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Lance-Adams syndrome (LAS) was first described in 1963 by Lance and Adams, who cited four cases of posthypoxic action myoclonus. Since then, less than 150 cases have been reported world-wide. LAS differs from acute posthypoxic myoclonus, which usually occurs within twelve hours of the anoxic event, with the patient remaining in a deep coma with an extremely poor prognosis. Patients with LAS retain neurological function and develop myoclonus days or weeks after their hypoxic event. This report describes the case of a 64-year-old male who developed LAS following cardiac arrest. His progression from ICU to outpatient was followed through multiple electroencephalograms.

Objective To investigate the mechanisms by which Perampanel (PER) reduces the severity of action myoclonus, we studied on MEG signals the changes occurring in cortico-muscular coherence (CMC) and cortico-cortical connectivity in patients with progressive myoclonus epilepsies. Methods The subjects performed an isometric extension of the hand; CMC and cortico-cortical connectivity were assessed using autoregressive models and generalized partial-directed coherence. The contralateral (Co) sensors showing average CMC values >0.7 of the maximum (set to 1) were grouped as central (C) regions of interest (ROI), while adjacent sensors showing CMC values >0.3 were grouped as Surrounding (Sr) ROIs. Results Under PER treatment, CMC decreased on Co C and Sr ROIs, but also on homologous ipsilateral (Ip) ROIs; out-degrees and betweenness centrality increased in Co ROIs and decreased in Ip ROIs. The flow from Ip to Co ROIs and from activated muscles to Ip C ROI decreased. Conclusion The improvement of myoclonus corresponded to decreased CMC and recovered leadership of the cortical regions directly involved in the motor task, with a reduced interference of ipsilateral areas. Significance Our study highlights on mechanisms suitable to treating myoclonus and suggests the role of a reduced local synchronization together a better control of distant synaptic effects.

Movement disorder, although rare, is increasingly being recognized as the initial presenting sign of the hyperglycemic state. Although chorea-ballism has frequently been reported among diabetics, monoballism is a very rare phenomenon. While myoclonus is common, diaphragmatic myoclonus is extremely rare. Moreover, diaphragmatic myoclonus as the initial presenting manifestation has never been reported before. Herein, we report an index case of a 62-year-old previously undiagnosed diabetic lady presented with acute onset constellation of multiple abnormal movements viz. monoballism, focal myoclonus, action myoclonus, and diaphragmatic myoclonus. All of them disappeared with achieving normoglycemia. This case underscores the importance of rapid capillary blood glucose testing in any patient presenting with acute onset abnormal movements. This approach can especially be rewarding as it helps in the rapid diagnosis of a reversible catastrophe and avoiding unnecessary costly investigations.

Background: Post-hypoxic myoclonus (PHM) is characterized by generalized myoclonus after hypoxic brain injury. Myoclonus is often functionally impairing and refractory to medical therapies. Deep brain stimulation (DBS) has been used to treat myoclonus-dystonia, but few cases of PHM have been described. Case report: A 33-year-old woman developed severe, refractory generalized myoclonus after cardiopulmonary arrest from drowning. We performed MRI-guided asleep bilateral pallidal DBS placement, resulting in improvement in action myoclonus at one year. Discussion: Our case contributes to growing evidence for DBS for PHM. Interventional MRI guided DBS technique can be used for safe and accurate lead placement. Highlights: We report a case of a patient who developed post-hypoxic myoclonus after cardiopulmonary arrest from drowning, who later underwent deep brain stimulation to treat refractory myoclonus. This is the first case to describe asleep, interventional MRI-guided technique for implanting DBS leads in post-hypoxic myoclonus.

Background Kufor-Rakeb syndrome (KRS) is a rare autosomal recessive neurologic disease with diverse phenotypic features. Herein we report an Iranian KRS family with seizure and action myoclonus in addition to other typical manifestations of this syndrome. Method All family members underwent careful neurologic examination. Exome sequencing was performed and ATP13A2 variation genotyped in all family members. Results Cognitive deficits, hypokinesia, rigidity, spasticity, brisk deep tendon reflexes, upward gaze palsy, tremor, and facial-faucial-finger mini-myoclonus were the common manifestations of all affected siblings. Two cases had seizure and the most severely affected sibling demonstrated severe action myoclonus. Exome sequencing identified a homozygous nonsense mutation c.2455C>T;p.Arg819* in ATP13A2 gene. Conclusions We reported five KRS affected siblings who manifested myoclonus and seizure. The most severely affected one demonstrated action myoclonus, which has not been reported so far.

