Myoclonus: current concepts and recent advances

Spinal Myoclonus: Is It An Anesthetic Mystery?

The goal is to present a descriptive study related an unprecedent case of spinal myoclonus (SM) following subarachnoid anesthesia (SA). SM are sudden, brief, involuntary non-generalized spasms that can be an adverse effect of drug administration via neuraxial routes. Female, 67y, ASA II, proposed for hip replacement surgery, with normal preoperative exams. 7min after SA with 10mg of bupivacaine 0,5%, no motor blockade observed, and patient complained of unbearable pain in legs and perineum and bilateral, asymmetrical and arrhythmic myoclonic movements in the lower limbs. The latter solved after 48h of general anesthesia and rocuronium perfusion, amongst other therapeutics. Accordingly, intrathecal bupivacaine appears to be the SM most likely cause, regarding the absence of neurologic and electrolyte disorders, spinal cord direct trauma, drug exchange and normal perioperative examination, imaging and laboratory testing.It is mandatory to always take the patients' anaesthetic histories and recognize, treat and report rare anaesthetic complications.

Sensory evoked potentials in patients with Rett syndrome through the lens of animal studies: Systematic review

OBJECTIVE

Systematically review the abnormalities in event related potential (ERP) recorded in Rett Syndrome (RTT) patients and animals in search of translational biomarkers of deficits related to the particular neurophysiological processes of known genetic origin (MECP2 mutations).

METHODS

Pubmed, ISI Web of Knowledge and BIORXIV were searched for the relevant articles according to PRISMA standards.

RESULTS

ERP components are generally delayed across all sensory modalities both in RTT patients and its animal model, while findings on ERPs amplitude strongly depend on stimulus properties and presentation rate. Studies on RTT animal models uncovered the abnormalities in the excitatory and inhibitory transmission as critical mechanisms underlying the ERPs changes, but showed that even similar ERP alterations in auditory and visual domains have a diverse neural basis. A range of novel approaches has been developed in animal studies bringing along the meaningful neurophysiological interpretation of ERP measures in RTT patients.

CONCLUSIONS

While there is a clear evidence for sensory ERPs abnormalities in RTT, to further advance the field there is a need in a large-scale ERP studies with the functionally-relevant experimental paradigms.

SIGNIFICANCE

The review provides insights into domain-specific neural basis of the ERP abnormalities and promotes clinical application of the ERP measures as the non-invasive functional biomarkers of RTT pathophysiology.

Population-scale hand tremor analysis via anonymized mouse cursor signals

Tremors are a common movement disorder with a spectrum of benign and pathological causes, including neurodegenerative disease, alcohol withdrawal, and physical overexertion. Studies of tremors in clinical practice are limited in size and scope and depend on explicit tracking of tremor characteristics by clinicians. Data drawn from small numbers of patients observed in short-duration sessions pose challenges for understanding the nature and distribution of tremors over a large population. Methods are presented to estimate hand tremors based on anonymized computer mouse cursor movement data collected from millions of users of a web search engine. To determine the feasibility of using this signal for the estimation of the prevalence of tremors over a large population, the characteristics of tremor-like movements are computed and compared against user data that can be interpreted as self-reports, the findings of published clinical studies, and a target selection study where participants self-report hand tremors and known causes. The results demonstrate significant alignment between estimated tremors and both self-reports and clinical findings. Those with cursor tremor events are more likely to report tremor-related search interests. Variations in cursor tremor quantity and cursor tremor frequency with demographics mirror those from clinical studies. Distributions of cursor tremor frequencies vary as expected for different medical conditions. Overall, the study finds evidence for the validity of harnessing anonymized mouse cursor motion as a population-scale tremor sensor for epidemiologic studies. Feasible future applications include opt-in services for screening and for monitoring the progression of illness.

Low-dose perampanel improves refractory cortical myoclonus by the dispersed and suppressed paroxysmal depolarization shifts in the sensorimotor cortex

OBJECTIVE

To elucidate the effects of perampanel (PER) on refractory cortical myoclonus for dose, etiology and somatosensory-evoked potential (SEP) findings.

METHODS

We examined 18 epilepsy patients with seizure and cortical myoclonus. Based on data accumulated before and after PER treatment, correlations among clinical scores in myoclonus and activities of daily life (ADL); early cortical components of SEP; and PER blood concentration, were analyzed.

RESULTS

PER (mean dose: 3.2 ± 2.1 mg/day) significantly improved seizures, myoclonus and ADL and significantly decreased the amplitude of and prolonged latency of giant SEP components. The degree of P25 and N33 prolongations (23.8 ± 1.6 to 24.7 ± 1.7 ms and 32.1 ± 4.0 to 33.7 ± 3.4 ms) were significantly correlated with improved ADL score (p = 0.019 and p = 0.025) and blood PER concentration (p = 0.011 and p = 0.025), respectively.

