Myoclonus: current concepts and recent advances

Clinical characteristics and etiology of transient myoclonic state in the elderly

OBJECTIVES

To clarify clinical picture of transient myoclonic state in elderly patients.

METHODS

The Aizawa Hospital database was searched to identify all patients with transient myoclonic state with or without asterixis between April 2006 and June 2013. Medical records, brain images and laboratory data including electroencephalograms and electromyograms were reviewed.

RESULTS

We found 26 patients: 10 women and 16 men, and their ages ranged from 56 to 96 years (79.7 ± 9.9 years, mean ± standard deviation). The affected sites of the myoclonic jerks were predominantly the lower face, neck and upper extremities. The myoclonus appeared at conscious resting condition, slightly exaggerated by posturing or action. Asterixis was observed in eight patients. Single myoclonic bursts were 1.70 ± 0.94 s long. The interval of myoclonic bursts was 4.47 ± 2.44 s. Single myoclonic bursts were composed of 9.5 ± 2.5 Hz myoclonic contractions, and single myoclonic contractions were 44.4 ± 12.3 ms in duration. Most of the patients suffered from chronic diseases, but they were basically independent in activity of daily living. Oral administration of clonazepam was effective.

CONCLUSIONS

Transient myoclonic state has relatively stereotyped features. The pathophysiology may include some metabolic abnormality on a background of age-related arteriosclerotic changes. Its prognosis is benign, and prompt oral administration of clonazepam abolishes it. Further investigations will be needed to clarify its cause and pathophysiology.

A Case of Hemiabdominal Myoclonus

Myoclonus consists of sudden, brief, involuntary jerky muscular contractions. Central and peripheral nervous system lesions are involved in the pathogenesis of this movement disorder. Symptomatic or secondary spinal myoclonus is the most common form. A 68-year-old woman was diagnosed with hemiabdominal spinal myoclonus. Occasional and very mild involuntary repetitive movements of the hemiabdomen began immediately after surgery for uterine cancer. After surgery for laparocele, secondary to the uterine cancer surgery, performed under spinal anesthesia, there was severe worsening of movements. Neuroradiological investigations failed to demonstrate spinal injury, while neurophysiological studies showed impairment of the right central somatosensory pathway. Considering the low resolution of magnetic resonance imaging in the evaluation of thoracic level, we suggest an extensive neurophysiological evaluation in patients with spinal myoclonus.

Memantine-induced Myoclonus in a Patient with Alzheimer Disease

BACKGROUND

Myoclonus can be a clinical manifestation of numerous neurodegenerative disorders and an adverse drug reaction to medications used in their treatment.

CASE REPORT

Herein, we report memantine-induced myoclonus in a patient with Alzheimer disease. The myoclonus seen in our patient was generalized (proximal limbs and trunk), present at rest and with action, and stimulus sensitive. A structured evaluation with the Unified Myoclonus Rating Scale showed that the myoclonus had no significant effect on functional capacity. After discontinuation of memantine, myoclonus slowly resolved over the course of several weeks.

DISCUSSION

Memantine may cause myoclonus in susceptible individuals.

Electroencephalographic Findings in Posthypoxic Myoclonus

The physical examination findings of early posthypoxic myoclonus (PHM) are associated with poor prognosis. Recent findings indicate that patients with multifocal PHM, assumed to have a cortical origin, have a comparable outcome to resuscitated patients without PHM. Generalized PHM, assumed to have a subcortical myoclonus origin, is still associated with a bad clinical outcome. It is not known whether the electroencephalographic (EEG) findings differ between the multifocal and generalized myoclonus groups nor is the clinical significance clearly defined. Forty-three patients with PHM were retrospectively derived from an EEG database. Patients were categorized as having multifocal (i), generalized (ii), or undetermined (iii) PHM. Outcome was expressed in cerebral performance category scores. The EEG background was categorized into isoelectric (I), low voltage (II), burst suppression (III), status epilepticus (SE; IV), diffuse slowing (V), and mild encephalopathic or normal (VI). 17 patients had generalized PHM and 23 had multifocal PHM (3 undetermined). The EEG showed more SE in generalized compared to multifocal PHM (64% vs 13%, P< .001). Diffuse slowing was more often present in multifocal PHM (52% vs 17%, P < .05). Early-onset myoclonus occurred significantly more often in generalized PHM, and early generalized PHM was invariantly associated with poor outcome. In conclusion, patients with generalized PHM showed more SE. These EEG findings might be either subcortical corollaries or primarily cortical phenomena. Our retrospective results conflict with currently used clinical criteria for myoclonus classification, and we suggest that more refined difference may be needed for accurate assessment of PHM. To better understand PHM, prospective research with standardized clinical assessment and quantitative EEG analysis is needed.

