Myoclonus: current concepts and recent advances

Limb-Shaking And Transient Ischemic Attack: A Systematic Review

BACKGROUND

Limb-shaking is one of the transient ischemic attacks (TIA) 'chameleons.' This literature review aims to evaluate the clinical, epidemiological profile, pathologic mechanisms, and management of limb-shaking TIA.

REVIEW SUMMARY

Relevant reports in Medline's (PubMed) database were identified and assessed by 2 reviewers without language restriction from 1985 to 2022. A total of 82 reports containing 161 cases that developed limb-shaking TIA were reported. The mean and median age were 61.36 (SD: 15.29) and 62 years (range: 4-93 y). Most of the individuals affected were males (64.34%). Limb-shaking was reported as unilateral in 83.33% of the patients. Limb-shaking presented with other neurological deficits in 44.33% of the individuals, in which the most common concurrent neurological deficit was the weakness of at least 1 limb. A recurrence of the "shaking" phenomenon was observed in 83 individuals. A trigger of limb-shaking was reported in 69 cases, and the most common was changing body position. The internal carotid artery was the most frequent vessel involved in limb-shaking. A chronically occluded internal carotid artery was observed in 42 individuals. Hypertension was the most common comorbidity. The management was conservative in 42.30% of the cases. The most frequent misdiagnoses were seizures. A full recovery was achieved in 56.60% of the individuals.

CONCLUSIONS

Limb-shaking TIA could be defined as involuntary, rhythmic, brief (<5 min), recurrent, jerky movement usually precipitated by activities that may reduce cerebral blood flow. The "shaking" phenomenon was primarily described as a manifestation of symptomatic complete internal carotid artery obstruction.

Symptoms and problems reported by patients with non-cancer diseases through open-ended questions in specialist palliative care: a national register-based study

PURPOSE

Since 2010, a comprehensive symptom/problem (S/P) assessment has been carried out in Danish specialist palliative care using the EORTC QLQ-C15-PAL questionnaire and the open-ended "Write In three Symptoms/Problems" (WISP) instrument. On WISP patients can report up to three S/Ps not included in the EORTC QLQ-C15-PAL. However, little is known about which S/Ps patients with non-cancer diseases report using WISP. Therefore, we investigated the prevalence and severity of S/Ps reported on WISP by non-cancer patients in specialist palliative care and compared these S/Ps with those previously reported by cancer patients.

METHODS

This register-based study collected data from the Danish Palliative Care Database. We included adult patients with non-cancer diseases answering the EORTC QLQ-C15-PAL at admittance to specialist palliative care between 2016 and 2021. WISP responses were qualitatively categorized, and their prevalence and severity calculated.

RESULTS

Of the 2323 patients with non-cancer diseases answering the EORTC QLQ-C15-PAL, 812 (34.9%) reported at least one S/P using WISP. A total of 1340 S/Ps were reported on WISP, of which 56.7% were not included in the EORTC QLQ-C15-PAL (i.e., were new). Edema, existential problems, dizziness, cough, and dysphagia were the most prevalent new S/Ps. Overall, 88.7% of the S/Ps were scored as moderate-severe. The prevalence of S/Ps reported on WISP did not significantly differ between cancer and non-cancer patients, except for existential problems, dysphagia, myoclonus, speaking problems, sweats, and vomiting.

CONCLUSION

The similarities and differences in the prevalence of the most common S/Ps reported on WISP confirm that WISP improves symptom assessment regardless of patient diagnosis.

Utility of Neurophysiological Evaluation in Movement Disorders Clinical Practice

Background

Quantitative and objective neurophysiological assessment can help to define the predominant phenomenology and provide diagnoses that have prognostic and therapeutic implications for movement disorders.

Objectives

Evaluate the agreement between initial indications and final diagnoses after neurophysiological evaluations in a specialized movement disorders center.

Methods

Electrophysiological studies conducted for movement disorders from 2003 to 2021 were reviewed. The indications were classified according to predominant phenomenology and the diagnoses categorized in subgroups of phenomenology.

Results

A total of 509 studies were analyzed. 51% (259) of patients were female, with a mean age of 51 years (ranges 5 to 89 years). The most common reasons for referral were evaluation of functional movement disorders (FMD), followed by jerky movements, tremor and postural instability. Regarding FMD referrals, there was a diagnostic change in 13% of the patients after electrophysiological assessment. The patients with jerky movements as indication had a diagnosis other than myoclonus in 27% of them, and tremor was not confirmed in 20% of the cases. In patients with an electrophysiological diagnosis of FMD, it was not suspected in 30% of the referrals. Similarly, tremor was not mentioned in the referral of 17% of the patients with this electrophysiological diagnosis and myoclonus was not suspected in 13% of the cases.

Conclusions

Electrophysiological assessment has utility in the evaluation of movement disorders, even in patients evaluated by movement disorders neurologists. More studies are needed to standardize the protocols between centers and to promote the availability and use of these techniques among movement disorders clinics.

Post-hypoxic myoclonus; what we know and gaps in knowledge

Post-hypoxic myoclonus (PHM) is a rare neurological complication having two different variants depending on acute or chronic onset after cardiopulmonary resuscitation following cardiac arrest: myoclonic status epilepticus (MSE) and Lance-Adams syndrome (LAS) respectively. Clinical and simultaneous electro-encephalographic (EEG) and electromyographic (EMG) tracing can distinguish between the two. Anecdotal treatment with benzodiazepines and anaesthetics (in the case of MSE) have been tried. Although limited evidence is available, valproic acid, clonazepam and levetiracetam, either in combination with other drugs or alone, have shown to control epilepsy associated with LAS effectively. Deep brain stimulation is a novel and promising advance in LAS treatment.

Gabapentin-Associated Movement Disorders: A Literature Review

BACKGROUND

Gabapentin (GBP)-induced movement disorders (MDs) are under-recognized adverse drug reactions. They are commonly not discussed with patients, and their sudden occurrence can lead to misdiagnosis. This literature review aims to evaluate the clinical-epidemiological profile, pathological mechanisms, and management of GBP-associated MD.