CONCLUSIONS

Low-dose PER markedly improved myoclonus and ADL in patients with refractory cortical myoclonus. Our results suggest that SEP, particularly P25 latency, can be used as a potential biomarker for assessing the objective effects of PER on intractable cortical myoclonus.

SIGNIFICANCE

In this study, PER lessened the degree of synchronized discharges in the postsynaptic neurons in the primary motor cortex.

A Novel Pathogenic Variant in MT-CO2 Causes an Isolated Mitochondrial Complex IV Deficiency and Late-Onset Cerebellar Ataxia

Both nuclear and mitochondrial DNA defects can cause isolated cytochrome c oxidase (COX; complex IV) deficiency, leading to the development of the mitochondrial disease. We report a 52-year-old female patient who presented with a late-onset, progressive cerebellar ataxia, tremor and axonal neuropathy. No family history of neurological disorder was reported. Although her muscle biopsy demonstrated a significant COX deficiency, there was no clinical and electromyographical evidence of myopathy. Electrophysiological studies identified low frequency sinusoidal postural tremor at 3 Hz, corroborating the clinical finding of cerebellar dysfunction. Complete sequencing of the mitochondrial DNA genome in muscle identified a novel MT-CO2 variant, m.8163A>G predicting p.(Tyr193Cys). We present several lines of evidence, in proving the pathogenicity of this heteroplasmic mitochondrial DNA variant, as the cause of her clinical presentation. Our findings serve as an important reminder that full mitochondrial DNA analysis should be included in the diagnostic pipeline for investigating individuals with spinocerebellar ataxia.

Tremor after long term lithium treatment; is it cortical myoclonus?

Introduction

Tremor is a common side effect of treatment with lithium. Its characteristics can vary and when less rhythmical, distinction from myoclonus can be difficult.

Methods

We identified 8 patients on long-term treatment with lithium that developed upper limb tremor. All patients were assessed clinically and electrophysiologically, with jerk-locked averaging (JLA) and cross-correlation (CC) analysis, and five of them underwent brain MRI examination including spectroscopy (MRS) of the cerebellum.

Results

Seven patients (6 female) had action and postural myoclonus and one a regular postural and kinetic tremor that persisted at rest. Mean age at presentation was 58 years (range 42-77) after lengthy exposure to lithium (range 7-40 years). During routine monitoring all patients had lithium levels within the recommended therapeutic range (0.4-1 mmol/l). There was clinical and/or radiological evidence (on cerebellar MRS) of cerebellar dysfunction in 6 patients. JLA and/or CC suggested a cortical generator of the myoclonus in seven patients. All seven were on antidepressants and three additionally on neuroleptics, four of them had gluten sensitivity and two reported alcohol abuse.

Conclusions

A synergistic effect of different factors appears to be contributing to the development of cortical myoclonus after chronic exposure to lithium. We hypothesise that the cerebellum is involved in the generation of cortical myoclonus in these cases and factors aetiologically linked to cerebellar pathology like gluten sensitivity and alcohol abuse may play a role in the development of myoclonus. Despite the very limited evidence in the literature, lithium induced cortical myoclonus may not be so rare.

Intrathecal morphine combined with ropivacaine induces spinal myoclonus in cancer patients with an implanted intrathecal drug delivery system: Three case reports

RATIONALE

Although intrathecal opioid infusion has been used for decades for the treatment of severe pain, myoclonus as one of the complications of this therapeutic modality is now beginning to be recognized more.

PATIENTS CONCERNS

Here, we report three patients who developed myoclonus after dose adjustment in intrathecal drug delivery system for the treatment of refractory cancer pain.

DIAGNOSIS

Spinal myoclonus is a sudden, brief, shock-like muscle contractions originating from the central nervous system. In our cases, it occurred after opioid administration via intrathecal delivery system with no abnormality found in laboratory or imaging examinations.

INTERVENTIONS

Spinal myoclonus can be treated effectively by reducing the dose or infusion rate as described in case 1, or changing from an intrathecal to systemic administration in case 2, or correcting infusion and bolus parameters mistakes in case 3.

OUTCOMES

All patients recovered quickly after stopping or decreasing the intrathecal drug infusion.

LESSONS

Prevention is more important than treatment as for spinal myoclonus. Pain management teams should be aware of this distressing complication. Dose of intrathecal drugs should not exceed the recommended maximal daily doses by guidelines and patient education is important for successful intrathecal analgesic therapy.

Segmental Spinal Myoclonus Complicating Lumbar Transforaminal Epidural Steroid Injection

OBJECTIVE

Lumbar transforaminal epidural steroid injection is commonly used for treating lumbar radicular pain. We report a case of segmental spinal myoclonus that developed during lumbar transforaminal epidural injection with local anesthetic and steroid.

