Myokymia and neuromyotonia 2004

Bedside clinical assessment of patients with common upper limb tremor and algorithmic approach

The diagnostic approach for patients with tremor is challenging due to the complex and overlapping phenotypes among tremor syndromes. The first step in the evaluation of tremor is to identify the tremulous movement and exclude the tremor mimics. The second step is to classify the tremor syndrome based on the characteristics of tremor from historical clues and focused examination (Axis 1). Comprehensive tremor examinations involve the assessment of tremor in different conditions (rest, action or mixed, position or task-specific), distribution of tremor (upper limb, lower limb, head, jaw), positive signs for functional tremor (FT) if suspected (distractibility, entrainment, co-contraction), and associated neurological signs including parkinsonism, dystonic posture, cerebellar/brainstem signs, neuropathy, and cognitive impairment. A pivotal feature in this step is to determine any distinct feature of a specific isolated or combined tremor syndrome. In this review, we propose an algorithm to assess upper limb tremors. Ancillary testing should be performed if clinical evaluation is unclear. The choice of investigation depends on the types of tremors considered to narrow down the spectrum of etiology (Axis 2). Laboratory blood tests are considered for acute onset and acute worsening of tremors, while structural neuroimaging is indicated in unilateral tremors with acute onset, nonclassical presentations, and a combination of neurological symptoms. Neurophysiological study is an important tool that aids in distinguishing between tremor and myoclonus, etiology of tremor and document specific signs of FT. Treatment is mainly symptomatic based depending on the etiology of the tremor and the patient's disabilities.

Paraneoplastic Cerebellar Degeneration Associated with Breast Cancer: A Case Report and a Narrative Review

Paraneoplastic neurological syndromes (PNSs) are an uncommon complication of cancer, affecting nearby 1/10,000 subjects with a tumour. PNSs can involve all the central and peripheral nervous systems, the muscular system, and the neuromuscular junction, causing extremely variable symptomatology. The diagnosis of the paraneoplastic disease usually precedes the clinical manifestations of cancer, making an immediate recognition of the pathology crucial to obtain a better prognosis. PNSs are autoimmune diseases caused by the expression of common antigens by the tumour and the nervous system. Specific antibodies can help clinicians diagnose them, but unfortunately, they are not always detectable. Immunosuppressive therapy and the treatment of cancer are the cornerstones of therapy for PNSs. This paper reports a case of PNSs associated with breast tumours and focuses on the most common paraneoplastic neurological syndromes. We report a case of a young female with a clinical syndrome of the occurrence of rigidity in the right lower limb with postural instability with walking supported and diplopia, with a final diagnosis of paraneoplastic cerebellar degeneration and seronegative rigid human syndrome associated with infiltrating ductal carcinoma of the breast.

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.

Case report: Complex paraneoplastic syndromes in thymoma with nephrotic syndrome, cutaneous amyloidosis, myasthenia gravis, and Morvan’s syndrome

Background

Apart from myasthenia gravis (MG), thymoma is associated with a wide spectrum of autoimmune paraneoplastic syndromes (PNSs). Here, we report on a rare case presenting with four different PNSs, namely, MG, membranous nephropathy, cutaneous amyloidosis, and Morvan’s syndrome associated with thymoma.

Case presentation

A middle-aged man was frequently hospitalized because of nephrotic syndrome (stage I membranous nephropathy), cutaneous amyloidosis, and MG with acetylcholine receptor (AChR) antibody and titin antibody positivity. Chest CT showed a thymic mass in the left anterior mediastinum, and he received intravenous immunoglobulin (IVIG), methylprednisolone pulse therapy, thoracoscopic thymoma resection, and radiotherapy. Postoperative pathological examination revealed a type B2 thymoma. During the perioperative stage, his electrocardiogram (ECG) showed myocardial infarction-like ECG changes; however, his levels of cardiac enzymes and troponin were normal, and he had no symptoms of precardiac discomfort. Six months after thymectomy, his nephrotic syndrome and MG symptoms were relieved; however, he presented with typical manifestations of Morvan’s syndrome, including neuromyotonia, severe insomnia, abnormal ECG activity, and antibodies against leucine-rich glioma-inactivated 1 (LGI1) and γ-amino-butyric acid-B receptor (GABABR). His symptoms did not improve after repeated IVIG and steroid therapies. Finally, he received low-dose rituximab, and his symptoms gradually resolved.

Conclusion

This case serves to remind us that apart from MG, thymoma is also associated with other autoimmune PNSs such as membranous nephropathy, cutaneous amyloidosis, and Morvan’s syndrome. Autoimmune PNSs can present concurrently with or after surgical or medical therapy for thymoma. For Morvan’s syndrome post-thymectomy with LGI1 antibody positivity, B-cell depletion therapy such as intravenous rituximab is an effective treatment.

Acetazolamide-Induced Periorbital Myokymia: A Case Report

Acetazolamide, a carbonic anhydrase inhibitor, is primarily used in the treatment of glaucoma, due to its role in decreasing intraocular pressure by lowering the production of aqueous humor. Additionally, by lowering cerebrospinal fluid (CSF) production, it is also used in the treatment of raised intracranial pressure. Drug-induced myokymia has rarely been reported, with known triggers being clozapine, gabapentin and flunarizine, and topiramate. Acetazolamide-induced myokymia itself has only been reported once before, to the best of our knowledge, and the exact mechanism behind this occurrence remains unknown. We, therefore, report a rare case of periorbital myokymia induced by the use of acetazolamide in a patient diagnosed with idiopathic intracranial hypertension. The nature of her symptoms was significant, as they caused her considerable distress, and subsided almost immediately upon discontinuation of the drug.

