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

Redefined giant somatosensory evoked potentials: Evoked epileptic complexes of excitatory and inhibitory components

OBJECTIVE

Giant somatosensory evoked potentials (SEPs) are observed in patients with cortical myoclonus. Short-latency components (SLC), are regarded as evoked epileptic activities or paroxysmal depolarization shifts (PDSs). This study aimed to reveal the electrophysiological significance of the middle-latency component (MLC) P50 of the SEPs.

METHODS

Twenty-two patients with cortical myoclonus having giant SEPs (patient group) and 15 healthy controls were included in this study. Waveform changes in SEPs before and after perampanel (PER) treatment were evaluated in the patient group. The wide range, time-frequency properties underlying the waveforms were compared between the groups.

RESULTS

After PER treatment, SLC was prolonged and positively correlated with PER concentration, whereas MLC showed no correlation with PER concentration. Time-frequency analysis showed a power increase (156 Hz in all patients, 624 Hz in benign adult familial myoclonus epilepsy patients) underlying SLC and a power decrease (156 Hz, 624 Hz) underlying MLC in the patient group.

CONCLUSIONS

The high-frequency power increase in SLCs and decrease in MLCs clearly reflected PDS and subsequent hyperpolarization, respectively. This relationship was similar to that of interictal epileptiform discharges, suggesting that giant SEPs evoke epileptic complexes of excitatory and inhibitory components.

SIGNIFICANCE

MLCs of giant SEPs reflected inhibitory components.

Changes in cerebellar output abnormally modulate cortical myoclonus sensorimotor hyperexcitability

Cortical myoclonus is produced by abnormal neuronal discharges within the sensorimotor cortex, as demonstrated by electrophysiology. Our hypothesis is that the loss of cerebellar inhibitory control over the motor cortex, via cerebello-thalamo-cortical connections, could induce the increased sensorimotor cortical excitability that eventually causes cortical myoclonus. To explore this hypothesis, in the present study we applied anodal transcranial direct current stimulation over the cerebellum of patients affected by cortical myoclonus and healthy controls and assessed its effect on sensorimotor cortex excitability. We expected that anodal cerebellar transcranial direct current stimulation would increase the inhibitory cerebellar drive to the motor cortex and therefore reduce the sensorimotor cortex hyperexcitability observed in cortical myoclonus. Ten patients affected by cortical myoclonus of various aetiology and 10 aged-matched healthy control subjects were included in the study. All participants underwent somatosensory evoked potentials, long-latency reflexes and short-interval intracortical inhibition recording at baseline and immediately after 20 min session of cerebellar anodal transcranial direct current stimulation. In patients, myoclonus was recorded by the means of surface EMG before and after the cerebellar stimulation. Anodal cerebellar transcranial direct current stimulation did not change the above variables in healthy controls, while it significantly increased the amplitude of somatosensory evoked potential cortical components, long-latency reflexes and decreased short-interval intracortical inhibition in patients; alongside, a trend towards worsening of the myoclonus after the cerebellar stimulation was observed. Interestingly, when dividing patients in those with and without giant somatosensory evoked potentials, the increment of the somatosensory evoked potential cortical components was observed mainly in those with giant potentials. Our data showed that anodal cerebellar transcranial direct current stimulation facilitates-and does not inhibit-sensorimotor cortex excitability in cortical myoclonus syndromes. This paradoxical response might be due to an abnormal homeostatic plasticity within the sensorimotor cortex, driven by dysfunctional cerebello-thalamo-cortical input to the motor cortex. We suggest that the cerebellum is implicated in the pathophysiology of cortical myoclonus and that these results could open the way to new forms of treatment or treatment targets.

Familial adult myoclonus epilepsy: a pragmatic approach

Familial Adult Myoclonus Epilepsy (FAME), with a prevalence of < 1/35 000, is known under different acronyms. The disease is transmitted in an autosomal dominant manner and is characterized by the occurrence of cortical myoclonic tremor, overt myoclonus, and rare bilateral tonic-clonic seizures. FAME is considered neurodegenerative, although it is relatively slow in progression. Diagnosis is based on specific neurophysiological testing, namely jerk-locked back-averaging, somatosensory evoked potentials, long latency reflex, and motor evoked potentials, among others. Imaging data, including functional magnetic resonance imaging, indicate a cortical origin of the cortical myoclonic tremor and decreased cerebellar activation. Cerebellar changes in Purkinje cells have been noted, from few neuropathology reports, in patients from isolated pedigrees. The differential diagnosis includes essential tremor, some forms of genetic generalized epilepsy, and progressive myoclonus epilepsies. Treatment is mainly symptomatic.