CASE REPORT

A 58-year-old woman with failed back surgery syndrome presented with low back and right L3 and L4 radicular pain. As she had responded well previously to diagnostic selective nerve root injection with local anesthetic at the right L3 and L4 levels, lumbar transforaminal epidural steroid injection at the same levels was scheduled. During injection of ropivacaine and triamcinolone at the right L3-4 intervertebral foramen, she complained of back pain and immediately developed involuntary contraction of her right hip. The procedure was terminated. No new neurological deficit was detected when she was examined 15 minutes after the procedure. There were no abnormalities from blood tests and magnetic resonance imaging of the lower thoracic and lumbar spine. A neurologist subsequently made the clinical diagnosis of segmental spinal myoclonus. The myoclonus improved over 1 month and eventually resolved completely.

CONCLUSIONS

Segmental spinal myoclonus is a rare complication after lumbar transforaminal epidural steroid and local anesthetic injection. Pain physicians should be aware of this potential complication.

Spinal myoclonus: a rare presentation of cervical myelopathy

Myoclonus describes a movement disorder characterised by brief, abrupt and involuntary contractions of muscles or groups of muscles, usually associated with intracranial lesions, with limited evidence linking it to spinal pathologies. The pathophysiology of spinal myoclonus is extensive and multifactorial. Infection, intramedullary and extramedullary space-occupying lesions, trauma, vascular abnormalities, degenerative processes and cervical spondylosis have been implicated with the disease, the latter been associated with cervical stenosis with no reported cases linking it to an underlying cervical disc herniation. Although medical therapy with clonazepam, levetiracetam, valproate, tetrabenazine hydrochloride and spinal block injections has been equivocal, spinal myoclonus secondary to disc herniation requires surgical intervention. This report describes a case of segmental spinal myoclonus, secondary to a herniated cervical intervertebral disc. After corpectomy and a cage-augmented fusion technique, the myoclonic symptoms resolved. To our knowledge, this was the first report to describe the successful management of discogenic spinal myoclonus with spinal surgery.

Electro-clinical characteristics and prognostic significance of post anoxic myoclonus

OBJECTIVE

To systematically examine the electro-clinical characteristics of post anoxic myoclonus (PAM) and their prognostic implications in comatose cardiac arrest (CA) survivors.

METHODS

Fifty-nine CA survivors who developed myoclonus within 72 h of arrest and underwent continuous EEG monitoring were included in the study. Retrospective chart review was performed for all relevant clinical variables including time of PAM onset ("early onset" when within 24 h) and semiology (multi-focal, facial/ocular, whole body and limbs only). EEG findings including background, reactivity, epileptiform patterns and EEG correlate to myoclonus were reviewed at 6, 12, 24, 48 and 72 h after the return of spontaneous circulation (ROSC). Outcome was categorized as either with recovery of consciousness (Cerebral Performance Category (CPC) 1-3) or without recovery of consciousness (CPC 4-5) at the time of discharge.

RESULTS

Seven of the 59 patients (11.9%) regained consciousness, including 6/51 (11.8%) with early onset PAM. Patients with recovery of consciousness had shorter time to ROSC, and were more likely to have preserved brainstem reflexes and normal voltage background at all times. No patient with suppression burst or low voltage background (N = 52) at any point regained consciousness. In the subset where precise electro-clinical correlation was possible, all (5/5) those with recovery of consciousness had multi-focal myoclonus and most (4/5) had midline-maximal spikes over a continuous background. No patient with any other semiology (N = 21) regained consciousness.

CONCLUSIONS

Early onset PAM is not always associated with lack of recovery of consciousness. EEG can help discriminate between patients who may or may not regain consciousness by the time of hospital discharge.

Benign Neonatal Sleep Myoclonus Evokes Somatosensory Responses

PURPOSE

Benign neonatal sleep myoclonus is a common nonepileptic condition occurring in neurologically normal full-term newborns. During jerks, EEG has always been described as normal. The aim of this study was to describe EEG changes associated with the myoclonic jerks.

METHODS

Polygraphic video-EEG recordings of four full-term neonates presenting benign neonatal sleep myoclonus were studied. Myoclonic jerks were analyzed regarding their topography, frequency, propagation pattern, and reflex component. EEG averaging time-locked to myoclonic jerks and to somatosensory stimuli (realized by tapping on palms and feet) was performed to study eventual EEG correlates of myoclonus and to asses somatosensory evoked responses-for the latter, two control newborns were added.

RESULTS

Visual analysis of the EEG disclosed theta band slow waves on central and vertex electrodes concomitant to myoclonic jerks and jerk-locked back-averaging disclosed a sequence of deflections, not preceding, but following the myoclonus. This response predominated on the vertex electrode (CZ) and consisted of five components (N1, P1, N2, P2, and N3), with only the three later components being constantly present (at 110, 200, and 350-500 ms, respectively). Back-averaging locked to the tactile stimuli in four subjects and two control newborns showed similar components and were comparable to those described in the literature as late somatosensory evoked responses in full-term newborns.