Autoimmune neuromyotonia

PURPOSE OF REVIEW

Autoimmune neuromyotonia encompasses a group of rare immune-mediated neurological disorders frequently associated with anti-contactin-associated protein-like 2 (CASPR2) antibodies and featuring clinical and electrical signs of peripheral nerve hyperexcitability (PNH). We aim to summarize the current knowledge on immune-mediated neuromyotonia, focusing on clinical presentations, pathophysiology, and management.

RECENT FINDINGS

Neuromyotonia is a major feature of several autoimmune neurological syndromes characterized by PNH with or without central neurological system involvement. Experimental and clinical evidence suggest that anti-CASPR2 antibodies are directly pathogenic in autoimmune neuromyotonia patients.

SUMMARY

Neuromyotonia, a form of PNH, is a major feature in several syndromes associated with anti-CASPR2 antibodies, including cramp-fasciculation syndrome, Isaacs syndrome, Morvan syndrome, and autoimmune limbic encephalitis. Diagnosis relies on the identification of motor, sensory, and autonomic signs of PNH along with other neurological symptoms, anti-CASPR2 antibody-positivity, and of characteristic electroneuromyographic abnormalities. Paraneoplastic associations with thymoma are possible, especially in Morvan syndrome. Patients usually respond to immune-active treatments, including steroids, intravenous immunoglobulins, plasma exchanges, and rituximab.

Snakebite Causing Facial and Lingual Tremors: A Case Report

Snakebite is a significant public health problem causing around 2.7 envenomations and 138,000 deaths globally. History may sometimes be unclear or misleading, which can cause a delay in diagnosis. Neuroparalytic, hemotoxic, and myotoxic are the common snake bite manifestations. Neuroparalytic snake bites rarely cause involuntary movements. Here we report a case of a 26-year-old female patient who sustained a snake bite and developed tremors in the face and tongue. She improved with mechanical ventilation, anti-snake venom, atropine-neostigmine, and calcium gluconate. She was discharged after seven days of hospital stay and now maintaining regular follow-up in the outpatient clinic.

Dystonia, chorea, hemiballismus and other dyskinesias

Hyperkinesias are heterogeneous involuntary movements that significantly differ in terms of clinical and semeiological manifestations, including rhythm, regularity, speed, duration, and other factors that determine their appearance or suppression. Hyperkinesias are due to complex, variable, and largely undefined pathophysiological mechanisms that may involve different brain areas. In this chapter, we specifically focus on dystonia, chorea and hemiballismus, and other dyskinesias, specifically, levodopa-induced, tardive, and cranial dyskinesia. We address the role of neurophysiological studies aimed at explaining the pathophysiology of these conditions. We mainly refer to human studies using surface and invasive in-depth recordings, as well as spinal, brainstem, and transcortical reflexology and non-invasive brain stimulation techniques. We discuss the extent to which the neurophysiological abnormalities observed in hyperkinesias may be explained by pathophysiological models. We highlight the most relevant issues that deserve future research efforts. The potential role of neurophysiological assessment in the clinical context of hyperkinesia is also discussed.

Clinical Reasoning: A 73-Year-Old Woman With Episodic Dysarthria and Horizontal Binocular Diplopia

A 73-year-old woman presented with transient episodes of dysarthria and horizontal diplopia. She had stereotactic radiosurgery 18 years prior for a retroclival meningioma. Neurologic examination was notable for right-sided tongue deviation, tongue fasciculations, and intermittent impaired abduction of the right eye. MRI ruled out recurrence or progression of the retroclival meningioma. EEG failed to reveal electrographic seizures. EMG showed spontaneous depolarizations in bursts that sounded like "marching soldiers" in the right hemitongue, consistent with myokymia. Focal myokymia is an unusual EMG finding that is usually seen in demyelinating disorders, after radiation, or in neoplastic/inflammatory conditions. The clinical presentation and EMG findings were most consistent with delayed radiation-induced myokymia. Similar cases of transient dysarthria and tongue myokymia from radiation have been infrequently reported in the literature; however, this case uniquely exhibited additional episodes of transient horizontal diplopia, which was possibly from ocular myokymia or neuromyotonia. Although there are limited data, sodium channel inhibitors (e.g., carbamazepine, oxcarbazepine, and lacosamide) have shown some success to provide symptomatic relief, most likely secondary to their ability to inhibit underlying peripheral nerve hyperexcitability. Our patient was started on lacosamide 50 mg twice a day with a notable decrease in symptom frequency. This case illustrates the importance of detailed clinical and electrodiagnostic studies in making the diagnosis of delayed radiation-induced myokymia with episodic dysarthria and provides guidance on potential therapeutics.