A case of severe action myoclonus after pulmonary arrest is described. Although there was benefit from oral pharmacotherapy, action myoclonus remained disabling. A favorable response to baclofen during an intrathecal trial led to eventual placement of an intrathecal baclofen pump. The present case illustrates the potential utility of intrathecal baclofen for treating this condition. Level of Evidence V

Objectives: Chronic post-hypoxic myoclonus, known as Lance-Adams syndrome (LAS), is a rare complication of successful cardiopulmonary resuscitation. It is characterized by intention myoclonus, cerebellar ataxia, and preserved intellect. The basis of the disease and its long-term prognosis remain unclear. Case report: The authors present a 53-year-old woman with a history of asthma bronchiale who suffered from myoclonus after hypoxic brain damage due to cardiac arrest. Advanced electrophysiological (quantitative EEG) and MR (MR spectroscopy) techniques were employed. Conclusions: Over long-term observation the results suggested permanent synaptic rearrangements of the neuronal networks due to brain plasticity in the patient after the brain hypoxia.

Chronic posthypoxic action myoclonus is usually recognized as multifocal or generalized and, in most cases, causes severe disability. It is also commonly associated with other neurological symptoms, such as ataxia. We report two cases of focal predominant postanoxic action myoclonus and review the limited relevant literature. The first case presented with action and stimulus sensitive myoclonus in the lower limbs that caused him limited disability. He had not received any diagnosis in almost 2 years. The second patient exhibited predominantly focal facial myoclonus, although she was more limited by dysphasia and hemiplegia as a consequence of an ischemic stroke. Both patients responded to antiepileptic drugs. We found 9 of 159 previously reported cases with this focal distribution. Physicians should be aware of this limited phenotype given that the unusual focal nature of the movements may result in incorrect diagnosis and treatment.

A 62-year-old man was resuscitated after an in-hospital pulseless electrical activity (PEA) cardiac arrest. He awakened after 24 hours but after another 24-hour interval, he had worsening action and stimulus-induced myoclonus.[1–3][1] He was able to relax fully without movement but any

Predicting the neurological outcome in survivors of cardiorespiratory arrest is difficult. A distinction has been made between acute and chronic posthypoxic myoclonus, called myoclonic status epilepticus and Lance–Adams syndrome (LAS), respectively, with the acute condition carrying a bad prognosis. Here, we report a case of a 37-year-old female who developed seizures after a successful cardiopulmonary resuscitation. The available literature on such cases is very rare and has generally mentioned a poor outcome. However, our patient was successfully managed and showed clinical features of LAS. Thus, making an early diagnosis and proper management of hypoxic brain insults is positively related to improving the patient's functional outcome.

Objective The objective of this study was to explore the short-term effects of repetitive transcranial magnetic stimulation (rTMS) on action myoclonus. Methods Nine patients with Unverricht–Lundborg (EPM1) progressive myoclonus epilepsy type underwent two series of 500 stimuli at 0.3 Hz through round coil twice a day for five consecutive days. Clinical and neurophysiological examinations were performed two hours before starting the first rTMS session and two hours after the end of the last rTMS session. Results Eight patients completed the protocol; one discontinued because of a transient increase in spontaneous jerks. The unified myoclonus rating scale indicated a 25% reduction in posttreatment myoclonus with action score associated with an increase in the cortical motor threshold and lengthening of the cortical silent period (CSP). The decrease in the myoclonus with action scores correlated with the prolongation of CSP. Conclusions Repetitive transcranial magnetic stimulation can be safely used in patients with EPM1, improves action myoclonus, and partially restores deficient cortical inhibition.

