Classification of progressive myoclonus epilepsies and related disorders. Marseille Consensus Group

The natural history of progressive myoclonus ataxia

Progressive myoclonus ataxia (PMA) is a rare clinical syndrome characterized by the presence of progressive myoclonus and ataxia, and can be accompanied by mild cognitive impairment and infrequent epileptic seizures. This is the first study to describe the natural history of PMA and identify clinical, electrophysiological, and genetic features explaining the variability in disease progression. A Dutch cohort of consecutive patients meeting the criteria of the refined definition of PMA was included. The current phenotype was assessed during in-person consultation by movement disorders experts, and retrospective data was collected to describe disease presentation and progression, including brain imaging and therapy efficacy. Extensive genetic and electrophysiological tests were performed. The presence of cortical hyperexcitability was determined, by either the identification of a cortical correlate of myoclonic jerks with simultaneous electromyography-electroencephalography or a giant somatosensory evoked potential. We included 34 patients with PMA with a median disease duration of 15 years and a clear progressive course in most patients (76%). A molecular etiology was identified in 82% patients: ATM, CAMTA1, DHDDS, EBF3, GOSR2, ITPR1, KCNC3, NUS1, POLR1A, PRKCG, SEMA6B, SPTBN2, TPP1, ZMYND11, and a 12p13.32 deletion. The natural history is a rather homogenous onset of ataxia in the first two years of life followed by myoclonus in the first 5 years of life. Main accompanying neurological dysfunctions included cognitive impairment (62%), epilepsy (38%), autism spectrum disorder (27%), and behavioral problems (18%). Disease progression showed large variability ranging from an epilepsy free PMA phenotype (62%) to evolution towards a progressive myoclonus epilepsy (PME) phenotype (18%): the existence of a PMA-PME spectrum. Cortical hyperexcitability could be tested in 17 patients, and was present in 11 patients and supported cortical myoclonus. Interestingly, post-hoc analysis showed that an absence of cortical hyperexcitability, suggesting non-cortical myoclonus, was associated with the PMA-end of the spectrum with no epilepsy and milder myoclonus, independent of disease duration. An association between the underlying genetic defects and progression on the PMA-PME spectrum was observed. By describing the natural history of the largest cohort of published patients with PMA so far, we see a homogeneous onset with variable disease progression, in which phenotypic evolution to PME occurs in the minority. Genetic and electrophysiological features may be of prognostic value, especially the determination of cortical hyperexcitability. Furthermore, the identification of cortical and non-cortical myoclonus in PMA helps us gain insight in the underlying pathophysiology of myoclonus.

Conventional and novel anti-seizure medications reveal a particular role for GABAA in a North Sea progressive myoclonus Epilepsy Drosophila model

OBJECTIVE

North Sea Progressive Myoclonus Epilepsy (NS-PME) is a rare genetic disorder characterized by ataxia, myoclonus and seizures with a progressive course. Although the cause of NS-PME is known, namely a homozygous mutation in the GOSR2 gene (c.430 G>T; p. Gly144Trp), sufficient treatment is lacking. Despite combinations of on average 3-5 anti-seizure medications (ASMs), debilitating myoclonus and seizures persist. Here we aimed to gain insight into the most effective anti-convulsive target in NS-PME by evaluating the individual effects of ASMs in a NS-PME Drosophila model.

METHOD

A previously generated Drosophila model for NS-PME was used displaying progressive heat-sensitive seizures. We used this model to test 1. a first-generation ASM (sodium barbital), 2. common ASMs used in NS-PME (clonazepam, valproic acid, levetiracetam, ethosuximide) and 3. a novel third-generation ASM (ganaxolone) with similar mode of action to sodium barbital. Compounds were administered by adding them to the food in a range of concentrations. After 7 days of treatment, the percentage of heat-induced seizures was determined and compared to non-treated but affected controls.

RESULTS

As previously reported in the NS-PME Drosophila model, sodium barbital resulted in significant seizure suppression, with increasing effect at higher dosages. Of the commonly prescribed ASMs, clonazepam and ethosuximide resulted in significant seizure suppression, whereas both valproic acid and levetiracetam did not show any changes in seizures. Interestingly, ganaxolone did result in seizure suppression as well.

CONCLUSION

Of the six drugs tested, three of the four that resulted in seizure suppression (sodium barbital, clonazepam, ganaxolone) are primary known for their direct effect on GABAA receptors. This suggests that GABAA could be a potentially important target in the treatment of NS-PME. Consequently, these findings add rationale to the exploration of the clinical effect of ganaxolone in NS-PME and other progressive myoclonus epilepsies.

Myoclonus: Differential diagnosis and current management

Myoclonus classically presents as a brief (10-50 ms duration), non-rhythmic jerk movement. The etiology could vary considerably ranging from self-limited to chronic or even progressive disorders, the latter falling into encephalopathic pictures that need a prompt diagnosis. Beyond the etiological classification, others evaluate myoclonus' body distribution (i.e., clinical classification) or the location of the generator (i.e., neurophysiological classification); particularly, knowing the anatomical source of myoclonus gives inputs on the observable clinical patterns, such as EMG bursts duration or EEG correlate, and guides the therapeutic choices. Among all the chronic disorders, myoclonus often presents itself as a manifestation of epilepsy. In this context, myoclonus has many facets. Myoclonus occurs as one, or the only, seizure manifestation while it can also present as a peculiar type of movement disorder; moreover, its electroclinical features within specific genetically determined epileptic syndromes have seldom been investigated. In this review, following a meeting of recognized experts, we provide an up-to-date overview of the neurophysiology and nosology surrounding myoclonus. Through the dedicated exploration of epileptic syndromes, coupled with pragmatic guidance, we aim to furnish clinicians and researchers alike with practical advice for heightened diagnostic management and refined treatment strategies. PLAIN LANGUAGE SUMMARY: In this work, we described myoclonus, a movement characterized by brief, shock-like jerks. Myoclonus could be present in different diseases and its correct diagnosis helps treatment.

