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PubMed1994

Spinal myoclonus resembling belly dance.

A 63-year-old man presented with an 11-month history of progressive myoclonus in the right abdominal wall. Administration of clonazepam reduced the frequency and amplitude. When the therapy was discontinued, the frequency and amplitude of the myoclonus increased, and synchronous and weak myoclonus also was observed in the left abdomen. The trunk was twisted just after the appearance of the abdominal myoclonus associated with myoclonic jerks spreading from the rostral to caudal paraspinal muscles. Later in the clinical course, the myoclonus became stimulus sensitive and was induced by tendon tap given anywhere on the body, with the latency ranging from 50 to 150 ms irrespective of the sites of tapping. Myoclonus seen in the abdominal wall was segmental and considered to be of spinal origin. The reflex myoclonus had a 150-ms refractory period. It can be postulated that increased excitability of anterior horn cells at a certain segment might make a spino-bulbo-spinal reflex manifest at the corresponding segment. This myoclonus is considered to be a new form of spinal reflex myoclonus, because the abdominal myoclonic jerk seems to trigger another myoclonic jerk involving the paraspinal muscles.

Abdominal Muscles↗
PubMed1990

Postural myoclonus associated with long-term administration of neuroleptics in schizophrenic patients.

Postural myoclonus associated with long-term administration of neuroleptics was demonstrated in schizophrenic patients. Sixty patients who had been taking neuroleptics for more than 3 months were investigated for myoclonus and the relationships between postural myoclonus and age, duration of illness, duration of medication, current daily dose, cumulative dose, occurrence of abnormal finger movement, parkinsonism, and tardive dyskinesia were evaluated. Twenty-three patients (38%) showed postural myoclonus when holding the hands forward with the elbow joints flexed at about 90%. Male patients showed a higher incidence of myoclonus than female patients. Patients with myoclonus had been given significantly higher doses of neuroleptics than those without myoclonus. There was a significant correlation between the occurrence of myoclonus and abnormal finger movement. Electromyographic recordings in 7 patients with prominent myoclonus revealed that arrhythmic jerks occurred in the extensor carpi radialis and posterior deltoid muscles and that the jerks on the left and right side were not synchronized. Clonazepam reduced the frequency of the myoclonic activity.

Adult↗
PubMed1991

Drugs influencing the GABAergic neurotransmission have no effect on the non-epileptic myoclonus of baboons.

In Papio papio baboons benzodiazepines can facilitate the appearance of a naturally occurring non-epileptic myoclonus, suggesting a possible role of GABAergic transmission in their physiopathology. Nevertheless, as this myoclonus is blocked by physostigmine, the effect of benzodiazepines is probably due to their indirect action on the cholinergic system. Therefore, in this study, we report the effects on the non-epileptic myoclonus of drugs influencing GABAergic transmission. Systemic injections of progabide (GABA precursor), baclofen (GABAB receptor agonist) and allylglycine (glutamic acid decarboxylase inhibitor) did not modify or induce the non-epileptic myoclonus. In the same way, localized chronic injections of GABA into various cerebral structures (prefrontal and motor cortical areas, reticular magnocellular nucleus and substantia nigra) had no effect. When the two types of myoclonus were present in the same photosensitive animal, the epileptic myoclonus induced by photic stimulation was blocked by benzodiazepines but was not influenced by physostigmine, thus differing from the non-epileptic myoclonus. This suggests that different neurochemical mechanisms are involved in the two types of myoclonus, the non-epileptic myoclonus not being directly influenced by the GABAergic transmission.

Animals↗
PubMed1998

Myoclonus and epilepsy in childhood: 1996 Royaumont meeting.