We describe a boy, 3 years and 6 months old, who experienced a rolandic seizure accompanied by a cluster of atypical absence seizures, the EEGs for which corresponded to those of atypical benign partial epilepsy (ABPE). Of note, this patient suffered from developmental delay beginning in infancy and exhibited giant middle-latency somatosensory evoked potentials with action myoclonus. With the exceptions of ethosuximide, acetazolamide, and adrenocorticotropic hormone, which have been reported to be effective in ABPE, the atypical absence seizures were intractable despite extensive treatment with various anticonvulsants. The drugs that were effective led to a remarkable reduction in seizure frequency and EEG improvement, but the efficacy was temporary. The patient demonstrated moderate mental retardation without regression and could not walk with support or speak any meaningful words at the age of 3 years and 6 months. Based on thorough differential diagnosis, although further studies will be necessary, we propose that this boy may present a new phenotype of ABPE: ABPE with action myoclonus.

Background To explore the cortical network sustaining action myoclonus and to found markers of the resulting functional impairment, we evaluated the distribution of the cortico-muscular coherence (CMC) and the frequency of coherent cortical oscillations with magnetoencephalography (MEG). All patients had EPM1 (Unverricht-Lundborg) disease known to present with prominent and disabling movement-activated myoclonus. Methods Using autoregressive models, we evaluated CMC on MEG sensors grouped in regions of interests (ROIs) above the main cortical areas. The movement was a repeated sustained isometric extension of the right hand and right foot. We compared the data obtained in 10 EPM1 patients with those obtained in 10 age-matched controls. Results As expected, CMC in beta band was significantly higher in EPM1 patients compared to controls in the ROIs exploring the sensorimotor cortex, but, it was also significantly higher in adjacent ROIs ipsilateral and contralateral to the activated limb. Moreover, the beta-CMC peak occurred at frequencies significantly slower and more stable frequencies in EPM1 patients with respect to controls. The frequency of the beta-CMC peak inversely correlated with the severity of myoclonus. Conclusions the high and spatially extended beta-CMC peaking in a restricted range of low-beta frequencies in EPM1 patients, suggest that action myoclonus may result not only from an enhanced local synchronization but also from a specific oscillatory activity involving an expanded neuronal pool. The significant relationship between beta-CMC peak frequency and the severity of the motor impairment can represent a useful neurophysiological marker for the patients’ evaluation and follow-up.

Background: Acquired neurogenic stuttering has been considered a fairly uncommon clinical occurrence; speech-activated myoclonus is a rare entity that can mimic stuttering and is caused by a wide array of etiologies. Case Report: Here we report a patient with myoclonus–dystonia syndrome (MDS), due to an identified disease-causing mutation, who displayed speech-activated myoclonus mimicking stuttering. Discussion: In MDS, myoclonus has only infrequently been reported to affect speech. This case further expands the spectrum of conditions causing the rare clinical phenomenon of speech-activated myoclonus., Tremor and Other Hyperkinetic Movements, Tremor and Other Hyperkinetic Movements

Benign Adult Familial Myoclonic Epilepsy (BAFME) is an autosomal dominant disorder characterized by adult-onset cortical tremor or action myoclonus predominantly in the upper limbs, and generalized seizures. We investigated a Thai BAFME family. Clinical and electrophysiological studies revealed that 13 were affected with BAFME. There were a total of 24 individuals studied. Genetic analysis by genome-wide linkage study (GWLS) was performed using 400 microsatellite markers and excluded linkage of the previous BAFME loci, 8q23.3-q24.1, and 2p11.1-q12.2. GWLS showed that the disease-associated region in our Thai family was linked to a newly identified locus on chromosome 3q26.32-3q28. This locus represents the fourth chromosomal region for BAFME.