CONCLUSIONS

Myoclonic jerks in benign neonatal sleep myoclonus can evoke visually identifiable EEG potentials on vertex electrodes corresponding to somatosensory responses. This EEG aspect may be misleading and could give rise to an anti-seizure treatment that mostly worsens the condition.

Rating Scales for Movement Disorders With Sleep Disturbances: A Narrative Review

Introduction: In recent years, a wide variety of rating scales and questionnaires for movement disorders have been developed and published, making reviews on their contents, and attributes convenient for the potential users. Sleep disorders are frequently present in movement disorders, and some movement disorders are accompanied by specific sleep difficulties. Aim: The aim of this study is to perform a narrative review of the most frequently used rating scales for movement disorders with sleep problems, with special attention to those recommended by the International Parkinson and Movement Disorders Society. Methods: Online databases (PubMed, SCOPUS, Web of Science, Google Scholar), related references from papers and websites and personal files were searched for information on comprehensive or global rating scales which assessed sleep disturbances in the following movement disorders: akathisia, chorea, dystonia, essential tremor, myoclonus, multiple system atrophy, Parkinson's disease, progressive supranuclear palsy, and tics and Tourette syndrome. For each rating scale, its objective and characteristics, as well as a summary of its psychometric properties and recommendations of use are described. Results: From 22 rating scales identified for the selected movement disorders, only 5 included specific questions on sleep problems. Movement Disorders Society-Unified Parkinson's Disease Rating scale (MDS-UPDRS), Non-Motor Symptoms Scale and Questionnaire (NMSS and NMSQuest), Scales for Outcomes in Parkinson's Disease (SCOPA)-Autonomic and Progressive Supranuclear Palsy Rating Scale (PSPRS) were the only rating scales that included items for assessing sleep disturbances. Conclusions: Despite sleep problems are frequent in movement disorders, very few of the rating scales addresses these specific symptoms. This may contribute to an infra diagnosis and mistreatment of the sleep problems in patients with movement disorders.

Long-Term Effects of Middle Ear Tendon Resection on Middle Ear Myoclonic Tinnitus, Hearing, and Hyperacusis

Objective: To evaluate the therapeutic effects of middle ear tendon resection (METR) on middle ear myoclonic tinnitus (MEMT) and to investigate its long-term effects on hearing and hyperacusis. Materials and Methods: Thirty-seven patients with MEMT with a mean age of 33.2 ± 11.8 years were included in this study. METR was performed on all 37 MEMT patients (41 ears) between November 2004 and August 2016. The mean follow-up period was 16.1 months. We examined changes in tinnitus and accompanying stress and depression in patients after surgery, and examined the hearing changes and the occurrence of complications including hyperacusis. Results: After surgery, 34 (91.9%) patients exhibited complete resolution of MEMT during their follow-up period, and 3 patients showed a partial response. The mean Visual Analog Scale (VAS) scores for tinnitus severity, the Tinnitus Handicap Inventory (THI), and stress index decreased significantly after surgery (p < 0.05, paired t test). No patient developed hearing loss or hyperacusis following surgery. Preexisting hyperacusis even improved in most of the patients with intractable MEMT after surgery. Recurrence of the symptom occurred in only 1 patient, who underwent revision surgery with improvement. We observed 1 case of postoperative delayed facial palsy with complete recovery in 2 weeks. Conclusions: METR seems to be an effective and safe treatment option for intractable MEMT, considering its high control rate of tinnitus and no long-term harmful effects on hearing and hyperacusis.

Improving neurophysiological biomarkers for functional myoclonic movements

Introduction

Differentiating between functional jerks (FJ) and organic myoclonus can be challenging. At present, the only advanced diagnostic biomarker to support FJ is the Bereitschaftspotential (BP). However, its sensitivity is limited and its evaluation subjective. Recently, event related desynchronisation in the broad beta range (13–45 Hz) prior to functional generalised axial (propriospinal) myoclonus was reported as a possible complementary diagnostic marker for FJ. Here we study the value of ERD together with a quantified BP in clinical practice.

Methods

Twenty-nine patients with FJ and 16 patients with cortical myoclonus (CM) were included. Jerk-locked back-averaging for determination of the ‘classical’ and quantified BP, and time-frequency decomposition for the event related desynchronisation (ERD) were performed. Diagnostic gain, sensitivity and specificity were obtained for individual and combined techniques.

Results

We detected a classical BP in 14/29, a quantitative BP in 15/29 and an ERD in 18/29 patients. At group level we demonstrate that ERD in the broad beta band preceding a jerk has significantly higher amplitude in FJ compared to CM (respectively −0.14 ± 0.13 and +0.04 ± 0.09 (p < 0.001)). Adding ERD to the classical BP achieved an additional diagnostic gain of 53%. Furthermore, when combining ERD with quantified and classical BP, an additional diagnostic gain of 71% was achieved without loss of specificity.

Conclusion

Based on the current findings we propose to the use of combined beta ERD assessment and quantitative BP analyses in patients with a clinical suspicion for all types of FJ with a negative classical BP.

