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)

An 11-year-old girl who had the positive-negative myoclonus and the history of the generalized tonic clonic seizure was electrophysiologically studied. She had no siblings with either myoclonus or epilepsy, and her intellectual level was normal. She had no other neurological deficits including ataxia, pyramidal and extrapyramidal signs. Surface EMG showed a brief increase in the EMG activity followed by the silent period associated with positive and negative myoclonus during sustained wrist extension. Giant SEP and C reflex (38.6 ms) following electric stimulation of the median nerve at the wrist were obtained in the resting condition and the silent period (about 180 ms) following C reflex was obtained during voluntary contraction. Jerk-locked back averaging of the EEG time-locked to the onset of the myoclonic discharge recorded from the right biceps muscle showed a cortical spike at the left central region preceding the myoclonus onset by 12.6 ms. The latency of C reflex in this case was very short compared with that of previously reported cortical reflex myoclonus. The estimated cortical delay between the arrival of the somatosensory volley and the motor cortex discharge responsible for the C reflex was -1.0 ms and this value was shorter than that in patients with typical cortical reflex myoclonus (mean 3.7 +/- 1.1 ms). Conditioning stimuli (C) of the right median nerve at the wrist started to facilitate the amplitude of the motor evoked potential recorded from the right abductor pollicis brevis muscle after magnetic test stimuli (T) of the left motor cortex at 20 ms of the C-T interval. This C-T interval was shorter than that (24.6 +/- 1.6 ms) in patients with the typical cortical myoclonus. These electrophysiological findings suggested the shorter reflex pathway of the cortical reflex myoclonus in this case than in typical cortical reflex myoclonus. We speculated that the myoclonus was based upon the direct sensory projection from the thalamus to the motor cortex in this case.
 ...
PMID:[A case of cortical reflex positive-negative myoclonus--electrophysiological study]. 950 69

We report a patient with familial myoclonus showing an extremely benign clinical course. The patient was a 70-year-old woman, who first noticed shaking of hands at age of 25. The symptom did not worsen for more than 40 years. She visited our hospital at the age of 70 because of disturbance in chores because of worsening of her hand shaking in the past one year. A family history showed that 4 members had similar symptoms and that the two were afflicted with fits of loss of consciousness. On neurologic examination, rhythmic myoclonic jerks were noted in all the extremities, more in the upper limbs, both at rest and during action. Tandem gait was mildly disturbed. The remainings of neurologic examination were normal. SEP and jerk-locked back averaging provided evidence of cortical myoclonus. EEG showed multifocal polyspike discharges. Gene analysis for DRPLA, pyruvate and lactate levels in serum and the cerebrospinal fluid, serum amino acid levels, and CSF HVA and 5-HIAA levels were all normal. No brain atrophy was noted in cranial MRI. Myoclonus was markedly reduced after administration of clonazepam. The clinical features and electrophysiological data of our patient are consistent with the clinical diagnosis of familial essential myoclonus and epilepsy/benign adult familial myoclonic epilepsy.
 ...
PMID:[A case of familial myoclonus showing extremely benign clinical course]. 980 89

Myoclonus, defined as shock-like involuntary movement, may be physiological or caused by a very wide variety of hereditary and acquired conditions. Because myoclonus can originate from different disorders and lesions affecting quite varied levels of the central and peripheral nervous systems, it represents from many points of view a diagnostic challenge. Moreover, new entities have been recently individualized, such as cortical tremor, which deserve renewed attention. The aim of this review is to propose a rationale for a diagnostic approach based on clinical and electrophysiological grounds. In this setting, we successively address 1) the clinical features allowing a positive diagnosis of myoclonus; 2) the clinical clues to the etiology; 3) the relevance of the clinical context to the diagnosis; and 4) the contribution of neurophysiology. Differentiating myoclonus from tics, spasm, chorea and dystonia can be difficult, and a careful reappraisal of clinical features allowing precise identification is presented. Moreover, the topographical distribution of myoclonus, the temporal pattern of muscle recruitment, the condition of occurrence and the rhythm of the event, may provide clinical clues relevant to the diagnosis. Myoclonus without associated epilepsy, myoclonus with epilepsy, myoclonus with encephalopathy, parkinsonism and/or dementia represent overlapping clinical categories, although they remain useful for the diagnostic approach. Using electrophysiology (including back-averaging EEG, MEG, SEP, C-reflex studies) to determine the origin of myoclonus may not allow us to focus on the underlying condition. Indeed, in many instances, the myoclonus is cortical in origin, but the pathology is found elsewhere.
 ...
PMID:[Myoclonus in the adult: diagnostic approach]. 1128 Oct 67