Drug-resistant generalized epilepsies: Revisiting the frontiers of idiopathic generalized epilepsies

The 2017 International League Against Epilepsy (ILAE) classification suggested that the term "genetic generalized epilepsies" (GGEs) should be used for the broad group of epilepsies with so-called "generalized" seizure types and "generalized" spike-wave activity on EEG, based on a presumed genetic etiology. Within this framework, idiopathic generalized epilepsies (IGEs) are described as a subset of GGEs and include only four epileptic syndromes: childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and epilepsy with generalized tonic-clonic seizures alone. The recent 2022 ILAE definition of IGEs is based on the current state of knowledge and reflects a community consensus and is designed to evolve as knowledge advances. The term "frontiers of IGEs" refers to the actual limits of our understanding of these four syndromes. Indeed, among patients presenting with a syndrome compatible with the 2022 definition of IGEs, we still observe a significant proportion of patients presenting with specific clinical features, refractory seizures, or drug-resistant epilepsies. This leads to the discussion of the boundaries of IGEs and GGEs, or what is accepted within a clinical spectrum of a definite IGE. Here, we discuss several entities that have been described in the literature for many years and that may either constitute rare features of IGEs or a distinct differential diagnosis. Their recognition by clinicians may allow a more individualized approach and improve the management of patients presenting with such entities.

Irregular Tremulous Movements and Infrequent Seizures: A Clinical-Electrophysiological Diagnosis of Benign Adult Familial Myoclonus Epilepsy

We report a case involving a 31-year-old male without any known precipitating injuries presenting with involuntary finger movements and rare seizures. There was a noted family history of tremulous movements. Yet the characteristics of his finger movements were irregular and not typical of essential tremor (ET). Electrophysiological examinations, including video EEG, showed no epileptic discharges, and brain MRI results were normal. However, somatosensory evoked potentials (SEP) revealed the presence of giant SEP, and a positive cortical (C)-reflex was observed, leading to a clinical diagnosis of benign adult familial myoclonus epilepsy (BAFME). Management with valproic acid and perampanel resulted in a significant reduction of symptoms. This case highlights the necessity of considering BAFME in the differential diagnosis for atypical tremorous finger movements, especially with a relevant family history, and the critical role of electrophysiological findings indicative of cortical hyperexcitability.

Progressive myoclonic epilepsy as an expanding phenotype of NGLY1-associated congenital deglycosylation disorder: A case report and review of the literature

INTRODUCTION

NGLY1-associated congenital disorder of deglycosylation (CDDG1: OMIM #615273) is a rare autosomal recessive disorder caused by a functional impairment of endoplasmic reticulum in degradation of glycoproteins. Neurocognitive dysfunctions have been documented in patients with CDDG1; however, deteriorating phenotypes of affected individuals remain elusive.

CASE PRESENTATION

A Japanese boy with delayed psychomotor development showed ataxic movements from age 5 years and myoclonic seizures from age 12 years. Appetite loss, motor and cognitive decline became evident at age 12 years. Electrophysiological studies identified paroxysmal discharges on myoclonic seizure and a giant somatosensory evoked potential. Perampanel was effective for controlling myoclonic seizures. Exome sequencing revealed that the patient carried compound heterozygous variants in NGLY1, NM_018297.4: c.857G > A and c.-17_12del, which were inherited from mother and father, respectively. A literature review confirmed that myoclonic seizures were observed in 28.5% of patients with epilepsy. No other patients had progressive myoclonic epilepsy or cognitive decline in association with loss-of-function variations in NGLY1.

CONCLUSION

Our data provides evidence that a group of patients with CDDG1 manifest slowly progressive myoclonic epilepsy and cognitive decline during the long-term clinical course.

Rethinking the neurophysiological concept of cortical myoclonus

Cortical myoclonus is thought to result from abnormal electrical discharges arising in the sensorimotor cortex. Given the ease of recording of cortical discharges, electrophysiological features of cortical myoclonus have been better characterized than those of subcortical forms, and electrophysiological criteria for cortical myoclonus have been proposed. These include the presence of giant somatosensory evoked potentials, enhanced long-latency reflexes, electroencephalographic discharges time-locked to individual myoclonic jerks and significant cortico-muscular connectivity. Other features that are assumed to support the cortical origin of myoclonus are short-duration electromyographic bursts, the presence of both positive and negative myoclonus and cranial-caudal progression of the jerks. While these criteria are widely used in clinical practice and research settings, their application can be difficult in practice and, as a result, they are fulfilled only by a minority of patients. In this review we reappraise the evidence that led to the definition of the electrophysiological criteria of cortical myoclonus, highlighting possible methodological incongruencies and misconceptions. We believe that, at present, the diagnostic accuracy of cortical myoclonus can be increased only by combining observations from multiple tests, according to their pathophysiological rationale; nevertheless, larger studies are needed to standardise the methods, to resolve methodological issues, to establish the diagnostic criteria sensitivity and specificity and to develop further methods that might be useful to clarify the pathophysiology of myoclonus.