Treatment of segmental continuous hypertrophic myokymia of the limb with botulinum A toxin

Myokymia is defined as fluctuating hyperexcitability of muscle fibers caused by repetitive spontaneous contraction of motor units. Myokymia is generally benign with self-resolution, although symptomatic treatment with benzodiazepines, anticonvulsants, and muscle relaxants can be used. Botulinum toxins can also be utilized, although they are mostly used for symptomatic facial myokymia. Here, we report two patients who developed continuous myokymia, resulting in secondary hypertrophy, stiffness, and discomfort in the affected muscles. The first patient had a history of a tethered spinal cord and developed continuous myokymia in the S1 and S2 radicular regions of the left leg. The second patient underwent radiation therapy for lung cancer and developed brachial plexopathy with abnormal activity in the muscles supplied by the musculocutaneous nerve in the right arm. Both patients experienced sleep disturbance, focal discomfort, and restlessness. The anticonvulsants and muscle relaxants were ineffective. Chemodenervation with botulinum A toxin was initiated using either onabotulinumtoxinA or abobotulinumtoxinA. Both patients experienced a substantial reduction in myokymia, with ongoing reversal of muscle hypertrophy and significant improvement in reported subjective symptoms. Treatment with botulinum toxins can be highly effective in patients with symptomatic segmental continuous hypertrophic myokymia and may be considered first-line therapy.

Post-Irradiation Facial Neuromyotonia/Myokymia: A Hemifacial Spasm Mimic

Background:

Hemifacial spasm is diagnosed on a clinical base, with certain atypical features alerting the physician for mimics.

Phenomenology shown:

Hemifacial neuromyotonia/myokymia characterized by tonic hemifacial contraction followed by multifocal undulating hemifacial twitches.

Educational value:

These features are a red flag for (post-irradiation) facial neuromyotonia/myokymia which generally responds well to low dose carbamazepine.

Video Presentation of Myokymia in a Snakebite

Patients with snakebites have highly variable presentations, and delayed diagnosis may lead to unfavorable outcomes. Here, we describe the case of a snakebite in a 23-year-old male who presented with myokymias. On management with mechanical ventilation and anti-snake venom, the patient improved and was discharged. The presence of myokymias may be an early clue to diagnosis and the need for mechanical ventilation in a patient with a snakebite.

Presynaptic Paraneoplastic Disorders of the Neuromuscular Junction: An Update

The neuromuscular junction (NMJ) is the target of a variety of immune-mediated disorders, usually classified as presynaptic and postsynaptic, according to the site of the antigenic target and consequently of the neuromuscular transmission alteration. Although less common than the classical autoimmune postsynaptic myasthenia gravis, presynaptic disorders are important to recognize due to the frequent association with cancer. Lambert Eaton myasthenic syndrome is due to a presynaptic failure to release acetylcholine, caused by antibodies to the presynaptic voltage-gated calcium channels. Acquired neuromyotonia is a condition characterized by nerve hyperexcitability often due to the presence of antibodies against proteins associated with voltage-gated potassium channels. This review will focus on the recent developments in the autoimmune presynaptic disorders of the NMJ.

Microsurgery and Neuromodulation for Facial Spasms

Facial spasms are of various types. Hemifacial spasm (HFS) is characterized by unilateral tonic-clonic contractions of facial muscles, following a specific pattern of disease progression. It has well-delineated clinical, radiological and electrophysiological features. We have conducted an extensive review of existing literature on the subject, as regards etiopathogenesis, clinical features, investigations and management options for facial spasms. Primary Hemifacial spasm (HFS) may be treated using pharmacotherapy, botulinum toxin injections or microvascular decompression surgery. Microvascular decompression has the potential to reverse the pathological changes of the disease and has proved to be the most successful of all treatment options. Other facial spasms are exceedingly difficult to treat and may need neuromodulation as an option. The following article attempts to review the clinical features and therapeutic approaches to managing patients with facial spasms.

Acute non-traumatic tetraparesis - Differential diagnosis

INTRODUCTION

Potentially life-threatening disorders may present in the emergency department with acute tetraparesis, and their recognition is crucial for an appropriate management and timely treatment. Our review aims to systematize the differential diagnosis of acute non-traumatic tetraparesis.

RESULTS

Causes of tetraparesis can be classified based on the site of defect: upper motor neuron (UMN), peripheral nerve, neuromuscular junction or muscle. History of present illness should include the distribution of weakness (symmetric/asymmetric or distal/proximal/diffuse) and associated clinical features (pain, sensory findings, dysautonomia, and cranial nerve abnormalities such as diplopia and dysphagia). Neurological examination, particularly tendon reflexes, helps further in the localization of nerve lesions and distinction between UMN and lower motor neuron. Ancillary studies include blood and cerebral spinal fluid analysis, neuroaxis imaging, electromyography, muscle magnetic resonance and muscle biopsy.

CONCLUSIONS

Acute tetraparesis is still a debilitating and potentially serious neurological condition. Despite all the supplementary ancillary tests, the neurological examination is the key to achieve a correct diagnosis. The identification of life-threatening neurologic disorders is pivotal, since failing to identify patients at risk of complications, such as acute respiratory failure, may have catastrophic results.

Quantitative analysis of myokymic discharges in radiation versus nonradiation cases

INTRODUCTION

Myokymic discharges are classically associated with nerve injury from prior radiation but may occur in other neuromuscular disorders. Using quantitative analysis we aimed to identify the spectrum of conditions in which myokymic discharges are present and determine if there are electrophysiological features that distinguish postradiation from nonradiation causes of myokymia.

METHODS

We reviewed the clinical history of all patients examined in our electromyography labs with myokymic discharges recorded from June 2017 to February 2020. Quantitative analysis of each myokymic discharge was performed using a custom MATLAB script, assessing features such as burst frequency, spikes per burst, and burst regularity.