Seizures in Alzheimer's disease

Alzheimer's disease (AD) increases the risk for late-onset seizures and neuronal network abnormalities. An elevated co-occurrence of AD and seizures has been established in the more prevalent sporadic form of AD. Recent evidence suggests that nonconvulsive network abnormalities, including seizures and other electroencephalographic abnormalities, may be more commonly found in patients than previously thought. Patients with familial AD are at an even greater risk for seizures, which have been found in patients with mutations in PSEN1, PSEN2, or APP, as well as with APP duplication. This review also provides an overview of seizure and electroencephalography studies in AD mouse models. The amyloid-β (Aβ) peptide has been identified as a possible link between AD and seizures, and while Aβ is known to affect neuronal activity, the full-length amyloid precursor protein (APP) and other APP cleavage products may be important for the development and maintenance of cortical network hyperexcitability. Nonconvulsive epileptiform activity, such as seizures or network abnormalities that are shorter in duration but may occur with higher frequency, may contribute to cognitive impairments characteristic of AD, such as amnestic wandering. Finally, the review discusses recent studies using antiepileptic drugs to rescue cognitive deficits in AD mouse models and human patients. Understanding the mechanistic link between epileptiform activity and AD is a research area of growing interest. Further understanding of the connection between neuronal hyperexcitability and Alzheimer's as well as the potential role of epileptiform activity in the progression of AD will be beneficial for improving treatment strategies.

Bilateral muscular tinnitus due to myoclonus of extrinsic auricular muscles

The muscular tinnitus due to an extrinsic auricular myoclonus is an extremely rare disorder which demonstrates a semirhythmic involuntary movement of the ear. We report a 33-year-old man with clicking tinnitus caused by focal myoclonic jerks of bilateral posterior auricularis muscle and bilateral temporalis muscle. This muscular tinnitus persisted except for when he was sleeping or breath holding. His symptom responded poorly to medical therapy but was controlled by botulinum toxin type A injection under electromyography monitoring with favorable outcome. Previous reports of this condition and possible therapeutic approaches are discussed.

Palato-pharyngo-laryngeal myoclonus … an unusual cause of dysphagia

Dysphagia is a common problem in the elderly patient. Palato-pharyngo-laryngeal myoclonus, however, is a rare cause of this. We report a case of a 78-year-old man with dysphagia due to palato-pharngo-laryngeal myoclonus that was ultimately managed conservatively with a good functional outcome.

Isolated transient myoclonus in the elderly: an under-recognized condition?

BACKGROUND

Cases of transient myoclonus without other neurological manifestations in the elderly have very rarely been reported.

OBJECTIVE

To report clinical features of elderly people with isolated transient myoclonus.

METHODS

Clinical and laboratory features of 11 consecutive patients with isolated transient myoclonus (six men and five women; mean age, 75 years) were reviewed. Transient myoclonus was defined as an acute onset of tremulous myoclonus with/without asterixis in adults without other neurological symptoms.

RESULTS

Preceding infections were recorded in five patients (pneumonia, two; upper respiratory tract infection, two; and septic arthritis of the shoulder, one). Myoclonus predominantly affected the head and/or neck (n=10) and upper extremities (n=11), compared with the trunk (n=2) and lower extremities (n=6). Asterixis was observed in six patients. Laboratory testing, neuroimaging, and electroencephalograms revealed no specific abnormalities. With or without treatment using benzodiazepines, myoclonus in all patients resolved completely within 1-4 days, although five had recurrence 2-19 months after their first episodes. Among these five patients, the accompanying asterixis patterns (presence or not) in four were different in the first and subsequent episodes.

CONCLUSIONS

Isolated transient myoclonus with or without asterixis may be more common than generally believed, and it could be a clinical entity or disease spectrum. Transient myoclonus is a benign condition in the elderly, but can be under-reported or misdiagnosed. Therefore, it is important to recognize that the elderly may have this syndrome.