Nine Hereditary Movement Disorders First Described in Asia: Their History and Evolution

Clinical case studies and reporting are important to the discovery of new disorders and the advancement of medical sciences. Both clinicians and basic scientists play equally important roles leading to treatment discoveries for both cures and symptoms. In the field of movement disorders, exceptional observation of patients from clinicians is imperative, not just for phenomenology but also for the variable occurrences of these disorders, along with other signs and symptoms, throughout the day and the disease course. The Movement Disorders in Asia Task Force (TF) was formed to help enhance and promote collaboration and research on movement disorders within the region. As a start, the TF has reviewed the original studies of the movement disorders that were preliminarily described in the region. These include nine disorders that were first described in Asia: Segawa disease, PARK-Parkin, X-linked dystonia-parkinsonism, dentatorubral-pallidoluysian atrophy, Woodhouse-Sakati syndrome, benign adult familial myoclonic epilepsy, Kufor-Rakeb disease, tremulous dystonia associated with mutation of the calmodulin-binding transcription activator 2 gene, and paroxysmal kinesigenic dyskinesia. We hope that the information provided will honor the original researchers and help us learn and understand how earlier neurologists and basic scientists together discovered new disorders and made advances in the field, which impact us all to this day.

Familial Adult Myoclonus Epilepsy: A Non-Coding Repeat Expansion Disorder of Cerebellar-Thalamic-Cortical Loop

Familial adult myoclonus Epilepsy (FAME) is a non-coding repeat expansion disorder that has been reported under different acronyms and initially linked to four main loci: FAME1 (8q23.3-q24.1), FAME 2 (2p11.1-q12.1), FAME3 (5p15.31-p15.1), and FAME4 (3q26.32-3q28). To date, it is known that the genetic mechanism underlying FAME consists of the expansion of similar non-coding pentanucleotide repeats, TTTCA and TTTTA, in different genes. FAME is characterized by cortical tremor and myoclonus usually manifesting within the second decade of life, and infrequent seizures by the third or fourth decade. Cortical tremor is the core feature of FAME and is considered part of a spectrum of cortical myoclonus. Neurophysiological investigations as jerk-locked back averaging (JLBA) and corticomuscular coherence analysis, giant somatosensory evoked potentials (SEPs), and the presence of long-latency reflex I (or C reflex) at rest support cortical tremor as the result of the sensorimotor cortex hyperexcitability. Furthermore, the application of transcranial magnetic stimulation (TMS) protocols in FAME patients has recently shown that inhibitory circuits are also altered within the primary somatosensory cortex and the concomitant involvement of subcortical networks. Moreover, neuroimaging studies and postmortem autoptic studies indicate cerebellar alterations and abnormal functional connectivity between the cerebellum and cerebrum in FAME. Accordingly, the pathophysiological mechanism underlying FAME has been hypothesized to reside in decreased sensorimotor cortical inhibition through dysfunction of the cerebellar-thalamic-cortical loop, secondary to primary cerebellar pathology. In this context, the non-coding pentameric expansions have been proposed to cause cerebellar damage through an RNA-mediated toxicity mechanism. The elucidation of the underlying pathological mechanisms of FAME paves the way to novel therapeutic possibilities, such as RNA-targeting treatments, possibly applicable to other neurodegenerative non-coding disorders.

Perampanel as a novel treatment for subcortical myoclonus in myoclonus-dystonia syndrome

BACKGROUND

Myoclonus-dystonia (MD) is a syndrome characterized by subcortical myoclonus and milder dystonia. The main causative gene is the epsilon sarcoglycan gene (SGCE), but other genes may be involved. Response to medications is variable, with poor tolerability limiting their use.

CASE PRESENTATION

We present the case of a patient with severe myoclonic jerks and mild dystonia since childhood. At first neurological visit at the age of 46 years old, she presented brief myoclonic jerks predominating in the upper limbs and neck, mild at rest and elicited by action, posture and tactile stimulus. Myoclonus was accompanied by mild neck and right arm dystonia. Neurophysiological tests suggested subcortical origin of myoclonus, brain MRI was unremarkable. Myoclonus-dystonia was diagnosed, and genetic testing identified a novel mutation in SGCE gene (c.907delC) in heterozygosis. Over time she assumed a large variety of anti-epileptics without beneficial effect on myoclonus and low tolerability. Add-on treatment with Perampanel was started, with a beneficial effect. No adverse events were reported. Perampanel is the first selective non-competitive AMPA receptor antagonist approved in add-on for focal and generalized tonic-clonic seizures. To our knowledge, this is the first trial of Perampanel in MD.

CONCLUSIONS

We presented the case of a patient with MD due to SGCE mutation who was treated with Perampanel with beneficial effects. We propose Perampanel as a novel treatment for myoclonus in MD.