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Differentiating between functional jerks and organic myoclonus is often difficult.

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The sensitivity of a positive bereitschaftspotential for diagnosing FJ is low.

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FJ are preceded by event related desynchronisation (ERD) in the beta band.

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Combining beta ERD and BP improves diagnosing FJ.

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The ERD method is of special relevance in possible FJ patients with a negative BP.

The interrelation between clinical presentation and neurophysiology of posthypoxic myoclonus

Objective

Posthypoxic myoclonus (PHM) in the first few days after resuscitation can be divided clinically into generalized and focal (uni‐ and multifocal) subtypes. The former is associated with a subcortical origin and poor prognosis in patients with postanoxic encephalopathy (PAE), and the latter with a cortical origin and better prognosis. However, use of PHM as prognosticator in PAE is hampered by the modest objectivity in its clinical assessment. Therefore, we aimed to obtain the anatomical origin of PHM with use of neurophysiological investigations, and relate these to its clinical presentation.

Methods

This study included 20 patients (56 ± 18 y/o, 68% M, 2 survived, 1 excluded) with EEG‐EMG‐video recording. Three neurologists classified PHM into generalized or focal PHM. Anatomical origin (cortical/subcortical) was assessed with basic and advanced neurophysiology (Jerk‐Locked Back Averaging, coherence analysis).

Results

Clinically assessed origin of PHM did not match the result obtained with neurophysiology: cortical PHM was more likely present in generalized than in focal PHM. In addition, some cases demonstrated co‐occurrence of cortical and subcortical myoclonus. Patients that recovered from PAE had cortical myoclonus (1 generalized, 1 focal).

Interpretation

Hypoxic damage to variable cortical and subcortical areas in the brain may lead to mixed and varying clinical manifestations of myoclonus that differ of those patients with myoclonus generally encountered in the outpatient clinic. The current clinical classification of PHM is not adequately refined to play a pivotal role in guiding treatment decisions to withdraw care. Our neurophysiological characterization of PHM provides specific parameters to be used in designing future comprehensive studies addressing the potential role of PHM as prognosticator in PAE.

Effect of repetitive transcranial magnetic stimulation on action myoclonus: A pilot study in patients with EPM1

OBJECTIVE

The objective of this study was to explore the short-term effects of repetitive transcranial magnetic stimulation (rTMS) on action myoclonus.

METHODS

Nine patients with Unverricht-Lundborg (EPM1) progressive myoclonus epilepsy type underwent two series of 500 stimuli at 0.3Hz through round coil twice a day for five consecutive days. Clinical and neurophysiological examinations were performed two hours before starting the first rTMS session and two hours after the end of the last rTMS session.

RESULTS

Eight patients completed the protocol; one discontinued because of a transient increase in spontaneous jerks. The unified myoclonus rating scale indicated a 25% reduction in posttreatment myoclonus with action score associated with an increase in the cortical motor threshold and lengthening of the cortical silent period (CSP). The decrease in the myoclonus with action scores correlated with the prolongation of CSP.

CONCLUSIONS

Repetitive transcranial magnetic stimulation can be safely used in patients with EPM1, improves action myoclonus, and partially restores deficient cortical inhibition.

Comparative pathogenesis of rabies in bats and carnivores, and implications for spillover to humans

Bat-acquired rabies is becoming increasingly common, and its diagnosis could be missed partly because its clinical presentation differs from that of dog-acquired rabies. We reviewed the scientific literature to compare the pathogenesis of rabies in bats and carnivores-including dogs-and related this pathogenesis to differences in the clinical presentation of bat-acquired and dog-acquired rabies in human beings. For bat-acquired rabies, we found that the histological site of exposure is usually limited to the skin, the anatomical site of exposure is more commonly the face, and the virus might be more adapted for entry via the skin than for dog-acquired rabies. These factors could help to explain several differences in clinical presentation between individuals with bat-acquired and those with dog-acquired rabies. A better understanding of these differences should improve the recording of a patient's history, enable drawing up of a more sophisticated list of clinical characteristics, and therefore obtain an earlier diagnosis of rabies after contact with a bat or carnivore that has rabies.

[Myoclonus as a movement disorder]

Myoclonus is often a diagnostic and therapeutic challenge due to its broad phenomenological variability and limited therapeutic options. This article gives a short survey and characterizes in detail two common types of myoclonus, cortical myoclonus and reticular reflex myoclonus. Clinical testing and electrophysiological investigations provide relevant local diagnostic indications for the generating structure(s). Such indications would influence not only the strategies of neuroimaging and laboratory investigations aimed at clarifying the underlying cause but also the selection of drugs to suppress myoclonus.

