Benign myoclonic epilepsy: long-term follow-up of 11 new cases

ILAE classification and definition of epilepsy syndromes with onset in neonates and infants: Position statement by the ILAE Task Force on Nosology and Definitions

The International League Against Epilepsy (ILAE) Task Force on Nosology and Definitions proposes a classification and definition of epilepsy syndromes in the neonate and infant with seizure onset up to 2 years of age. The incidence of epilepsy is high in this age group and epilepsy is frequently associated with significant comorbidities and mortality. The licensing of syndrome specific antiseizure medications following randomized controlled trials and the development of precision, gene-related therapies are two of the drivers defining the electroclinical phenotypes of syndromes with onset in infancy. The principal aim of this proposal, consistent with the 2017 ILAE Classification of the Epilepsies, is to support epilepsy diagnosis and emphasize the importance of classifying epilepsy in an individual both by syndrome and etiology. For each syndrome, we report epidemiology, clinical course, seizure types, electroencephalography (EEG), neuroimaging, genetics, and differential diagnosis. Syndromes are separated into self-limited syndromes, where there is likely to be spontaneous remission and developmental and epileptic encephalopathies, diseases where there is developmental impairment related to both the underlying etiology independent of epileptiform activity and the epileptic encephalopathy. The emerging class of etiology-specific epilepsy syndromes, where there is a specific etiology for the epilepsy that is associated with a clearly defined, relatively uniform, and distinct clinical phenotype in most affected individuals as well as consistent EEG, neuroimaging, and/or genetic correlates, is presented. The number of etiology-defined syndromes will continue to increase, and these newly described syndromes will in time be incorporated into this classification. The tables summarize mandatory features, cautionary alerts, and exclusionary features for the common syndromes. Guidance is given on the criteria for syndrome diagnosis in resource-limited regions where laboratory confirmation, including EEG, MRI, and genetic testing, might not be available.

Myoclonic epilepsy in infancy with preceding or concurrent afebrile generalized tonic-clonic seizures in Chinese children

OBJECTIVE

To investigate the general characteristics and the category of myoclonic epilepsy in infancy (MEI) with or without afebrile generalized tonic-clonic seizures (GTCS).

METHODS

Thirty-three children were retrospectively recruited from approximately 42,814 video-electroencephalogram (VEEG) recordings monitored in our department over last nearly 10years. Myoclonic seizures (MS) must be identified by VEEG in all patients. The clinical, EEG features and outcome were analyzed among these patients.

RESULTS

The 33 patients (25 boys and 8 girls) were divided into three groups: 11 patients with typical MEI; 16 patients with MEI experienced afebrile GTCS before MS onset; and 6 patients with MEI presented afebrile GTCS occurring concurrently with MS. No significant differences were found among the three groups, including gender distribution, family history, personal history of febrile seizures, the age at seizure onset and control, the duration of MS, the interval between age at onset and seizure control, the age at EEG normalization, the interval between seizure onset age and EEG normalization age and normal psychomotor development at the end of follow-up. More patients in group two and group three were controlled by two or three kinds of antiepileptic drugs compared with those in group one.

CONCLUSIONS

In this study, three groups of patients had similar clinical, EEG features and outcome. Afebrile GTCS was associated with a stronger cortical hyperexcitability. It was worth considering whether MEI with preceding or concurrent afebrile GTCS should be recognized as subgroups or different epileptic syndromes independent of MEI.

Early childhood myoclonic epilepsy: An independent genetic generalized epilepsy with myoclonic seizures as the main seizure type

OBJECTIVE

To elucidate the characteristics of the myoclonic seizures alone, or predominant myoclonus combined with generalized tonic-clonic seizures (GTCS) and/or absences, in early childhood, and discuss its classification.

METHODS

Forty-two children were retrospectively recruited between January 2006 and June 2015.

RESULTS

The mean age of seizure onset was 40.5months. They were divided into 4 groups: myoclonic seizures alone; predominant myoclonus combined with GTCS; predominant myoclonus combined with absences; predominant myoclonus combined with both GTCS and absences. Interictal EEG showed generalized spike- or polyspike-wave discharges at 2-4Hz. Seizures were controlled in 22 patients at a mean age of 60.5months. The psychomotor development was normal (30/37) or mildly delayed (7/37).

CONCLUSIONS

We reported a cohort of patients with early childhood myoclonic epilepsy (ECME), with the following characteristics: Seizures started below 5years old in otherwise normal children; Seizure types included myoclonic seizures alone or combined with GTCS and/or absences; Febrile or afebrile GTCS might appear firstly; Interictal EEG showed generalized spike- or polyspike-wave; Seizures usually were in remission before adolescence with normal development or mild cognitive or behavioral deficits in most.

SIGNIFICANCE

ECME might be an independent epileptic syndrome not established by International League Against Epilepsy (ILAE) previously.

