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

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

Scalp topography of the giant SEP and the pre-myoclonus spike demonstrated by jerk-locked back averaging was studied by using a computer-assisted evoked potential mapping technique in 5 patients with cortical reflex myoclonus. The initial positive peak of giant SEP was localized to the postcentral region contralateral to the stimulus and was associated with a negative potential field of the same latency at the frontal region in all cases. The main positive peak of pre-myoclonus spike was localized to the postcentral region contralateral to the myoclonus in 4 cases, and maximal at the midline postcentral region extending contralaterally with respect to the myoclonus in 1 case. The postcentral positive peak was associated with a frontal negativity in 2 of the 5 cases. In those 2 cases, the main components of giant SEP and the pre-myoclonus spike showed a similar scalp distribution with respect to the hand which was stimulated or myoclonic jerks were recorded from, although the latter was much smaller and less sharp than the former. These findings support our previous hypothesis that those 2 activities might be generated, at least in part, by common physiological mechanisms. In 3 other cases, however, the postcentral positive peak of the pre-myoclonus spike was not associated with a frontal negativity.
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PMID:Scalp topography of giant SEP and pre-myoclonus spike in cortical reflex myoclonus. 170 17

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

The technique of transcranial magnetic stimulation of the motor cortex is a new neurophysiological examination of the central motor pathways. In clinical application a reduced MEP/M wave amplitude ratio had a higher correlation with hyperreflexia than did a delayed MEP onset latency. The inhibitory period (IP) which is a transient suppression of muscle action potentials following motor evoked potentials (MEP) by magnetic cortical stimulation is caused primarily by inhibitory process in the motor cortex, because the duration of IP did not depend on the amplitude of MEPs, MEP distribution over the motor cortex or severity of voluntary contraction. Furthermore, the IP was shorter and the amplitude of MEP was increased when ipsilateral motor cortex stimulation to the thenar muscle preceded the contralateral cortex stimulation. C response in a patient with familial essential myoclonus was significantly suppressed by the magnetic stimulation of the sensory cortex locally and during the IP. The uncrossed pyramidal tract was proved by motor cortex stimulation in a patient with hemorrhage in the right thalamus and internal capsule who showed a right hemiparesis. The enhancement of cortical SEP amplitudes (P23 and N30) were noted when the median nerve was stimulated at 50 msec following magnetic stimulation over the sensory cortex locally. SEPs by twin coil stimulation at thoracic and lumbar root levels are useful in detecting the lesions of spinal cord or roots. Sympathetic skin responses and sudomotor potentials are recorded easily by the neck magnetic stimulation, and are useful method for evaluating sympathetic nerve function.
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PMID:[Transcranial magnetic stimulation]. 777 29

An 18-year-old male manifesting intellectual deterioration and negative myoclonus was diagnosed as Lafora disease by the demonstration of Lafora bodies in the skin and muscle biopsy. The cortical evoked potential to electric stimulation of the median nerve at wrist showed the giant SEP, suggesting hyperexcitability of the sensory motor cortex. Cerebral blood flow, and cerebral glucose and oxygen metabolism were investigated by positron emission tomography (PET) in order to clarify the pathophysiological process in Lafora disease. The result showed diffusely decreased cortical glucose metabolic rate and cerebral blood flow, and moderately lowered oxygen metabolic rate. There was no increase in blood flow or glucose and oxygen metabolism in the sensorimotor cortex in spite of the presence of giant SEP. The ratio of the glucose to oxygen metabolism was not different from the mean value obtained from nine normal subjects. Based on these findings and review of the literature, it is unlikely that there is a significant deficit in cortical energy metabolism in patients with Lafora disease and it would be less plausible to have some enzymatic deficits in glucose metabolic process.
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PMID:[Cerebral blood flow and metabolism in Lafora disease]. 778 Dec 35