RESULTS

Eighty-eight distinct myokymic discharges (70 patients) were analyzed: 51 postradiation recordings from 35 patients and 37 recordings from 35 nonradiation patients. The diagnostic spectrum of nonradiation cases was diverse, with common causes being median neuropathy (n = 8), cervical (n = 7), and lumbar (n = 5) radiculopathy, and motor neuron disease (n = 5). On quantitative analysis, postradiation myokymia had an increased burst-to-silence ratio (median, 0.29; nonradiation, 0.08) and greater peak number (median, 15; nonradiation, 7). Except for one patient with hereditary peripheral nerve hyperexcitability, all patients who had two or more muscles demonstrating myokymic discharges belonged to postradiation group.

CONCLUSIONS

Myokymic discharges can be seen in diverse neuromuscular conditions; most common in our cohort was chronic median neuropathy. Postradiation myokymia appears to have distinguishing morphological features when quantitatively analyzed compared with nonradiation cases.

Sustained atypical myokymia of the abductor pollicis brevis with a focal slowing of the median nerve motor axons at the wrist

OBJECTIVE

We report a case of sustained atypical myokymia associated with short bursts of neuromyotonic discharges involving the abductor pollicis brevis (APB) muscle and describe a useful way of detecting a focal slowing involving a small number of median nerve motor fibers with a concentric needle using the filter setting for single fiber electromyography (EMG).

METHODS AND RESULTS

A 62-year-old woman developed right thumb twitches at regular interval of 1.7-3.3 s (0.6-0.3 Hz), which continued for more than four months. Muscle twitches remained the same during altered hand position, psychological stress, or sleep. A concentric needle inserted in the active zone of the APB muscle revealed myokymic bursts with a characteristic of neuromyotonic discharges. Inching study, stimulating at 5 mm increment along the median nerve and recording with a concentric needle using a filter setting for single fiber EMG, revealed a focal slowing of the motor fibers at a point 5-10 mm distal from the distal crease of the wrist, an entrapment site occasionally seen in the carpal tunnel syndrome. One injection of botulinum toxin type A eliminated the myokymia, which then recurred two and a half years later, showing less prominent muscle twitches.

CONCLUSIONS

Sustained atypical myokymia seen in our case represented bursts of neuromyotonic discharges originated from a focal demyelinating lesion involving a few median nerve motor fibers.

Autoimmune Channelopathies at Neuromuscular Junction

The neuromuscular junction, also called myoneural junction, is a site of chemical communication between a nerve fiber and a muscle cell. There are many types of channels at neuromuscular junction that play indispensable roles in neuromuscular signal transmission, such as voltage-gated calcium channels and voltage-gated potassium channels on presynaptic membrane, and acetylcholine receptors on post-synaptic membrane. Over the last two decades, our understanding of the role that autoantibodies play in neuromuscular junction disorders has been greatly improved. Antibodies against these channels cause a heterogeneous group of diseases, such as Lambert-Eaton syndrome, Isaacs' syndrome and myasthenia gravis. Lambert-Eaton syndrome is characterized by late onset of fatigue, skeletal muscle weakness, and autonomic symptoms. Patients with Isaacs' syndrome demonstrate muscle cramps and fasciculation. Myasthenia gravis is the most common autoimmune neuromuscular junction channelopathy characterized by fluctuation of muscle weakness. All these disorders have a high risk of tumor. Although these channelopathies share some common features, they differ for clinical features, antibodies profile, neurophysiological features, and treatments. The purpose of this review is to give a comprehensive insight on recent advances in autoimmune channelopathies at the neuromuscular junction.

Movement Disorders Related to Gluten Sensitivity: A Systematic Review

Gluten related disorders (GRD) represent a wide spectrum of clinical manifestations that are triggered by the ingestion of gluten. Coeliac disease (CD) or gluten sensitive enteropathy is the most widely recognised, but extra-intestinal manifestations have also been increasingly identified and reported. Such manifestations may exist in the absence of enteropathy. Gluten sensitivity (GS) is another term that has been used to include all GRD, including those where there is serological positivity for GS related antibodies in the absence of an enteropathy. Gluten ataxia (GA) is the commonest extraintestinal neurological manifestation and it has been the subject of many publications. Other movement disorders (MDs) have also been reported in the context of GS. The aim of this review was to assess the current available medical literature concerning MDs and GS with and without enteropathy. A systematic search was performed while using PubMed database. A total of 48 articles met the inclusion criteria and were included in the present review. This review highlights that the phenomenology of gluten related MDs is broader than GA and demonstrates that gluten-free diet (GFD) is beneficial in a great percentage of such cases.

Peripheral Nerve Hyperexcitability Syndromes

PURPOSE OF REVIEW

This article provides a review of the clinical phenotypes and evaluation of peripheral nerve hyperexcitability syndromes. These rare diagnoses include cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. Recent investigations have led to an understanding of the autoimmune underpinnings of these conditions and their specific associated antibodies. As the presentation of peripheral nerve hyperexcitability syndromes includes muscle stiffness, twitches, and spasms, which are also shared with certain central nervous system and myopathic conditions, the differential diagnosis of peripheral nerve hyperexcitability syndromes is reviewed.

RECENT FINDINGS

Peripheral nerve hyperexcitability syndromes share clinical and electrodiagnostic evidence of motor nerve instability; however, their clinical presentations are varied. Case reviews have helped us understand the spectrum of symptoms associated with the three peripheral nerve hyperexcitability syndromes reviewed here: cramp-fasciculation syndrome, Isaacs syndrome, and Morvan syndrome. More recently, research has focused on understanding the voltage-gated potassium channel complex antibodies as well as neoplasms associated with these conditions.