METHODS

Two reviewers identified and assessed relevant reports in six databases without language restriction between 1990 and 2023.

RESULTS

A total of 99 reports of 204 individuals who developed a MD associated with GBP were identified. The MDs encountered were 135 myoclonus, 22 dyskinesias, 7 dystonia, 3 akathisia, 3 stutterings, 1 myokymia, and 1 parkinsonism. The mean and median ages were 54.54 (SD: 17.79) and 57 years (age range: 10-89), respectively. Subjects were predominantly male (53.57%). The mean and median doses of GBP when the MD occurred were 1324.66 (SD: 1117.66) and 1033 mg/daily (GBP dose range: 100-9600), respectively. The mean time from GBP-onset to GBP-associated MD was 4.58 weeks (SD: 8.08). The mean recovery time after MD treatment was 4.17 days (SD: 4.87). The MD management involved GBP discontinuation. A total of 82.5% of the individuals had a full recovery in the follow-up period.

CONCLUSIONS

Myoclonus (GRADE A) and dyskinesia (GRADE C) were the most common movement disorders associated with GBP.

Spinal muscular atrophy-like phenotype in a mouse model of acid ceramidase deficiency

Mutations in ASAH1 have been linked to two allegedly distinct disorders: Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). We have previously reported FD-like phenotypes in mice harboring a single amino acid substitution in acid ceramidase (ACDase), P361R, known to be pathogenic in humans (P361R-Farber). Here we describe a mouse model with an SMA-PME-like phenotype (P361R-SMA). P361R-SMA mice live 2-3-times longer than P361R-Farber mice and have different phenotypes including progressive ataxia and bladder dysfunction, which suggests neurological dysfunction. We found profound demyelination, loss of axons, and altered sphingolipid levels in P361R-SMA spinal cords; severe pathology was restricted to the white matter. Our model can serve as a tool to study the pathological effects of ACDase deficiency on the central nervous system and to evaluate potential therapies for SMA-PME.

A Case of Drug-Resistant Myoclonus Improved by Only Slight Adjustment to the Hemodialysis Setting

Myoclonus, a rare complication in patients with end-stage renal disease, is typically ameliorated through hemodialysis. The present case concerns an 84-year-old male with chronic renal failure undergoing hemodialysis, presenting involuntary movements in his limbs, which gradually worsened from the initiation of hemodialysis without constant elevation of serum blood urea nitrogen and electrolytes levels. Surface electromyography revealed characteristic findings consistent with myoclonus. He was diagnosed with subcortical-nonsegmental myoclonus related to hemodialysis, and the myoclonus was significantly alleviated after slightly increasing the post-dialysis target weight even though drug treatment was ineffective. This case suggests that drug-resistant myoclonus in patients with renal failure may be improved by adjusting hemodialysis settings, even in cases of atypical dialysis disequilibrium syndrome.

Neurophysiology of Juvenile and Progressive Myoclonic Epilepsy

SUMMARY

Myoclonus can be epileptic or nonepileptic. Epileptic myoclonus has been defined in clinical, neurophysiological, and neuroanatomical terms. Juvenile myoclonic epilepsy (JME) is typically considered to be an adolescent-onset idiopathic generalized epilepsy with a combination of myoclonic, generalized tonic-clonic, and absence seizures and normal cognitive status that responds well to anti-seizure medications but requires lifelong treatment. EEG shows generalized epileptiform discharges and photosensitivity. Recent observations indicate that the clinical picture of JME is heterogeneous and a number of neuropsychological and imaging studies have shown structural and functional abnormalities in the frontal lobes and thalamus. Advances in neurophysiology and imaging suggest that JME may not be a truly generalized epilepsy, in that restricted cortical and subcortical networks appear to be involved rather than the entire brain. Some patients with JME may be refractory to anti-seizure medications and attempts have been made to identify neurophysiological biomarkers predicting resistance. Progressive myoclonic epilepsy is a syndrome with multiple specific causes. It is distinct from JME because of the occurrence of progressive neurologic dysfunction in addition to myoclonus and generalized tonic-clonic seizures but may sometimes be difficult to distinguish from JME or misdiagnosed as drug-resistant JME. This article provides an overview of progressive myoclonic epilepsy and focuses on the clinical and neurophysiological findings in the two most commonly recognized forms of progressive myoclonic epilepsy-Unverricht-Lundborg disease (EPM1) and Lafora disease (EPM2). A variety of neurophysiological tests can be used to distinguish between JME and progressive myoclonic epilepsy and between EPM1 and EPM2.

How to Do an Electrophysiological Study of Myoclonus

SUMMARY

Diagnosing and characterizing myoclonus can be challenging. Many authors agree on the need to complement the clinical findings with an electrophysiological study to characterize the movements. Besides helping to rule out other movements that may look like myoclonus, electrophysiology can help localize the source of the movement. This article aims to serve as a practical manual on how to do a myoclonus study. For this purpose, the authors combine their experience with available evidence. The authors provide detailed descriptions of recording poly-electromyography, combining electroencephalography and electromyography, Bereitschaftspotentials, somatosensory evoked potentials, and startle techniques. The authors discuss analysis considerations for these data and provide a simplified algorithm for their interpretation. Finally, the authors discuss some factors that they believe have hindered the broader use of these useful techniques.

Neurophysiological and Clinical Correlates of Acute Posthypoxic Myoclonus

SUMMARY

Prognostication following cardiorespiratory arrest relies on the neurological examination, which is supported by neuroimaging and neurophysiological testing. Acute posthypoxic myoclonus (PHM) is a clinical entity that has prognostic significance and historically has been considered an indicator of poor outcome, but this is not invariably the case. "Malignant" and more "benign" forms of acute PHM have been described and differentiating them is key in understanding their meaning in prognosis. Neurophysiological tests, electroencephalogram in particular, and clinical phenotyping are crucial in defining subtypes of acute PHM. This review describes the neurophysiological and phenotypic markers of malignant and benign forms of acute PHM, a clinical approach to evaluating acute PHM following cardiorespiratory arrest in determining prognosis, and gaps in our understanding of acute PHM that require further study.