Familial adult myoclonus epilepsy: Neurophysiological investigations

Familial adult myoclonus epilepsy (FAME) also described as benign adult familial myoclonus epilepsy (BAFME) is a high-penetrant autosomal dominant condition featuring cortical myoclonus of varying frequency and occasional/rare convulsive seizures. In this update we provide a detailed overview of the main neurophysiological findings so far reported in patients with FAME/BAFME. After reviewing the diagnostic contribution of each neurophysiological technique, we discuss the possible mechanisms underlying cortical hyperexcitability and suggest the involvement of more complex circuits engaging cortical and subcortical structures, such as the cerebellum. We, thus, propose that FAME/BAFME clinical features should arise from an "abnormal neuronal network activity," where the cerebellum represents a possible common denominator. In the last part of the article, we suggest that future neurophysiological studies using more advanced transcranial magnetic stimulation (TMS) protocols could be used to evaluate the functional connectivity between the cerebellum and cortical structures. Finally, non-invasive brain stimulation techniques such as repetitive TMS or transcranial direct current stimulation could be assessed as potential therapeutic tools to ameliorate cortical excitability.

Post hypoxic myoclonus: A tale of two minds

Post hypoxic myoclonus (PHM) is considered a poor prognostic sign and may influence decisions regarding withdrawal of treatment. PHM is generally categorized in literature as either acute or chronic (also commonly referred to as Lance-Adams Syndrome) based on the onset of myoclonus. However, it may be more accurate to differentiate between the various presentations of PHM based on the clinical characteristics and electroencephalogram (EEG) findings for prognostication. Here, we describe a case of a 33-year-old female who presented after a cardiopulmonary arrest. MRI of the brain and cervical spine on admission were unremarkable. Twelve hours later, she developed generalized, stimulus-sensitive myoclonus suggestive of acute PHM. Various medications were trialed, and her symptoms eventually improved on clonazepam. On day 14, she started having resting and intention myoclonus, and dysarthria, consistent with LAS. Several adjustments were again made to her regimen, and she was eventually switched from clonazepam to baclofen which improved her resting myoclonus. This case highlights that PHM can present differently and have a markedly different outcome. It is important to develop a better understanding of the various types of PHM so as to avoid premature withdrawal of care.

Replacement of Valproic Acid with New Anti-Seizure Medications in Idiopathic Generalized Epilepsy

Background: Little is known regarding the non-inferiority of new anti-seizure medications (ASMs) in terms of replacing valproic acid (VPA) in patients with idiopathic generalized epilepsy (IGE). We hypothesized that replacement of VPA with new ASMs would offer non-inferior or better control of seizure frequency. The purpose of this study was to compare epileptic seizure frequency between the subset of patients with IGE who were on VPA and the subset of patients with IGE who replaced VPA with new ASMs. Methods: Patients with IGE who were on or had been on VPA between January 2016 and March 2022 were divided into a group that replaced VPA with new ASMs (VPA-replace group) and a group that remained on VPA (VPA-continue group). We then compared the groups in terms of seizure frequency and myoclonus. Results: Of the 606 patients on VPA between January 2016 and March 2022, 156 patients with IGE were enrolled to this study (VPA-replace group, n = 68; VPA-continue group, n = 88). The VPA-replace group included significantly more females than the VPA-continue group (p < 0.001). The VPA-replace group also showed significantly higher seizure frequency before replacement (p < 0.001), but not after replacement (p = 0.074). Patients on monotherapy displayed improved seizure frequency with new ASMs (p < 0.001). Among the new ASMs, perampanel (PER) significantly improved seizure frequency (p = 0.002). Forty-two patients in the VPA-replace group who had myoclonus achieved significant improvements (p < 0.001). Among these, patients on PER monotherapy (p < 0.001) or PER + lamotrigine (0.016) showed significantly improved myoclonus scale scores. Conclusions: This study shows the non-inferiority of new ASMs compared to VPA, with better seizure control using new ASMs in subsets of patients with IGE on monotherapy.

Persistent Hiccups Induced by Supratentorial Infarcts and Successful Treatments With Combination of Perampanel and Baclofen: A Case Report

CASE

A 52-year-old man developed a cerebral infarction from the right middle cerebral artery occlusion, and the infarction extensively damaged the right insula. Three months after the onset of the cerebral infarction, persistent hiccups appeared, occurring during sleep. The thoracic and abdominal cavities showed no lesions; hence, the hiccups were considered to be caused by central nervous system dysfunction. Administration of metoclopramide, chlorpromazine, and diazepam were ineffective, while levetiracetam had a partial effect. Combining perampanel with baclofen finally suppressed the symptoms.

DISCUSSION

Lesions at the right insula impair respiratory reflex and may present with hiccups as a symptom of respiratory reflex disinhibition. Here, we review similar cases of treatment-resistant hiccups, as well as perampanel and baclofen efficacy in myoclonus cases.

CONCLUSIONS

Our patient's case suggested that perampanel with baclofen may be effective for myoclonus due to respiratory reflex disinhibition and can be used to treat hiccups derived from cerebral infarctions.

Long-term efficacy of low-dose perampanel for progressive myoclonus epilepsy in a patient with Gaucher disease type 3

PURPOSE

We report the case of a patient with progressive myoclonus epilepsy due to Gaucher disease type 3 whose seizures and ability to perform activities of daily living were significantly improved after starting low-dose perampanel therapy.