A 43-year-old man was admitted to our hospital due to unstable walking, head tilting to the left and difficulty in extending his arm. He was quite healthy until the age of 20 years, when these symptoms appeared and progressed slowly afterward. Due to his unstable walking, he started to use a wheelchair when he was 39 years old. He had no family history of similar disease. On admission, neurological examination revealed spasmodic torticollis, ataxic speech and marked limb and truncal ataxia. Myoclonic jerky flexion of the forearm was induced when he raised and extended his forearm. He also showed mild hyperreflexia in the lower limbs without pathological reflexes. He had weakness and atrophy of the left supraspinatus, infraspinatus, deltoid and biceps brachii muscles and mild superficial sensory impairment in the left axillary nerve territory due to cervical spondylotic radiculopathy of the left C5 root. MRI of the brain demonstrated severe bilateral atrophy of the cerebellar hemispheres and vermis but minimal atrophy of the cerebrum and brainstem. Because surface electromyography revealed continuous discharge with phasic components in the biceps and wrist flexor muscles on extending the upper limbs, the jerky flexion movement of the forearm was considered to be primarily dystonia. Although no giant SEP was observed, a C-response was detected in the long-loop reflex in response to right median nerve stimulation. Nuclear examinations showed diffuse hypoperfusion and decreased glucose metabolism in the cerebellum. Based on these findings, we hypothesized that cerebellar dysfunction may have induced severe dystonic movement resembling myoclonus. We would like to name this complicated involuntary movement an "arm thrust". This is the first case to be reported of sporadic, chronic, progressive cerebellar ataxia accompanied by severe dystonic movement, especially on stretching the forearms, that mimics myoclonic movement.
 ...
PMID:[A case of cerebellar ataxia showing severe dystonia masquerading as myoclonic jerky movements on arm extension]. 1235 58

We investigated the association between clinical and neurophysiological characteristics in patients with a clinical diagnosis of probable corticobasal degeneration (CBD), and searched for neurophysiological features supporting the diagnosis in life. Ten patients with clinically probable CBD underwent comprehensive neurological evaluation and brain MRI. Long latency reflexes (LLR), upper limb somatosensory (SEP) and motor evoked (MEP) potentials were recorded. The mini-mental state examination (MMSE), the phonemic verbal fluency test (PVFT) and the De Renzi ideomotor apraxia test were also performed. Polygraphic EEG was performed in the six patients with myoclonus. The SEP N30 frontal component was absent bilaterally in four patients, was absent on the left side in one, and had increased latency in other three. MEPs were abnormal in four patients (three had prolonged central motor conduction time, one of whom also had increased MEP threshold, and one had increased MEP threshold). All six patients with myoclonus had enhanced LLRs at rest, which were also of abnormally increased amplitude during motor activation; latencies were generally shorter than in classic cortical reflex myoclonus. On back-averaging, no EEG spikes time-locked to EMG activity were found in any myoclonus patient. Five patients were demented by MMSE, eight had ideomotor apraxia scores in the ideomotor apraxia range and five had defective verbal fluency. Brain MRI revealed asymmetric cortical atrophy in all patients, particularly evident frontoparietally. Neurophysiological techniques, particularly LLR, can assist CBD diagnosis especially in patients with myoclonus. Patients with evident parkinsonism had greater SEP N30 (frontal) abnormalities, while most patients with marked paresis had slower MEP times.
 ...
PMID:Neurophysiological features in relation to clinical signs in clinically diagnosed corticobasal degeneration. 1275 52

We investigated the cortico-muscular coherence in a patient with posturally induced cortically originating negative myoclonus. We recorded simultaneously 50 channels EEG and EMG from quadriceps and biceps femoris muscles of the left upper leg. Three experimental conditions were investigated with the patient in a seated position: (i) recording during rest (Rest), (ii) recording while the patient had to hold his left leg horizontally stretched out (Postural), and (iii) recording while the patient had to hold his left leg horizontally stretched out against a vertical force (Postural against force). Coherence, phase difference and cumulant density were computed as indicators for cortico-muscular coupling. The cortical component preceding the silent period was shown by averaging and was reconstructed. During postural and postural against force conditions, the EEG over the vertex was significantly coherent with EMG, in alpha (7-15 Hz) and beta range (15-30 Hz). The strongest coherence peak was at 21 Hz. No high-frequency coherence was observed. The phase difference and the cumulant density estimate corresponded to a 32 ms time lag between motor cortex and muscles, with EEG leading. The broadening of the coherence spectrum at which the motor cortex drives the muscles together with the excessive coherence levels and the giant SEP could reflect the hyperexcitability of the sensorimotor cortex. The frequency content of the coherence may be characteristic for this type of myoclonus. The results lend support to the view that the frequency analysis may have some diagnostic potential in cortical myoclonus.
 ...
PMID:Cortico-muscular coupling in a patient with postural myoclonus. 1528 30