Treatment of myoclonus

Myoclonus creates significant disability for patients. This symptom or sign can have many different etiologies, presentations, and pathophysiological mechanisms. A thorough evaluation for the myoclonus etiology is critical for developing a treatment strategy. The best etiological classification scheme is a modified version from that proposed by Marsden et al. in 1982. Clinical neurophysiology, as assessed by electromyography and electroencephalography, can be used to classify the pathophysiology of the myoclonus using a neurophysiology classification scheme. If the etiology of the myoclonus cannot be reversed or treated, then symptomatic treatment of the myoclonus itself may be warranted. Unfortunately, there are few controlled studies for myoclonus treatments. The treatment strategy for the myoclonus is best derived from the neurophysiology classification scheme categories: 1) cortical, 2) cortical-subcortical, 3) subcortical-nonsegmental, 4) segmental, and 5) peripheral. A cortical physiology classification is most common. Levetiracetam is suggested as first-line treatment for cortical myoclonus, but valproic acid and clonazepam are commonly used. Cortical-subcortical myoclonus is the physiology demonstrated by myoclonic seizures, such as in primary epileptic myoclonus (e.g., juvenile myoclonic epilepsy). Valproic acid has demonstrated efficacy in such epileptic syndromes with other medications providing an adjunctive role. Clonazepam is used for subcortical-nonsegmental myoclonus, but other treatments, depending on the syndrome, have been used for this physiological type of myoclonus. Segmental myoclonus is difficult to treat, but clonazepam and botulinum toxin are used. Botulinum toxin is used for focal examples of peripheral myoclonus. Myoclonus treatment is commonly not effective and/or limited by side effects.

Late relapse myoclonus in a case of Lance-Adams syndrome

A 66-year-old man had a history of an anterior myocardial infarction followed by a successful cardiopulmonary resuscitation and a posthypoxic myoclonus, also known as Lance-Adams syndrome (LAS). Eight years ago, he was admitted to the emergency department with the same myoclonic jerks during an intercurrent respiratory infection. After treatment with clonazepam and resolution of the infection, the myoclonus promptly disappeared. This case report suggests that relapses of successfully treated LAS can occur in vulnerable patients, as it's a chronic form of myoclonus.

Late relapse myoclonus in a case of Lance-Adams syndrome

A 66-year-old man had a history of an anterior myocardial infarction followed by a successful cardiopulmonary resuscitation and a posthypoxic myoclonus, also known as Lance-Adams syndrome (LAS). Eight years ago, he was admitted to the emergency department with the same myoclonic jerks during an intercurrent respiratory infection. After treatment with clonazepam and resolution of the infection, the myoclonus promptly disappeared. This case report suggests that relapses of successfully treated LAS can occur in vulnerable patients, as it's a chronic form of myoclonus.

Motor tics evoked by striatal disinhibition in the rat

Motor tics are sudden, brief, repetitive movements that constitute the main symptom of Tourette syndrome (TS). Multiple lines of evidence suggest the involvement of the cortico-basal ganglia system, and in particular the basal ganglia input structure-the striatum in tic formation. The striatum receives somatotopically organized cortical projections and contains an internal GABAergic network of interneurons and projection neurons' collaterals. Disruption of local striatal GABAergic connectivity has been associated with TS and was found to induce abnormal movements in model animals. We have previously described the behavioral and neurophysiological characteristics of motor tics induced in monkeys by local striatal microinjections of the GABAA antagonist bicuculline. In the current study we explored the abnormal movements induced by a similar manipulation in freely moving rats. We targeted microinjections to different parts of the dorsal striatum, and examined the effects of this manipulation on the induced tic properties, such as latency, duration, and somatic localization. Tics induced by striatal disinhibition in monkeys and rats shared multiple properties: tics began within several minutes after microinjection, were expressed solely in the contralateral side, and waxed and waned around a mean inter-tic interval of 1-4 s. A clear somatotopic organization was observed only in rats, where injections to the anterior or posterior striatum led to tics in the forelimb or hindlimb areas, respectively. These results suggest that striatal disinhibition in the rat may be used to model motor tics such as observed in TS. Establishing this reliable and accessible animal model could facilitate the study of the neural mechanisms underlying motor tics, and the testing of potential therapies for tic disorders.