CASE

Our patient's generalized tonic-clonic seizures and myoclonus did not improve despite the administration of multiple antiseizure medications and enzyme replacement therapy. The myoclonus reduced following pharmacological chaperone therapy, but this effect was temporary, and the generalized tonic-clonic seizures continued to occur. However, the generalized tonic-clonic seizures disappeared following treatment with 2 mg/day of perampanel. In addition, the decrease in myoclonus dramatically improved motor function such as talking, eating, and walking and stabilized the patient's mental status. These effects have been sustained for more than 4 years.

CONCLUSION

Perampanel is expected to be effective in the treatment of progressive myoclonus epilepsy associated with Gaucher disease type 3 and should be considered the drug of choice for this condition.

White matter alterations in familial cortical myoclonic tremor with epilepsy type 1

OBJECTIVE

Although previous imaging studies have reported cerebellar gray matter loss in patients with familial cortical myoclonic tremor with epilepsy (FCMTE), the corresponding white matter alterations remain unknown. We investigated white matter structural changes in FCMTE1 and compared them with clinical and electrophysiological features.

METHODS

We enrolled 36 patients carrying heterozygous pathogenic intronic pentanucleotide insertions in the SAMD12 gene and 52 age- and sex-matched healthy controls. Diffusion tensor imaging-derived metrics, including fractional anisotropy, mean diffusivity (MD), axial diffusivity (AD), and radial diffusivity (RD) were calculated along with white matter voxel-based morphometry (VBM) analysis. We also examined correlations between MR metrics and clinical and electrophysiological features.

RESULTS

We detected widespread white matter reductions in MD, RD, and AD values in FCMTE patients, including in the commissural, projection, and association fibers. VBM analysis revealed that increases in white matter volume predominantly occurred in the right cerebellum and sagittal stratum. MD, RD, AD, and VBM analysis clearly indicated changes in the sagittal stratum. We found a positive correlation between VBM values in the right cerebellum and SEP P25-N33 amplitude. Decreased MD and AD values in the right sagittal stratum were detected in patients with versus without photophobia.

SIGNIFICANCE

FCMTE is a network disorder involving a wide range of cortical and subcortical structures, including the cerebellum, thalamus, thalamo-cortical connections, and cortico-cortical connections. The right sagittal stratum is closely related with visual symptoms, especially photophobia. Our findings indicate that cerebellum and cortical hyperexcitability are closely linked, and emphasize the important role of the cerebellum in the pathophysiological mechanisms of cortical tremor.

A Biomarker for Benign Adult Familial Myoclonus Epilepsy: High-Frequency Activities in Giant Somatosensory Evoked Potentials

BACKGROUND

Benign adult familial myoclonus epilepsy (BAFME) is one of the diseases that cause cortical myoclonus (CM) with giant somatosensory evoked potentials (SEPs). There are no useful diagnostic biomarkers differentiating BAFME from other CM diseases.

OBJECTIVE

To establish reliable biomarkers including high-frequency oscillations (HFOs) with giant SEPs for the diagnosis of BAFME.

METHODS

This retrospective case study included 49 consecutive CM patients (16 BAFME and 33 other CM patients) who exhibited giant P25 or N35 SEPs. SEPs were processed by a band-pass filter of 400-1000 Hz to analyze HFOs. Clinical and SEP findings were compared between (1) BAFME and other CM groups and (2) patients with presence and absence of P25-HFOs (HFOs superimposed on giant P25). The diagnostic power of each factor for BAFME was calculated.

RESULTS

All 16 BAFME patients showed SEP P25-HFOs with significantly higher occurrence (P < 0.0001) compared with that of other CM groups. The presence of P25-HFOs significantly correlated with a BAFME diagnosis (P < 0.0001) and high SEP P25 and N35 amplitudes (P = 0.01 and P < 0.0001, respectively). BAFME was reliably diagnosed using P25-HFOs with high sensitivity (100%), specificity (87.9%), positive predictive value (80%), and negative predictive value (100%), demonstrating its superiority as a diagnostic factor compared to other factors.

CONCLUSIONS

P25-HFOs with giant SEPs is a potential biomarker for BAFME diagnosis. P25-HFOs may reflect cortical hyperexcitability partly due to paroxysmal depolarizing shifts in epileptic neuronal activities and higher degrees of rhythmic tremulousness than those in ordinary CM. © 2021 International Parkinson and Movement Disorder Society.

Cortico-muscular and cortico-cortical coherence changes resulting from Perampanel treatment in patients with cortical myoclonus

OBJECTIVE

To investigate the mechanisms by which Perampanel (PER) reduces the severity of action myoclonus, we studied on MEG signals the changes occurring in cortico-muscular coherence (CMC) and cortico-cortical connectivity in patients with progressive myoclonus epilepsies.