The Muddle of Myoclonus: Many Guises, 2 Disciplines, Consensus Needed

Myoclonus is often approached in different ways by epileptologists and movement disorder specialists, leading to confusion in the literature. Multiplicity and inconsistency over the past 2 centuries resulted in a lack of precision and ambiguity of the terminology. We show that this is a current problem in which one phenomenon has been described with many terms and vice versa. Of more importance, we discuss the conceptualization of myoclonus from perspectives of both fields and focus on the borderland that exists, especially in the spectrum of cortical and epileptic myoclonus. By giving 2 examples, we illustrate the conundrum: the spectrum of progressive myoclonus epilepsies and progressive myoclonic ataxias and "cortical tremor" observed in familial cortical myoclonic tremor with epilepsy or familial adult myoclonic epilepsy. We attempt to facilitate to bridge these subspecialties and form the base for a uniform understanding to take this issue forward toward future classifications, discussions, and scientific research.

ILAE Genetics Literacy series: Progressive myoclonus epilepsies

Progressive Myoclonus Epilepsy (PME) is a rare epilepsy syndrome characterized by the development of progressively worsening myoclonus, ataxia, and seizures. A molecular diagnosis can now be established in approximately 80% of individuals with PME. Almost fifty genetic causes of PME have now been established, although some remain extremely rare. Herein, we provide a review of clinical phenotypes and genotypes of the more commonly encountered PMEs. Using an illustrative case example, we describe appropriate clinical investigation and therapeutic strategies to guide the management of this often relentlessly progressive and devastating epilepsy syndrome. This manuscript in the Genetic Literacy series maps to Learning Objective 1.2 of the ILAE Curriculum for Epileptology (Epileptic Disord. 2019;21:129).

IRF2BPL: A new genotype for progressive myoclonus epilepsies

The progressive myoclonus epilepsies (PMEs) are a heterogeneous group of neurodegenerative disorders, typically presenting in late childhood. An etiologic diagnosis is achieved in about 80% of patients with PME, and genome-wide molecular studies on remaining, well-selected, undiagnosed cases can further dissect the underlying genetic heterogeneity. Through whole-exome sequencing (WES), we identified pathogenic truncating variants in the IRF2BPL gene in two, unrelated patients presenting with PME. IRF2BPL belongs to the transcriptional regulators family and it is expressed in multiple human tissues, including the brain. Recently missense and nonsense mutations in IRF2BPL were found in patients presenting with developmental delay and epileptic encephalopathy, ataxia, and movement disorders, but none with clear PME. We identified 13 other patients in the literature with myoclonic seizures and IRF2BPL variants. There was no clear genotype-phenotype correlation. With the description of these cases, the IRF2BPL gene should be considered in the list of genes to be tested in the presence of PME, in addition to patients with neurodevelopmental or movement disorders.

History of familial adult myoclonus epilepsy/benign adult familial myoclonic epilepsy around the world

Familial adult myoclonus epilepsy/benign adult familial myoclonic epilepsy (FAME/BAFME) has emerged as a specific and recognizable epilepsy syndrome with autosomal dominant inheritance found around the world. Here, we trace the history of this syndrome. Initially, it was likely conflated with other familial myoclonus epilepsies, especially the progressive myoclonus epilepsies. As the progressive myoclonus epilepsies became better understood clinically and genetically, this group began to stand out and was first recognized as such in Japan. Subsequently, families were recognized around the world and there was debate as to whether they represented one or multiple disorders. Clarification came with the identification of pentanucleotide repeats in Japanese families, and FAME/BAFME was quickly shown to be due to pentanucleotide expansions in at least six genes. These have geographic predilections and appear to have been caused by historically ancient initial mutations. Within and between families, there is some variation in the phenotype, explained in large part by expansion size, but whether there are features specific to individual genes remains uncertain.

Progressive myoclonus epilepsies due to SEMA6B mutations. New variants and appraisal of published phenotypes

Variants of SEMA6B have been identified in an increasing number of patients, often presenting with progressive myoclonus epilepsy (PME), and to lesser extent developmental encephalopathy, with or without epilepsy. The exon 17 is mainly involved, with truncating mutations causing the production of aberrant proteins with toxic gain of function. Herein, we describe three adjunctive patients carrying de novo truncating SEMA6B variants in this exon (c.1976delC and c.2086C > T novel; c.1978delC previously reported). These subjects presented with PME preceded by developmental delay, motor and cognitive impairment, worsening myoclonus, and epilepsy with polymorphic features, including focal to bilateral seizures in two, and non-convulsive status epilepticus in one. The evidence of developmental delay in these cases suggests their inclusion in the "PME plus developmental delay" nosological group. This work further expands our knowledge of SEMA6B variants causing PMEs. However, the data to date available confirms that phenotypic features do not correlate with the type or location of variants, aspects that need to be further clarified by future studies.

Negative myoclonus causes locomotory disability in progressive myoclonus epilepsy type EPM1- Unverricht-Lundborg disease

OBJECTIVE

Patients with Unverricht-Lundborg disease/EPM1 develop increasing locomotory disability or ataxia in the course of their disease. To test our hypothesis that negative myoclonus is the reason for this increasing ataxia, we investigated a possible correlation over time.

METHODS

In 15 patients with EPM1who were confirmed to have a mutation in the CSTB gene, polygraphic video-EEG-EMG recordings were performed in freely moving or standing patients. The criterion for the duration of the negative myoclonus was the measured length of the silent periods on the EMG.

RESULTS

All 15 patients had documented negative myoclonus when standing and walking. The mean duration of silent periods significantly increased from 100 (SD: 19.1) ms at time point T1 to 128 (SD: 26.6) ms at T2 in seven of eight patients, based on two recordings and a mean interval of 12.8 (SD: 4.9) years. Using a cross-sectional approach, all 15 patients were classified based on whether they were ambulatory, could walk with aid, or needed a wheelchair. Ambulatory patients had a mean duration of 97.3 (SD: 16.5) ms, patients who could walk with aid had a mean duration of 106.7 (SD: 16) ms, and patients who were wheelchair-bound had a mean duration of 138 (SD: 23.6) ms. In addition to the prolongation of the silent periods, there was an observed increase in frequency of the negative myoclonus, becoming more continuous and tremulous.

SIGNIFICANCE

Using simultaneous EEG/EMG recordings in freely moving or standing patients, we have shown that the locomotor disability or ataxia is due to negative myoclonus in voluntary innervated muscles. The reason for the progression is the prolongation of the silent periods as measured by the duration of the negative myoclonus and their increase in frequency.