Generalized 1Hz, burst-and-slow-wave complexes were observed in a comatosed patient with acute disseminated encephalomyelitis (ADEM) when she showed extremely intractable, generalized convulsions and fragmented myoclonus in the whole body. Two types of short-latency SEPs were obtained separately during the burst and slow phase of the EEG (SEP-burst and SEP-slow, respectively), which showed a two fold greater amplitude of N20 in the former than in the latter. This suggests enhanced responsiveness to the peripheral stimuli during the burst phase as compared with the slow phase. CSF and serum were positive for autoantibodies to NMDA receptors. The "burst and slow complexes" reported here are considered to be an atypical EEG pattern of a generalized epileptic phenomenon.
 ...
PMID:"Burst and slow complexes" in nonconvulsive epileptic status. 1656 28

In median nerve somatosensory evoked potentials, the cortical N35 amplitude sometimes exceeds the P25 amplitude (C3'/C4' referred to Fz; "enhanced N35" feature). Six hundred consecutive patient median nerve SEPs were retrospectively analysed and compared with 27 controls. The feature was more often present in patients with dystonia (62%) than in patients with other disorders (22%; relative risk for the condition 2.8; Fisher's exact p=0.003) or control subjects (7.4%; odds ratio 20; p=0.0006). Similarly, the feature was more often present in patients with myoclonus (38%) than in patients with other disorders (22%; relative risk 1.7; p=0.02) or control subjects (odds ratio 7.5; p=0.006). There was no clear relationship of the feature to short latency SEP abnormalities except in cases of myoclonus. Further comparison was made of the characteristics of 72 patients each, with and without the feature, whose short latency SEP components were normal. The relationship of the feature to dystonia or myoclonus held true in this case-controlled arm of the study. The sensitivity and specificity were 65% and 78% respectively for any form of dystonia; 43% and 79% respectively for any form of myoclonus. The feature was even more specific in both conditions when compared with controls (93%). Most cases of dystonia with an identifiable cause in this study were of secondary forms. It is known that this feature often occurs in association with "giant" SEPs in some myoclonic conditions. However, its occurrence in dystonia may be a useful new finding in an established test, helping to identify a condition where there is increasing evidence for disordered sensorimotor integration.
 ...
PMID:The "enhanced N35" somatosensory evoked potential: its associations and potential utility in the clinical evaluation of dystonia and myoclonus. 1727 14

Enlarged cortical components of somatosensory evoked potentials (giant SEPs) recorded by electroencephalography (EEG) and abnormal somatosensory evoked magnetic fields (SEFs) recorded by magnetoencephalography (MEG) are observed in the majority of patients with cortical myoclonus (CM). Studies on simultaneous recordings of SEPs and SEFs showed that generator mechanism of giant SEPs involves both primary sensory and motor cortices. However the generator sources of giant SEPs have not been fully understood as only one report describes clearly giant SEPs following lower limb stimulation. In our study we performed a combined EEG-MEG recording on responses elicited by electric median and tibial nerve stimulation in a patient who developed consequently to methyl bromide intoxication CM with giant SEPs to median and tibial nerve stimuli. SEPs wave shapes were identified on the basis of polarity-latency components (e.g. P15-N20-P25) as defined by earlier studies and guidelines. At EEG recording, the SEP giant component did not appear in the latency range of the first cortical component for median nerve SEP (N20), but appeared instead in the range of the P37 tibial nerve SEP, which is currently identified as the first cortical component elicited by tibial nerve stimuli. Our MEG and EEG SEPs recordings also showed that components in the latency range of P37 were preceded by other cortical components. These findings suggest that lower limb P37 does not correspond to upper limb N20. MEG results confirmed that giant SEFs are the second component from both tibial (N43m-P43m) and median (N27m-P27m) nerve stimulation. MEG dipolar sources of these giant components were located in the primary sensory and motor area.
 ...
PMID:Giant early components of somatosensory evoked potentials to tibial nerve stimulation in cortical myoclonus. 2748 68

The high temporal resolution of neurophysiological recordings makes them particularly suited to faithfully describing the time course of rapid events such as myoclonus and to precisely measure its time relationship with other related activities. In progressive myoclonus epilepsies (PMEs) polygraphy with simultaneous EMG-EEG recordings is a crucial tool for defining the characteristic of myoclonic jerks their topography over different muscles (namely antagonists), their time course and relationship with vigilance muscle activation and stimulations. Moreover on polygraphic recordings it is possible to detect EEG activities associated to myoclonic jerks and define their time relationship with myoclonus thus differentiating cortical types of myoclonus from subcorticallly generated ones. Tanks to the back averaging technique non obvious time-locked EEG potentials can be detected on polygraphy , furthermore in stimulus sensitive myoclonus the analysis can include the potential evoked by the somatosensory stimulus (SEP). The polygraphic recording also gives information on muscle activity suppression occurring after jerk or as pure negative myoclonus. Besides the time domain analysis, techniques based on frequency analysis have been developed to evaluate EEG-EMG coherence. The neurophysiological techniques provide investigators and clinicians with an invaluable information to define the type of myoclonus and its generating circuitry thus substantially contributing in the diagnosis and management of PMEs.
 ...
PMID:Neurophysiology of myoclonus and progressive myoclonus epilepsies. 2770 8


<< Previous 1 2