Myoclonus

Recurrent Falls as the Only Clinical Sign of Cortical-Subcortical Myoclonus: A Case Report

Some authors use the term cortical-subcortical myoclonus to identify a specific type of myoclonus, which differs from classical cortical myoclonus in that the abnormal neuronal activity spreads between the cortical and subcortical circuits, producing diffuse excitation. The EEG shows generalized spike-and-wave discharges that correlate with the myoclonic jerks. We report the case of a 79-year-old patient with a history of right thalamic deep hemorrhagic stroke, with favorable evolution. Fifteen years later, he was readmitted to the emergency department for episodes characterized by sudden falls without loss of consciousness. An EEG with EMG recording channel on the right deltoid muscle was performed, which documented frequent diffuse spike-wave and polyspike-wave discharges, temporally related to myoclonic jerks in the lower limbs. Brain MRI showed the persistence of a small right thalamic hemosiderin residue at the site of the previous hemorrhage. Antiseizure treatment with levetiracetam was started, with rapid clinical and electroencephalographic improvement. Our case may represent a lesion model of generalized epilepsy with myoclonic seizures. Furthermore, it highlights that lower limb myoclonus of cortical-subcortical origin may be an underestimate cause of gait disturbances and postural instability. Then, it may be reasonable to include the EEG in the diagnostic work-up of patients with recurrent falls.

Palato-Pharyngo-Laryngeal Rhythmic Myoclonus in Neuro-Bechet Syndrome: A Case Report

OBJECTIVE

Behcet's syndrome (BS) is a chronic, relapsing multisystemic inflammatory perivasculitis and can affect any tissue, including the nervous system. Neuro-Bechet's syndrome (NBS) most commonly affects the CNS parenchyma and presents with a subacute brainstem syndrome that includes cranial neuropathies. Here we describe a rare case of palato-pharyngo-laryngeal myoclonus as a manifestation of NBS and discuss it from a laryngology perspective.

METHODS

Case report at tertiary care center. Informed consent was obtained from patient. IRB approved as non-human subjects research.

RESULTS

A 52-year-old male presented with a progressive history of ataxia, fatigue, apathy, dysphagia, depressed mood, dizziness, poor appetite, subjective fever and recurrent orogenital lesions. He was diagnosed with NBS and treated with methylprednisolone, followed by infliximab and methotrexate. Despite treatment, his severe spastic dysarthria, dysphagia, and aspiration worsened over the next few months, necessitating a gastrotomy tube. With concern for laryngospasm, he was referred to otolaryngology and found to have synchronous and symmetric palatal, pharyngeal, and laryngeal rhythmic myoclonus bilaterally at a frequency of 2 Hz with inappropriate vocal cord closure. Treatment with baclofen and a scopolamine patch improved his breathing and reduced choking events.

CONCLUSIONS

Palato-pharyngo-laryngeal rhythmic myoclonus can be a presentation of brainstem NBS in the otolaryngology clinic. We theorize perivascular disease in NBS results in a brainstem lesion in the denato-rubro-olivary tract, which results in hypertrophic olivary degeneration and subsequent activation of the inferior olives oscillatory activity, causing palato-pharyngo-laryngeal rhythmic myoclonus. Common symptoms include significant dysarthria, dysphonia, and dysphagia with concern for obstructive sleep apnea and airway compromise. Treatments include pharmacologic therapy, laryngeal botox, and tracheostomy in cases of significant airway compromise.

Progression of myoclonus subtypes in subacute sclerosing panencephalitis

OBJECTIVES

Diagnostic criteria of subacute sclerosing panencephalitis (SSPE) include myoclonus, a well-recognized clinical feature. Here, we studied the electrophysiological features of myoclonus with regards to disease staging in SSPE patients.

METHODS

We included 10 patients diagnosed with SSPE between 2010 and 2018, along with 21 healthy subjects. All participants had detailed electrophysiological evaluation including polymyographic analysis, blink reflex after trigeminal stimulation, auditory startle response, startle response after somatosensory stimuli, F-waves, and long-loop reflexes. Clinical findings were retrieved from the medical records.

RESULTS

Patients were categorized into Gascon stage 2B (n = 5, 50%), 2A (n = 2, 20%), 3B (n = 2, 20%) and 4A (n = 1, 10%) at the time of electrophysiological evaluation. Two patients had cortical myoclonus, four had possible cortico-subcortical myoclonus, and four had brainstem myoclonus. Patients were categorized into Gascon stages 2a and 2b had possible cortico-subcortical myoclonus (85.7%). However, none of the patients with stage 3b or 4a had possible cortico-subcortical subtype but all had the brainstem subtype.