Intratympanic Botulinum Toxin Injection as a New Therapeutic Modality for Middle Ear Myoclonic Tinnitus

OBJECTIVE

Middle ear myoclonic tinnitus (MEMT) is a disease caused by myoclonus or abnormal contractive movement of middle ear muscles (MEMs). This translational study was conducted to propose intratympanic botulinum toxin (IT-BTX) injection as a new therapeutic modality to treat MEMT.

STUDY DESIGN

Animal experiment and nonrandomized controlled clinical trial.

SETTING

Laboratory and medical center of an academic tertiary medical institution.

METHODS

For the animal study, male Sprague-Dawley rats were divided into 4 subgroups according to the sacrificing day after IT-BTX injection. After initial hearing tests, randomly assigned experimental ears were intratympanically injected with 1 unit/100 μL of BTX-A, whereas control ears were injected with normal saline. Changes in the hearing thresholds, morphometry of the cochleae, electron microscopy study, and immunofluorescence analysis of MEMs were evaluated. For the human study, 10 intractable MEMT patients were enrolled. The hearing thresholds and the degree of tinnitus distress were observed for changes after IT-BTX injection. All patients were followed up for 3 months.

RESULTS

As for the animal study, there were no significant changes in hearing thresholds and cochlear morphologies in all 4 subgroups of the rats. Significant MEM degenerations and immuno-detection of cleaved synaptosome-associated protein of 25 kDa (cSNAP-25) indicated the efficacy of IT-BTX. MEMT patients enrolled for the pilot clinical trial showed statistically significant improvement in tinnitus after IT-BTX injection. No major complications were noted.

CONCLUSION

The new therapeutic modality of IT-BTX injection for the treatment of MEMT seems highly promising with an excellent result.

Levodopa-Induced Dyskinesia in Parkinson's Disease: Pathogenesis and Emerging Treatment Strategies

The most commonly used treatment for Parkinson's disease (PD) is levodopa, prescribed in conjunction with carbidopa. Virtually all patients with PD undergo dopamine replacement therapy using levodopa during the course of the disease's progression. However, despite the fact that levodopa is the "gold standard" in PD treatments and has the ability to significantly alleviate PD symptoms, it comes with side effects in advanced PD. Levodopa replacement therapy remains the current clinical treatment of choice for Parkinson's patients, but approximately 80% of the treated PD patients develop levodopa-induced dyskinesia (LID) in the advanced stages of the disease. A better understanding of the pathological mechanisms of LID and possible means of improvement would significantly improve the outcome of PD patients, reduce the complexity of medication use, and lower adverse effects, thus, improving the quality of life of patients and prolonging their life cycle. This review assesses the recent advancements in understanding the underlying mechanisms of LID and the therapeutic management options available after the emergence of LID in patients. We summarized the pathogenesis and the new treatments for LID-related PD and concluded that targeting pathways other than the dopaminergic pathway to treat LID has become a new possibility, and, currently, amantadine, drugs targeting 5-hydroxytryptamine receptors, and surgery for PD can target the Parkinson's symptoms caused by LID.

Evaluation of the Patient With Paroxysmal Spells Mimicking Epileptic Seizures

BACKGROUND

The diagnostic issue of paroxysmal spells, including epileptic seizure (ES) mimics, is one that neurologists frequently encounter. This review provides an up-to-date overview of the most common causes of ES mimics encountered in the outpatient setting.

REVIEW SUMMARY

Paroxysmal spells are characterized by changes in awareness, attention, perception, or abnormal movements. These can be broadly classified as ES and nonepileptic spells (NES). NES mimics ES but are distinguished by their symptomatology and lack of epileptiform activity on electroencephalography. NES may have psychological or physiological underpinnings. Psychogenic non-ES are the most common mimics of ES. Physiological causes of NES include syncope, cerebrovascular, movement, and sleep-related disorders.

CONCLUSIONS

Distinguishing NES from ES at times may be challenging even to the most experienced clinicians. However, detailed history with an emphasis on the clinical clues, including taking a moment-by-moment history of the event from the patient and observers and physical examination, helps create an appropriate differential diagnosis to guide further diagnostic testing. An accurate diagnosis of NES prevents iatrogenic harm, including unnecessary exposure to antiseizure medications and overuse of health care resources. It also allows for the correct specialist referral and appropriate treatment.

Myoclonus and other jerky movement disorders

Myoclonus and other jerky movements form a large heterogeneous group of disorders. Clinical neurophysiology studies can have an important contribution to support diagnosis but also to gain insight in the pathophysiology of different kind of jerks. This review focuses on myoclonus, tics, startle disorders, restless legs syndrome, and periodic leg movements during sleep. Myoclonus is defined as brief, shock-like movements, and subtypes can be classified based the anatomical origin. Both the clinical phenotype and the neurophysiological tests support this classification: cortical, cortical-subcortical, subcortical/non-segmental, segmental, peripheral, and functional jerks. The most important techniques used are polymyography and the combination of electromyography-electroencephalography focused on jerk-locked back-averaging, cortico-muscular coherence, and the Bereitschaftspotential. Clinically, the differential diagnosis of myoclonus includes tics, and this diagnosis is mainly based on the history with premonitory urges and the ability to suppress the tic. Electrophysiological tests are mainly applied in a research setting and include the Bereitschaftspotential, local field potentials, transcranial magnetic stimulation, and pre-pulse inhibition. Jerks due to a startling stimulus form the group of startle syndromes. This group includes disorders with an exaggerated startle reflex, such as hyperekplexia and stiff person syndrome, but also neuropsychiatric and stimulus-induced disorders. For these disorders polymyography combined with a startling stimulus can be useful to determine the pattern of muscle activation and thus the diagnosis. Assessment of symptoms in restless legs syndrome and periodic leg movements during sleep can be performed with different validated scoring criteria with the help of electromyography.