Neurophysiology of Juvenile and Progressive Myoclonic Epilepsy

SUMMARY

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

A novel SEMA6B variant causes adult-onset progressive myoclonic epilepsy-11 in a Chinese family: A case report and literature review

This study describes a patient with progressive myoclonic epilepsy-11 (EPM-11), which follows autosomal dominant inheritance caused by a novel SEMA6B variant. Most patients develop this disease during infancy or adolescence with action myoclonus, generalized tonic-clonic seizures (GTCS), and progressive neurological deterioration. No cases of adult-onset EPM-11 have been reported yet. Here, we present one case of adult-onset EPM-11 who experienced gait instability, seizures, and cognitive impairment, and harbored a novel missense variant, c.432C>G (p.C144W). Our findings provide a foundation for a better understanding of the phenotypic and genotypic profiles of EPM-11. Further functional studies are recommended to elucidate the pathogenesis of this disease.

Ramsay Hunt syndrome: New impressions in the era of molecular genetics

More frequent use of next-generation sequencing led to a paradigm shift in assessing heredodegenerative diseases. This is particularly notable in progressive myoclonus epilepsy (PME) and progressive myoclonus ataxia (PMA) where a group of disorders linked to novel genetic mutations has now been added to these phenotypical realms. Despite the historical value of Ramsay Hunt's contribution defining the syndrome later known as PMA, recent genetic developments have made this eponym obsolete and a new definition and classification of PMA and PME seem necessary. A rational possibility is to adopt the wider term progressive myoclonus ataxia and epilepsy syndrome (PMAES), which can be subdivided into its main subtypes, PME and PMA, whenever clinical data is sufficient to make that distinction.

A novel variant of dehydrodolichol diphosphate synthase (DHDDS) mutation with adult-onset progressive myoclonus ataxia

We report a novel variant of DHDDS mutation in a patient with progressive adult-onset myoclonus ataxia. The mutation in our patient was different from previous reports of denovo mutations in DHDDS in 6 patients who showed tremor-like myoclonus and generalized epilepsy.

Progressive myoclonus epilepsy KCNC1 variant causes a developmental dendritopathy

OBJECTIVE

Mutations in KCNC1 can cause severe neurological dysfunction, including intellectual disability, epilepsy, and ataxia. The Arg320His variant, which occurs in the voltage-sensing domain of the channel, causes a highly penetrant and specific form of progressive myoclonus epilepsy with severe ataxia, designated myoclonus epilepsy and ataxia due to potassium channel mutation (MEAK). KCNC1 encodes the voltage-gated potassium channel KV 3.1, a channel that is important for enabling high-frequency firing in interneurons, raising the possibility that MEAK is associated with reduced interneuronal function.

METHODS

To determine how this variant triggers MEAK, we expressed KV 3.1bR320H in cortical interneurons in vitro and investigated the effects on neuronal function and morphology. We also performed electrophysiological recordings of oocytes expressing KV 3.1b to determine whether the mutation introduces gating pore currents.

RESULTS

Expression of the KV 3.1bR320H variant profoundly reduced excitability of mature cortical interneurons, and cells expressing these channels were unable to support high-frequency firing. The mutant channel also had an unexpected effect on morphology, severely impairing neurite development and interneuron viability, an effect that could not be rescued by blocking KV 3 channels. Oocyte recordings confirmed that in the adult KV 3.1b isoform, R320H confers a dominant negative loss-of-function effect by slowing channel activation, but does not introduce potentially toxic gating pore currents.

SIGNIFICANCE

Overall, our data suggest that, in addition to the regulation of high-frequency firing, KV 3.1 channels play a hitherto unrecognized role in neuronal development. MEAK may be described as a developmental dendritopathy.

Progressive Myoclonus Epilepsy Caused by a Homozygous Splicing Variant of SLC7A6OS

Exome sequencing was performed in 2 unrelated families with progressive myoclonus epilepsy. Affected individuals from both families shared a rare, homozygous c.191A > G variant affecting a splice site in SLC7A6OS. Analysis of cDNA from lymphoblastoid cells demonstrated partial splice site abolition and the creation of an abnormal isoform. Quantitative reverse transcriptase polymerase chain reaction and Western blot showed a marked reduction of protein expression. Haplotype analysis identified a ~0.85cM shared genomic region on chromosome 16q encompassing the c.191A > G variant, consistent with a distant ancestor common to both families. Our results suggest that biallelic loss-of-function variants in SLC7A6OS are a novel genetic cause of progressive myoclonus epilepsy. ANN NEUROL 2021;89:402-407.

Drug Treatment of Progressive Myoclonic Epilepsy

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

A detailed description of the phenotypic spectrum of North Sea Progressive Myoclonus Epilepsy in a large cohort of seventeen patients

INTRODUCTION

In 2011, a homozygous mutation in GOSR2 (c.430G > T; p. Gly144Trp) was reported as a novel cause of Progressive Myoclonus Epilepsy (PME) with early-onset ataxia. Interestingly, the ancestors of patients originate from countries bound to the North Sea, hence the condition was termed North Sea PME (NSPME). Until now, only 20 patients have been reported in literature. Here, we provide a detailed description of clinical and neurophysiological data of seventeen patients.

METHODS

We collected clinical and neurophysiological data from the medical records of seventeen NSPME patients (5-46 years). In addition, we conducted an interview focused on factors influencing myoclonus severity.

RESULTS

The core clinical features of NSPME are early-onset ataxia, myoclonus and seizures, with additionally areflexia and scoliosis. Factors such as fever, illness, heat, emotions, stress, noise and light (flashes) all exacerbated myoclonic jerks. Epilepsy severity ranged from the absence of or incidental clinical seizures to frequent daily seizures and status epilepticus. Some patients made use of a wheelchair during their first decade, whereas others still walked independently during their third decade. Neurophysiological features suggesting neuromuscular involvement in NSPME were variable, with findings ranging from indicative of sensory neuronopathy and anterior horn cell involvement to an isolated absent H-reflex.

CONCLUSION

Although the sequence of symptoms is rather homogeneous, the severity of symptoms and rate of progression varied considerably among individual patients. Common triggers for myoclonus can be identified and myoclonus is difficult to treat; to what extent neuromuscular involvement contributes to the phenotype remains to be further elucidated.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

SIGNIFICANCE

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

Update on Pharmacological Treatment of Progressive Myoclonus Epilepsies

BACKGROUND

Progressive myoclonus epilepsies (PMEs) are a group of rare inherited diseases featuring a combination of myoclonus, seizures and variable degree of cognitive impairment. Despite extensive investigations, a large number of PMEs remain undiagnosed. In this review, we focus on the current pharmacological approach to PMEs.