Episodic neurologic disorders: syndromes, genes, and mechanisms

Many neurologic diseases cause discrete episodic impairment in contrast with progressive deterioration. The symptoms of these episodic disorders exhibit striking variety. Herein we review what is known of the phenotypes, genetics, and pathophysiology of episodic neurologic disorders. Of these, most are genetically complex, with unknown or polygenic inheritance. In contrast, a fascinating panoply of episodic disorders exhibit Mendelian inheritance. We classify episodic Mendelian disorders according to the primary neuroanatomical location affected: skeletal muscle, cardiac muscle, neuromuscular junction, peripheral nerve, or central nervous system (CNS). Most known Mendelian mutations alter genes that encode membrane-bound ion channels. These mutations cause ion channel dysfunction, which ultimately leads to altered membrane excitability as manifested by episodic disease. Other Mendelian disease genes encode proteins essential for ion channel trafficking or stability. These observations have cemented the channelopathy paradigm, in which episodic disorders are conceptualized as disorders of ion channels. However, we expand on this paradigm to propose that dysfunction at the synaptic and neuronal circuit levels may underlie some episodic neurologic entities.

The eye of the beholder: inter-rater agreement among experts on psychogenic jerky movement disorders

OBJECTIVE

The current criteria for conversion disorder in the Diagnostic and Statistical Manual of Mental Disorders rely on the assumption that neurological disorders can be distinguished from conversion disorders through clinical assessment. This study aims to assess inter-rater agreement among clinicians with experience in the diagnosis of various hyperkinetic jerky movements, including psychogenic jerks.

METHODS

60 patients with psychogenic jerks, myoclonus or tics were rated by international experts using a standardised survey resembling daily clinical practice. The survey included the following diagnostic steps: a short video offering a visual impression of the patients and their jerky movements, medical history, neurological examination (on video), additional investigations and the findings of a standardised psychiatric interview. The diagnosis and diagnostic certainty were scored after each step.

RESULTS

After all clinical information was given, moderate inter-rater agreement was reached (κ=0.56±0.1) with absolute agreement (100%) of experts on the diagnosis in 12 (20%) patients and reasonable agreement (>75%) in 43 (72%) patients. Psychiatric evaluation did not contribute to inter-rater agreement or diagnostic certainty.

CONCLUSIONS

Our findings illustrate the fact that experienced movement disorder specialists moderately agree on the clinical diagnosis of jerky movements. Clinical assessment, especially by a team of clinicians in challenging individual cases, might improve diagnostic agreement.

Clinical features of dog- and bat-acquired rabies in humans

BACKGROUND

Clinical differences in rabies due to canine and bat rabies virus variants have been noted, but no detailed studies have been reported to support these observations.

METHODS

Using the Morbidity and Mortality Weekly Report and PubMed, we identified 142 case reports of rabies from North America, South America, Europe, Africa, and Asia. We systematically abstracted 126 selected data elements and compared clinical features and investigation results in dog- and bat-acquired cases of rabies.

RESULTS

Survivors and cases acquired from aerosolized viral exposure or tissue/organ transplant were excluded (n = 20). Of 122 cases, 49 (40.2%) were dog-acquired and 54 (44.3%) were bat-acquired. Bat-acquired cases of rabies were more often misdiagnosed and lacked a bite history. Encephalopathy, hydrophobia, and aerophobia were more common in dog-acquired rabies. Abnormal cranial nerve, motor, and sensory examinations, tremor, myoclonus, local sensory symptoms, symptoms at the exposure site, and local symptoms in the absence of a bite or scratch were more common in patients with bat-acquired rabies, as was increased cerebrospinal fluid protein (P = .031). Patients with paralytic rabies had longer survival times than those with encephalitic rabies, and also had shorter incubation periods if they had received postexposure prophylaxis.

CONCLUSIONS

Clinical differences in dog- and bat-acquired rabies may reflect differences in the route of viral spread of rabies virus variants in the nervous system, although certain variants could cause more severe dysfunction in neuronal subpopulations. Recognition that bat-acquired rabies may present with different clinical manifestations than dog-acquired rabies may help improve the early diagnosis of rabies.