Benign myoclonic epilepsy in infancy (BMEI): a longitudinal electroclinical study of 22 cases

PURPOSE

Benign myoclonic epilepsy in infancy (BMEI) is a nosologically well-defined entity, characterized by myoclonic seizures (MS) in normal children younger than 3 years and by a good long term prognosis. In some cases the seizures are reflex. We studied 22 cases to better define the electroclinical semeiology and evolution of the disorder.

METHODS

Serial electroclinical and neuropsychological assessments, both during wakefulness and during sleep, were performed in 22 otherwise healthy children with spontaneous (17) or reflex (5) MS, recorded by video-EEG-polygraphy since clinical onset.

RESULTS

Seizure onset was between 3 months and 4 years 10 months (50% during first year, 86% before the third year); in reflex cases onset, was earlier than the 14th month. MS recurred during wakefulness and slow sleep in all cases and during REM sleep in reflex cases. MS and related EEG discharges were synchronous or asynchronous. Often ictal EEG discharges were limited to the rolandic and vertex regions (falsely focal paroxysms). Several seizures were subtle and could have escaped recognition. Unusually frequent sleep startles were recorded mostly in reflex cases. MS were well controlled by treatment. At follow-up, between ages 3 and 19 years, four patients had occasional seizures; two had cognitive impairment and three had learning difficulties. No other seizures or cognitive deficits were observed in reflex cases.

CONCLUSIONS

Seizures associated with BMEI are rarely truly generalized and are often so subtle and related to falsely focal paroxysms that their frequency can be underestimated. The reflex form is a well-defined variant with an early onset, peculiar electroclinical features, and a good prognosis.

Developmental outcome in benign myoclonic epilepsy in infancy and reflex myoclonic epilepsy in infancy: A literature review and six new cases

Benign myoclonic epilepsy in infancy is a rare syndrome with just over 100 cases reported since the first syndromic description by Dravet and Bureau [Dravet, C., Bureau, M., 1981. The benign myoclonic epilepsy of infancy. Rev. Elecroencephalogr. Neurophysiol. Clin. 11, 438-444]. This includes 23 infants with reflex myoclonic epilepsy whose inclusion in the wider syndrome remains debatable. We have reviewed the literature and present data from six further cases. Prognosis in respect of long term seizure freedom is good with sodium valproate being the most effective medication. However, the cognitive outcome is much less certain with cognitive problems present in one-third of children who have long term follow up. The cognitive outcome in reflex myoclonic epilepsy of infancy is normal in all reported cases. The term benign may be appropriately used to describe the myoclonic seizures but must be used cautiously when counselling families about cognitive outcome. The clinical heterogeneity within this syndrome suggests that there may be a variety of genetic mechanisms that underlie the presentation. Clinicians should distinguish the syndrome of reflex myoclonic epilepsy in infancy from benign myoclonic epilepsy of infancy and all patients should continue developmental follow up for several years after diagnosis.

Benign Myoclonic Epilepsy in Infants: Electroclinical Features and Long-term Follow-up of 34 Patients

PURPOSE

Benign myoclonic epilepsy in infants (BMEI) is a rare epileptic syndrome characterized only by generalized myoclonic seizures (MSs) in normal children during the first 2 years. Our aim was to assess the electroclinical features and the follow-up of this syndrome.

METHODS

BMEI was confirmed by electroencephalogram (EEG) in four neuropediatric units in France between 1981 and 2002. Clinical and electroencephalographic findings at diagnosis and during the follow-up were collected. The Vineland scale or Wechsler scale or both were used to perform neuropsychological evaluations.

RESULTS

We report 34 patients with BMEI characterized by MSs occurring many times a day. The ictal EEG showed a generalized discharge of polyspikes, polyspikes-and-waves, or spikes-and-waves. The interictal EEG was usually normal. A family history of febrile seizures (FSs) or epilepsy was noted in six patients. A history of FSs was noted in 11 patients. Eleven patients had reflex MSs. Monotherapy with valproic acid was effective in 23 of 30 treated patients. The onset of epilepsy was known in all patients. Four patients had seizures after the initial symptoms. Juvenile myoclonic epilepsy developed in two patients, and cryptogenic partial epilepsy in another. Neuropsychological outcome was evaluated in 20 patients (10 with Wechsler scales and 17 with the Vineland scale). Cognitive functions were normal in 17 patients, whereas developmental delay was observed in three others.

CONCLUSIONS

BMEI is clinically characterized by myoclonic seizures involving the upper part of the body, occurring many times a day. The ictal EEG showed a generalized discharge of polyspikes, polyspikes-and-waves, or spikes-and-waves. The interictal EEG was usually normal. Reflex MSs were frequently observed, suggesting that two distinctive syndromes are not necessary. BMEI may be followed by juvenile myoclonic epilepsy. Despite a generally favorable neuropsychological outcome, mental retardation can be observed more frequently than in the general population.