METHODS

The subjects performed an isometric extension of the hand; CMC and cortico-cortical connectivity were assessed using autoregressive models and generalized partial-directed coherence. The contralateral (Co) sensors showing average CMC values >0.7 of the maximum (set to 1) were grouped as central (C) regions of interest (ROI), while adjacent sensors showing CMC values >0.3 were grouped as Surrounding (Sr) ROIs.

RESULTS

Under PER treatment, CMC decreased on Co C and Sr ROIs, but also on homologous ipsilateral (Ip) ROIs; out-degrees and betweenness centrality increased in Co ROIs and decreased in Ip ROIs. The flow from Ip to Co ROIs and from activated muscles to Ip C ROI decreased.

CONCLUSION

The improvement of myoclonus corresponded to decreased CMC and recovered leadership of the cortical regions directly involved in the motor task, with a reduced interference of ipsilateral areas.

SIGNIFICANCE

Our study highlights on mechanisms suitable to treating myoclonus and suggests the role of a reduced local synchronization together a better control of distant synaptic effects.

Perampanel Improves Cortical Myoclonus and Disability in Progressive Myoclonic Epilepsies: A Case Series and a Systematic Review of the Literature

Introduction: Progressive myoclonic epilepsies (PMEs) are a heterogenous group of genetic diseases presenting with epilepsy, cognitive impairment, and severe action myoclonus, which can severely affect daily life activities and independent walking ability. Perampanel is a recent commercially available antiseizure medication with high efficacy against generalized seizures. Some reports supported the role of perampanel in ameliorating action myoclonus in PMEs. Here, we aimed to describe a case series and provide a systematic literature review on perampanel effects on PMEs.

Methods: We report the perampanel effectiveness on myoclonus, daily life activities, and seizures on an original Italian multicenter case series of 11 individuals with PMEs. Then, using the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines, we performed a systematic review on perampanel effect on myoclonus and disability in PMEs. We searched PubMed, Scopus, and Google Scholar articles on perampanel and PMEs up to June 2020. No prospective trials were found. We reviewed 11 case series manuscripts reporting 104 cases of different PMEs.

Results: Here, we are reporting the effectiveness of perampanel in five individuals affected by Unverricht–Lundborg disease, three by Lafora disease, two by sialidosis, and one by an undetermined PME. Nine out of 11 individuals improved their disability related to the action myoclonus (two with Lafora disease did not). Among the 104 persons with PMEs collected by the systematic review, we found that more than half of the patients receiving perampanel exhibited an amelioration of action myoclonus and, consequently, of their independence in daily life activities. The Unverricht–Lundborg disease seemed to show the best clinical response to perampanel, in comparison with the other more severe PMEs. A significant seizure reduction was achieved by almost all persons with active epilepsy. Only 11% of PME patients dropped out due to inefficacy.

Conclusions: Perampanel demonstrated a beneficial effect with regard to action myoclonus, disability, and seizures and was well-tolerated in people with PMEs, independently from their genetic diagnosis. Given the limited scientific evidence, broader prospective trials should be encouraged.

Lance-Adams Syndrome Treated by Perampanel in the Acute Term

Lance-Adams syndrome (LAS) is chronic post-hypoxic myoclonus after a hypoxic encephalopathy. Recently, the report on LAS in the chronic term treated by perampanel (PER) is increasing. However, PER’s efficacy in the “acute term” has not been reported. Here, we report an LAS patient who markedly improved when PER was added to his existing treatment regime in the acute term. The 65-year-old patient presented with a return of spontaneous circulation after cardiopulmonary arrest. He developed myoclonus on the admission day, and it led to tonic-clonic convulsion. We started levetiracetam 3000 mg/day, lacosamide 400 mg/day, general anesthesia using midazolam 180 mg/day, dexmedetomidine 1000 μg/day, and fentanyl 1.2 mg/day. We could stop the convulsions after 18 h from the onset. We tried to reduce sedatives, but his convulsion recurred. We added PER 2 mg/day for three days, PER 4 mg/day for next four days, then used PER 8 mg/day and we could gradually reduce the sedatives. Single-photon emission computed tomography on day 40 showed cerebral blood flow (CBF) increase at the bilateral anterior lobes of the cerebellum, medial temporal lobes, and supplementary motor and premotor areas, while CBF decrease at the brain surface of the frontal, parietal, and temporal lobes. The myoclonus disappeared since day 12, and he was transferred to another rehabilitation hospital on day 56. The optimal treatment strategy has not been established for LAS, but our case suggested that PER could be one of the choices to treat LAS in the acute term.