SUMMARY

The diagnosis of peripheral nerve hyperexcitability syndromes requires a high index of suspicion, support from the physical examination, familiarity with the spectrum of symptoms associated with peripheral nerve hyperexcitability syndromes, and recognition of diagnostic EMG features. Voltage-gated potassium channel complex antibodies are associated with these conditions. Optimum treatment and autoimmune pathogenesis remain areas of active research.

Paroxysmal motor disorders: expanding phenotypes lead to coalescing genotypes

Paroxysmal movement disorders encompass varied motor phenomena. Less recognized features and wide phenotypic and genotypic heterogeneity are impediments to straightforward molecular diagnosis. We describe a family with episodic ataxia type 1, initially mis‐characterized as paroxysmal dystonia to illustrate this diagnostic challenge. We summarize clinical features in affected individuals to highlight underappreciated aspects and provide comprehensive phenotypic description of the rare familial KCNA1 mutation. Delayed diagnosis in this family is emblematic of the broader challenge of diagnosing other paroxysmal motor disorders. We summarize genotypic and phenotypic overlap and provide a suggested diagnostic algorithm for approaching patients with these conditions.

Botulinum Toxin Treatment of Movement Disorders

Botulinum neurotoxins (BoNTs) are now among the most widely used therapeutic agents in clinical medicine with indications applied to the fields of movement disorders, pain disorders, and autonomic dysfunction. In this literature review, the efficacy and utility of BoNTs in the field of movement disorders are assessed using the criteria of the Guideline Development Subcommittee of the American Academy of Neurology. The literature supports a level A efficacy (established) for BoNT therapy in cervical dystonia and a level B efficacy (probably effective) for blepharospasm, hemifacial spasm, laryngeal dystonia (spasmodic dysphonia), task-specific dystonias, essential tremor, and Parkinson rest tremor. It is the view of movement disorder experts, however, that despite the level B efficacy, BoNTs should be considered treatment of first choice for blepharospasm, hemifacial spasm, laryngeal, and task-specific dystonias. The emerging data on motor and vocal tics of Tourette syndrome and oromandibular dystonias are encouraging but the current level of efficacy is U (undetermined) due to lack of published high-quality studies.

Botulinum Toxin Treatment in Multiple Sclerosis-a Review

Purpose of review The purpose of this review is to provide updated information on the role of botulinum neurotoxin (BoNT) therapy in multiple sclerosis (MS). This review aims to answer which symptoms of multiple sclerosis may be amenable to BoNT therapy. Recent findings We searched the literature on the efficacy of BoNTs for treatment of MS symptoms up to April 1st 2017 via the Yale University Library's search engine including but not limited to Pub Med and Ovis SP. The level of efficacy was defined according to the assessment's criteria set forth by the Subcommittee on Guideline Development of the American Academy of Neurology. Significant efficacy was found for two indications based on the available blinded studies (class I and II) and has been suggested for several others through open-label clinical trials. Summary There is level A evidence (effective- two or more class I) that injection of BoNT-A into the bladder's detrusor muscle improves MS-related neurogenic detrusor overactivity (NDO) and MS-related overactive (OA) bladder. There is level B evidence (probably effective- two class II studies) for utility of intramuscular BoNT-A injections for spasticity of multiple sclerosis. Emerging data based on retrospective class IV studies demonstrates that intramuscular injection of BoNTs may help other symptoms of MS such as focal tonic spasms, focal myokymia, spastic dysphagia, and double vision in internuclear ophthalmoplegia. There is no data on MS-related trigeminal neuralgia and sialorrhea, two conditions which have been shown to respond to BoNT therapy in non-MS population.

Tongue myokymia presenting twelve years after radiation therapy

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Radiation therapy may damage the hypoglossal nerve causing axonal hyperexcitability and myokymia of the tongue.

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Delayed effects of radiation therapy might be seen decades later.

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Detecting myokymic discharges is significative in differential diagnosis.

Objective

This case is a patient with tongue myokymia following radiation therapy 12 years earlier, documented using video and EMG.

Case report

A 68-year-old woman with a history of nasopharyngeal carcinoma presented with subacute onset of difficulty in speaking and involuntary movements of her tongue approximately 12 years after radiation therapy to head and neck. Electromyography displayed myokymic discharges. There was no evidence of recurrent malignancy.

Significance

Delayed effects of radiation therapy might be seen decades later. Myokymic discharges may reveal radiation-induced neuropathy.

Neuromuscular complications in cancer

Cancer is becoming a treatable and even often curable disease. The neuromuscular system can be affected by direct tumor invasion or metastasis, neuroendocrine, metabolic, dysimmune/inflammatory, infections and toxic as well as paraneoplastic conditions. Due to the nature of cancer treatment, which frequently is based on a DNA damaging mechanism, treatment related toxic side effects are frequent and the correct identification of the causative mechanism is necessary to initiate the proper treatment. The peripheral nervous system is conventionally divided into nerve roots, the proximal nerves and plexus, the peripheral nerves (mono- and polyneuropathies), the site of neuromuscular transmission and muscle. This review is based on the anatomic distribution of the peripheral nervous system, divided into cranial nerves (CN), motor neuron (MND), nerve roots, plexus, peripheral nerve, the neuromuscular junction and muscle. The various etiologies of neuromuscular complications - neoplastic, surgical and mechanic, toxic, metabolic, endocrine, and paraneoplastic/immune - are discussed separately for each part of the peripheral nervous system.