Sudden and brief involuntary movements of central nervous system (CNS) origin called myoclonus may be cortical (motor strip), thalamocortical (thalamocortical loop) or reticular (caudal reticular formation). Epileptic, cortical and thalamocortical myoclonus are combined with a spike which, when it is focal, needs back-averaging to be demonstrated. Negative myoclonus due to lapse of tone can only be demonstrated during antigravidic posture and may be combined with either a slow wave or the second, positive component of a polyspike-wave. Epileptic myoclonus must be distinguished from epileptic spasms and tonic seizures, and from non-epileptic myoclonus, tics, tremor and chorea. Myoclonus may occur in partial symptomatic (mainly Rasmussen and dysplasia), cryptogenic (frontal) or idiopathic (negative myoclonus in CSWS) epilepsy. Generalized myoclonus is part of inborn errors of metabolism, non-progressive encephalopathy (mainly Angelman) and idiopathic epilepsy (juvenile and infantile benign and severe forms, and myoclonic-astatic epilepsy). Carbamazepine, vigabatrin and eventually lamotrigine may worsen myoclonus whereas it may be improved by benzodiazepines, valproate, lamotrigine, zonisamide and piracetam according to etiology. Pathophysiology must take in account maturation processes, lesions and genetic predisposition. However, precise mechanisms remain unknown and only hypotheses can be proposed, that could clarify the age-related EEG and clinical expression of the various syndromes.

Anticonvulsants↗
PubMed2003

Exaggerated 16-20 Hz motor cortical oscillation in patients with positive or negative myoclonus.

BACKGROUND: Muscle jerks and their cortical correlates usually occur abruptly and arrhythmically in patients with positive or negative myoclonus. However, there have been several reports in which oscillatory pre-myoclonic cortical discharges occur in patients with repetitive myoclonus (Mov Disord 6 (1994) 633; Brain 119 (1996) 1307; Brain 124 (2001) 2459; Brain 126 (2003) 326). In the present paper, we describe 4 patients with non-repetitive positive or negative myoclonus whose jerks were preceded by 16-20 Hz oscillatory EEG potentials over the contralateral sensorimotor cortex. METHODS: Jerk-locked averaging (JLA) was performed in 3 patients with positive myoclonus two of which had benign familial myoclonus epilepsy whilst the other had tuberculous meningitis. Silent period locked averaging (SPLA) was performed in a patient with hepatic encephalopathy and asterixis. RESULTS: In the 3 patients with positive myoclonus, JLA revealed a sequence of 20 Hz EEG potentials preceding the myoclonus. The positive peak of the last oscillation preceded the onset of myoclonus by the cortico-muscular latency. In the patient with hepatic encephalopahty, SPLA showed that 16 Hz EEG oscillations over the contralateral motor cortex were associated with small EMG oscillations, and that the largest EEG wave of the oscillation preceded the onset of a large EMG discharge just prior to the EMG silence. These oscillatory activities are similar in frequency to the motor cortical oscillations seen in monkeys and humans during voluntary contraction. CONCLUSIONS: Abnormally enhanced rhythmic (16-20 Hz) activities in the motor cortex are associated with arrhythmic positive or negative myoclonus. The rhythmic activities may also be responsible for the generation of the tremulousness (or mini-asterixis) in metabolic encephalopahty.

Adult↗
PubMed2003

Myoclonus.

PURPOSE OF REVIEW: Myoclonus, one of the most common involuntary movement disorders, poses particular challenges for the treating physician. The evaluation of a patient with myoclonus depends completely on the clinical history and examination, supported when necessary by electrophysiology, neuroimaging and selected genetic and laboratory testing. The sudden, shock-like jerks which define myoclonus may be highly disabling, and when they persist, often require treatment. RECENT FINDINGS: In a paper published in this journal, we reviewed the published trials of antimyoclonic agents, and formulated a treatment algorithm based on the available evidence. In the current paper, we present our approach for evaluating patients with myoclonus, and suggest practical guidelines for treating patients based on the pre-2000 literature and on studies published in the last 2 years. The newer medications which are being used in management of myoclonus are levetiracetam and gamma-hydroxybutyric acid. Levetiracetam is especially useful for posthypoxic myoclonus and gamma-hydroxybutyric acid for alcohol-sensitive myoclonus. A combination of medications is often needed to obtain adequate control of symptoms. Botulinum toxin is also being introduced for focal myoclonus with encouraging results. SUMMARY: There are no approved medications for myoclonus, and most therapies are borrowed from the antiepileptic and psychiatric armamentarium. Nonetheless, there is a logic to the choice and dosing of antimyoclonic drugs, and we hope that by applying a few simple principles, neurologists will approach the care of these patients with confidence.

