZ-induced ENM seizures should be considered when a brief lapse of tone appears during CBZ treatment.
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PMID:Epileptic negative myoclonus induced by carbamazepine in a child with BECTS. Benign childhood epilepsy with centrotemporal spikes. 1051 96


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