Middle ear myoclonus: two informative cases and a systematic discussion of myogenic tinnitus

Background

The term middle ear myoclonus (MEM) has been invoked to explain symptoms of tinnitus presumably caused by the dysfunctional movement of either of the two muscles that insert in the middle ear: tensor tympani and stapedius. MEM has been characterized through heterogeneous case reports in the otolaryngology literature, where clinical presentation is variable, phenomenology is scarcely described, the pathogenic muscle is usually not specified, natural history is unknown, and the presumptive definitive treatment, tensor tympani or stapedius tendon lysis, is inconsistently effective. It is not surprising that no unique acoustogenic mechanism or pathophysiologic process has been identified to explain MEM, one of several descriptive diagnoses associated with the complicated disorders of myogenic tinnitus.

Methods

Here, we explore MEM from the neurologist’s perspective. Following the detailed descriptions of two informative cases from our clinic, we systematically evaluate the different mechanisms and movement disorder phenomena that could lead to a diagnosis of MEM.

Results

From a functional neuroanatomic perspective, we explain how tensor tympani MEM is best explained as a form of peritubal myogenic tinnitus, similar to the related disorder of essential palatal tremor. From a pathogenic perspective, we discuss how MEM symptomatology may reflect different mechanical and neurologic processes. We emphasize the diagnostic imperative to recognize when myogenic tinnitus is consistent with a psychogenic origin.

Discussion

Both individual patient care and further elucidation of MEM will rely on more detailed clinical characterization as well as multidisciplinary input from neurology, otolaryngology, and dentistry.

Myoclonus and epilepsy

Epileptic myoclonus can be defined as an elementary electroclinical manifestation of epilepsy involving descending neurons, whose spatial (spread) or temporal (self-sustained repetition) amplification can trigger overt epileptic activity and can be classified as cortical (positive and negative), secondarily generalized, thalamo-cortical, and reticular. Cortical epileptic myoclonus represents a fragment of partial or symptomatic generalized epilepsy; thalamo-cortical epileptic myoclonus is a fragment of idiopathic generalized epilepsy. Reflex reticular myoclonus represents the clinical counterpart of fragments of hypersynchronous epileptic activity of neurons in the brainstem reticular formation. Epileptic myoclonus, in the setting of an epilepsy syndrome, can be only one component of a seizure, the only seizure manifestations, one of the multiple seizure types or a more stable condition that is manifested in a nonparoxysmal fashion and mimics a movement disorder. This complex correlation is more obvious in patients with epilepsia partialis continua in which cortical myoclonus and overt focal motor seizures usually start in the same somatic (and cortical) region. In patients with cortical tremor this correlation is less obvious and requires neurophysiological studies to be demonstrated.

Deep brain stimulation for other tremors, myoclonus, and chorea

Deep brain stimulation (DBS) is a well established treatment for essential tremor and for the tremor associated with Parkinson's disease. The efficacy of DBS in these common tremors has led some investigators to apply the technique to rarer tremors such as such as Holmes' tremor, posttraumatic tremor, orthostatic tremor, and the tremor associated with multiple sclerosis. Likewise, DBS of the thalamus and globus pallidus directly suppresses levodopa-induced dyskinesias in Parkinson's disease, suggesting the application of DBS to other hyperkinetic states such as Huntington's disease, tardive dyskinesia, and hemiballism. Myoclonus has also been treated with DBS, especially in cases where it is associated with dystonia. This chapter reviews the reported results of DBS for these conditions. Due to the rarity of these indications, most of the literature reviewed takes the form of case reports or small single-center case series.

Myoclonus following a Peripheral Nerve Block

Myoclonus is an extremely rare perioperative complication following neuraxial anesthesia. It has also been reported to occur due to peripheral nerve lesions. We report a case of self-limiting myoclonus following a routine peripheral nerve block in an otherwise healthy patient.

Familial cortical myoclonus with a mutation in NOL3

OBJECTIVE

Myoclonus is characterized by sudden, brief involuntary movements, and its presence is debilitating. We identified a family suffering from adult onset, cortical myoclonus without associated seizures. We performed clinical, electrophysiological, and genetic studies to define this phenotype.

METHODS

A large, 4-generation family with a history of myoclonus underwent careful questioning, examination, and electrophysiological testing. Thirty-five family members donated blood samples for genetic analysis, which included single nucleotide polymorphism mapping, microsatellite linkage, targeted massively parallel sequencing, and Sanger sequencing. In silico and in vitro experiments were performed to investigate functional significance of the mutation.