METHODS

References were mainly identified through PubMed search until February 2017 and backtracking of references in pertinent studies.

RESULTS

The majority of available data on the efficacy of antiepileptic medications in PMEs are primarily anecdotal or observational, based on individual responses in small series. Valproic acid is the drug of choice, except for PMEs due to mitochondrial diseases. Levetiracetam and clonazepam should be considered as the first add-on treatment. Zonisamide and perampanel represent promising alternatives. Phenobarbital and primidone should be reserved to patients with resistant disabling myoclonus or seizures. Lamotrigine should be used with caution due to its unpredictable effect on myoclonus. Avoidance of drugs known to aggravate myoclonus and seizures, such as carbamazepine and phenytoin, is paramount. Psychiatric (in particular depression) and other comorbidities need to be adequately managed. Although a 3- to 4-drug regimen is often necessary to control seizures and myoclonus, particular care should be paid to avoid excessive pharmacological load and neurotoxic side effects. Target therapy is possible only for a minority of PMEs.

CONCLUSIONS

Overall, the treatment of PMEs remains symptomatic (i.e. pharmacological treatment of seizures and myoclonus). Further dissection of the genetic background of the different PMEs might hopefully help in the future with individualised treatment options.

A "Triple Trouble" Case of Facioscapulohumeral Muscular Dystrophy Accompanied by Peripheral Neuropathy and Myoclonic Epilepsy

Background

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by asymmetric muscular deficit of facial, shoulder-girdle muscles, and descending to lower limb muscles, but it exists in several extramuscular manifestations or overlapping syndromes. Herein, we report a "complex disease plus" patient with FSHD1, accompanied by peripheral neuropathy and myoclonic epilepsy.

Methods

Standard clinical assessments, particular auxiliary examination, histological analysis, and molecular analysis were performed through the new Comprehensive Clinical Evaluation Form, pulsed-field gel electrophoresis-based Southern blot, Multiplex Ligation-dependent Probe Amplification (MLPA), whole exome sequencing (WES), and targeted methylation sequencing.

Results

The patient presented with mild facial weakness, humeral poly-hill sign, scapular winging, peroneal weakness, drop foot, pes cavus, and myoclonic epilepsy. Furthermore, electrophysiology revealed severely demyelinated and axonal injury. The muscle and nerve biopsy revealed broadly fiber Type II grouping atrophy and myelinated nerve fibers that significantly decreased with thin myelinated fibers and onion bulbs changes. Generalized sharp and sharp-slow wave complexes on electroencephalography support the diagnosis toward myoclonic epilepsy. In addition, molecular testing demonstrated a co-segregated 20-kb 4q35-EcoRI fragment and permissive allele A, which corresponded with D4Z4 hypomethylation status in the family. Both the patient's mother and brother only presented the typical FSHD but lacked overlapping syndromes. However, no mutations for hereditary peripheral neuropathy and myoclonic epilepsy were discovered by MLPA and WES.

Conclusions

The present study described a "tripe trouble" with FSHD, peripheral neuropathy, and myoclonic epilepsy, adding the spectrum of overlapping syndromes and contributing to the credible diagnosis of atypical phenotype. It would provide a direct clue on medical care and genetic counseling.

Progressive myoclonus ataxia: Time for a new definition?

BACKGROUND

The clinical demarcation of the syndrome progressive myoclonus ataxia is unclear, leading to a lack of recognition and difficult differentiation from other neurological syndromes.

OBJECTIVES

The objective of this study was to apply a refined definition of progressive myoclonus ataxia and describe the clinical characteristics in patients with progressive myoclonus ataxia and with isolated cortical myoclonus.

METHODS

A retro- and prospective analysis was performed in our tertiary referral center between 1994 and 2014. Inclusion criteria for progressive myoclonus ataxia patients were the presence of myoclonus and ataxia with or without infrequent (all types, treatment responsive) epileptic seizures. Inclusion criteria for isolated cortical myoclonus was the presence of isolated cortical myoclonus. Clinical and electrophysiological characteristics data were systematically scored.

RESULTS

A total of 14 progressive myoclonus ataxia patients (males, 7; females, 7), median age 14.5 years, and 8 isolated cortical myoclonus patients (males, 2; females, 6), median age 23.5 years, were identified. In 93% of the progressive myoclonus ataxia patients, ataxia started first (median 2 years) followed by myoclonus (4 years) and finally infrequent epilepsy (9.3 years), with a progressive course in 93%. In 64% of the progressive myoclonus ataxia patients, a genetic underlying etiology was identified, including 3 not earlier reported causative progressive myoclonus ataxia genes. In isolated cortical myoclonus patients, myoclonus started at (median) 12 years with progression over time in 63% and a single epileptic seizure in 1 patient. No genetic causes were identified.

CONCLUSION

Using a refined definition, we could create a rather homogenous progressive myoclonus ataxia group. Patients with isolated cortical myoclonus have a different course and do not appear to evolve in progressive myoclonus ataxia. The refined progressive myoclonus ataxia definition is a successful first step toward creating a separate syndrome for both clinical practice and future genetic research. © 2018 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Teenage-onset progressive myoclonic epilepsy due to a familial C9orf72 repeat expansion

BACKGROUND

The progressive myoclonic epilepsies (PME) are a heterogeneous group of disorders in which a specific diagnosis cannot be made in a subset of patients, despite exhaustive investigation. C9orf72 repeat expansions are emerging as an important causal factor in several adult-onset neurodegenerative disorders, in particular frontotemporal lobar degeneration and amyotrophic lateral sclerosis. An association with PME has not been reported previously.

OBJECTIVE

To identify the causative mutation in a Belgian family where the proband had genetically unexplained PME.

RESULTS

We report a 33-year old woman who had epilepsy since the age of 15 and then developed progressive cognitive deterioration and multifocal myoclonus at the age of 18. The family history suggested autosomal dominant inheritance of psychiatric disorders, epilepsy, and dementia. Thorough workup for PME including whole exome sequencing did not reveal an underlying cause, but a C9orf72 repeat expansion was found in our patient and affected relatives. Brain biopsy confirmed the presence of characteristic p62-positive neuronal cytoplasmic inclusions.