A Case of Lance Adams Syndrome in a Patient with Attempted Hanging

Lance Adams syndrome is the term used to describe late post-hypoxic myoclonus. Here we describe a patient who developed action and intention myoclonus after 7 days of attempted partial hanging. The similarity of Lance Adams syndrome, which is a treatable condition to a cerebellar syndrome, and the diagnostic difficulties have been highlighted.

Clinical neurophysiology of Parkinson's disease and parkinsonism

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This review is part of the series on the clinical neurophysiology of movement disorders and focuses on Parkinson’s disease and parkinsonism.

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The pathophysiology of cardinal parkinsonian motor symptoms and myoclonus are reviewed.

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The recordings from microelectrode and deep brain stimulation electrodes are reported in detail.

This review is part of the series on the clinical neurophysiology of movement disorders. It focuses on Parkinson’s disease and parkinsonism. The topics covered include the pathophysiology of tremor, rigidity and bradykinesia, balance and gait disturbance and myoclonus in Parkinson’s disease. The use of electroencephalography, electromyography, long latency reflexes, cutaneous silent period, studies of cortical excitability with single and paired transcranial magnetic stimulation, studies of plasticity, intraoperative microelectrode recordings and recording of local field potentials from deep brain stimulation, and electrocorticography are also reviewed. In addition to advancing knowledge of pathophysiology, neurophysiological studies can be useful in refining the diagnosis, localization of surgical targets, and help to develop novel therapies for Parkinson’s disease.

Speech-induced action myoclonus

BACKGROUND

Speech-induced action myoclonus may occur as a component of a generalized myoclonus syndrome. However, it may also present in isolation, or with a paucity of other findings, and be diagnostically challenging.

OBJECTIVES

To report a retrospective case series of restricted speech-induced action myoclonus.

METHODS

We reviewed cases of speech-induced action myoclonus evaluated at Mayo Clinic Rochester from 1989 to 2020. We eliminated cases where a more generalized myoclonic disorder was also present. Clinical, imaging, and electrophysiologic data were extracted.

RESULTS

Four cases were identified in which speech-induced action myoclonus of craniofacial muscles was the predominant clinical presentation. All described cranial muscle twitching induced by speaking, and two cases also reported speech interruptions. Diagnosis was confirmed by expert speech pathologists in all cases. Diagnostic aids included modulation with different speech tasks and speaking rates, and surface electrophysiology which confirmed craniofacial myoclonus induced by speaking tasks (three cases). Previous misdiagnosis included functional, dystonic, neuromuscular junction pathology, or hemifacial spasm. Two cases had isolated speech-induced myoclonus, and the other two had coexistent upper limb tremor. Potential etiologic factors were identified in three cases - medication (2), epilepsy (1) - while in one patient no cause was identified. One patient partially improved with anti-myoclonic medication and speech therapy.

CONCLUSIONS

Speech-induced action myoclonus may occur in isolation and is frequently misdiagnosed. Diagnostic aids include modulation with different speech tasks and speaking rates, and surface electrophysiology.

Surgical Treatment of Propriospinal Myoclonus: A Case Report

Propriospinal myoclonus (PSM) is a rare segmental movement disorder characterized by repetitive irregular myoclonic jerks of the trunk and/or axial limbs at the resting state. It is imperative to make a correct diagnosis as other movement disorders can be mistaken for or mask PSM. Therefore, a battery of neuroimaging and neurophysiological testing must be undertaken. In our case report, we discuss a patient who was diagnosed with PSM concurrently with cervical degenerative stenosis and then had a successful outcome via surgical decompression and arthrodesis of the cervical spine. We documented the patient’s postoperative course and achievement of complete remission, sustained at a 41-month follow-up. We then grouped our case together with five other PSM cases in the literature to offer readers a broader context of the role of surgical spinal intervention in ameliorating PSM.

Middle ear myoclonus: Systematic review of results and complications for various treatment approaches

OBJECTIVE

To perform a systematic review of the diagnosis and treatment of patients with pulsatile tinnitus secondary to middle ear myoclonus.

DATABASES REVIEWED

PubMed, EMBASE, and Scopus.

METHODS

A systematic review was performed using standardized methodology. Computerized and manual searches were performed to identify studies of all ages (patients) who had middle ear myoclonus (intervention). All study designs were assessed. Extracted data included demographics, clinical features, duration of followup as well as the diagnosis and reversibility of symptoms with medical or surgical intervention. Studies were included if they included subjects with middle ear myoclonus. Exclusion criteria included letters/commentaries and reviews.

RESULTS

Twenty articles representing 115 subjects with middle ear myoclonus were included. The mean age was 29.7 (range 6-67). The follow-up period ranged from 5 weeks to 36 months. Primary treatment consists of medical therapy utilising anxiolytics, antiepileptics, botulinum toxin and surgical treatment involving division of middle ear muscular tendon(s). In total, 60 patients underwent middle ear muscular tenotomies, with division of both stapedius and tensor tympani tendons being the most prevalent (88%). Limitations in the data arose from study design, related comorbidities such as palatal myoclonus, and concomitant drug administration. No study provided any objective criteria to diagnose this condition or evaluate post-treatment outcome.

CONCLUSION

Middle ear myoclonus is an entity that is poorly assessed in the literature. There is a lack of consensus regarding the criteria and strategies for both diagnosing and treating this condition. Although level of evidence of current studies remains modest, it is felt that a stepwise approach is deemed best, with therapeutic decisions being made on an individual basis, evaluating each patient's specific circumstances and priorities.