Myoclonic Disorders

Few movement disorders seem to make a straightforward approach to diagnosis and treatment more difficult and frustrating than myoclonus, due to its plethora of causes and its variable classifications. Nevertheless, in recent years, exciting advances have been made in the elucidation of the pathophysiology and genetic basis of many disorders presenting with myoclonus. Here, we provide a review of all of the important types of myoclonus encountered in pediatric and adult neurology, with an emphasis on the recent developments that have led to a deeper understanding of this intriguing phenomenon. An up-to-date list of the genetic basis of all major myoclonic disorders is presented. Randomized studies are scarce in myoclonus therapy, but helpful pragmatic approaches at diagnosis as well as treatment have been recently suggested.

Contrast induced spinal myoclonus after percutaneous coronary intervention

We present a case of a 77-year-old man diagnosed with contrast-induced spinal myoclonus following primary percutaneous coronary intervention. After being admitted with a diagnosis of anteroseptal myocardial infarction, he underwent primary percutaneous coronary intervention to the left anterior descending artery and was prescribed aspirin, clopidogrel, and intravenous heparin. The following day he developed non-intentional irregular jerky movements confined to the truncal area. In view of rhythmic jerking confined to muscles innervated by a restricted segment of the spinal cord, resistance to supra-spinal influences and voluntary action, and no preceding electroencephalography activity in the contralateral sensorimotor cortex, a diagnosis of spinal myoclonus was made. Spinal myoclonus is a rare entity in which myoclonic movements occur in muscles originating from few (segmental), or many adjacent spinal motor roots (propriospinal). Structural lesions are found in the majority of cases but the actual pathophysiology is still unknown. Contrast-induced spinal myoclonus is an even rarer phenomenon with few published reports. We describe postulated mechanisms and the management of this phenomenon. <Learning objective: Myoclonus is a jerky movement due to abrupt involuntary contractions involving agonist and antagonist muscles. Spinal myoclonus is a rare disorder where myoclonic movements occur in muscles originating from spinal motor roots. The cause is usually a structural lesion, but in rare cases it can be induced by contrast. A video of this rare phenomenon is available with this article and the proposed pathophysiological mechanisms and treatment are discussed.>.

Post-hypoxic myoclonus: Differentiating benign and malignant etiologies in diagnosis and prognosis

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Myoclonus status epilepticus may be reflected by generalized epileptiform discharges and burst suppression on EEG.

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Patients with Lance-Adams syndrome often demonstrate focal epileptiform activity at the vertex on EEG.

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EEG is vital in evaluating post-hypoxic myoclonus; studies are needed to assess its utility in predicting outcomes.

Neurological function following cardiac arrest often determines prognosis. Objective tests, including formal neurological examination and neurophysiological testing, are performed to provide medical providers and decision-makers information to help guide care based on the extent of neurologic injury. The demonstration of post-hypoxic myoclonus on examination has been described to portend poor outcome after cardiac arrest, but recent studies have challenged this idea given that different forms of post-hypoxic myoclonus predict disparate prognoses.

The presence of myoclonus status epilepticus (MSE) usually signals a poor outcome, especially if generalized. Lance-Adams syndrome (LAS), another form of post-hypoxic myoclonus, carries a better prognosis. Differentiating subtypes of post-hypoxic myoclonus is therefore critical. This can be difficult in the acute setting with clinical examination alone due to the use of sedation to facilitate mechanical ventilation, and neurophysiological studies may be more reliable.

In this review, we describe and compare clinical and neurophysiological features of MSE and LAS. Generalized epileptiform activity and burst suppression on electroencephalography tend to be more common in MSE, and focal epileptiform activity at the vertex may define LAS. Those with multifocal MSE may have better outcomes than those with generalized MSE. We conclude that neurophysiological testing is vital acutely after cardiac arrest when post-hypoxic myoclonus is present to help determine prognostication and guide decision-making.

Post-Anoxic Reticular Reflex Myoclonus in a Child and Proposed Classification of Post-Anoxic Myoclonus

OBJECTIVE

We describe a child with post-anoxic myoclonus of the reticular reflex type and discuss the classification of post-anoxic myoclonus.

PATIENT DESCRIPTION

A nine-year-old boy with severe hypoxic-ischemic encephalopathy due to submersion developed early epileptic spasms followed by stimulus sensitive multifocal generalized myoclonus and later dystonia. Video electromyography (EMG) polygraphy performed before treatment demonstrated that the discharges associated with the myoclonus lasted less than 50 milliseconds. Cortical myoclonus was excluded by jerk-locked averaging using arm muscles, which showed no cortical correlates. The recruitment order on EMG polygraphy was consistent with a brainstem generator for the myoclonus, characteristic of reticular reflex myoclonus. Both myoclonus and dystonia responded to clonazepam. He remains in a persistent vegetative state.

CONCLUSIONS

Reticular reflex myoclonus can be demonstrated by detailed neurophysiological assessment in children as in adults, and it has a similar poor prognosis in children. Post-anoxic myoclonus can have several mechanisms and should not be considered synonymous with Lance-Adams myoclonus.