Anticonvulsants↗
PubMed1990

Idiopathic palatal myoclonus.

Two cases with idiopathic palatal myoclonus without other neurological deficits were described. They did not have any other neurological deficits other than myoclonus of branchial muscles. In these cases, the myoclonus disappeared during natural or induced sleep. In Case 1, the myoclonus ceased transiently when the patient was calculating or receiving an injection. In Case 2, the myoclonus disappeared with intravenous injection of saline as a placebo. Detailed examinations, including brain CT, MRI and multiple evoked potentials, showed normal results. The myoclonus in Case 2 disappeared after we had explained that her disease was benign. Since the clinical features and laboratory data in idiopathic palatal myoclonus are quite different from those in palatal myoclonus with other neurological deficits, idiopathic palatal myoclonus is considered to be a separate syndrome. Invasive examinations or excessive medications should be avoided because of its benign prognosis.

Adolescent↗
PubMed1976

L-5-hydroxytryptophan in treatment of several different syndromes in which myoclonus is prominent.

The serotonin precursor L-5-hydroxytryptophan is useful therapy for patients with posthypoxic intention myoclonus. L-5-hydroxytryptophan plus carbidopa was administered to eight patients with this disorder or other syndromes in which myoclonus is prominent. This treatment (1) decreased the frequency of occurrence and amplitude of intention myoclonus in two patients with posthypoxic intention myoclonus and in one with idiopathic myoclonus, (2) had no effect in one patient with congenital encephalopathy and myoclonus, and (3) increased the frequency of occurrence and amplitude of myoclonus in two patients with lipid storage disease, one with myoclonic epilepsy, and in an additional patient with idiopathic myoclonus. Therefore, L-5-hydroxytryptophan does not effect improvement in all forms of myoclonus; it should be given with caution because it produces a high incidence of side effects. A patient's response to L-5-hydroxytryptophan therapy may be important in a diagnostic classification of myoclonic syndromes based on differences in indoleamine neurotransmitter function.

5-Hydroxytryptophan↗
PubMed2004

Drug-induced myoclonus: frequency, mechanisms and management.

Myoclonus is a sudden, abrupt, brief, 'shock-like' involuntary movement caused by muscular contractions ('positive myoclonus') or a sudden brief lapse of muscle contraction in active postural muscles ('negative myoclonus' or 'asterixis'). Various disorders can cause myoclonus including neurodegenerative and systemic metabolic disorders and CNS infections. In addition, myoclonus has been described as an adverse effect of some drugs. Level II evidence is available to indicate that levodopa, cyclic antidepressants and bismuth salts can cause myoclonus, while there is less robust evidence to associate numerous other drugs with the induction of myoclonus. The pharmacological mechanisms responsible for this adverse effect are not well established, although increased serotonergic transmission may be involved in the induction of myoclonus by several drugs. Drug-induced myoclonus usually resolves after withdrawal of the offending drug, but in some cases specific treatments are needed.

Antacids↗
PubMed1991

[A case of familial essential myoclonus--electrophysiological study].

A case of familial essential myoclonus was reported with electrophysiological studies. A 58-year-old female presented with involuntary movement (myoclonic jerk) since age 6 years. At the age over 50, she developed difficulty in writing and fine finger movements. Two years ago, the diagnosis of hyperthyroidism was made, but she did not take any anti-thyroid medication. She was admitted to our hospital for further evaluation of myoclonus. On family history, her grandson (4-years-old) had myoclonus. On general physical examination, she showed a diffuse goiter. On neurological examination, she showed spontaneous myoclonus in the face, neck, trunk and the proximal limb muscles, especially in the left upper and right lower extremities. The myoclonus was exacerbated with auditory stimulation and emotional tension, but there was no temporal relationship between each stimulus and myoclonus. There was no myoclonus during sleep. Finger-to-nose test showed coarse intention myoclonus. Laboratory examinations including lysosomal enzyme assay revealed no abnormalities except for the decrease in total cholesterol (118 mg/dl) and the increase in serum lactate (19.7 mg/dl). The serum concentration of thyroxin was 18.4 micrograms/dl, that of triiodothyronine 3.0 ng/ml, and that of thyroid stimulating hormone (TSH) 0.027 microIU/ml. Anti-thyroglobulin antibody and anti-microsomal antibody were positive (X100, X6400). Neurological laboratory tests were normal including cerebrospinal fluid, peripheral nerve conduction study, electromyogram (EMG), muscle biopsy, cranial computed tomography and magnetic resonance imaging, and positron emission tomography. Electron transport system of the biopsied muscle was normal. So, we made a diagnosis of familial essential myoclonus and hyperthyroidism. In the electrophysiological studies, the electroencephalogram (EEG) was within normal limits.(ABSTRACT TRUNCATED AT 250 WORDS)