RESULTS

We identified 11 members of a Canadian Mennonite family suffering from adult onset, slowly progressive, disabling, multifocal myoclonus. Somatosensory evoked potentials indicated a cortical origin of the myoclonus. There were no associated seizures. Some severely affected individuals developed signs of progressive cerebellar ataxia of variable severity late in the course of their illness. The phenotype was inherited in an autosomal dominant fashion. We demonstrated linkage to chromosome 16q21-22.1. We then sequenced all coding sequence in the critical region, identifying only a single cosegregating, novel, nonsynonymous mutation, which resides in the gene NOL3. Furthermore, this mutation was found to alter post-translational modification of NOL3 protein in vitro.

INTERPRETATION

We propose that familial cortical myoclonus is a novel movement disorder that may be caused by mutation in NOL3. Further investigation of the role of NOL3 in neuronal physiology may shed light on neuronal membrane hyperexcitability and pathophysiology of myoclonus and related disorders.

White matter abnormalities in gene-positive myoclonus-dystonia

Myoclonus-dystonia is an autosomal dominantly inherited movement disorder clinically characterized by myoclonic jerks and dystonic movements of the upper body. Functional imaging and structural gray matter imaging studies in M-D suggest defective sensorimotor integration and an association between putaminal volume and severity of dystonia, possibly because of neuronal plasticity. As we expect changes in the connections between the cortical and subcortical regions, we performed a combination of white matter voxel-based morphometry (wVBM) and diffusion tensor imaging (DTI) to detect macro- and microstructural white matter changes, respectively, in DYT-11 mutations carriers (M-D). Sixteen clinically affected DYT-11 mutation carriers and 18 control subjects were scanned with 3-Tesla MRI to compare white matter volume, fractional anisotropy, and mean diffusivity between groups. In DYT11 mutation carriers, increased white matter volume and FA and decreased mean diffusivity were found in the subthalamic area of the brain stem, including the red nucleus. Furthermore, decreased mean diffusivity was found in the subgyral cortical sensorimotor areas. The white matter changes found in the subthalamic area of the brain stem, connecting the cerebellum with the thalamus, are compatible with the hypothesis that abnormal function in M-D involves a network that includes the cerebellum, brain stem, and basal ganglia. Whether these changes are causative or an effect of M-D requires further study.

Myoclonus

Myoclonus is a hyperkinetic movement disorder characterized by quick, involuntary jerks. It encompasses a vast range of etiologies and widespread anatomic locations. Treatment frequently requires multiple agents and is often only partially beneficial. These patients pose a considerable challenge for the clinician, further complicated by the fact that many of the treatment choices lack evidence-based support. In the past few years, publications regarding therapy have been largely observational case reports or series. Although the literature on treatment of cortical myoclonus appears to be growing, evidence regarding myoclonus of noncortical origin is less well established. Investigation of more satisfactory treatments is needed, as this condition can be disturbing, debilitating, and sometimes harmful for patients. Continuing investigations are using various animal models (mostly of posthypoxic myoclonus), electrophysiologic studies, new imaging techniques such as diffusion tensor imaging, and genetic studies. Meanwhile, the clinical approach to diagnosing and classifying myoclonus remains largely unchanged. This review updates readers on current investigations and suggests guidelines for diagnosing and treating myoclonus.

Amantadine-induced myoclonus in a patient with progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a tauopathy that generally results in a hypokinetic disorder. Treatment is largely symptomatic, with some small studies indicating a benefit with dopaminergic therapy. Myoclonus is a hyperkinetic disorder that can be seen as part of later stage Parkinson's disease and in multiple system atrophy, but is rarely seen in PSP. Here we report a case of myoclonus precipitated by amantadine in a patient with PSP.

Post-stroke Movement Disorders: Clinical Manifestations and Pharmacological Management

Involuntary abnormal movements have been reported after ischaemic and haemorrhagic stroke. Post stroke movement disorders can appear as acute or delayed sequel. At the moment, for many of these disorders the knowledge of pharmacological treatment is still inadequate. Dopaminergic and GABAergic systems may be mainly involved in post-stroke movement disorders. This article provides a review on drugs commonly used in post-stroke movement disorders, given that some post-stroke movement disorders have shown a partial benefit with pharmacological approach.

Acute posthypoxic myoclonus after cardiopulmonary resuscitation

Background

Acute posthypoxic myoclonus (PHM) can occur in patients admitted after cardiopulmonary resuscitation (CPR) and is considered to have a poor prognosis. The origin can be cortical and/or subcortical and this might be an important determinant for treatment options and prognosis. The aim of the study was to investigate whether acute PHM originates from cortical or subcortical structures, using somatosensory evoked potential (SEP) and electroencephalogram (EEG).