Use of botulinum toxin type A for the treatment of radiation therapy-induced myokymia and neuromyotonia in a dog

CASE DESCRIPTION A 5-year-old castrated male Maltese was evaluated for intermittent clinical signs of muscle cramping and abnormal movements of the skin of the right pelvic limb at the site where an infiltrative lipoma had twice been resected. After the second surgery, the surgical field was treated with radiation therapy (RT). The clinical signs developed approximately 14 months after completion of RT. CLINICAL FINDINGS When clinical signs were present, the right biceps femoris and semitendinosus muscles in the area that received RT were firm and had frequently visible contractions, and the skin overlying those muscles had episodic vermiform movements. Electromyography of those muscles revealed abnormal spontaneous activity with characteristics consistent with myokymic discharges and neuromyotonia. Magnetic resonance imaging of the affected leg revealed no evidence of tumor regrowth. The myokymia and neuromyotonia were considered secondary to RT. TREATMENT AND OUTCOME 4 U of Clostridium botulinum toxin type A (BoNT-A) neurotoxin complex was injected into the affected muscles at each of 6 sites twice during a 24-hour period (ie, 48 U of BoNT-A were administered). The clinical signs were completely resolved 10 days after BoNT-A treatment and were controlled by repeated BoNT-A treatment every 3 to 4 months for > 1 year. CLINICAL RELEVANCE To our knowledge, this is the first report of myokymia and neuromyotonia secondary to RT in a dog. For the dog of this report, injection of BoNT-A into the affected muscles was safe, effective, and easy to perform.

The episodic ataxia type 1 mutation I262T alters voltage-dependent gating and disrupts protein biosynthesis of human Kv1.1 potassium channels

Voltage-gated potassium (Kv) channels are essential for setting neuronal membrane excitability. Mutations in human Kv1.1 channels are linked to episodic ataxia type 1 (EA1). The EA1-associated mutation I262T was identified from a patient with atypical phenotypes. Although a previous report has characterized its suppression effect, several key questions regarding the impact of the I262T mutation on Kv1.1 as well as other members of the Kv1 subfamily remain unanswered. Herein we show that the dominant-negative effect of I262T on Kv1.1 current expression is not reversed by co-expression with Kvβ1.1 or Kvβ2 subunits. Biochemical examinations indicate that I262T displays enhanced protein degradation and impedes membrane trafficking of Kv1.1 wild-type subunits. I262T appears to be the first EA1 mutation directly associated with impaired protein stability. Further functional analyses demonstrate that I262T changes the voltage-dependent activation and Kvβ1.1-mediated inactivation, uncouples inactivation from activation gating, and decelerates the kinetics of cumulative inactivation of Kv1.1 channels. I262T also exerts similar dominant effects on the gating of Kv1.2 and Kv1.4 channels. Together our data suggest that I262T confers altered channel gating and reduced functional expression of Kv1 channels, which may account for some of the phenotypes of the EA1 patient.

Eyelid myokymia in patients with migraine taking topiramate

OBJECTIVE

Although ocular side effects of topiramate are common, neuroophthalmologic manifestations such as blepharospasm, myokymia and oculogyric crisis are scarcely reported.

METHODS

We present a serie of 8 patients with migraine who developed eyelid myokymia after treatment with topiramate. We reviewed all patients with migraine treated with topiramate attending the headache outpatient clinic of our hospital from January 2008 to December 2012.

RESULTS

During the study period, a total of 140 patients with migraine were treated with topiramate in our headache clinic. Eight presented eyelid myokymia after beginning treatment with topiramate (5,7%). Topiramate was stopped and myokymia disappeared in all patients, it was prescribed again and eyelid myokymia reappeared with their previous characteristics in all patients.

CONCLUSIONS

Eyelid myokymia is an underreported side-effect of topiramate in patients with migraine, of unknown cause, so that in future, further studies are need to examine whether patients with migraine are predisposed or not to this adverse effect.

Paraneoplastic disorders in thymoma patients

Thymic malignancy is often associated with paraneoplastic neurological diseases (PNDs) and recognition of these disorders is important for physicians who treat these patients. The most common thymoma-associated PNDs are myasthenia gravis (MG), acquired neuromyotonia (Isaacs' syndrome), encephalitis, Morvan's syndrome, and myositis. Diagnosis of these disorders is complex but often aided by testing for specific autoantibodies, including those to the acetylcholine receptor for MG and to contactin-associated protein-like 2, protein of the voltage-gated potassium channel complex, in patients with acquired neuromyotonia, Morvan's syndrome, or encephalitis. Patients who manifest these disorders should be screened for thymoma at diagnosis, and worsening of these PNDs may be associated with recurrent thymoma. These disorders can cause profound disability but usually respond to immunotherapy, and often improve with thymoma treatment. Close cooperation among a team of specialists is required to take proper care of these patients.

Neuromyotonia with polyneuropathy, prominent psychoorganic syndrome, insomnia, and suicidal behavior without antibodies: a case report

Introduction

Peripheral nerve hyperexcitability disorders are characterized by constant muscle fiber activity. Acquired neuromyotonia manifests clinically in cramps, fasciculations, and stiffness. In Morvan’s syndrome the signs of peripheral nerve hyperexcitability are accompanied by autonomic symptoms, sensory abnormalities, and brain disorders.