Biodistribution and radiation dosimetry of the positron emission tomography probe for AMPA receptor, [11C]K-2, in healthy human subjects

[¹¹C]K-2, a radiotracer exhibiting high affinity and selectivity for α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs), is suitable for the quantification of AMPARs in living human brains and potentially useful in the identification of epileptogenic foci in patients. This study aimed to estimate the radiation doses of [¹¹C]K-2 in various organs and calculate the effective dose after injection of [¹¹C]K-2 in healthy human subjects. Twelve healthy male subjects were registered and divided into two groups (370 or 555 MBq of [¹¹C]K-2), followed by 2 h whole-body scans. We estimated the radiation dose of each organ and then calculated the effective dose for each subject. The highest uptake of [¹¹C]K-2 was observed in the liver, while the brain also showed relatively high uptake. The urinary bladder exhibited the highest radiation dose. The kidneys and liver also showed high radiation doses after [¹¹C]K-2 injections. The effective dose of [¹¹C]K-2 ranged from 5.0 to 5.2 μSv/MBq. Our findings suggest that [¹¹C]K-2 is safe in terms of the radiation dose and adverse effects. The injection of 370–555 MBq (10 to 15 mCi) for PET studies using this radiotracer is applicable in healthy human subjects and enables serial PET scans in a single subject.

Efficacy of perampanel in epilepsy patients with autism spectrum disorder

AIM

The aim of this study was to assess the usefulness of perampanel (PER), and to identify the relationship between behavioral impairments and electroencephalogram (EEG) findings in epilepsy patients with autism spectrum disorder (ASD).

METHODS

Participants were ASD patients with epilepsy recruited between June 1, 2016 and June 30, 2018. Inclusion criteria were: seizures refractory to two appropriate antiseizure medications (ASMs); presence of neuropsychological impairments; and ≥12 months of monitoring. PER was administered once daily, starting at a dose of 2 mg/day, increased to 12 mg/day. Seizure/EEG responders were identified as participants showing a >50 % reduction in seizure/interictal epileptiform discharge (IED) frequency (indicated as complete disappearance and response). Behavioral responders were identified as participants with a ≥50 % reduction in scores of the Japanese manuals for the Aberrant Behavior Checklist (ABC-J).

RESULTS

Eleven (64.7 %) of 17 patients were considered to be both seizure and EEG responders. Five (45.5 %) of these 11 patients with seizure/EEG response were considered as behavioral responders. Mean ABC-J scores were significantly decreased at 12 months after PER administration (p = 0.0002). A correlation between decreased IED frequency and ABC-J score was evident in frontal IEDs, but not in non-frontal IEDs. Participants presenting with frontal IEDs showed a significantly higher correlation between seizures/EEG and behavioral improvements (p = 0.023). Moreover, 2 of 6 patients without seizure/EEG improvement were considered as behavioral responders. No patients discontinued PER.

CONCLUSIONS

The results from this study suggest the utility of PER treatment in reducing clinical seizures and IEDs for ASD patients with intractable epilepsy, at least in some patients. Moreover, the present results also indicate the usefulness of PER in improving neuropsychiatric impairments, including behavioral disturbances in ASD related to improvement of clinical seizures/frontal IEDs, but also unrelated to seizure/EEG improvement in at least some ASD patients.

Exploring the Evidence for Broad-Spectrum Effectiveness of Perampanel: A Systematic Review of Clinical Data in Generalised Seizures

BACKGROUND

The effectiveness of adjunctive perampanel has not been systematically assessed in seizure types other than its approved indications of focal seizures and primary generalised tonic-clonic seizures (PGTCS) in idiopathic generalised epilepsies (IGEs).

OBJECTIVE

We aimed to identify and review available evidence on outcomes with perampanel in generalised seizures and epilepsies to examine its potential as a broad-spectrum anti-seizure medication.

METHODS

Bibliographic databases of publications, clinical trials, and conference abstracts were searched up to August 2020 to identify studies reporting seizure or safety outcomes in patients of any age, with any type of epilepsy-associated generalised seizures treated with perampanel. Data extracted from selected records were tabulated by seizure type and syndrome, and analysed qualitatively (PROSPERO protocol CRD42020201564).

RESULTS

Ninety-one reports met inclusion criteria and were selected: 15 reports of 1 randomised controlled trial (RCT), 8 reports of 4 non-randomised interventional studies, 37 reports of observational studies, 21 case reports and 10 systematic reviews and meta-analyses. Extracted data included 359 patients with PGTCS of any aetiology, 251 with myoclonic seizures, 112 with absence seizures, 50 with tonic seizures and 32 children with epileptic spasms. The most commonly reported epilepsy type was IGE (N = 378) and the most common syndromes were juvenile myoclonic epilepsy (N = 92), progressive myoclonic epilepsies (N = 59) and absence epilepsies (N = 43). The RCT provided Class I evidence of the efficacy and tolerability of adjunctive perampanel for PGTCS in patients aged ≥ 12 years with IGE. Data from other studies provides weaker (observational) evidence of its effectiveness in multiple generalised seizure types, including myoclonic, absence and tonic seizures. There were no patterns suggesting seizure worsening or aggravation in any seizure or epilepsy type.

CONCLUSIONS

The identified studies suggest the potential of perampanel as a broad-spectrum antiseizure medication. Much of the available data, however, come from non-randomised, non-controlled studies and are open to high risk of bias. Further studies are warranted to provide more robust evidence.

