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)

A 21-year-old woman, who had no particular familial history, was admitted to our hospital because of hand tremor and gait disturbance. On neurological examination, she showed muscle weakness in the proximal extremities. There was an ataxia on heel-to-shin testing. Action and postural myoclonus involving the extremities were also noted. In addition, with dorsiflexion of the hands, asterixis-like movement was manifested. Pyruvate was 1.0 mg/dl and lactate was 24.1 mg/dl in cerebrospinal fluid. Brain CT scan revealed mild cerebellar atrophy. EEG showed synchronous diffuse slow wave. Median nerve SEPs showed a large N20-P25 component (20 microV). Median nerve C-reflex was not evoked. With dorsiflexion of the hands, the asterixis-like movement was induced with brief cessation of surface EMG activity in the forearm muscles, as shown by the accelerometer trace. Biopsy specimens of the biceps brachii muscle revealed numerous ragged-red fibers. By PCR-RFLP method with use of a mismatched primer, we analyzed mitochondrial DNA extracted from peripheral leukocytes. The A to G mutation at nucleotide position 8,344 in a tRNA(Lys) gene of a mitochondrial genome was detected. In this patient, clonazepam was effective on the asterixis-like movements. From existence of positive myoclonus, giant SEPs and efficacy of clonazepam, we considered this movement to be negative myoclonus. Our study indicated the possibility that such an involuntary movement could be induced by certain posture in patients with MERRF.
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PMID:[Myoclonus epilepsy associated with ragged-red fibers--report of a patient with negative myoclonus]. 149 Mar 14

Three brothers with dyssynergia cerebellaris myoclonica received alcohol to study the correlation between improvement of myoclonus and alteration in somatosensory evoked potentials (SEPs). Alcohol considerably improved myoclonus for about six hours in two patients (cases 1 and 2) but had only a mild effect in one (case 3). All three patients had giant cortical SEPs. The amplitudes of median N20-P25 and P25-N35 components and tibial N30-P40 and P40-N50 components were considerably decreased after alcohol ingestion in two patients (cases 1 and 2) but unchanged or slightly decreased in one (case 3). The peak latencies of those components were not affected by alcohol. There was thus a good correlation between the suppression of myoclonus and the decrease in giant SEP amplitude.
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PMID:Effects of alcohol on myoclonus and somatosensory evoked potentials in dyssynergia cerebellaris myoclonica. 174 45

To elucidate the sensitivity to pain stimuli in patients with cortical reflex myoclonus, pain-related somatosensory evoked potentials (pain SEPs) following CO2 laser stimulation and conventional electrically-stimulated SEPs (electric SEPs) were compared in four patients with cortical reflex myoclonus. The P25 peak of electric SEPs was considerably enhanced but the P320 potential of pain SEPs was of normal amplitude in all patients. After medication, myoclonus was reduced and the amplitude of P25 was decreased, but P320 showed no change. In our previous study of the scalp distribution in normal subjects, a subcortical site, probably the thalamus, was considered to be the generator source of P320. Because most pain stimuli do not reach the cortex, patients with cortical reflex myoclonus are not sensitive to pain stimuli and P320 in pain SEPs is not enhanced.
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PMID:Pain-related somatosensory evoked potentials in cortical reflex myoclonus. 210 12

We report a case of myoclonus from overnight exposure to methyl bromide. Myoclonus was either spontaneous or induced by somatosensory stimulation or voluntary movements, multifocal and sometimes generalized. Median SEP showed normal size P14-N20, but giant parietal P25, N33 and frontal P22-N30 waves. Back-averaging showed a biphasic EEG spike of maximal amplitude at the central region contralateral to the corresponding myoclonic jerk recorded from abductor pollicis brevis and preceding it by a short interval consistent with conduction in corticospinal pathways. Long latency reflexes from cutaneous and mixed nerve stimulation were enhanced. The above electrophysiological findings suggest that myoclonus following methyl bromide poisoning belongs to the cortical reflex myoclonus category.
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PMID:Methyl bromide myoclonus: an electrophysiological study. 232 37

Pathologically enhanced somatosensory evoked potentials (giant SEPs) were recorded in 10 patients with cortical myoclonus of various origins. With non-cephalic reference electrodes a giant frontal negativity corresponding to normal N30 was found over the contra- and ipsilateral hemispheres which was not simply a phase reversal of the well-known enhanced parietal P25. The preceding far-field P14, parietal N20 and frontal P22 were of normal size. A similar result was found when SEPs were studied during the action of etomidate, an ultrashort-acting non-barbiturate hypnotic which produced a marked increase of the parietal P25 and frontal N30 after intravenous administration. These increased components, on the other hand, were abolished when recording was repeated immediately after application of electroconvulsive shock whereas P14, N20, and P22 remained more or less unchanged in both conditions. Our results indicate that there are neuronal elements in the sensorimotor cortex which are more resistant to influences such as narcotic drugs and seizure activity than others, being highly modifiable by these alterations. It is speculated whether these highly modifiable cortical systems are those in which giant SEPs, as well as pharmacologically increased SEP components, arise.
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PMID:Frontal and parietal components of enhanced somatosensory evoked potentials: a comparison between pathological and pharmacologically induced conditions. 245 99