Background: Myoclonus-dystonia (M-D) is genetic and clinically heterogeneous. Identification and description of rare M-D syndromes may contribute to gene identification. Results: Here, we describe a new, autosomal dominant M-D syndrome in a 3-generation pedigree showing anticipation. Patients have progressive action-induced multifocal dystonia and generalized myoclonus. A remarkable feature of the syndrome is action myoclonus in the lower extremities triggered by upright posture, causing instability. Electrophysiological characterization shows a 12-Hz peak in the EMG autospectrum and corticomuscular and intermuscular coherences. Conclusions: A new familial M-D syndrome with progressive action myoclonus and dystonia is described. (C) 2011 Movement Disorder Society

Electroclinical, morphological, biochemical and molecular genetic data from 17 patients affected by progressive myoclonus epilepsies (PME) are reported. Twelve patients were characterized by prominent action myoclonus, sporadic seizures, mild ataxia, lack of dementia and persistence of normal EEG background activity; three patients showed a more rapid worsening of symptomatology, characterized by early mental impairment, massive and action myoclonus, cerebellar signs and tonic clonic seizures; in these patients EEG background activity was slow, even in early stages of the disease. In two patients, previously classified as cryptogenetic PME, a mitochondrial aetiology was recognized by the presence of ragged red fibers in muscle biopsy and by a reduction of the respiratory chains enzymes. Molecular genetical investigation of mtDNA demonstrated the reported heteroplasmic point mutation at nt 8344 of mtDNA in the two MERRF patients, while it was negative in all of the others.

Introduction. Chronic post-anoxic myoclonus, also known as Lance-Adams syndrome, may develop following hypoxic brain injury, and is resistant to pharmacological therapy. Case report. The patient we presented developed post-anoxic action myoclonus with severe, completely incapacitating myoclonic jerks. Myoclonus did not respond to the treatment with commonly used agents, i.e. valproate and clonazepam alone or in combination. Improvement of the action myoclonus was observed only after adding levetiracetam. Conclusion. Although Lance-Adams syndrome may not be fully curable at this point, levetiracetam appears to be a promising agent that can significantly improve functional level and overall quality of life of patients with this disorder.

We studied changes in event-related desynchronization/synchronization (ERD/ERS) patterns in patients with Unverricht-Lundborg disease (ULD), presenting with prominent action myoclonus. We analyzed the movement-related ERD/ERS in alpha and beta frequency bands in 15 patients using self-paced finger extension as a motor paradigm and we compared the results with those obtained in 12 healthy volunteers. In all ULD patients, alpha- and beta-ERD regularly occurred with onset and location similar to that found in healthy controls, but the desynchronization of alpha activity was significantly greater than in controls (C3: -64.4+/-9.8% vs. -49.7+/-14.8%; p=0.004). Moreover, in the patients, both alpha- and beta-ERD spread toward frontal electrodes. In controls, the post-movement beta-ERS regularly occurred; it was absent in eight patients with severe action myoclonus, while, in seven patients with mild or moderate myoclonus, the beta-peak was significantly smaller with respect to that measured in controls (55.6+/-15.1% vs. 153.9+/-99.8%, p=0.006). The failure of beta-ERS well-correlated with motor impairment resulting from action myoclonus, whereas SSEPs and long-loop reflexes performed to detect signs of cortical hyperexcitability showed inconsistent changes. In ULD patients, ERD/ERS changes indicate an increased activation of motor cortex during movement planning and a great reduction of post-excitatory inhibition of motor cortex. The changes involving beta-ERS had a significant relationship with the functional disability in individual patients and might play a pathogenic role in the motor dysfunction.

Editors' Note: Critiquing “Orthostatic myoclonus associated with Caspr2 antibodies,” van Gerpen et al. disagree with the diagnosis of orthostatic myoclonus (OM), which, according to their experience, clinically manifests as low-amplitude, tremulous movements, restricted to the legs during standing; appears as semirhythmic bursts lasting less than 50 milliseconds on surface EMG; and lacks prominent action myoclonus in the legs. Govert et al., authors of the case report, defend their diagnosis and explain that OM can be present in the arms and can have subtle action myoclonus. In reference to “Antibiotic-associated encephalopathy,” Dr. Stip argues that there is no clear evidence to link macrolides to altered dopamine levels or NMDA receptor activity and that macrolides have poor CSF …

Lance-Adams syndrome (LAS) is a rare complication of successful cardiopulmonary resuscitation and is often accompanied by action myoclonus. LAS is seen in patients who have undergone a cardiorespiratory arrest, later regained consciousness, and then developed myoclonus days or weeks after the event. Less than 150 cases of LAS have been reported in the worldwide medical literature. Here, we present a 32-year-old man who suffered from myoclonus after hypoxic brain damage due to hanging himself. This case was diagnosed as Lance-Adams syndrome according to a history of hypoxic brain damage, the clinical features, and the neuroimages such as brain SPECT. Making an early diagnosis and properly managing LAS is positively related to improving the patient's functional outcome. If patients have posthypoxic myoclonus after successful cardiopulmonary resuscitation, we should consider the diagnosis of LAS and initiate a proper rehabilitation program.