[A case of the successful treatment of severe myoclonus with Lance-Adams syndrome by add-on perampanel showing long term effects]

Perampanel is an α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor antagonist that has been marked as an antiepileptic drug for partial-onset and primary generalized tonic-clonic seizures. There have been some recent reports of perampanel being effective against cortical myoclonus by Lafora disease and Unverricht-Lundborg disease. We herein report a 49-year-old man who presented with myoclonus due to Lance-Adams syndrome (LAS) after cardiopulmonary arrest caused by a severe bronchial asthma attack. Perampanel was very effective against myoclonus induced by LAS even in the chronic state, over 10 years after the remote onset. Perampanel should be considered for the treatment of extremely refractory myoclonus due to LAS.

Physiology-Based Treatment of Myoclonus

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

The Effectiveness of Perampanel for Myoclonic Seizures in Down Syndrome with Isodicentric Chromosome 21

Epileptic seizures are common in the elderly Down syndrome population. We encountered a patient with Down syndrome in whom karyotyping showed the rare isodicentric chromosome 21 and who suffered from myoclonic seizures. A 52-year-old woman with Down syndrome experienced sudden onset of drowsiness and frequent myoclonic jerks in the upper body. Video-EEG recordings demonstrated generalized polyspike-wave discharges consistent with myoclonic jerks, which were exacerbated by photo-stimulation. Her myoclonus completely resolved with perampanel administration. Perampanel was effective for myoclonic seizures in our patient. We suggest that perampanel is an option as first-line therapy for epilepsy and myoclonus in elderly Down syndrome patients.

Perampanel for nonepileptic myoclonus in Angelman syndrome

BACKGROUND

Angelman syndrome (AS) is a neurodegenerative disorder caused by functional loss of the maternal ubiquitin-protein ligase 3A gene. Nonepileptic myoclonus, also described as tremulous movement, often occurs during puberty and increases in adulthood. The involuntary movement in AS has not been defined patho-physiologically and the drugs used such as levetiracetam and piracetam are not always effective. Recently, the alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionate (AMPA) receptor antagonist, perampanel (PER), was used to alleviate myoclonus in progressive myoclonus epilepsy. Herein, we tested the efficacy of PER for nonepileptic myoclonus.

METHODS AND RESULTS

Four patients with AS, aged from 20 to 40 years at the beginning of treatment, were enrolled in our study. All patients reported disruption to their daily lives from the myoclonus movement. They experienced mild to moderate improvement with the starting dose of 2 mg. The dose was increased to 4 mg in one patient to achieve sufficient efficacy, while two had their dose reduced to 1 mg due to dizziness or possible exacerbation of myoclonus. The last patient continued to take the starting dose. Follow-up over 16-20 months revealed a significant reduction in the severity of nonepileptic myoclonus in all patients.

CONCLUSION

Our study suggests that PER could be one of the promising drugs for nonepileptic myoclonus in AS.

Ionotropic Glutamate Receptors in Epilepsy: A Review Focusing on AMPA and NMDA Receptors

It is widely accepted that glutamate-mediated neuronal hyperexcitation plays a causative role in eliciting seizures. Among glutamate receptors, the roles of N-methyl-D-aspartate (NMDA) and α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors in physiological and pathological conditions represent major clinical research targets. It is well known that agonists of NMDA or AMPA receptors can elicit seizures in animal or human subjects, while antagonists have been shown to inhibit seizures in animal models, suggesting a potential role for NMDA and AMPA receptor antagonists in anti-seizure drug development. Several such drugs have been evaluated in clinical studies; however, the majority, mainly NMDA-receptor antagonists, failed to demonstrate adequate efficacy and safety for therapeutic use, and only an AMPA-receptor antagonist, perampanel, has been approved for the treatment of some forms of epilepsy. These results suggest that a misunderstanding of the role of each glutamate receptor in the ictogenic process may underlie the failure of these drugs to demonstrate clinical efficacy and safety. Accumulating knowledge of both NMDA and AMPA receptors, including pathological gene mutations, roles in autoimmune epilepsy, and evidence from drug-discovery research and pharmacological studies, may provide valuable information enabling the roles of both receptors in ictogenesis to be reconsidered. This review aimed to integrate information from several studies in order to further elucidate the specific roles of NMDA and AMPA receptors in epilepsy.

Improvement of "Bouncy Gait" in Lance-Adams Syndrome with Perampanel

Lance-Adams syndrome (LAS) is chronic post-hypoxic myoclonus that is often associated with sudden lapses in muscle tone (negative myoclonus) in the legs, causing a disabling "bouncy gait." Given its relative rarity, there are no controlled treatment studies of LAS. The majority of cases require polypharmacy management, with an incomplete response. "Bouncy gait," in particular, is notoriously medication-refractory. Here, we report a patient with long-standing LAS who improved markedly when low-dose perampanel was added to his existing treatment regime consisting of clonazepam, levetiracetam, sodium valproate, and acetazolamide.