Electrophysiological characteristics and anatomical differentiation of epileptic and non-epileptic myoclonus

Background

Electrophysiological techniques have been used for discriminating myoclonus from other hyperkinetic movement disorders and for classifying the myoclonus subtype. This study was carried out on patients with different subtypes of myoclonus to determine the electrophysiological characteristics and the anatomical classification of myoclonus of different etiologies. This study included 20 patients with different subtypes of myoclonus compared with 30 control participants. Electrophysiological study was carried out for all patients by somatosensory evoked potential (SSEP) and electroencephalography (EEG) while the control group underwent SSEP. SSEP was evaluated in patients and control groups by stimulation of right and left median nerves.

Results

This study included 50 cases with myoclonus of different causes with mean age of 39.3 ± 15.7 and consisted of 23 males and 27 females. Twenty-nine (58%) of the patients were epileptics, while 21 (42%) were non-epileptics. Cases were classified anatomically into ten cases with cortical myoclonus (20%), 12 cases with subcortical myoclonus (24%), and 28 cases with cortical–subcortical myoclonus (56%). There was a significant difference regarding the presence of EEG findings in epileptic myoclonic and non-epileptic myoclonic groups (P = 0.005). Also, there were significant differences regarding P24 amplitude, N33 amplitude, P24–N33 peak-to-peak complex amplitude regarding all types of myoclonus. Primary myoclonic epilepsy (PME) demonstrated significant giant response, juvenile myoclonic epilepsy (JME) demonstrated no enhancement compared to controls, while secondary myoclonus demonstrated lower giant response compared to PME.

Conclusion

Somatosensory evoked potential and electroencephalography are important for the diagnosis and anatomical sub-classification of myoclonus and so may help in decision-making regarding to the subsequent management.

Scorpion Envenomation of Lactating Rats Decreases the Seizure Threshold in Offspring

Few data are available in the literature describing the long-term effects of envenoming in the perinatal period. In this study, the relationship between envenoming of lactating rats and possible behavioral changes in the mother and in her offspring were investigated. Lactating Wistar rats received a single dose of T. serrulatus crude venom on postnatal days 2 (V2), 10 (V10) or 16 (V16), and had their maternal behavior evaluated. The seizure threshold was evaluated in adulthood offspring. A decrease in maternal care during envenoming was observed in V2 and V10 groups. The retrieval behavior was absent in the V2 group, and a lower seizure threshold in the adult offspring of all groups was observed. During envenoming, mothers stayed away from their offspring for a relatively long time. Maternal deprivation during the early postnatal period is one of the most potent stressors for pups and could be responsible, at least in part, for the decrease in the convulsive threshold of the offspring since stress is pointed to as a risk factor for epileptogenesis. Furthermore, the scorpionic accident generates an intense immune response, and inflammation in neonates increases the susceptibility to seizures in adulthood. Therefore, maternal envenoming during lactation can have adverse effects on offspring in adulthood.

Characterization of Postanoxic Tonic Eyelid Opening: A Poorly Recognized Prognostic Sign

Background

Postanoxic myoclonus is a known poor prognostic sign, and other postanoxic spontaneous movements have been reported but poorly described. We aim to describe the electroclinical phenomenon of postanoxic eyelid openings in context of its possible prognostic value.

Methods

We collected clinical data on postcardiac arrest patients with suspicious eyelid movements noted on continuous EEG monitoring. The eyelid movements captured on the video were correlated with the EEG findings and final clinical outcome. Neuroimaging data were reviewed when available. We also conducted a thorough literature review on this topic.

Results

A total of 10 patients (5 females) with average age of 56.1 (±14.4) years were included. The mean cardiopulmonary resuscitation duration was 18.9 (±11.3) minutes. Postanoxic eyelid-opening movements occurred at variable intervals (0.5-570 seconds) in each individual. Close examination of eyelid opening (available in 6 patients) revealed them to be tonic movements, lasting an average of 3 (±0.8) seconds and always succeeded the onset of burst of EEG activity in a burst-suppression background. This is a transient phenomenon, lasting a median duration of 30 (interquartile range 7.75-36) hours. MRI findings in 3 patients demonstrated diffuse cortical ischemic injury with relative sparing of the brainstem. All patients died within 2-7 days following cardiac arrest.

Conclusions

Contrary to previous descriptions, the postanoxic tonic eyelid openings (PATEO) are repetitive but nonperiodic, nonmyoclonic movements. Their close and specific temporal correlation with the burst of EEG activity suggests that this could be considered an ictal phenomenon requiring an intact midbrain based on MRI findings.

Tremor-like subcortical myoclonus in STXBP1 encephalopathy

The phenotypic spectrum of STXBP1-related encephalopathy ranges from infantile epileptic encephalopathy to intellectual disability with nonsyndromic or absent epilepsy. Although being frequently reported, the tremor associated with STXBP1 has not been fully characterized to date. The aim of our study was to describe it. We recruited patients with intellectual disability due to STXBP1 variants, regardless of their epileptic phenotype, who had tremor at examination and who underwent neurophysiological testing including polymyographic registration of upper limbs muscles activity at rest, during posture maintenance and action. Six patients met the inclusion criteria over four years. Clinically, all had a postural and action distal tremor increased by emotions. Neurophysiological recordings showed a specific myoclonus pattern and were highly suggestive of a subcortical generator. The tremor-like observed in STXBP1 encephalopathy is due to a subcortical pseudo-rhythmic myoclonus.

Myoclonus- A Review

Myoclonus is a hyperkinetic movement disorder characterized by a sudden, brief, involuntary jerk. Positive myoclonus is caused by abrupt muscle contractions, while negative myoclonus by sudden cessation of ongoing muscular contractions. Myoclonus can be classified in various ways according to body distribution, relation to activity, neurophysiology, and etiology. The neurophysiological classification of myoclonus by means of electrophysiological tests is helpful in guiding the best therapeutic strategy. Given the diverse etiologies of myoclonus, a thorough history and detailed physical examination are key to the evaluation of myoclonus. These along with basic laboratory testing and neurophysiological studies help in narrowing down the clinical possibilities. Though symptomatic treatment is required in the majority of cases, treatment of the underlying etiology should be the primary aim whenever possible. Symptomatic treatment is often not satisfactory, and a combination of different drugs is often required to control the myoclonus. This review addresses the etiology, classification, clinical approach, and management of myoclonus.