SCA13 causes dominantly inherited non-progressive myoclonus ataxia

INTRODUCTION

Spinocerebellar ataxia 13 (SCA13) is a rare autosomal dominant cerebellar ataxia. To our knowledge, its association to movement disorders has never been described. We aimed at reporting 8 new SCA13 cases with a focus on movement disorders especially myoclonus.

METHODS

We performed a detailed neurological examination and neurophysiological recording in 8 patients consecutively diagnosed with SCA13 between December 2013 and October 2015 and followed up in two French tertiary centers.

RESULTS

We identified mild subcortical myoclonus in all patients, with a homogenous clinical and electrophysiological pattern. Myoclonus ataxia was very slowly progressive, like the other symptoms of the disease, whatever the age of onset. Patients with R423H mutation had an earlier age of onset than patients with R420H mutation.

CONCLUSIONS

Myoclonus appears to be frequent in SCA13. SCA13 should be considered facing non-progressive autosomal dominant myoclonus ataxia, and polymyographic recording should be included in the diagnosis work.

The clinical heterogeneity of drug-induced myoclonus: an illustrated review

A wide variety of drugs can cause myoclonus. To illustrate this, we first discuss two personally observed cases, one presenting with generalized, but facial-predominant, myoclonus that was induced by amantadine; and the other presenting with propriospinal myoclonus triggered by an antibiotic. We then review the literature on drugs that may cause myoclonus, extracting the corresponding clinical phenotype and suggested underlying pathophysiology. The most frequently reported classes of drugs causing myoclonus include opiates, antidepressants, antipsychotics, and antibiotics. The distribution of myoclonus ranges from focal to generalized, even amongst patients using the same drug, which suggests various neuro-anatomical generators. Possible underlying pathophysiological alterations involve serotonin, dopamine, GABA, and glutamate-related processes at various levels of the neuraxis. The high number of cases of drug-induced myoclonus, together with their reported heterogeneous clinical characteristics, underscores the importance of considering drugs as a possible cause of myoclonus, regardless of its clinical characteristics.

Post-hypoxic Myoclonus: Current Concepts, Neurophysiology, and Treatment

Background

Myoclonus may occur after hypoxia. In 1963, Lance and Adams described persistent myoclonus with other features after hypoxia. However, myoclonus occurring immediately after hypoxia may demonstrate different syndromic features from classic Lance–Adams syndrome (LAS). The aim of this review is to provide up-to-date information about the spectrum of myoclonus occurring after hypoxia with emphasis on neurophysiological features.

Methods

A literature search was performed on PubMed database from 1960 to 2015. The following search terms were used: “myoclonus,” “post anoxic myoclonus,” “post hypoxic myoclonus,” and “Lance Adams syndrome.” The articles describing clinical features, neurophysiology, management, and prognosis of post-hypoxic myoclonus cases were included for review.

Results

Several reports in the literature were separated clinically into “acute post-hypoxic myoclonus,” which occurred within hours of severe hypoxia, and “chronic post-hypoxic myoclonus,” which occurred with some recovery of mental status as the LAS. Acute post-hypoxic myoclonus was generalized in the setting of coma. Chronic post-hypoxic myoclonus presented as multifocal cortical action myoclonus that was significantly disabling. There was overlap of neurophysiological findings for these two syndromes but also different features. Treatment options for these two distinct clinical–neurophysiologic post-hypoxic myoclonus syndromes were approached differently.

Discussion

The review of clinical and neurophysiological findings suggests that myoclonus after hypoxia manifests in one or a combination of distinct syndromes: acute and/or chronic myoclonus. The mechanism of post-hypoxic myoclonus may arise either from cortical and/or subcortical structures. More research is needed to clarify mechanisms and treatment of post-hypoxic myoclonus.

A Case of Fatal Serotonin Syndrome-Like Human Rabies Caused by Tricolored Bat-Associated Rabies Virus

Human rabies is a fatal disease, transmitted by saliva of infected animals, and the diagnosis requires a high index of suspicion. Very few cases are reported annually in the United States. We present a case of human rabies without a clear exposure history that masqueraded as serotonin syndrome.

Myoclonus: Pathophysiology and Treatment Options

OPINION STATEMENT

Treatment of myoclonus requires an understanding of the physiopathology of the condition. The first step in treatment is to determine if there is an epileptic component to the myoclonus and treat accordingly. Secondly, a review of medications (e.g., opiates) and comorbidities (e.g., hepatic or renal failure) is required to establish the possibility of iatrogenic and reversible conditions. Once those are eliminated, delineation between cortical, cortico-subcortical, subcortical, brainstem, and spinal generators can determine the first-line treatment. Cortical myoclonus can be treated with levetiracetam, valproic acid, and clonazepam as first-line agents. Phenytoin and carbamazepine may paradoxically worsen myoclonus. Subcortical and brainstem myoclonus can be treated with clonazepam as a first-line agent, but levetiracetam and valproic acid can be tried as well. L-5-Hydroxytryptophan and sodium oxybate are agents used for refractory cases. Spinal myoclonus does not respond to anti-epileptic drugs, and clonazepam is a first-line agent. Botulinum toxin treatment can be useful for focal cases of spinal myoclonus. The etiology of propriospinal myoclonus is controversial, and a functional etiology is suspected in most cases. Treatment can include clonazepam, levetiracetam, baclofen, valproate, carbamazepine, and zonisamide. Functional myoclonus requires multimodal and multidisciplinary treatment that may include psychotropic drugs and physical and occupational therapy. Close collaboration between neurologists and psychiatrists is required for effective treatment. Finally, deep brain stimulation targeting the globus pallidus pars-interna bilaterally has been used in myoclonus-dystonia when pharmacological treatments have been exhausted.