This case study describes the variety of techniques used in occupational therapy to restore function in a severely incapacitated client suffering from action myoclonus. While most studies on myoclonus centre on drug treatment, this article discusses the key role occupational therapy can play in motor relearning. It is suggested that occupational therapy was successful in helping a client with profound functional problems to regain some level of independence.

Background: Perinatal anoxia rarely causes myoclonus as the main neurologic abnormality. The exact neuronal mechanism underlying myoclonus induced by perinatal anoxia remains unknown. Some studies have indicated that the development of involuntary movements may be related to the maturation of the thalamus after birth. Objectives and Methods: Here, we describe the first case of a patient who developed action myoclonus after experiencing perinatal anoxia and was successfully treated by chronic deep brain stimulation (DBS) of the thalamus (thalamic DBS). Results andConclusion: The effectiveness of chronic thalamic DBS in this patient supports the concept of involvement of the thalamus in postperinatal anoxic myoclonus.

El Síndrome de Lance-Adams descrito en 1963, es una rara complicación que sigue tardíamente a episodios hipóxicos o de hipotensión prolongada, ya recuperados. Se caracteriza por mioclonías de acción y ataxia cerebelosa. Se describen dos pacientes estudiados con este síndrome. Son dos hombres de 51 y 72 años que después de un paro cardiorrespiratorio breve, de recuperación completa, iniciaron mioclonías de intención, activadas por movimientos voluntarios, posturas, estímulos sonoros, táctiles y afectivos. Acompañado además de un síndrome cerebeloso, ataxia de la marcha y alteraciones del control postural. Cursaron con RM (Resonancia Magnética), EEG (Electroencefalograma) y parámetros metabólicos sin relevancia patológica. Las mioclonías fueron controladas con ácido valproico y clonazepam. La interpretación neurofisiológica de este desajuste motor es la alteración en el funcionamiento del patrón central de circuitos generadores (PCCG) ubicado en la región mesencefálica. Las lesiones hipóxicas de las neuronas de Purkinje del vermis y paravermianas del cerebelo, que tienen un efecto inhibitorio para este sistema, producen una atenuación del control motor del PCCG, generando desajuste en la secuencia de la contracción de las motoneuronas de la médula espinal, que comienzan a dispararse de manera independientemente. Como ocurre con la mayoría de las lesiones cerebelosas, con el tiempo tienden a compensarse y por consiguiente a disminuir las mioclonías. Lance-Adams syndrome was described in 1963 is a rare complication due to recovered hypoxic episodes or prolonged hypotension events. Is characterized by action myoclonus and cerebellar ataxia. We report two patients studied with this syndrome. A 51 year-old men and a 72 years-old men fully recovered after a brief cardiorespiratory arrest they developed intention myoclonus, triggered by voluntary movements, posture, also by sounds, touches and emotional stimuli. It also was accompanied by cerebellar syndrome, ataxia and posture control alterations. They had a Magnetic Resonance (MR), EEG and normal metabolic parameters. Myoclonus was treated with sodium valproate and clonazepam. The neurophysiologic interpretation of this motor imbalance is an abnormal functioning of the Central Pattern Generator Netwoks (CPGN) located in the mesencephalic region. Hypoxic lesions in vermian purkinje and paravermal cerebellum neurons have an inhibitory effect in this system, producing motor control attenuation, generating an imbalance in the motoneurons of the spinal cord contraction sequence, which starts shooting in an uncoordinated way. As in almost all cerebellar lesions with time they tend to compensate and to diminish myoclonus.