Sleep, neuronal hyperexcitability, inflammation and neurodegeneration: Does early chronic short sleep trigger and is it the key to overcoming Alzheimer's disease?

Evidence links neuroinflammation to Alzheimer's disease (AD); however, its exact contribution to the onset and progression of the disease is poorly understood. Symptoms of AD can be seen as the tip of an iceberg, consisting of a neuropathological build-up in the brain of extracellular amyloid-β (Aβ) plaques and intraneuronal hyperphosphorylated aggregates of Tau (pTau), which are thought to stem from an imbalance between its production and clearance resulting in loss of synaptic health and dysfunctional cortical connectivity. The glymphatic drainage system, which is particularly active during sleep, plays a key role in the clearance of proteinopathies. Poor sleep can cause hyperexcitability and promote Aβ and tau pathology leading to systemic inflammation. The early neuronal hyperexcitability of γ-aminobutyric acid (GABA)-ergic inhibitory interneurons and impaired inhibitory control of cortical pyramidal neurons lie at the crossroads of excitatory/inhibitory imbalance and inflammation. We outline, with a prospective framework, a possible vicious spiral linking early chronic short sleep, neuronal hyperexcitability, inflammation and neurodegeneration. Understanding the early predictors of AD, through an integrative approach, may hold promise for reducing attrition in the late stages of neuroprotective drug development.

Demystifying the spontaneous phenomena of motor hyperexcitability

Possessing a discrete functional repertoire, the anterior horn cell can be in one of two electrophysiological states: on or off. Usually under tight regulatory control by the central nervous system, a hierarchical network of these specialist neurons ensures muscular strength is coordinated, gradated and adaptable. However, spontaneous activation of these cells and their axons can result in abnormal muscular twitching. The muscular twitch is the common building block of several distinct clinical patterns, namely fasciculation, myokymia and neuromyotonia. When attempting to distinguish these entities electromyographically, their unique temporal and morphological profiles must be appreciated. Detection and quantification of burst duration, firing frequency, multiplet patterns and amplitude are informative. A common feature is their persistence during sleep. In this review, we explain the accepted terminology used to describe the spontaneous phenomena of motor hyperexcitability, highlighting potential pitfalls amidst a bemusing and complex collection of overlapping terms. We outline the relevance of these findings within the context of disease, principally amyotrophic lateral sclerosis, Isaacs syndrome and Morvan syndrome. In addition, we highlight the use of high-density surface electromyography, suggesting that more widespread use of this non-invasive technique is likely to provide an enhanced understanding of these motor hyperexcitability syndromes.

Opsoclonus-myoclonus syndrome, a post-infectious neurologic complication of COVID-19: case series and review of literature

Opsoclonus-myoclonus-ataxia syndrome is a heterogeneous constellation of symptoms ranging from full combination of these three neurological findings to varying degrees of isolated individual sign. Since the emergence of coronavirus disease 2019 (COVID-19), neurological symptoms, syndromes, and complications associated with this multi-organ viral infection have been reported and the various aspects of neurological involvement are increasingly uncovered. As a neuro-inflammatory disorder, one would expect to observe opsoclonus-myoclonus syndrome after a prevalent viral infection in a pandemic scale, as it has been the case for many other neuro-inflammatory syndromes. We report seven cases of opsoclonus-myoclonus syndrome presumably parainfectious in nature and discuss their phenomenology, their possible pathophysiological relationship to COVID-19, and diagnostic and treatment strategy in each case. Finally, we review the relevant data in the literature regarding the opsoclonus-myoclonus syndrome and possible similar cases associated with COVID-19 and its diagnostic importance for clinicians in various fields of medicine encountering COVID-19 patients and its complications.

Neurologic complications of cardiac arrest

Cardiac arrest is a catastrophic event with high morbidity and mortality. Despite advances over time in cardiac arrest management and postresuscitation care, the neurologic consequences of cardiac arrest are frequently devastating to patients and their families. Targeted temperature management is an intervention aimed at limiting postanoxic injury and improving neurologic outcomes following cardiac arrest. Recovery of neurologic function governs long-term outcome after cardiac arrest and prognosticating on the potential for recovery is a heavy burden for physicians. An early and accurate estimate of the potential for recovery can establish realistic expectations and avoid futile care in those destined for a poor outcome. This chapter reviews the epidemiology, pathophysiology, therapeutic interventions, prognostication, and neurologic sequelae of cardiac arrest.

Physiology-Based Treatment of Myoclonus

Myoclonus can cause significant disability for patients. Myoclonus has a strikingly diverse array of underlying etiologies, clinical presentations, and pathophysiological mechanisms. Treatment of myoclonus is vital to improving the quality of life of patients with these disorders. The optimal treatment strategy for myoclonus is best determined based upon careful evaluation and consideration of the underlying etiology and neurophysiological classification. Electrophysiological testing including EEG (electroencephalogram) and EMG (electromyogram) data is helpful in determining the neurophysiological classification of myoclonus. The neurophysiological subtypes of myoclonus include cortical, cortical-subcortical, subcortical-nonsegmental, segmental, and peripheral. Levetiracetam, valproic acid, and clonazepam are often used to treat cortical myoclonus. In cortical-subcortical myoclonus, treatment of myoclonic seizures is prioritized, valproic acid being the mainstay of therapy. Subcortical-nonsegmental myoclonus may be treated with clonazepam, though numerous agents have been used depending on the etiology. Segmental and peripheral myoclonus are often resistant to treatment, but anticonvulsants and botulinum toxin injections may be of utility depending upon the case. Pharmacological treatments are often hampered by scarce evidence-based knowledge, adverse effects, and variable efficacy of medications.