Methods

Patients with acute PHM (focal myoclonus or status myoclonus) within 72 hours after CPR were retrospectively selected from a multicenter cohort study. All patients were treated with hypothermia. Criteria for cortical origin of the myoclonus were: giant SEP potentials; or epileptic activity, status epilepticus, or generalized periodic discharges on the EEG (no back-averaging was used). Good outcome was defined as good recovery or moderate disability after 6 months.

Results

Acute PHM was reported in 79/391 patients (20%). SEPs were available in 51/79 patients and in 27 of them (53%) N20 potentials were present. Giant potentials were seen in 3 patients. EEGs were available in 36/79 patients with 23/36 (64%) patients fulfilling criteria for a cortical origin. Nine patients (12%) had a good outcome. A broad variety of drugs was used for treatment.

Conclusions

The results of this study show that acute PHM originates from subcortical, as well as cortical structures. Outcome of patients admitted after CPR who develop acute PHM in this cohort was better than previously reported in literature. The broad variety of drugs used for treatment shows the existing uncertainty about optimal treatment.

Abnormal nuclear envelope in the cerebellar Purkinje cells and impaired motor learning in DYT11 myoclonus-dystonia mouse models

Myoclonus-dystonia (M-D) is a movement disorder characterized by myoclonic jerks with dystonia. DYT11 M-D is caused by mutations in SGCE which codes for ɛ-sarcoglycan. SGCE is maternally imprinted and paternally expressed. Abnormal nuclear envelope has been reported in mouse models of DYT1 generalized torsion dystonia. However, it is not known whether similar alterations occur in DYT11 M-D. We developed a mouse model of DYT11 M-D using paternally inherited Sgce heterozygous knockout (Sgce KO) mice and reported that they had myoclonus and motor coordination and learning deficits in the beam-walking test. However, the specific brain regions that contribute to these phenotypes have not been identified. Since ɛ-sarcoglycan is highly expressed in the cerebellar Purkinje cells, here we examined the nuclear envelope in these cells using a transmission electron microscope and found that they are abnormal in Sgce KO mice. Our results put DYT11 M-D in a growing family of nuclear envelopathies. To analyze the effect of loss of ɛ-sarcoglycan function in the cerebellar Purkinje cells, we produced paternally inherited cerebellar Purkinje cell-specific Sgce conditional knockout (Sgce pKO) mice. Sgce pKO mice showed motor learning deficits, while they did not show abnormal nuclear envelope in the cerebellar Purkinje cells, robust motor deficits, or myoclonus. The results suggest that ɛ-sarcoglycan in the cerebellar Purkinje cells contributes to the motor learning, while loss of ɛ-sarcoglycan in other brain regions may contribute to nuclear envelope abnormality, myoclonus and motor coordination deficits.

Management of the post-cardiac arrest syndrome

BACKGROUND

Recent advances in resuscitation science have revolutionized care of the cardiac arrest patient. Dramatic departures from time-honored advanced cardiac life support therapies, such as cardiocerebral resuscitation and bundled post-arrest care, have given rise to a new paradigm of resuscitation practices, which has boosted the rate of neurologically intact survival.

OBJECTIVES

This article reviews the pathophysiology of the post-cardiac arrest syndrome, the collective pathophysiology after return of spontaneous circulation, and presents management pearls specifically for the emergency physician. This growing area of scientific inquiry must be managed appropriately to sustain improved outcomes.

DISCUSSION

The emergency physician must understand this pathophysiology, manage resuscitated patients according to the latest evidence, and coordinate with appropriate inpatient resources.

CONCLUSION

The new approach to cardiac arrest care is predicated on a chain of survival that spans the spectrum of care from the prehospital arena through the emergency, intensive, and inpatient settings. The emergency physician is a crucial link in this chain.

Systematic Review of Management Strategies for Middle Ear Myoclonus

Objective. Middle ear myoclonus is a rare condition with distinct characteristics at presentation. Diagnosis is based primarily on history, clinical examination, and long-time-based tympanometry. No consensus exists regarding treatment at present. This review was designed to identify relevant studies on current investigation and management.