We report a 3-year-11-month-old boy who manifested action myoclonus only. Histochemical analysis of the quadriceps muscle revealed subsarcolemmal hyperactivity. The administration of 5-hydroxytryptophan and carbidopa dramatically improved the action myoclonus and reduced an amplitude of giant somatosensory evoked potentials. A nosological relation of this case with "essential myoclonus" and mitochondrial encephalomyopathy was discussed.

Three patients who were hospitalized due to cerebrovascular incident with different lesions localization presented with ipsilateral epileptic syndromes with action myoclonus of the hands and in one case associated with active myoclonus of the same half of the face. The aim was to prove the existence of a direct correlation between cerebrovascular incident as the cause and developed action myoclonus as a result of cerebral lesions by analysing the pathophysiological basis of this entity. The analysed results were obtained through laboratory, serial electroencephalograph monitoring, CD-MAV, computerized tomography or magnetic resonance imaging of the brain and magnetic resonance angiography of blood vessels of the brain. Based on results, the base for the introduction of anticonvulsant therapy, which completely suppressed the clinical picture, was set. This supports the direct relation between cerebrovascular lesions as pathoanatomic substrate and action myoclonus as a pathophysiological substrate. The mechanism of myoclonus as a result of cerebrovascular disease is largely unknown. The essence of the discussion is based on the possible pathophysiological mechanisms of secondary myoclonus. Further analysis should give a deeper insight into the damage mechanisms, but also the survival of neurons that can help and lead to new ways of treating cerebrovascular disease.

We conducted an open-label, dose-finding, blinded-rating trial of gamma-hydroxybutyric acid (Xyrem) in a single patient with severe alcohol-responsive posthypoxic myoclonus refractory to treatment with standard antimyoclonic agents. Xyrem was given in divided doses during the day and was well tolerated. Intensity of myoclonus was measured using the Unified Myoclonus Rating Scale, and blinded videotape review demonstrated complete resolution of myoclonus at rest and stimulus-sensitive myoclonus. Action myoclonus and functional performance also improved in ways that were practically meaningful, allowing her to feed herself, to accomplish daily hygiene tasks, and to walk with assistance. The possible mechanisms of action and potential uses of this agent in other alcohol-responsive movement disorders are discussed.

Posthypoxic and postencephalitic myoclonus is often poorly controlled with current treatments. The authors successfully treated three patients with posthypoxic and postencephalitic myoclonus by using levetiracetam, a new antiepileptic drug. Levetiracetam appears to be a promising agent for treating action myoclonus caused by hypoxic and encephalitic brain injury-the degree of functional improvement may depend on the severity of associated motor dysfunction.

Publisher Summary This chapter presents various aspects of posthypoxic action myoclonus. In the chronic stage, spontaneous myoclonus is less frequent, and the picture is dominated by action myoclonus, which occurs particularly at the onset of movement or when changing posture. The action-induced myoclonus in posthypoxic patients has a very typical electromyography (EMG) and electroencephalogram (EEG) pattern. The action jerks are caused by runs of hypersynchronized EMG discharges, individual components of which may be no longer in duration than the EMG response to a tendon tap. It is suggested that EEG spikes represented discharge of motor cortical cells that initiated the muscle jerks through conduction in rapidly conducting corticospinal pathways. It is postulated that the EEG slow waves represented inhibition of cortical activity, which withdrew descending facilitation from the motoneurone pool resulting in the silent period. It is suggested that some patients with posthypoxic myoclonus may have reflex jerks that appear to involve a reticular center rather than the cortex. It is found that the reflex jerks in body muscles appeared to be conducted by a more slowly conducting reticulospinal pathway.

Acetazolamide treatment significantly improves action myoclonus in Ramsay Hunt Syndrome. A family with two brothers and a sister, and a sporadic case with Ramsay Hunt Syndrome and uncontrollable action myoclonus, are described where addition of oral acetazolamide lead to marked improvement in their action myoclonus.

In order to determine what kind of voluntary movement induces action myoclonus, we gave two siblings with sialidosis two kinds of tasks. When the patients were asked to move their index fingers following a smoothly moving target, action myoclonus became prominent. In contrast, when they were asked to perform the same movements with their eyes closed, they could move their index fingers very smoothly. This shows that action myoclonus was induced by visually guided movement, but not by self-paced movement. Our observations might reflect a disorder of the cerebellum, which controls visually guided movement.