Neurologic Manifestations of Enterovirus 71 Infection in Korea

Enterovirus 71 frequently involves the central nervous system and may present with a variety of neurologic manifestations. Here, we aimed to describe the clinical features, magnetic resonance imaging (MRI) findings, and cerebrospinal fluid (CSF) profiles of patients presenting with neurologic complications of enterovirus 71 infection. We retrospectively reviewed the records of 31 pediatric patients hospitalized with acute neurologic manifestations accompanied by confirmed enterovirus 71 infection at Ulsan University Hospital between 2010 and 2014. The patients' mean age was 2.9 ± 5.5 years (range, 18 days to 12 years), and 80.6% of patients were less than 4 years old. Based on their clinical features, the patients were classified into 4 clinical groups: brainstem encephalitis (n = 21), meningitis (n = 7), encephalitis (n = 2), and acute flaccid paralysis (n = 1). The common neurologic symptoms included myoclonus (58.1%), lethargy (54.8%), irritability (54.8%), vomiting (48.4%), ataxia (38.7%), and tremor (35.5%). Twenty-five patients underwent an MRI scan; of these, 14 (56.0%) revealed the characteristic increased T2 signal intensity in the posterior region of the brainstem and bilateral cerebellar dentate nuclei. Twenty-six of 30 patients (86.7%) showed CSF pleocytosis. Thirty patients (96.8%) recovered completely without any neurologic deficits; one patient (3.2%) died due to pulmonary hemorrhage and shock. In the present study, brainstem encephalitis was the most common neurologic manifestation of enterovirus 71 infection. The characteristic clinical symptoms such as myoclonus, ataxia, and tremor in conjunction with CSF pleocytosis and brainstem lesions on MR images are pathognomonic for diagnosis of neurologic involvement by enterovirus 71 infection.

Familial segmental spinal myoclonus: a rare clinical feature of Friedreich’s ataxia

Introduction

Friedreich’s ataxia (FRDA) is the most common autosomal recessive inherited ataxia. It is characterized by onset before the age of 25 year, progressive limb and truncal ataxia, lower limb areflexia, extensor plantars, dysarthria and impaired posterior column sensations. Other important associated features are skeletal deformity, hypertrophic cardiomyopathy and diabetes mellitus. Most of the patients (98%) have an unstable homozygous trinucleotide (GAA) expansion in intron-1 of chromosome 9 and 2% patients are compound heterozygous for GAA expansion and point mutations.

Case description

We observed an adolescence onset FRDA exhibiting spinal segmental myoclonus (SSM) in a family. Triplet repeat primed polymerase chain reaction (TP-PCR) demonstrated unstable expansion of >66 GAA repeats.

Conclusions

SSM is a unique and rare manifestation of FRDA. This might be the first case report of SSM in FRDA patient.

Electronic supplementary material

The online version of this article (doi:10.1186/s40064-015-1121-5) contains supplementary material, which is available to authorized users.

A novel diagnostic approach to patients with myoclonus

Myoclonus is a hyperkinetic movement disorder characterized by brief, involuntary muscular jerks. Recognition of myoclonus and determination of the underlying aetiology remains challenging given that both acquired and genetically determined disorders have varied manifestations. The diagnostic work-up in myoclonus is often time-consuming and costly, and a definitive diagnosis is reached in only a minority of patients. On the basis of a systematic literature review up to June 2015, we propose a novel diagnostic eight-step algorithm to help clinicians accurately, efficiently and cost-effectively diagnose myoclonus. The large number of genes implicated in myoclonus and the wide clinical variation of these genetic disorders emphasize the need for novel diagnostic techniques. Therefore, and for the first time, we incorporate next-generation sequencing (NGS) in a diagnostic algorithm for myoclonus. The initial step of the algorithm is to confirm whether the movement disorder phenotype is consistent with, myoclonus, and to define its anatomical subtype. The next steps are aimed at identification of both treatable acquired causes and those genetic causes of myoclonus that require a diagnostic approach other than NGS. Finally, other genetic diseases that could cause myoclonus can be investigated simultaneously by NGS techniques. To facilitate NGS diagnostics, we provide a comprehensive list of genes associated with myoclonus.