CONCLUSION

C9orf72 mutation analysis should be considered in patients with PME and psychiatric disorders or dementia, even when the onset is in late childhood or adolescence.

Variable course of Unverricht-Lundborg disease

Objective:

To explore the course of Unverricht-Lundborg disease (EPM1) and identify the risk factors for severity, we investigated the time course of symptoms and prognostic factors already detectable near to disease onset.

Methods:

We retrospectively evaluated the features of 59 Italian patients carrying the CSTB expansion mutation, and coded the information every 5 years after the disease onset in order to describe the cumulative time-dependent probability of reaching disabling myoclonus, relevant cognitive impairment, and inability to work, and evaluated the influence of early factors using the log-rank test. The risk factors were included in a Cox multivariate proportional hazards regression model.

Results:

Disabling myoclonus occurred an average of 32 years after disease onset, whereas cognitive impairment occurred a little later. An age at onset of less than 12 years, the severity of myoclonus at the time of first assessment, and seizure persistence more than 10 years after onset affected the timing of disabling myoclonus and cognitive decline. Most patients became unable to work years before the appearance of disabling myoclonus or cognitive decline.

Conclusions:

A younger age at onset, early severe myoclonus, and seizure persistence are predictors of a more severe outcome. All of these factors may be genetically determined, but the greater hyperexcitability underlying more severe seizures and myoclonus at onset may also play a role by increasing cell damage due to reduced cystatin B activity.

The history of progressive myoclonus epilepsies

The history of the progressive myoclonus epilepsies (PMEs) spans more than a century. However, the recent history of PMEs begins with a consensus statement published in the wake of the Marseille PME workshop in 1989 (Marseille Consensus Group, 1990). This consensus helped define the various types of PME known at the time and set the agenda for a new era of genetic research which soon lead to the discovery of many PME genes. Prior to the Marseille meeting, and before the molecular era, there had been much confusion and controversy. Because investigators had but limited and biased experience with these rare disorders due to the uneven, skewed distribution of PMEs around the world, opinions and nosologies were based on local expertise which did not match well with the experiences of other researchers and clinicians. The three major areas of focus included: (1) the nature and limits of the concept of PME in varying scopes, which was greatly debated; (2) the description of discrete clinical entities by clinicians; and (3) the description of markers (pathological, biological, neurophysiological, etc.) which could lead to a precise diagnosis of a given PME type, with, in the best cases, a reliable correlation with clinical findings. In this article, we shall also examine the breakthroughs achieved in the wake of the 1989 Marseille meeting and recent history in the field, following the identification of several PME genes. As in other domains, the molecular and genetic approach has challenged some established concepts and has led to the description of new PME types. However, as may already be noted, this approach has also confirmed the existence of the major, established types of PME, which can now be considered as true diseases.

Report of progressive myoclonus ataxia (PMA) in two Chinese pedigrees

OBJECTIVE

To describe the clinical characteristics of patients diagnosed with progressive myoclonus ataxia (PMA) from two Chinese pedigrees.

METHODS

An analysis of clinical data is presented and inferences drawn.

RESULTS

The propositus from pedigree-I (9-year-old female) could not walk stably and had a history of frequent falls. The symptoms aggravated over time until she lost the ability to take care of herself. Her physical and mental development (including cognitive ability) was normal. She had an ataxic gait, ataxic dysarthria, bilateral horizontal nystagmus and visible limb myoclonus. She failed the bilateral finger-to-nose and heel-knee-tibia tests and could not walk in a straight line. Babinski signs were not observed. EEG tracing during sleep showed low-amplitude spikes and spike-and-slow waves in the bilateral frontal and mid-frontal areas. Her magnetic resonance imaging scan was normal. In pedigree-II, the propositus (a 54-year-old male) could not walk stably and had a history of occasional falls for the past 34 years. The symptoms aggravated gradually until he lost the ability to perform routine daily activities. There was no history of convulsions. His physical and mental faculties, as well as the neurological findings were similar to those of the pedigree-I. Both proposituses did not respond well to symptomatic treatment. A novel mutation has been identified in SGCE gene (NM_003919:exon3:c.360delT:p.A120fs) using exome sequencing.

CONCLUSION

PMA patients from the two pedigrees had autosomal dominant mode of inheritance, with variability in the age of onset and disease severity. The cardinal symptoms were myoclonic seizures and ataxia without mental retardation.

Intermittent head drops: the differential spectrum

Intermittent Head Drops are episodic head flexion movements that can occur in a number of conditions. Typically, the term has mainly been related to epileptic episodes, but the spectrum of clinical conditions associated with this feature is wide-ranging even if never discussed in detail. By searching the electronic database, we may find that apart from the epileptic conditions, Intermittent Head Drops have been in fact reported in the setting of movement disorders, sleep disorders and even internal medicine disorders, such as Sandifer syndrome. We render an in-depth description of this characteristic phenomenon in different diseases, describing the clinical clues and neurophysiological patterns that may help the clinician to distinguish between the different settings of occurrence.

Brivaracetam in Unverricht-Lundborg disease (EPM1): Results from two randomized, double-blind, placebo-controlled studies

OBJECTIVE

To evaluate efficacy, tolerability, and safety of adjunctive brivaracetam (BRV) in patients with Unverricht-Lundborg disease (EPM1).

METHODS

Two prospective, multicenter, double-blind, phase III trials (N01187/NCT00357669; N01236/NCT00368251) in patients (≥16 years) with genetically ascertained EPM1, showing moderate-severe myoclonus (action myoclonus score ≥30/160), randomized (1:1:1) to twice-daily BRV (N01187: 50 or 150 mg/day; N01236: 5 or 150 mg/day), or placebo. Both studies comprised a baseline period (2 weeks), 2-week up-titration period, 12-week stable-dose maintenance period, and down-titration or entry into long-term follow-up study. Symptoms of myoclonus were assessed by Unified Myoclonus Rating Scale (UMRS). Primary efficacy end point was percent reduction from baseline in action myoclonus score (UMRS section 4) at last treatment visit. Safety assessments included treatment-emergent adverse events (TEAEs).