Electroencephalography↗
PubMed1995

[Pathophysiologies of dystonia and myoclonus--consideration from the standpoint of treatment].

Pathophysiologies of disorders with dystonia or myoclonus were studied by evaluating the effects of treatment. Naturally, the main lesion of the dystonia responding to levodopa is in the nigrostriatal dopamine neuron. The target of stereotaxic operations is ventrolateral palladium for postural dystonia and the nucleus ventralis oralis posterior (Vop) thalamus for action dystonia. Torsion dystonia with lesion in the striatum and/or the pallidum causes axial torsion, it may be postural through the descending pathway and action through Vop. Stereotaxic operations on these pathways have shown to be effective. Focal dystonia is a reflection of abnormal co-activation of cortical motor neurons, occurring in a particular voluntary movement. Botulinus toxin injected into the affected muscle should be effective. Of myoclonus with epilepsy, cortical reflex myoclonus or cortical induced reticular myoclonus responds to valproic acid. However, no antiepileptic drugs are effective on those with primary brainstem lesion. Reticular reflex myoclonus due to asphyxia responds to ventralis intermedius thalamotomy. Idiopathic myoclonus associated with dystonia is particular because it responds to ventrolateral thalamotomy. Myoclonus except for idiopathic myoclonus with dystonia is associated with atonic NREM suggesting dysfunction of the dorsal raphe serotonergic neuron or the brainstem nucleus reticularis gigantocellularis, the causative neuron for experimental uremic myoclonus. Treatment for these neurons is necessary.

Age of Onset↗
PubMedDate not supplied

Pathophysiology of sensorimotor cortex in cortical myoclonus.

We have studied greatly enhanced cortical responses to somatosensory stimuli [giant somatosensory evoked potential (SEP) or magnetic field (SEF)] and cortical activities preceding the myoclonus (premyoclonus spike) in patients with cortical myoclonus, using magnetoencephalographic (MEG) techniques. A P1m component of giant SEF was estimated as a dipole positioned on the postcentral gyrus in all giant SEFs. This indicates that abnormally enhanced responses to sensory stimuli originate from the sensory cortex. In most of the patients with cortical reflex myoclonus, a dipole for the premyoclonus spike was also localized on the postcentral gyrus, which suggests that abnormal activation of the sensory cortex produces the spontaneous myoclonus. In one patient with galactosialidosis, two dipoles, one on the postcentral and the other on the precentral gyrus, could reasonably explain the premyoclonus spike. In the other patient with cortical reflex myoclonus, the premyoclonus spike associated with jerks of the lower limb muscle was estimated to be one dipole on the superior frontal gyrus just anterior to the paracentral lobule. This suggests that both spontaneous myoclonus and enhanced long loop reflex are generated by abnormal activation of the motor cortex in this patient. In a patient with epilepsia partialis continua who had no long loop reflexes, the premyoclonus spike was demonstrated to be positioned on the precentral gyrus, which indicates that abnormal activation of the motor cortex causes the spontaneous myoclonus in this patient. Our MEG studies demonstrated that abnormalities of the sensory or motor cortices contribute differently to the generation of myoclonus in cortical myoclonus, despite the fact that the sensory cortex is the main contributor in most of them.

Electric Stimulation↗
PubMed1997

Long-term neurologic outcome in children with opsoclonus-myoclonus associated with neuroblastoma: a report from the Pediatric Oncology Group.