Buspirone-associated Movement Disorder: A Literature Review

Buspirone (BUS) belongs to the azapirone chemical class. The aim of this literature review is to evaluate the clinical epidemiological profile, pathological mechanisms, and management of BUS-associated movement disorders (MD). Relevant reports in six databases were identified and assessed by two reviewers without language restriction. A total of 25 reports containing 65 cases were assessed. The MD associated with BUS were: dyskinesia in 14 cases, 10 of akathisia, 8 of myoclonus, 6 of Parkinsonism, and 6 of dystonia. The cases not clearly defined were 7 tension, 14 incoordination, and the undefined number of dyskinesia, tics, and Parkinsonism. The mean age was 45.23 years (range: 15-74). The male was the predominant sex in 60.86% and the most common BUS-indication was anxiety disorder. The mean BUS-dose was 42.16 mg (range: 5-100). The time from the beginning of BUS administration to the MD onset was one month or less in 76%. The time from BUS withdrawal to complete recovery was within one month in 87.5%. The most common management was BUS withdrawal. In 16 patients the follow-up was reported: 14 had a full recovery, but in two (1 dyskinesia + 1 dystonia) the symptoms continued after the BUS withdrawal. MD associated with BUS were scarcely reported in the literature. Moreover, in the majority of cases, no clear description of the clinical profile, neurological examination, or the time data of the movement disorder onset and recovery were given.

Myoclonus: An Electrophysiological Diagnosis

Background

Many different movement disorders have similar "jerk-like" phenomenology and can be misconstrued as myoclonus. Different types of myoclonus also share similar phenomenological characteristics that can be difficult to distinguish solely based on clinical exam. However, they have distinctive physiologic characteristics that can help refine categorization of jerk-like movements.

Objectives

In this review, we briefly summarize the clinical, physiologic, and pathophysiologic characteristics of different types of myoclonus. The methodology and technical considerations for the electrophysiologic assessment of jerk-like movements are reviewed. A simplistic pragmatic approach for the classification of myoclonus and other jerk-like movements based on objective electrophysiologic characteristics is proposed.

Conclusions

Clinical neurophysiology is an underutilized tool in the diagnosis and treatment of movement disorders. Various jerk-like movements have distinguishing physiologic characteristics, differentiated in the milliseconds range, which is beyond human capacity. We argue that the categorization of movement disorders as myoclonus can be refined based on objective physiology that can have important prognostic and therapeutic implications.

How can neurophysiological studies help with movement disorders characterization in clinical practice? A review

BACKGROUND

Neurophysiological studies are ancillary tools to better understand the features and nature of movement disorders. Electromyography (EMG), together with electroencephalography (EEG) and accelerometer, can be used to evaluate a hypo and hyperkinetic spectrum of movements. Specific techniques can be applied to better characterize the phenomenology, help distinguish functional from organic origin and assess the most probable site of the movement generator in the nervous system.

OBJECTIVE

We intend to provide an update for clinicians on helpful neurophysiological tools to assess movement disorders in clinical practice.

METHODS

Non-systematic review of the literature published up to June 2019.

RESULTS

A diversity of protocols was found and described. These include EMG analyses to define dystonia, myoclonus, myokymia, myorhythmia, and painful legs moving toes pattern; EMG in combination with accelerometer to study tremor; and EEG-EMG to study myoclonus. Also, indirect measures of cortical and brainstem excitability help to describe and diagnose abnormal physiology in Parkinson's disease, atypical parkinsonism, dystonia, and myoclonus.

CONCLUSION

These studies can be helpful for the diagnosis and are usually underutilized in neurological practice.

The Link Between Amitriptyline and Movement Disorders: Clinical Profile and Outcome

INTRODUCTION

Amitriptyline (AMT) is a tricyclic antidepressant. In this review, we evaluate the clinical and epidemiological profile, pathological mechanisms and management of AMT-associated movement disorders.

MATERIALS AND METHODS

A search for relevant reports in 6 databases was performed. Studies that reported patients developed only ataxia or tremor after AMT use were excluded.

RESULTS

A total of 48 reports on 200 cases were found. AMT-associated movement disorders included myoclonus (n = 26), dyskinesia (n = 11), dystonia (n = 8), stutter (n = 5), akathisia (n = 3) and restless legs syndrome (n = 1). For less well-defined cases, 99 patients had dyskinesia, 19 had psychomotor disturbances, 3 had myoclonus, 11 had dystonia, 12 had Parkinsonism and 1 each had akathisia and extrapyramidal symptoms. Mean and standard deviation (SD) and median ages were 45.40 years (SD 16.78) and 40 years (range 3.7-82 years), respectively. Over half were women (58.13%) and the most common indication was depression. Mean and median AMT doses were 126 mg (SD 128.76) and 75 mg (range 15-800 mg), respectively. In 68% of patients, onset of movement disorders was <1 month; time from AMT withdrawal to complete recovery was <1 month in 70% of cases. A weak negative linear correlation (r = -0.0904) was found between onset of movement disorders and AMT dose. AMT withdrawal was the most common treatment.

CONCLUSION

Amitriptyline is associated with various movement disorders, particularly myoclonus, dystonia and dyskinesias. Stutters and restless legs syndrome are some of the less common associations.

Pregabalin-associated movement disorders: A literature review

Central nervous system adverse effects are commonly reported with pregabalin (PGB). On the other hand, movement disorders (MDs) associated with this drug were rarely described. However, their occurrence could significantly affect the quality of life of PGB users. This literature review aims to evaluate the clinical epidemiological profile, pathological mechanisms, and management of PGB-associated MDs. Relevant reports in six databases were identified and assessed by two reviewers without language restriction. A total of 46 reports containing 305 cases from 17 countries were assessed. The MDs encountered were as follows: 184 individuals with ataxia, 61 with tremors, 39 with myoclonus, 8 with parkinsonism, 1 with restless legs syndrome, 1 with dystonia, 1 with dyskinesia, and 1 with akathisia. The mean age was 62 years (range: 23-94). The male sex was slightly predominant with 54.34%. The mean PGB dose when the MD occurred was 238 mg, and neuropathic pain was the most common indication of PGB. The time from PGB start to MD was < 1 month at 75%. The time from PGB withdrawal to recovery was < 1 week at 77%. All the individuals where the follow-up was reported had a full recovery. The most common management was PGB withdrawal. In the literature, the majority of the cases did not report information about timeline events, neurological examination details, or electrodiagnostic studies. The best management for all MDs is probably PGB withdrawal. If the patient is on dialysis program, perhaps an increased number of sessions will decrease recovery time. Furthermore, the addition of a benzodiazepine could accelerate recovery.