RESULTS

N01187: 50 patients randomized, 47 completed; N01236: 56 patients randomized, 54 completed. Median (min-max) percent reduction from baseline in action myoclonus score is the following-N01187: placebo 5.6 (-81.3 to 53.8), pooled BRV group (primary efficacy analysis) 21.4 (-50.0 to 73.6), BRV 50 mg/day 26.3 (-35.8 to 69.2), BRV 150 mg/day 16.9 (-50.0 to 73.6); N01236: placebo 17.5 (-170 to 61.5), BRV 5 mg/day -4.6 (-430 to 81.8), BRV 150 mg/day (primary efficacy analysis) 12.3 (-58.3 to 96.9). Estimated differences versus placebo were not statistically significant. TEAEs were reported by 72-75% placebo-treated and 56-83% BRV-treated patients.

SIGNIFICANCE

Effect of BRV on action myoclonus was not statistically significant. However, action myoclonus score showed wide intrapatient variability and may not have been the optimal tool to measure severity of myoclonus in EPM1. Both studies had very high completion rates (95.3% overall), and a high percentage of patients (88.7% overall) entered long-term follow-up; both likely to be influenced by good tolerability. These studies demonstrate the feasibility of rigorous trials in progressive myoclonic epilepsy.

Epilepsy genetics: the ongoing revolution

Epilepsies have long remained refractory to gene identification due to several obstacles, including a highly variable inter- and intrafamilial expressivity of the phenotypes, a high frequency of phenocopies, and a huge genetic heterogeneity. Recent technological breakthroughs, such as array comparative genomic hybridization and next generation sequencing, have been leading, in the past few years, to the identification of an increasing number of genomic regions and genes in which mutations or copy-number variations cause various epileptic disorders, revealing an enormous diversity of pathophysiological mechanisms. The field that has undergone the most striking revolution is that of epileptic encephalopathies, for which most of causing genes have been discovered since the year 2012. Some examples are the continuous spike-and-waves during slow-wave sleep and Landau-Kleffner syndromes for which the recent discovery of the role of GRIN2A mutations has finally confirmed the genetic bases. These new technologies begin to be used for diagnostic applications, and the main challenge now resides in the interpretation of the huge mass of variants detected by these methods. The identification of causative mutations in epilepsies provides definitive confirmation of the clinical diagnosis, allows accurate genetic counselling, and sometimes permits the development of new appropriate and specific antiepileptic therapies. Future challenges include the identification of the genetic or environmental factors that modify the epileptic phenotypes caused by mutations in a given gene and the understanding of the role of somatic mutations in sporadic epilepsies.

Progressive myoclonus epilepsy in Down syndrome patients with dementia

This study aimed to elucidate the natural history of senile myoclonic epilepsy, a type of myoclonic epilepsy associated with Alzheimer's disease in adult Down syndrome patients. Twelve Down syndrome patients over the age of 40 years with myoclonic epilepsy and Alzheimer's disease underwent clinical, neuropsychological, neurophysiological, and neuroradiological study. The kariotypes, APOE polymorphisms, all exons in the PSEN1 and PSEN2 genes, and exons 16 and 17 in the APP gene were determined for all patients. CSF Aβ42, p-tau181, and t-tauAg were determined for two patients. Three main stages appeared during the course of the syndrome. The first stage was characterized by dementia onset (mean age: 51 ± 6.6 years), diffuse EEG abnormalities during sleep, and cerebral atrophy determined using neuroimaging. During the second stage, myoclonic epilepsy manifested (mean age: 51.4 ± 7.2 years) with myoclonic jerks time-locked to diffuse epileptiform abnormalities upon awakening, which was controlled with antiepileptic drugs. During the third stage (mean age: 54.8 ± 7.6 years), myoclonic seizures were replaced with nonepileptic myoclonus, and cerebellar signs, severe dementia, and photosensitivity developed. All patients showed complete trisomy 21. Mutations were ruled out on the APP, PSEN1, and PSEN2 genes, and APOE analysis revealed ε3/ε3 homozygosity. CSF biomarkers showed a decrease in Aβ42 and an increase in p-tau181. The natural history of senile myoclonic epilepsy is consistent with progressive myoclonus epilepsy. Chromosome 21 is implicated in its pathophysiology; however, other genetic and/or environmental risk factors cannot be excluded. The absence of the APOE type 4 allele could predict its progression.

Progressive myoclonic epilepsies: definitive and still undetermined causes

OBJECTIVE

To define the clinical spectrum and etiology of progressive myoclonic epilepsies (PMEs) in Italy using a database developed by the Genetics Commission of the Italian League against Epilepsy.

METHODS

We collected clinical and laboratory data from patients referred to 25 Italian epilepsy centers regardless of whether a positive causative factor was identified. PMEs of undetermined origins were grouped using 2-step cluster analysis.

RESULTS

We collected clinical data from 204 patients, including 77 with a diagnosis of Unverricht-Lundborg disease and 37 with a diagnosis of Lafora body disease; 31 patients had PMEs due to rarer genetic causes, mainly neuronal ceroid lipofuscinoses. Two more patients had celiac disease. Despite extensive investigation, we found no definitive etiology for 57 patients. Cluster analysis indicated that these patients could be grouped into 2 clusters defined by age at disease onset, age at myoclonus onset, previous psychomotor delay, seizure characteristics, photosensitivity, associated signs other than those included in the cardinal definition of PME, and pathologic MRI findings.

CONCLUSIONS

Information concerning the distribution of different genetic causes of PMEs may provide a framework for an updated diagnostic workup. Phenotypes of the patients with PME of undetermined cause varied widely. The presence of separate clusters suggests that novel forms of PME are yet to be clinically and genetically characterized.

Vagus nerve stimulation in Lafora body disease

Introduction

Lafora body disease (LBD) is a rare autosomal recessive disorder characterized by progression to inexorable dementia and frequent occipital seizures, in addition to myoclonus and generalized tonic–clonic seizures (GTCSs). It belongs to the group of progressive myoclonus epilepsies (PMEs), rare inherited neurodegenerative diseases with great clinical and genetic differences, as well as poor prognosis. Since those patients have a pharmacoresistant disease, an adjunctive treatment option is vagus nerve stimulation (VNS). To date, there are four reported cases of the utility of VNS in PME — in Unverricht–Lundborg disease (ULD), myoclonic epilepsy with ragged-red fibers (MERRF), Gaucher's disease, and in one case that remained unclassified.