Data Source. A systematic electronic literature search of MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Cochrane Trials register, and Web of Science was conducted for articles describing middle ear myoclonus through to May 2011. English- and non-English-language articles that focused on investigation and treatment were considered for review.

Review Method. Two authors independently reviewed the articles for study design, treatment, intervention, and outcome. Data from human and experimental studies were considered.

Results. A total of 21 articles were identified for this review. Most studies were found to be case reports or small case series. In general, there was no evidence of a conclusive diagnostic test or treatment for middle ear myoclonus.

Conclusion. There is a need for high-quality prospective controlled trials to determine the most effective management of middle ear myoclonus. The authors describe a treatment algorithm based on the data available and clinical knowledge.

Classifying myoclonus: a riddle, wrapped in a mystery, inside an enigma

Myoclonus is complex, and is likely to encompass a number of relatively disparate phenomena. A widely used approach to the classification of myoclonus is a physiological one, in which the major forms are cortical and subcortical. In this classification, cortical forms of myoclonus are defined by the presence of enlarged somatosensory evoked potentials (SEP), back-averaged potentials, and enhanced long latency reflexes, whereas subcortical forms are largely delineated by the absence of these features. In addition to cortical and subcortical types, the presence of generalized spike and wave discharges on EEG indicate the presence of cortical-subcortical interactions, analogous to absence seizures of idiopathic generalized epilepsy. However, a number of difficulties arise in applying these criteria to many forms of myoclonus: One can conclude that it is likely that many forms of myoclonus lie on a spectrum between myoclonus and tremor. Some have clearcut evidence for being of cortical origin, whereas others are cortical-subcortical or purely subcortical. The role of subcortical structures in influencing electrophysiological phenomena is poorly understood, and merits further investigation.

Abnormal nuclear envelopes in the striatum and motor deficits in DYT11 myoclonus-dystonia mouse models

DYT11 myoclonus-dystonia (M-D) is a movement disorder characterized by myoclonic jerks with dystonic symptoms and caused by mutations in paternally expressed SGCE, which codes for ε-sarcoglycan. Paternally inherited Sgce heterozygous knock-out (KO) mice exhibit motor deficits and spontaneous myoclonus. Abnormal nuclear envelopes have been reported in cellular and mouse models of early-onset DYT1 generalized torsion dystonia; however, the relationship between the abnormal nuclear envelopes and motor symptoms are not clear. Furthermore, it is not known whether abnormal nuclear envelope exists in non-DYT1 dystonia. In the present study, abnormal nuclear envelopes in the striatal medium spiny neurons (MSNs) were found in Sgce KO mice. To analyze whether the loss of ε-sarcoglycan in the striatum alone causes abnormal nuclear envelopes, motor deficits or myoclonus, we produced paternally inherited striatum-specific Sgce conditional KO (Sgce sKO) mice and analyzed their phenotypes. Sgce sKO mice exhibited motor deficits in both beam-walking and accelerated rotarod tests, while they did not exhibit abnormal nuclear envelopes, alteration in locomotion, or myoclonus. The results suggest that the loss of ε-sarcoglycan in the striatum contributes to motor deficits, while it alone does not produce abnormal nuclear envelopes or myoclonus. Development of therapies targeting the striatum to compensate for the loss of ε-sarcoglycan function may rescue the motor deficits in DYT11 M-D patients.

Postresuscitation care

Caring in the emergency department for the patient with return of spontaneous circulation after cardiac arrest is challenging. A coordinated and systematic approach to post-cardiac arrest care can improve the mortality and the chance of meaningful neurologic recovery. By achieving appropriate targets for oxygenation, ventilation, and hemodynamic parameters, along with initiating therapeutic hypothermia and arranging early percutaneous coronary intervention, the emergency physician can have the most significant impact on patients who have just been revived from death.

Spinal Myoclonus Developed during Cervical Epidural Drug Infusion in Postherpetic Neuralgia Patient

Postherpetic neuralgia is the most frequent complication of herpes zoster. Treatment of this neuropathic pain syndrome is difficult and often disappointing. Although postherpetic neuralgia is generally a self-limited condition, it can last indefinitely. Continuous epidural blockade for patients with acute zoster can shorten the duration of treatment. However, continuous epidural block has some complications such as infection, dural puncture, and total spinal and nerve damages. We report a case of myoclonus during continuous epidural block with ropivacaine, morphine, and ketamine in an acute zoster patient.