A retrospective data collection was performed on 29 children diagnosed with neuroblastoma and opsoclonus-myoclonus between 1983-1993 from Pediatric Oncology Group institutions. The aim was to describe neurologic outcome in children with neuroblastoma and opsoclonus-myoclonus. Age at diagnosis ranged from one month to 4 years (median age, 18 months). The duration of opsoclonus-myoclonus symptoms prior to the diagnosis of neuroblastoma ranged from 6 days to 17 months (median duration, 6 weeks). There was a prevalence of low stage disease according to the POG staging system: stage A (n = 18), stage B (n = 3), stage C (n = 7), stage D (n = 1). There was a predominance of paraspinal primary tumors. There was no case of Nmyc amplification (0/17), and 2/8 cases were diploid. Treatment for neuroblastoma consisted of surgery alone in 19/29 (18 stage A, 1 stage C in thorax), and surgery plus chemotherapy in 10/ 29. No patient received radiotherapy. Treatment for opsoclonus-myoclonus ranged varied. Six children received no treatment for opsoclonus-myoclonus. The following agents were used ACTH (n = 14), prednisone (n = 12), IV IgG (n = 6), immuran (n = 2), depakote (n = 1), and inderal (n = 1). Eighteen of 29 children (62%) had resolution of opsoclonus-myoclonus symptoms. The range of time for recovery was a few days to 3 years. However the majority recovered over several months. Twenty of 29 children (69%) had persistent neurologic deficits including speech delay, cognitive deficits, motor delay, and behavioral problems. Of the 9 children who had complete recovery of opsoclonus-myoclonus without neurologic sequelae, age at diagnosis and duration of symptoms were not different from the entire group. Interestingly, 6/9 children with complete recovery received chemotherapy as part of their treatment. In conclusion, persistent neurologic deficits are characteristic for children with neuroblastoma and opsoclonus-myoclonus. Treatment with chemotherapy may improve the neurologic outcome.

Female↗
PubMed2003

Abnormal corticomuscular coherence is associated with the small amplitude cortical myoclonus in Parkinson's disease.

Coherence is the degree of time-locked correlation between two signals as a function of frequency. The purpose of this study was to test the following hypotheses: (1) corticomuscular coherence is abnormally increased in those Parkinson's disease (PD) patients with small amplitude cortical myoclonus, and (2) corticomuscular coherence peaks around the time of the myoclonus electromyographic (EMG) discharge. We studied Parkinson's disease patients with and without myoclonus and controls. The data were digitally collected and processed off-line with EMG rectification, creation of 511-msec epochs, Fast-Fourier transform, and coherence analysis. In the 12 to 30 Hz frequency band, but not at 30 to 60 Hz or above, coherence peaks were observed in the PD subjects with myoclonus that were significantly greater than in the control subjects (P < 0.001) and in PD subjects without myoclonus (P < 0.001). The abnormal coherence values are evidence for abnormal rhythmic activity in cortical motor areas in those Parkinson's disease patients with myoclonus. In combination with previous findings on back-averaging, our results show that this myoclonus occurs when neuronal populations are driven to an extreme amount of synchronous activity with higher corticomuscular coherence values. These results have mechanistic implications for cortical dysfunction in Parkinson's disease and for cortical myoclonus in general.

Aged↗
PubMed1997

The clinical features and prognosis of chronic posthypoxic myoclonus.

The clinical and neurophysiologic features of 14 patients with chronic posthypoxic myoclonus are presented. Patients were first seen a mean of 2.5 years (range, 2 to 105 months) after the hypoxic event and followed up for 3.7 years (range, 7 to 84 months) thereafter. All patients had had a cardiorespiratory arrest, most caused by an acute asthmatic attack (11 cases). All patients had multifocal action myoclonus. Eleven patients had additional stimulus-sensitive myoclonus. There was late improvement in the myoclonic syndrome and the level of disability in all but one patient. Three patients were eventually able to discontinue antimyoclonic medication, and five patients were able to walk unaided. Cognitive deficits were found in seven patients and were usually mild. Other neurologic deficits were rare. Electrophysiologic investigation confirmed cortical action myoclonus in every case, although this could be combined with cortical reflex myoclonus, an exaggerated startle response, or brainstem reticular reflex myoclonus. We conclude that posthypoxic myoclonus typically consists of multifocal cortical action myoclonus that improves with time. It is only rarely associated with severe additional neurologic deficit.