Case presentation

A 19-year-old male patient had progressive myoclonus, GTCSs that often progressed to status epilepticus (SE), progressive cerebellar and extrapyramidal symptomatology, and dementia, and his disease was pharmacoresistant. We confirmed the diagnosis of LBD by genetic testing. After VNS implantation, in the one-year follow-up period, there was a complete reduction of GTCS and SE, significant regression of myoclonus, and moderate regression of cerebellar symptomatology.

Conclusion

To our knowledge, this is the first reported case of the utility of VNS in LBD. Vagus nerve stimulation therapy may be considered a treatment option for different clinical entities of PME. Further studies with a larger number of patients are needed.

Genetics of epilepsy and relevance to current practice

Genetic factors are likely to play a major role in many epileptic conditions, spanning from classical idiopathic (genetic) generalized epilepsies to epileptic encephalopathies and focal epilepsies. In this review we describe the genetic advances in progressive myoclonus epilepsies, which are strictly monogenic disorders, genetic generalized epilepsies, mostly exhibiting complex genetic inheritance, and SCN1A-related phenotypes, namely genetic generalized epilepsy with febrile seizure plus and Dravet syndrome. Particular attention is devoted to a form of familial focal epilepsies, autosomal-dominant lateral temporal epilepsy, which is a model of non-ion genetic epilepsies. This condition is associated with mutations of the LGI1 gene, whose protein is secreted from the neurons and exerts its action on a number of targets, influencing cortical development and neuronal maturation.

Familial cortical myoclonus with a mutation in NOL3

OBJECTIVE

Myoclonus is characterized by sudden, brief involuntary movements, and its presence is debilitating. We identified a family suffering from adult onset, cortical myoclonus without associated seizures. We performed clinical, electrophysiological, and genetic studies to define this phenotype.

METHODS

A large, 4-generation family with a history of myoclonus underwent careful questioning, examination, and electrophysiological testing. Thirty-five family members donated blood samples for genetic analysis, which included single nucleotide polymorphism mapping, microsatellite linkage, targeted massively parallel sequencing, and Sanger sequencing. In silico and in vitro experiments were performed to investigate functional significance of the mutation.

RESULTS

We identified 11 members of a Canadian Mennonite family suffering from adult onset, slowly progressive, disabling, multifocal myoclonus. Somatosensory evoked potentials indicated a cortical origin of the myoclonus. There were no associated seizures. Some severely affected individuals developed signs of progressive cerebellar ataxia of variable severity late in the course of their illness. The phenotype was inherited in an autosomal dominant fashion. We demonstrated linkage to chromosome 16q21-22.1. We then sequenced all coding sequence in the critical region, identifying only a single cosegregating, novel, nonsynonymous mutation, which resides in the gene NOL3. Furthermore, this mutation was found to alter post-translational modification of NOL3 protein in vitro.

INTERPRETATION

We propose that familial cortical myoclonus is a novel movement disorder that may be caused by mutation in NOL3. Further investigation of the role of NOL3 in neuronal physiology may shed light on neuronal membrane hyperexcitability and pathophysiology of myoclonus and related disorders.

Early microglial activation precedes neuronal loss in the brain of the Cstb-/- mouse model of progressive myoclonus epilepsy, EPM1

Progressive myoclonus epilepsy of Unverricht-Lundborg type (EPM1) is a hereditary neurodegenerative disorder caused by mutations in the cystatin B (CSTB) gene encoding an inhibitor of cysteine proteases. Here, we provide the first detailed description of the onset and progression of pathologic changes in the CNS of Cstb-deficient (Cstb) mice. Our data reveal early and localized glial activation in brain regions where neuron loss subsequently occurs. These changes are most pronounced in the thalamocortical system, with neuron loss occurring first within the cortex and only subsequently in the corresponding thalamic relay nucleus. Microglial activation precedes the emergence of myoclonia and is followed by successive astrocytosis and selective neuron loss. Neuron loss was not detected in thalamic relay nuclei that displayed no glial activation. Microglia showed morphologic changes during disease progression from that of phagocytic brain macrophages in young animals to having thickened branched processes in older animals. These novel data on the timing of pathologic events in the CSTB-deficient brain highlight the potential role of glial activation at the initial stages of the disease. Determining the precise sequence of the neurodegenerative events in Cstb mouse brains will lay the basis for understanding the pathophysiology of EPM1.

Clinical and neurophysiologic features of progressive myoclonus epilepsy without renal failure caused by SCARB2 mutations

PURPOSE

Mutations of the SCARB2 gene cause action myoclonus renal failure syndrome (AMRF), a rare condition that combines progressive myoclonus epilepsy (PME) with severe renal dysfunction. We describe the clinical and neurophysiologic features of PME associated with SCARB2 mutations without renal impairment.

METHODS

Clinical and neurophysiologic investigations, including wakefulness and sleep electroencephalography (EEG), polygraphic recording (with jerk-locked back-averaging and analysis of the EEG-EMG (electromyography) relationship by coherence spectra and phase calculation), multimodal evoked potentials, and electromyography were performed on five Italian patients with SCARB2 mutations.

KEY FINDINGS

The main clinical features were adolescent-young adulthood onset, progressive action myoclonus, ataxia, absence of cognitive deterioration and, in most cases, epilepsy. The severity of the epilepsy could vary from uncontrolled seizures and status epilepticus in patients with adolescent onset to absent or rare seizures in patients with adult onset. Relevant neurophysiologic findings were a pronounced photosensitivity and massive action myoclonus associated with rhythmic myoclonic jerks at a frequency of 12-20 Hz, clinically resembling a postural tremor. The cortical origin of rhythmic myoclonus was demonstrated mainly by coherence and phase analysis of EEG-EMG signals indicating a significant EEG-EMG coupling and a direct corticospinal transfer.

SIGNIFICANCE

Our patients with SCARB2 mutations showed the clinical and neurophysiologic phenotype of PME, in which epilepsy could be extremely severe, extending the spectrum reported in the typical AMRF syndrome. Patients with PME of unknown origin of adolescent or young adult onset, with these neurophysiologic features, should be tested for SCARB2 mutations, even in the absence of renal impairment.