CONCLUSION

Association was seen between subtypes of myoclonus and clinical staging in SSPE. This suggests that myoclonus in SSPE may primarily involve the cortex and cortico-subcortical structures such as the thalamus at earlier stages of disease, and then involve more caudal structures as the disease progresses.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

Time-frequency analysis of intracranial EEG in patients with myoclonic seizures

Myoclonic seizures are defined as generalized seizures according to the classification of seizure by the International League Against Epilepsy (ILAE). The pathogenesis of myoclonic seizures is not yet clear. There are very few studies on the focal surgical treatment of myoclonic seizures. The aim of this study is to investigate the characteristics of myoclonic seizure onset in different bands of the intracranial electroencephalogram (EEG) and their dynamic changes in temporal and spatial evolution. We studied four patients with myoclonic seizures who were under the focal resection of the epileptogenic zone. We retrospectively analyzed the semiology, electrocorticogram (ECoG) and imaging data of these patients, and conducted time-frequency analysis of broadband ECoG activity. We found that myoclonic seizures without clinical lateralizing signs could be improved by the resection of the epileptogenic zone. The ECoG power in different frequency bands increased to a peak at 0.5s before the clinical seizure onset and decreased quickly afterwards. The power of alpha activity was highest during the preictal and ictal periods. The central zone had higher power than the epileptogenic zone in all frequency bands during the preictal period, but this difference was not statistically significant. Our results suggest that myoclonic seizures in some patients might have a focal origination, with a fast bilateral propagating network in all frequency bands, especially the alpha band.

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.

Deep Brain Stimulation in a Case of Mitochondrial Disease

Background

DBS has proven to be an effective therapy for Parkinson's disease, essential tremor, and primary dystonia. Mixed results have been reported in case series for other hyperkinetic disorders, and sparse data are available regarding secondary movement disorders. We report on the clinical effects of bilateral globus pallidus internus (GPi) DBS, a progressive mitochondrial cytopathy.

Methods

A single patient with myoclonus and dystonia syndrome secondary to a mitochondrial cytopathy with history of perinatal hypoxia was identified from our University of Florida DBS database. Demographics, clinical, surgical, and DBS data were documented.

Results

At 6 months post-DBS, we observed a 32% (361 to 527) improvement on quality of life (36-item Medical Outcome Study Short-Form Health Survey; SF-36). Objective clinical scales revealed a 33% (143 to 96) improvement in the Unified Myoclonus Rating Scale (UMRS) total score. The UMRS action myoclonus subsection revealed a 29% (69 to 46) improvement. No significant changes were observed in the Burke-Fahn-Mardsen Dystonia Rating Scale (BFMDRS). After 1-year follow-up, a worsening of 59% (527 to 215) was observed in the SF-36 scale, of 19% (28.5 to 35) in the BFMDRS, and of 23% (96 to 124) in the UMRS. However, the frequency and intensity of action myoclonus scores remained lower when compared to baseline scores.

Conclusions

Although we observed a loss of benefit in the long term for most quality-of-life and clinical outcomes, the DBS effects on action myoclonus seemed to remain stable. Longer follow-up studies are necessary to confirm our short-term and unblinded findings.

Myoclonus in mitochondrial disorders

Myoclonus is a possible manifestation of mitochondrial disorders, and its presence is considered, in association with epilepsy and the ragged red fibers, pivotal for the syndromic diagnosis of MERRF (myoclonic epilepsy with ragged red fibers). However, its prevalence in mitochondrial diseases is not known. The aims of this study are the evaluation of the prevalence of myoclonus in a big cohort of mitochondrial patients and the clinical characterization of these subjects. Based on the database of the "Nation-wide Italian Collaborative Network of Mitochondrial Diseases," we reviewed the clinical and molecular data of mitochondrial patients with myoclonus among their clinical features. Myoclonus is a rather uncommon clinical feature of mitochondrial diseases (3.6% of 1,086 patients registered in our database). It is not strictly linked to a specific genotype or phenotype, and only 1 of 3 patients with MERRF harbors the 8344A>G mutation (frequently labeled as "the MERRF mutation"). Finally, myoclonus is not inextricably linked to epilepsy in MERRF patients, but more to cerebellar ataxia. In a myoclonic patient, evidences of mitochondrial dysfunction must be investigated, even though myoclonus is not a common sign of mitochondriopathy. Clinical, histological, and biochemical data may predict the finding of a mitochondrial or nuclear DNA mutation. Finally, this study reinforces the notion that myoclonus is not inextricably linked to epilepsy in MERRF patients, and therefore the term "myoclonic epilepsy" seems inadequate and potentially misleading.

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

BACKGROUND

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Presentation of opsoclonus myoclonus ataxia syndrome with glutamic acid decarboxylase antibodies

In this rare case, the patient presented with opsoclonus, myoclonus and ataxia. Serological and imaging studies revealed high glutamic acid decarboxylase antibody (GAD-Ab) levels. High-dose corticosteroids were of no benefit and subsequent intravenous immunoglobulin (IVIg) administration proved resolution of the condition. Levetiracetam proved useful in symptomatically controlling the myoclonus. Follow-up GAD-Ab levels were within normal limits.