Drug Treatment of Progressive Myoclonic Epilepsy

The progressive myoclonic epilepsies (PMEs) represent a rare but devastating group of syndromes characterized by epileptic myoclonus, typically action-induced seizures, neurological regression, medically refractory epilepsy, and a variety of other signs and symptoms depending on the specific syndrome. Most of the PMEs begin in children who are developing as expected, with the onset of the disorder heralded by myoclonic and other seizure types. The conditions are considerably heterogenous, but medical intractability to epilepsy, particularly myoclonic seizures, is a core feature. With the increasing use of molecular genetic techniques, mutations and their abnormal protein products are being delineated, providing a basis for disease-based therapy. However, genetic and enzyme replacement or substrate removal are in the nascent stage, and the primary therapy is through antiepileptic drugs. Epilepsy in children with progressive myoclonic seizures is notoriously difficult to treat. The disorder is rare, so few double-blinded, placebo-controlled trials have been conducted in PME, and drugs are chosen based on small open-label trials or extrapolation of data from drug trials of other syndromes with myoclonic seizures. This review discusses the major PME syndromes and their neurogenetic basis, pathophysiological underpinning, electroencephalographic features, and currently available treatments.

Segmental Spinal Myoclonus After a Cervical Transforaminal Epidural Steroid Injection

In clinical practice, cervical transforaminal epidural steroid injection is commonly used for alleviating pain. We report a case of segmental spinal myoclonus that developed after cervical transforaminal local anesthetic and steroid injection. A 39-yr-old man presented involuntary movements of the bilateral upper trapezius muscles after cervical transforaminal epidural steroid injection on the right C6 and C7 roots with a 5 mg of dexamethasone injectate mixed with 0.5 ml of 1% lidocaine and 0.5 ml of normal saline at each level. His myoclonus was semirhythmic and continuously persisted at a frequency of approximately 30 episodes per minute. The myoclonus continued even at rest and during sleep. In addition, it was resistive to stimulus, such as touch and voluntary action. Based on the clinical features, the patient was diagnosed as having a segmental spinal myoclonus. Clonazepam 0.25 mg was administered three times daily. The myoclonus gradually improved and resolved completely within 2 wks. Segmental spinal myoclonus is one of rare complications after cervical transforaminal epidural steroid injection. Clinicians should be aware of the likelihood of this potential complication.

Telemedicine for Hyperkinetic Movement Disorders

Telemedicine is the use of electronic communication technology to facilitate healthcare between distant providers and patients. In addition to synchronous video conferencing, asynchronous video transfer has been used to support care for neurology patients.

There is a growing literature on using telemedicine in movement disorders, with the most common focus on Parkinson’s disease. There is accumulating evidence for videoconferencing to diagnose and treat patients with hyperkinetic movement disorders and to support providers in remote underserviced areas. Cognitive testing has been shown to be feasible remotely. Genetic counseling and other counseling-based therapeutic interventions have also successfully performed in hyperkinetic movement disorders.

We use a problem-based approach to review the current evidence for the use of telemedicine in various hyperkinetic movement disorders. This Viewpoint attempts to identify possible telemedicine solutions as well as discussing unmet needs and future directions.

Myoclonus

PURPOSE OF REVIEW

This article offers clinicians a strategic approach for making sense of a symptom complex that contains myoclonus. The article presents an evaluation strategy that highly leverages the two major classification schemes of myoclonus. The goal of this article is to link evaluation strategy with diagnosis and treatment of myoclonus.

RECENT FINDINGS

The growth of medical literature has helped better define myoclonus etiologies. Physiologic study of myoclonus types and etiologies with electrophysiologic testing has provided greater clarity to the pathophysiology of the myoclonus in various diseases. Although studies have been limited, the role of newer treatment agents and methods has made progress.

SUMMARY

Myoclonus has hundreds of different etiologies. Classification is necessary to evaluate myoclonus efficiently and pragmatically. The classification of myoclonus etiology, which is grouped by different clinical presentations, helps determine the etiology and treatment of the myoclonus. The classification of myoclonus physiology using electrophysiologic test results helps determine the pathophysiology of the myoclonus and can be used to strategize symptomatic treatment approaches. Both basic ancillary testing (including EEG and imaging) and more comprehensive testing may be necessary. Treatment of the underlying etiology is the ideal approach. However, if such treatment is not possible or is delayed, symptomatic treatment guided by the myoclonus physiology should be considered. More controlled study of myoclonus treatment is needed. Further research on myoclonus generation mechanisms should shed light on future treatment possibilities.

Tremor and myoclonus

Tremor and myoclonus are two common hyperkinetic movement disorders. Tremor is characterized by rhythmic oscillatory movements while myoclonic jerks are usually arrhythmic. Tremor can be classified into subtypes including the most common types: essential, enhanced physiological, and parkinsonian tremor. Myoclonus classification is based on its anatomic origin: cortical, subcortical, spinal, and peripheral myoclonus. The clinical presentations are unfortunately not always classic and electrophysiologic investigations can be helpful in making a phenotypic diagnosis. Video-polymyography is the main technique to (sub)classify the involuntary movements. In myoclonus, advanced electrophysiologic testing, such as back-averaging, coherence analysis, somatosensory-evoked potentials, and the C-reflex can be of additional value. Recent developments in tremor point toward a role for intermuscular coherence analysis to differentiate between tremor subtypes. Classification of the movement disorder based on clinical and electrophysiologic features is important, as it enables the search for an etiological diagnosis and guides tailored treatment.