Benign myoclonic epilepsy in infancy: neuropsychological and behavioural outcome

Benign myoclonic epilepsy in infancy (BMEI) is a rare syndrome of idiopathic generalized epilepsies with onset below 3 years of age. It has been reported that BMEI is associated with a good prognosis, however, recently some studies suggest less favourable neuropsychological outcome. We report a long-term follow-up of seven patients with BMEI. Seizure outcome and neuropsychological, cognitive, and behavioural evolution were discussed for each of them. At the end of follow-up, 86% of children showed neuropsychological and intellectual disorders: two children had mental retardation, three patients achieved a borderline IQ and one normal but low IQ. All but one displayed neuropsychological disabilities including fine motor skill deficits, attention deficits, and language impairment and learning disorders. Our clinical data and the previous reports suggest that the early onset of the seizures may be one of the main factors of the illness giving rise to a less favourable outcome. Additional interacting factors such as delayed start of treatment, and efficacy of the drugs may play an important role, too. We believe that BMEI does not exert, different from some epileptic encephalopathies, a quick destroying effect but may interfere with the growth of developing functions, which results in long-term neuropsychological disabilities.

Epileptic Encephalopathies with Myoclonic Seizures in Infants and Children (Severe Myoclonic Epilepsy and Myoclonic-Astatic Epilepsy)

Myoclonic attacks are not characteristic of a specific syndrome. In infancy and early childhood, they are often observed in the context of syndromes that are associated with other types of seizures and with cognitive impairment but no obvious brain lesion. Characterization of the associated seizures and age of expression allows inclusion of a number of cases in two main subgroups: severe myoclonic epilepsy (SME, or Dravet syndrome) and myoclonic-astatic epilepsy (MAE). Severe myoclonic epilepsy is an epileptic encephalopathy with invariably poor outcome in which myoclonic seizures, though frequently observed, may be absent altogether in some children. Prolonged and repeated febrile and afebrile convulsive seizures starting in infancy are the main feature and are probably causally related to cognitive decline. One third of children harbor mutation of the SCN1A gene, but the genetics of SME is probably more complex than expected with simple monogenic disorders. Treatment is usually disappointing. Myoclonic-astatic epilepsy is perhaps more a conceptual category of idiopathic myoclonic epilepsy than a discrete syndrome. Childhood-onset myoclonic-astatic attacks are the characteristic seizures associated in most with episodes of nonconvulsive status and generalized tonic-clonic seizures. Outcome is unpredictable. Either remission within a few years with normal cognition or long-lasting intractability with cognitive impairment is possible. Likewise, the effectiveness of antiepileptic drugs is variable. A number of cases of myoclonic epilepsies in infancy and early childhood, however, remain unclassified, and intermediate forms between the different syndromes exist. They must be distinguished from other syndromes with frequent brief attacks and repeated falls, especially the Lennox-Gastaut syndrome. This differentiation is often difficult and may require extensive neurophysiologic studies.

Attentional disorders in patients with complex partial epilepsy

A study of concentrated attention patterns in epileptic patients was conducted with the objectives: characterization of the patients' epileptic condition; assessment of the concentrated attention levels in epileptic and nonepileptic individuals; comparison of the attention levels of the two groups. An evaluation was performed of 50 adult outpatients with complex partial seizures and 20 non-epileptic individuals (comparative group) at the Neuroepilepsy Ambulatory Unit, State University of Campinas SP, Brazil.

METHOD

characterization of seizure types, frequency and duration; concentrated attention assessment (Concentrated Attention Test - Toulouse-Pi ron); comparison of the epileptic with non-epileptic individuals.

RESULTS

A statistically significant difference was observed between the groups with regard to Correct Response, Wrong Response and No Response. A difference was observed in relation to Time, but it was statistically insignificant. The epileptic patients presented inferior cognitive performance in relation to concentrated attention when compared with the non-epileptic individuals, findings compatible with the clinical complaints.

Familial infantile myoclonic epilepsy: clinical features in a large kindred with autosomal recessive inheritance

PURPOSE

To describe the clinical features of a large kindred with familial infantile myoclonic epilepsy (FIME) with autosomal recessive inheritance, and to discuss the nosology of the early infantile myoclonic epilepsies (IMEs).

METHODS

The family descends from the intermarriage of two couples of siblings. In a previous study, we mapped the genetic locus to chromosome 16p13. We analyzed results of family records and personal history, psychomotor development, neurologic examination, epilepsy features, and EEG recordings for each subject.

RESULTS

FIME has a strong penetrance (eight affected of 14 subjects) and a homogeneous clinical picture. Like the benign form of infantile myoclonic epilepsy (BIME), FIME is a true idiopathic IME with unremarkable history, no neurologic or mental impairment, good response to treatment, and normal interictal EEG pattern. Conversely, onset with generalized epileptic seizures without fever (four patients) or with fever (one patient), frequency and duration of the myoclonic seizures, occurrence of generalized tonic--clonic seizures (GTCSs) in all patients and persistence of seizures into adulthood are characteristics of the severe infantile myoclonic epilepsy (SIME).

CONCLUSIONS

Clinical overlap probably exists among the myoclonic epilepsies of infancy. FIME differs from other forms of IME in its phenotypic features. The peculiar mode of inheritance is explained by the genetic background of the family. Genetic studies suggest linkage to chromosome 16 in familial cases of true IME.