Case presentation

A 70-year-old Caucasian man developed, in the course of 3 months, polyneuropathy with unpleasant dysesthesia of lower extremities and gradually increasing fasciculations, muscle stiffness and fatigue. Subsequently, he developed a prominent insomnia with increasing psychological changes and then he attempted a suicide. Electromyography confirmed a sensory-motor polyneuropathy of a demyelinating type. The findings included fasciculations as well as myokymia, doublets and multiplets, high frequency discharges, and afterdischarges, following motor nerve stimulation. No auto-antibodies were found either in his blood or cerebrospinal fluid. Magnetic resonance imaging of his brain showed small, unspecific, probably postischemic changes. A diagnosis of Morvan’s syndrome was confirmed; immunoglobulin (2g/kg body weight) was applied intravenously, and, subsequently, carbamazepine 2×200mg, venlafaxine 150mg, and mirtazapine each night were prescribed. His sleep improved, suicidal tendencies stopped, less fasciculations occurred, and muscle hypertonia also improved. Hyperexcitation also partially remitted including the electromyography finding.

Conclusions

We described here the case of a patient with Morvan’s syndrome; his case is rare because of severe psychical changes with a suicide attempt, short admission to a psychiatric ward, prominent electromyographic changes, and because antibodies were not detected. After therapy with immunoglobulins followed by corticosteroids with sodium channel blocker, his motor, autonomic, psychical signs and symptoms, and electromyography changes substantially improved.

A practice of caution: spontaneous action potentials or artifactual spikes?

Background

High density surface electromyogram (EMG) techniques with electrode arrays have been used to record spontaneous muscle activity, which is important, both for supporting the diagnosis of neuromuscular diseases and for laboratory based neurophysiological investigations. This short report addresses a practical issue we have experienced during recording of spontaneous muscle activity using electrode arrays from subjects with major neuromuscular disorders.

Findings

We show that recording artifacts can appear similar to spontaneous action potential spikes. Moreover, a causal filter may induce asymmetric distortions of an artifact and thus confuse it with a real action potential spike. As a consequence, for a single channel surface EMG recording, it might be difficult to judge whether a voltage transient is a real action potential or an artifact. Further investigation of the signal distributions among other channels of the array can be used to reach a more confident judgment.

Conclusions

During examination of spontaneous muscle activity using electrode arrays, caution is required for differentiation of physiological signals from artifactual spikes, which is important for accurate extraction of diagnostic or investigatory information.

Examination and clinical care of the patient with neuropathy

Examination of a patient with peripheral neuropathy starts with careful questioning of the patient about the history of symptoms and signs and of a possible familial disorder. Several steps are required during examination of the patient with peripheral neuropathy: first the pattern of neuropathy and site of lesions should be determined: roots, nerve trunks, focal, multifocal, length-dependent generalized polyneuropathy, the type of nerve fibers predominantly affected, the association with trophic changes and autonomic dysfunction, the course of the disease ranging from acute inflammatory polyneuritis or fulminant multifocal neuropathy to an extremely slow progression as in Charcot-Marie-Tooth syndromes. At the end of this first contact with the patient, the neurologist must decide which investigations seem necessary and their timing including electrophysiological tests, imaging, CSF examination, blood tests, nerve and muscle biopsy, DNA testing, etc. In some cases, life-threatening manifestations, including weakness of respiratory muscles or swallowing difficulty, or autonomic dysfunction, require urgent therapeutic decisions.

Neuro-glial interactions at the nodes of Ranvier: implication in health and diseases

Specific cell adhesion molecules (CAMs) are dedicated to the formation of axo-glial contacts at the nodes of Ranvier of myelinated axons. They play a central role in the organization and maintenance of the axonal domains: the node, paranode, and juxtaparanode. In particular, CAMs are essential for the accumulation of voltage-gated sodium channels at the nodal gap that ensures the rapid and saltatory propagation of the action potentials (APs). The mechanisms regulating node formation are distinct in the central and peripheral nervous systems, and recent studies have highlighted the relative contribution of paranodal junctions and nodal extracellular matrix. In addition, CAMs at the juxtaparanodal domains mediate the clustering of voltage-gated potassium channels which regulate the axonal excitability. In several human pathologies, the axo-glial contacts are altered leading to disruption of the nodes of Ranvier or mis-localization of the ion channels along the axons. Node alterations and the failure of APs to propagate correctly from nodes to nodes along the axons both contribute to the disabilities in demyelinating diseases. This article reviews the mechanisms regulating the association of the axo-glial complexes and the role of CAMs in inherited and acquired neurological diseases.

Neurophysiological approach to disorders of peripheral nerve

Disorders of the peripheral nerve system (PNS) are heterogeneous and may involve motor fibers, sensory fibers, small myelinated and unmyelinated fibers and autonomic nerve fibers, with variable anatomical distribution (single nerves, several different nerves, symmetrical affection of all nerves, plexus, or root lesions). Furthermore pathological processes may result in either demyelination, axonal degeneration or both. In order to reach an exact diagnosis of any neuropathy electrophysiological studies are crucial to obtain information about these variables. Conventional electrophysiological methods including nerve conduction studies and electromyography used in the study of patients suspected of having a neuropathy and the significance of the findings are discussed in detail and more novel and experimental methods are mentioned. Diagnostic considerations are based on a flow chart classifying neuropathies into eight categories based on mode of onset, distribution, and electrophysiological findings, and the electrophysiological characteristics in each type of neuropathy are discussed.