Progressive myoclonus epilepsies: clinical and genetic aspects

The progressive myoclonus epilepsies (PMEs) are a group of rare genetic disorders previously shrouded in nosological confusion. Recent advances have clarified the features of these disorders and provided a rational approach to diagnosis. The major causes of PME are now known to be Unverricht-Lundborg disease, myoclonus epilepsy ragged-red fiber (MERRF) syndrome, Lafora disease, neuronal ceroid lipofuscinoses, and sialidoses. Over the past 3 years, a series of molecular genetic findings have further refined the understanding of the PMEs. The specific mutation responsible for many cases of MERRF has been identified, and the genes for Unverricht-Lundborg disease and for juvenile neuronal ceroid lipofuscinosis have been linked to chromosomes 21 and 16, respectively. Although the PMEs are among the rarest of the inherited epilepsies, because of molecular genetic discoveries they may soon be the best understood at the neurobiologic level.

Genetics of epilepsy: an overview

Studies of the genetics of epilepsy have, until recently, involved epidemiologic or segregation analyses of phenotypic characteristics of a number of seizure disorders. Technical advances in molecular biology involving gene mapping and gene identification have made it possible to examine the heritability of various epilepsy syndromes. Using "reverse genetics" or positional cloning, it is possible to identify an abnormal protein through gene isolation and cloning. Genes are localized through analysis of linkage to phenotypic markers (proteins) or DNA markers such as restriction fragment length polymorphisms, variable number of tandem repeats, and dinucleotides. Methods used to obtain DNA of interest involve digestion of genomic DNA with specific restriction endonucleases or amplification of DNA by polymerase chain reaction technology. Gel electrophoresis is the basis for the separation of different sized DNA. Inherited disorders for which a gene has been cloned or localized have highly penetrant, well-defined clinical phenotypes with no remissions and abundant clinical material. Genetic epilepsies, however, are variably penetrant age-dependent disorders with heterogeneous clinical phenotypes. Despite these difficulties, three genetic epilepsies have been mapped to specific chromosomes: benign familial neonatal convulsions to 20q, juvenile myoclonic epilepsy to 6p, and Baltic progressive myoclonus epilepsy to 21q. Further progress in understanding genetic epilepsies will depend on better definition of syndrome phenotypes, isolation of the epilepsy gene(s), and identification of the abnormal protein(s).

Cystatin B deficiency sensitizes neurons to oxidative stress in progressive myoclonus epilepsy, EPM1

The progressive myoclonus epilepsies, featuring the triad of myoclonus, seizures, and ataxia, comprise a large group of inherited neurodegenerative diseases that remain poorly understood and refractory to treatment. The Cystatin B gene is mutated in one of the most common forms of progressive myoclonus epilepsy, Unverricht-Lundborg disease (EPM1). Cystatin B knockout in a mouse model of EPM1 triggers progressive degeneration of cerebellar granule neurons. Here, we report impaired redox homeostasis as a key mechanism by which Cystatin B deficiency triggers neurodegeneration. Oxidative stress induces the expression of Cystatin B in cerebellar granule neurons, and EPM1 patient-linked mutation of the Cystatin B gene promoter impairs oxidative stress induction of Cystatin B transcription. Importantly, Cystatin B knockout or knockdown sensitizes cerebellar granule neurons to oxidative stress-induced cell death. The Cystatin B deficiency-induced predisposition to oxidative stress in neurons is mediated by the lysosomal protease Cathepsin B. We uncover evidence of oxidative damage, reflected by depletion of antioxidants and increased lipid peroxidation, in the cerebellum of Cystatin B knock-out mice in vivo. Collectively, our findings define a pathophysiological mechanism in EPM1, whereby Cystatin B deficiency couples oxidative stress to neuronal death and degeneration, and may thus provide the basis for novel treatment approaches for the progressive myoclonus epilepsies.

[Unverricht-Lundborg disease manifesting tremulous myoclonus with rare convulsive seizures: a case report]

We report a 23-year-old woman who slowly developed progressive tremulous myoclonus and rare convulsive seizures beginning at the age of 9 and 11 years, respectively. She also showed a mild degree of ataxia and cognitive dysfunction. Convulsive seizures were well suppressed by valproic acid since the age of 17 years, but tremulous myoclonus gradually progressed and became rather intractable in spite of treatment by clonazepam and piracetam. Her cognitive dysfunction was mild (total IQ score in Wechsler Adult Intelligence Scale Revised being 85 points). In addition, she had a fear of walking which disabled her in the daily life although she could actually walk without assistance. The brain MRI showed a mild cerebellar atrophy, and FDG-PET showed a mild hypometabolism in the cerebellar hemispheres. Somatosensory evoked potentials (SEPs) showed enlarged P25 and N33 amplitudes (giant SEPs). A Cystatin B gene analysis exhibited a homozygous expansion of the dodecamer repeat, and thus we made a diagnosis of Unverricht-Lundborg disease (ULD). We also did gene analysis and SEP study to her parents after written informed consents were obtained. They had heterozygous expansion of the dodecamer repeat. The mother also showed enlarged P25 and N33 amplitudes, whereas the father showed normal amplitudes. It is known that degree of clinical symptoms varies among patients with ULD diagnosed by gene analysis. Gene analysis was helpful for a diagnosis of ULD in this patient because the ataxia and cognitive dysfunction were much milder than those commonly seen in patients with ULD.

Alpha-synuclein multiplications with parkinsonism, dementia or progressive myoclonus?

Duplications and triplications of the alpha-synuclein (SNCA) gene have been reported in Parkinson's disease patients belonging to the Southern Swedish "Lister family". Further genealogical research has now shown that these individuals are descended from a large kindred characterized by Herman Lundborg in 1901-1913. In the expanded pedigree, a total of 25 individuals had Parkinson's disease with an autosomal dominant pattern of inheritance. Hereditary dementia, and, historically, dementia praecox have been described in other family members. Furthermore, an autosomal recessively inherited pediatric disease with nocturnal tonic-clonic fits, subsequent progressive myoclonus, startle reactions, tremor and muscle rigidity was described by Lundborg in the same pedigree. The entity was later designated Unverricht-Lundborg disease (ULD) or progressive myoclonus epilepsy type 1 (EPM1). However, Lundborg's clinical description of this disease, based on 17 patients within this kindred, differs from the modern definition of EPM1, which relies on patients with a mutation in the cystatin B (CSTB) gene. We hypothesize that the former pediatric disease, as well as the parkinsonism and dementia phenotypes, are associated with duplications, triplications and possibly higher-order multiplications of the alpha-synuclein (SNCA) gene. This hypothesis is supported by the distribution of afflicted family members within the pedigree and by recently obtained genealogical information.