A 59-year-old female patient with atypical chronic herpes simplex encephalitis was reported. Initial symptom was persistent myoclonus involving the trunk and limb muscles, and later lateral gaze palsy to the left side, cerebellar ataxia, consciousness disturbance and other brainstem symptoms including absence of corneal and gag reflex and vocal cord palsy developed. The patient was successfully treated with high dose of acyclovir. Electroencephalogram was normal in the initial stage but later showed diffuse slow waves. Although CT scan and MRI showed no abnormal finding in the cerebral cortex, brainstem lesion was observed on PD weighted image of MRI. Lumbar puncture yielded a clear cerebrospinal fluid, with slightly elevated protein, increased lymphocytes, and elevated titer of herpes simplex virus type I. The serological data, albumin ratio (10.3), antibody index (12.3) and antibody ratio (7.1) were consistent with herpes simplex encephalitis. Ten days' administration of acyclovir, 1,200 mg a day and repeated three times, was prominently effective for the myoclonus and consciousness disturbance. A diagnosis of chronic herpes simplex encephalitis initially presenting with brainstem encephalitis was made. Judging from the clinical and EEG findings, the brainstem lesion was initially thought to be a cause of myoclonus in this case. However, somatosensory evoked potential (SPE) of both upper and lower extremities revealed enlarged amplitude (giant SEP), and long loop reflex was enhanced (C-reflex) on the left. Giant SEP and C-reflex imply cerebral cortex as the origin of the myoclonus. Brainstem inflammatory lesion might have involved the ascending inhibitory system, thus disinhibiting the cortical sensorimotor area and causing cortical myoclonus.
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PMID:[Chronic herpes simplex encephalitis initially presenting with persistent myoclonus]. 826 1

This report describes a patient with degenerative type of progressive myoclonus epilepsy (PME), who showed slowly progressive deterioration of the central nervous system; intellectual impairment, dysarthria, and involuntary movements, particularly action myoclonus and dystonia. The patient was a 19-year-old woman who had no hereditary factors. At the age of 4, she developed action myoclonus in the upper limbs bilaterally. Her condition became gradually worse, and at the age of 15, she was admitted to our hospital because of involuntary movement in the upper limbs. First physical examination revealed mild mental retardation, action myoclonus, dystonia, and delayed adolescence. As giant SEP characteristic of PME and Ramsay Hunt syndrome was found, she was tentatively diagnosed as having Ramsay Hunt syndrome without epilepsy, and delayed adolescence. Now, she is 19 years old, and unable to walk alone because of involuntary movements and paralysis. But she has not developed epilepsy. As she has not been compatible with progressive myoclonus epilepsy (PME) and progressive myoclonic ataxia (PMA) classified by Marseille Consensus Group, she has been diagnosed as having an atypical PME syndrome.
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PMID:[A case of degenerative type of progressive myoclonus epilepsy]. 841

Magnetic stimulation (MS) was performed in 9 patients with clinically diagnosed corticobasal degeneration (CBD), 10 patients with Parkinson's disease (PD) (under L-dopa therapy) and 10 age-matched healthy subjects (HS). Motor evoked potentials (MEPs) were recorded from the abductor pollicis brevis muscle (APB) in response to cortical stimulation and cervical stimulation (C7). In all patients with CBD, the duration of inhibitory period (IP), which was a transient suppression of muscle action potentials following MEPs by cortical stimulation, was significantly shorter than that in PD and HS. In 4 patients with CBD who presented with focal and distal myoclonus of one limb, long latency reflexes following electrical stimulation of the median nerve showed C-reflex, which had a latency of about 40 ms, but a giant SEP and a jerk-locked cortical potential were not demonstrated. With cervical MS, these 4 patients also showed long-latency (about 30 ms) evoked potentials (LEPs), which were much greater in latency from cervical stimulation-induced MEPs (cervical MEPs). LEPs may be mediated via a transcortical loop, because the sum of the latency of C-reflex and compound muscle action potential approximates that of LEP and cervical MEP. In patients with CBD, these findings suggest disturbance within the basal ganglia-thalamocortical motor circuit and a damage of the motor cortices including the primary motor cortex, premotor cortex and supplementary motor cortex.
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PMID:[A study of magnetic stimulation in patients with clinically diagnosed corticobasal degeneration]. 950 65


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