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

Electroencephalographic studies were carried out in 30 patients with various kinds of myoclonus. It was confirmed that the technique of jerk-locked averaging with a backward averaging program was useful for detecting cortical spikes in association with the spontaneously occurring myoclonus, which are not recognized on the convential polygraph, and for evaluating the temporal and topographical relationship between the spike and the myoclonus. By this technique, cortical spikes were shown to precede the myoclonus of a contralateral upper extremity muscle by 7 to 15 ms ith progressive myoclonic epilepsy showed a high amplitude somatosensory evoked potential (SEP) in response to electrical stimulation of the median nerve. The N33 component of this high amplitude SEP was found to be similar to the myoclonus-related cortical spike in their wave form, time relationship and topographical distribution, suggesting an involvement of similar physiological mechanisms in the genesis of both phenomena. Myoclonus in these patients is compatible with "pyramidal" or "cortical loop reflex" type.
 ...
PMID:Electroencephalographic studies myoclonus. 10 Dec 79

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.
 ...
PMID:Methyl bromide myoclonus: an electrophysiological study. 232 37

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.
 ...
PMID:Electroencephalographic correlates of myoclonus. 308 Aug 53

Recovery functions of somatosensory evoked potentials were studied by the paired stimulation technique in 61 patients with various neurological disorders. A less suppressive or hyperexcitable phase at short intervals, which had been shown in myoclonic patients, was seen in 22 patients. This abnormality was observed even in patients without myoclonus or involuntary movements, which suggests that this phenomenon is not mainly due to some dysfunction causing myoclonus or movement disorders. Less suppression at short intervals was observed for both N20-P25 and P25-N33 components in most of them. Less suppressive recovery of the N20-P25 component with normal recovery of the P25-N33 component was shown only in 3 patients with subcortical lesions with relative sparing of the cortical elements (Binswanger's subcortical encephalopathy). We conclude that less suppressive recovery of only the N20-P25 component suggests the presence of subcortical lesions.
 ...
PMID:Somatosensory evoked potential recovery (SEP-R) in various neurological disorders. 896 65

A 66-year-old man with clinically diagnosed corticobasal degeneration was studied electrophysiologically. The patient had bilateral forced grasping, rigidity, bradykinesia and hyperreflexia which were predominant on the right side, motor aphasia, constructional apraxia, forced laughing, dysequilibrium and myoclonus of the right upper extremity. Several anti-parkinsonism drugs were ineffective. Brain MRI revealed cortical atrophy of the fronto-temporo-parietal lobes with left predominance. On single photon emission computed tomography, cerebral blood perfusion was decreased, especially on the left side in the fronto-temporal lobes, basal ganglia and thalamus. Myoclonus was distal dominant, worse on action or posture, and was rhythmic, mimicking a tremor. On surface EMG recording of the myoclonus, agonist and antagonist muscle pairs were activated simultaneously and rhythmic activities with frequencies ranging from 7 to 8 Hz were seen. The patient had an enhanced C reflex with a relatively short latency (41.0 ms) after median nerve stimulation only at the right wrist. Additionally, during voluntary contraction, the time-constant EMG silence lasting for about 80-90 ms followed the C reflexes. On somatosensory evoked potentials (SEPs) to the median nerve stimulation, N20 latencies were normal and P25 and N33 amplitudes were not giant. There was no premovement corticat spike when a jerk-locked averaging method was used. Regarding motor evoked potentials (MEPs) elicited by magnetic brain stimulation, central motor conduction times were normal. The estimated cortical delay between the arrival of a somatosensory volley and the motor cortical discharge responsible for C reflex was 1.0 ms, which was shorter than those (3.1 +/- 0.9 ms) estimated in five patients with typical cortical reflex myoclonus. A conditioning stimulation (C) of the right median nerve produced marked facilitation of MEPs following magnetic stimulation of the left motor cortex, at conditioning-test intervals (C-T intervals) of 20-22 ms, whereas a conditioning stimulation of the left median nerve did not produce the same effect. These C-T intervals were thought to be very short, considering that N20 latency was 19.6 ms in this patient. The duration of the EMG silence following the C reflex corresponded to that of the EMG silence between muscle activities during his rhythmic myoclonus, and also the myoclonus was reset by occurrence of the C reflex. These electrophysiological findings indicate that his myoclonus was based upon the enhancement of direct sensory input from the thalamus to the motor cortex. Moreover, it is suggested that the existence of the time-constant EMG silence following the C reflex was related to the myoclonal rhythm.
 ...
PMID:[Electrophysiological study of a case of clinically diagnosed corticobasal degeneration with rhythmic myoclonus]. 950 71

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.
 ...
PMID:Successful treatment of progressive myoclonus epilepsy with TRH. 965 Jun 89

We report a 23-year-old woman who slowly developed progressive tremulous myoclonus and rare convulsive seizures beginning at the age of 9 and 11 years, respectively. She also showed a mild degree of ataxia and cognitive dysfunction. Convulsive seizures were well suppressed by valproic acid since the age of 17 years, but tremulous myoclonus gradually progressed and became rather intractable in spite of treatment by clonazepam and piracetam. Her cognitive dysfunction was mild (total IQ score in Wechsler Adult Intelligence Scale Revised being 85 points). In addition, she had a fear of walking which disabled her in the daily life although she could actually walk without assistance. The brain MRI showed a mild cerebellar atrophy, and FDG-PET showed a mild hypometabolism in the cerebellar hemispheres. Somatosensory evoked potentials (SEPs) showed enlarged P25 and N33 amplitudes (giant SEPs). A Cystatin B gene analysis exhibited a homozygous expansion of the dodecamer repeat, and thus we made a diagnosis of Unverricht-Lundborg disease (ULD). We also did gene analysis and SEP study to her parents after written informed consents were obtained. They had heterozygous expansion of the dodecamer repeat. The mother also showed enlarged P25 and N33 amplitudes, whereas the father showed normal amplitudes. It is known that degree of clinical symptoms varies among patients with ULD diagnosed by gene analysis. Gene analysis was helpful for a diagnosis of ULD in this patient because the ataxia and cognitive dysfunction were much milder than those commonly seen in patients with ULD.
 ...
PMID:[Unverricht-Lundborg disease manifesting tremulous myoclonus with rare convulsive seizures: a case report]. 1922 96