Article abstract-Posthypoxic and postencephalitic myoclonus is often poorly controlled with current treatments. The authors successfully treated three patients with posthypoxic and postencephalitic myoclonus by using levetiracetam, a new antiepileptic drug. Levetiracetam appears to be a promising agent for treating action myoclonus caused by hypoxic and encephalitic brain injury-the degree of functional improvement may depend on the severity of associated motor dysfunction.

Report of a 48-year-old patient presenting the syndrome of action myoclonus as described by Lance and Adams, during an acute renal decompensation. The action myoclonus appeared in the stage of acute metabolic acidosis and hyperosmolarity, and proved completely reversible. Action myoclonus has not before been reported as a symptom of metabolic disorder. It's prognosis in such a context seems much better than in post-anoxic cases in whom it always has proved persistent. The only sequel in our patient was a mild pyramidal and cerebellar syndrome confirming the statement of Lance and Adams that mild cerebellar ataxia is part of the action myoclonus syndrome.

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.

Clinical electrophysiological and neuroradiological examination of a case of unilateral intention and action myoclonus is reported. Brachial arteriography revealed an angioma located mainly in the lateral portion of the right posterior thalamus. Clinical and electrophysiological findings suggesting involvement of nonthalamic structures were absent. Our case, together with some cases previously described, raises the possibility that volitional myoclonus may be related to a relatively circumscribed damage of some diencephalic and/or mesencephalic structures. The rare occurrence of a hyperkinetic syndrome as principal symptom of a cerebral vascular malformation should be borne in mind in view of the potential risk of a stereotactic surgical procedure designated to alleviate the involuntary movements.

A patient, who suffered from nonprogressive athetotic-myoclonic hyperkinesia of the left arm and spastic paresis of the underdeveloped left leg since early childhood, experienced a febrile episode at the age of 23, after which a weakness and ataxia of the right limbs with frequent falling persisted; at the age of 28, he developed a right-sided rigidity, tremor at rest and mask-like face as sequelae of encephalitis disseminata exacerbations. The violent intention myoclonus of the left side of the body could be abolished by stereotactic coagulation in the V.o.p and V.o.a and zona incerta until death 11 days later. The athetotic myoclonic hyperkinesia is the consequence of a left-sided severe status marmoratus of the right putamen with extensive loss of nerve cells and shrinkage. The additional nerve cell loss in the right substantia nigra due to demyelinating encephalitic foci did not produce Parkinson symptoms, because these require a normal striatum. This loss did, however, exaggerate the original hyperkinesia to a violent intention myoclonus, which was abolished by interruption of dentatothalamic afferents to the V.o.p nucleus and of pallidothalamic afferents to the V.o.a nucleus. The Parkinson syndrome of the right side is due to demyelinating foci of different ages. The Parkinson symptoms were manifest on the right side, because the left status marmoratus did not severely reduce the striatal nerve cells. In this case, there is no indication that the introduction of the stereotactic electrode has precipitated new demyelinating foci.

Description of a patient with Huntington's chorea of adult onset who subsequently developed an action myoclonus.

Myoclonus induced by catechol in the guinea-pig is not altered by manipulation of cerebral 5-hydroxytryptamine (5-HT). The administration of catechol does not alter brain levels of 5-HT or its metabolite 5-hydroxyindole acetic acid. This form of myoclonus therefore is not of relevance to the 5-HT-sensitive post-anoxic action myoclonus occurring in man.

Comparatively high doses of muscimol induces myoclonic jerks in a particular strain of mice. 1-Hydroxy-3-amino-pyrrolidone-2 (HA-966) in doses of 1–10 mg/kg caused a dose-dependent blockade of this response of muscimol. Our earlier studies showed that the muscimol-induced myoclinic jerks fulfill certain criteria necessary to be considered as a valid animal model for postanoxic action myoclonus. On this basis it was concluded that HA-966 might prove to be of value in the management of this disorder.