The many faces of hemifacial spasm: differential diagnosis of unilateral facial spasms

Hemifacial spasm is defined as unilateral, involuntary, irregular clonic or tonic movement of muscles innervated by the seventh cranial nerve. Most frequently attributed to vascular loop compression at the root exit zone of the facial nerve, there are many other etiologies of unilateral facial movements that must be considered in the differential diagnosis of hemifacial spasm. The primary purpose of this review is to draw attention to the marked heterogeneity of unilateral facial spasms and to focus on clinical characteristics of mimickers of hemifacial spasm and on atypical presentations of nonvascular cases. In addition to a comprehensive review of the literature on hemifacial spasm, medical records and videos of consecutive patients referred to the Movement Disorders Clinic at Baylor College of Medicine for hemifacial spasm between 2000 and 2010 were reviewed, and videos of illustrative cases were edited. Among 215 patients referred for evaluation of hemifacial spasm, 133 (62%) were classified as primary or idiopathic hemifacial spasm (presumably caused by vascular compression of the ipsilateral facial nerve), and 4 (2%) had hereditary hemifacial spasm. Secondary causes were found in 40 patients (19%) and included Bell's palsy (n=23, 11%), facial nerve injury (n=13, 6%), demyelination (n=2), and brain vascular insults (n=2). There were an additional 38 patients (18%) with hemifacial spasm mimickers classified as psychogenic, tics, dystonia, myoclonus, and hemimasticatory spasm. We concluded that although most cases of hemifacial spasm are idiopathic and probably caused by vascular compression of the facial nerve, other etiologies should be considered in the differential diagnosis, particularly if there are atypical features.

Unilateral facial myokymia in a dog with an intracranial meningioma

A 23-month-old castrated male Cavalier King Charles spaniel was evaluated because of a 6-month history of unusual rippling/undulating movements of the right facial muscles that were continuous and persisted during sleep. Neurological examination revealed narrowing of the right palpebral fissure and unilateral right-sided facial myokymia that was characterised by myokymic, and to a lesser degree, neuromyotonic discharges on concentric needle electromyographic examination. After persisting unchanged for almost 2.5 years from its onset, the facial myokymia gradually disappeared over a 6-month period concomitant with the emergence of a persistent ipsilateral facial paralysis and head tilt. At 5 years and 9 months after the first examination, signs of ipsilateral lacrimal, pharyngeal and laryngeal dysfunction became evident and the dog was euthanased. Postmortem examination identified a malignant (WHO grade III) meningioma in the right cerebellopontomedullary angle that compressed the ventrolateral cranial medulla, effaced the jugular foramen and internal acoustic meatus and extended into the facial canal of the petrous temporal bone. Novel findings were the unique observation of isolated unilateral facial myokymia preceding diagnosis of a meningioma affecting facial nerve function within the caudal cranial fossa and the remarkably long duration of neurological signs (75 months) attributable to the neoplasm.

An introduction to dyskinesia--the clinical spectrum

The term movement disorder is used to describe a variety of abnormal movements, and may involve an excess or paucity of movement. Careful characterization of phenomenology is an essential component of diagnosis. Factors such as speed, amplitude, duration, distribution, rhythmicity, suppressibility and pattern of movement provide valuable information to guide the clinician in their assessment of the movement disorder. In this chapter, the clinical spectrum and phenomenology of dyskinesias will be reviewed.

The C-terminal domain of ßIV-spectrin is crucial for KCNQ2 aggregation and excitability at nodes of Ranvier

The spectrin cytoskeleton has an important function in the targeting of proteins to excitable membrane domains. In axons, βIV-spectrin stabilizes voltage-gated sodium (Nav) channel clusters at nodes of Ranvier and axon initial segments, two regions crucial for the generation and conduction of action potentials. Here, I investigated the physiology of the neuromuscular junction and peripheral nerves in quivering-3J mice, which show a frame-shift base insertion in the Spnb4 gene and lack the C-terminus of βIV-spectrin. The quivering-3J mice show prominent spontaneous and evoked hyperactivities at diaphragm neuromuscular junctions. These neuromyotonic and myokymic discharges were more prominent in adult animals when tremors and ataxia were pronounced. Recordings of sciatic and phrenic nerves showed that the hyperactivities originate in myelinated axons distally from nerve terminals. Axon and myelin structure in the PNS were unaffected in quivering-3J mice. Of interest, KCNQ2 subunit aggregates were undetectable at PNS and CNS nodes, whereas Nav and Kv1.1/Kv1.2 channels were properly concentrated at nodal and juxtaparanodal regions, respectively. The protein level of KCNQ2 subunits was normal in mutant animals, suggesting that KCNQ2 subunit absence stems from clustering or trafficking defects in axons. The quivering-3J nodes also presented high densities of ankyrin-G and CK2α, two cytosolic molecules involved with aggregating Nav and KCNQ2/3 channels in axons. Because βIV-spectrin does not interact with KCNQ2/3 subunits, it is suspected that βIV-spectrin regulates the distribution of KCNQ2/3 subunits in axonal subdomains via regulatory partners. Retigabine, an activator of KCNQ2/3 channels, attenuated the repetitive activities in quivering-3J mice, suggesting that depletion of KCNQ2 subunits at nodes initiates neuromyotonic/myokymic discharges. These findings demonstrate that spectrin cytoskeleton finely regulates ion channel distribution and implicates KCNQ2/3 subunits in axonal excitability and in myokymia aetiology.