Fifty-five consecutive cases of myoclonus owing to various etiologies were studied by conventional EEG-EMG polygraphic recordings and/or jerk-locked or back averaging. The technique of back-averaging was shown to be useful not only for detecting EEG correlates of myoclonus that are not recognizable on the routine polygraph but also for investigating the temporal and topographic relationship between the EEG activities and myoclonus. Thirteen of 17 cases of PME and related disorders, in whom back-averaging and SEP were studied, were shown to have both a myoclonus-related cortical spike over the contralateral central area, preceding the myoclonus of an upper extremity by 6 to 22 msec, and a giant SEP accompanied by an enhanced C reflex. In these cases of "cortical reflex myoclonus," the myoclonus-related spike was similar to the P25-N33 components of the giant SEP in its wave form, scalp topography, temporal relationship to myoclonus or to C reflex, succeeding cortical excitability, and drug effect. All of this suggests participation of common physiological mechanisms in those two activities. In two cases of PME, in which myoclonus involved bilateral proximal muscles synchronously, the myoclonus-related spike was maximal near the vertex, and there was no giant SEP. The significance of this subgroup remains undetermined. In six cases of the PME group, back-averaging was inapplicable because of rare occurrence of myoclonus, but they showed a typical giant SEP accompanied by an enhanced C reflex. In CJD, back-averaging demonstrated a sharp wave or PSD over the contralateral hemisphere, preceding the myoclonus by 50 to 85 msec. This form of myoclonus seems to be subcortical in origin. In essential myoclonus and oculopalatal-somatic myoclonus, there was neither myoclonus-related cortical spike nor giant SEP. Electrical stimulation of the peripheral nerve at variable intervals after the myoclonus onset (jerk-locked-SEP paradigm) was shown to be useful for investigating the influence of myoclonus on cortical excitability.
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PMID:Electroencephalographic correlates of myoclonus. 308 Aug 53

In order to clarify the generator mechanisms for giant cortical evoked potentials, scalp topographies of somatosensory evoked potentials (SEPs) following various types of stimulation, including electrical nerve trunk and finger stimulation and mechanical stimulation, were investigated in 5 patients with cortical reflex myoclonus. For SEPs evoked by median nerve stimulation, not only the P25 and N34 components in central and parietal regions but also N25 in the frontal region were markedly enlarged in each patient. Their scalp distributions were not significantly different from those of normal subjects. P25 and N25, but not N34, were considerably attenuated by interfering tactile stimulation applied to the hand. The components corresponding to P25, N25 and N34 following electrical stimulation of the digital nerves as well as mechanical stimulation of the finger were also remarkably large and showed scalp distributions similar to those for median nerve SEPs. It is therefore concluded that the giant cortical SEPs of cortical reflex myoclonus are generated in those areas of the primary sensory cortex which generate normal SEPs, in response to an input, at least in part, from cutaneous afferents on the basis of an extremely enhanced cortical excitability.
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PMID:Generator mechanisms of giant somatosensory evoked potentials in cortical reflex myoclonus. 367 5

Giant and asymmetric SEPs were recorded in a patient with predominantly unilateral, spontaneous and intention myoclonus due to voluntary intoxication with methyl bromide as soon as day 3 after intoxication. The N10 Erb's point potential, cervical N13 and scalp recorded P15 potentials were found to be normal in latency, morphology and amplitude. The somesthetic informations could be considered as normally processed up to the subcortical levels of the somatosensory pathways. The parietal cortical potentials N20 and P25 and the frontal cortical potentials P22 and N30, contralateral to myoclonus, were abnormally large. This suggests that myoclonus could be related with an abnormal reactivity of somatomotor and somatosensory cortices to the afferent volleys triggered by voluntary movements. The prerolandic components P22 and N30 were found to be relatively more enhanced than the parietal N20 and P15.
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PMID:[Rare cause of myoclonus with giant SEP's: methyl bromide poisoning. Apropos of a case with unilateral predominance]. 404 10

Scalp topography of giant SEPs to median nerve stimulation was studied in 4 patients with cortical myoclonus of various etiology. The positive peak (P30) at the contralateral parietal area was simultaneously accompanied by a negative peak at the frontal area (N30), and at least one of these two peaks was enhanced in 2 patients. Another positive peak (P25) and a negative peak (N35) were also identified at the peri-rolandic area with different latency from P30 and N30, respectively, in all patients. N35 was enhanced in 3 patients, and P25 in 2 patients. It is concluded that, as seen in normal subjects, tangential (P30-N30) and radial (P25 and N35) components of SEPs are most likely distinguishable in giant SEPs, and that either one or both of those components is enhanced in different ways depending on the patients.
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PMID:Peri-rolandic and fronto-parietal components of scalp-recorded giant SEPs in cortical myoclonus. 763 75

We describe two similar patients with a clinical diagnosis of corticobasal ganglionic degeneration (CBGD). After a period of increased action tremor, both patients developed a fixed posture in the right arm with a slow rhythmic myoclonus, which appeared to be caused by trains of highly synchronized and stimulus sensitive myoclonic discharges. Resetting of the spontaneous myoclonic discharges by peripheral and central stimulation and a jerk-locked cortical potential were demonstrated in one case. The somatosensory evoked potentials (SEPs) showed abnormal parietal curves with small N20-P25 amplitudes and without giant SEP characteristics. The latencies of the cortical event and of the late responses, and the duration and distribution of the discharges compare best with those of the cortical reflex type of myoclonus. Localized parietal cortical damage, as indicated by clinical evidence and imaging techniques, may well explain the absence of a giant SEP in these patients with CBGD.
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PMID:Unique myoclonic pattern in corticobasal degeneration. 775 55


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