Adult↗
PubMed1985

Estradiol and progesterone influence L-5-hydroxytryptophan-induced myoclonus in male guinea pigs: sex differences in serotonin-steroid interactions.

The effects of castration in males and sex differences in the effects of estradiol and progesterone on L-5-hydroxytryptophan (L-5-HTP)-induced myoclonus in guinea pigs were examined. Castration had no effect on L-5-HTP-induced myoclonus in males. There were sex differences in sensitivity to L-5-HTP. In the absence of steroids, L-5-HTP-induced myoclonus was higher in gonadectomized males than females. A low dose of estradiol benzoate (EB; 3.5 micrograms) given 46 h before L-5-HTP (100 mg/kg) enhanced myoclonus in gonadectomized females but not males. However, at a higher dose of EB (10 micrograms) and a lower dose of L-5-HTP (80 mg/kg), myoclonic responding was enhanced in males. These findings indicate that estradiol has a similar effect on L-5-HTP-induced myoclonus in males and females, but do not rule out the possibility of sex differences in sensitivity to L-5-HTP when both sexes are given estradiol priming. When L-5-HTP was given 6 h after 0.5 mg progesterone in estradiol-primed males, myoclonus was enhanced. Progesterone treatment reverses the facilitative effect of EB on L-5-HTP-induced myoclonus in females. Therefore, progesterone has opposite effects on L-5-HTP-induced myoclonus in males and females. These findings were discussed with respect to the interaction of steroids and 5-HT transmission in the regulation of steroid-dependent reproductive behavior.

5-Hydroxytryptophan↗
PubMed1978

Myoclonus developing after vermisectomy in photosensitive Papio papio.

Two vermisectomized photosensitive baboons exhibited two different types of myoclonus, one induced by intermittent light stimulation (ILS) and the other occuring "spontaneously". The characteristics of these two types of myoclonus are described from a clinical and from an ECoG point of view. Myoclonus induced by ILS (ML) started at the eyelids and secondarily invaded the face and body; it was always preceded by frontorolandic spike-waves or polyspike-waves. The "spontaneous" myoclonus which followed vermisectomy (MV) was "massive", but involved firstly the trunk and secondarily the face and limbs; no ECoG paraoxysm accompanied this myoclonus, but we observed a parietal evoked potential of small amplitude, 10--15 msec after its onset. If MLs can be considered as consequences of the fronto-rolandic paroxysmal discharges, MVs seem to originate in the brain stem but appear similar to action myoclonus. This experimental situation showing two types of myoclonus resembles human hereditary degenerative syndromes (dyssynergic cerebellar myoclonus, progressive myoclonic epilepsy), without being exactly comparable. The conditions in which MVs were seen and their modifications during sleep and by different drugs are described. The relationships between MVs and MLs and myoclonic epilepsy are discussed.

Animals↗
PubMed1984

Physostigmine antagonizes benzodiazepine-induced myoclonus in the baboon, Papio papio.

The antagonism of some benzodiazepine (Bz) actions by physostigmine was investigated in 4 Papio papio baboons. As a model of these actions, the myoclonus induced in this species by clonazepam i.m. administration was used. The baboon develops, 20-30 min after Bz i.m. injection, a non-epileptic myoclonus characterized by clinical symptomatology (jerks involving mainly the neck and the trunk bilaterally), by the absence of any correlative EEG discharge, and by its facilitation during movement. This Bz-induced myoclonus resembles the intention myoclonus of human patients, as seen for example after anoxia. In the present series, the effect of physostigmine i.v. injection on the frequency of clonazepam-induced myoclonus was tested. Physostigmine produces a rapid and total abolition of the myoclonus, and this effect lasts for a period which corresponds to the pharmacological activity of physostigmine. On the contrary, atropine i.v. injection considerably increases the amount of Bz-induced myoclonus. These results allow the existence of an anticholinergic action of benzodiazepines, reversed by physostigmine, and the theory that the myoclonus would be the consequence of a cholinergic system depression to be hypothesized.

Animals↗