Refractory grand mal seizures with onset during infancy including severe myoclonic epilepsy in infancy.

In 1978, Dravet proposed a clinical entity called severe myoclonic epilepsy in infancy (SMEI). In the same year, a patient group, which was later called high voltage slow wave-grand mal syndrome (HVSW-GM), is reported in Japan. Both syndromes are very similar, except for seizure manifestation: generalized tonic-clonic convulsions (GTC) with myoclonic and other polymorphic seizures in SMEI vs. GTC only in HVSW-GM. To study the pathophysiology of these refractory epilepsies, the author formulated new clinical diagnostic criteria common to both syndromes as follows: GTC with onset before the age of 1 year as the principal seizure type; an epilepsy entity unclassifiable either as partial or generalized by all the clinical data including EEG findings; mental and motor dysfunction absent prior to seizure onset but appearing later; absence of epileptiform activities on EEG in the initial stage; stubborn refractoriness to conventional antiepileptic medication. Twenty-two patients meeting all of five clinical criteria above mentioned were recruited in the study. Detailed analysis of clinico-electrical features and long-term follow-up of these patients led the author to the conclusion that GTC in combination with seizures of other types will contribute to an unfavorable pathophysiological or prognostic conditions, and, especially when GTC exists in combination with myoclonic seizures, the severity of epilepsy will increase. The author claimed that the three clinical entities, SMEI, HVSW-GM, and their variant form, share certain characteristics in common and may constitute a unique epilepsy syndrome for which a new name of infantile refractory grand mal syndrome (IRGMS) was offered. This is a more basic concept with broader spectrum than SMEI, encompassing not only SMEI but also related borderlands like HVSW-GM. More recently, the author observed that early zonisamide medication within 1 year after seizure onset may improve seizure prognosis in IRGMS, by preventing the development of myoclonic seizures.     

Clinical and molecular genetics of myoclonic-astatic epilepsy and severe myoclonic epilepsy in infancy (Dravet syndrome).

The majority of severe epileptic encephalopathies of early childhood are symptomatic where a clear etiology is apparent. There is a small subgroup, however, where no etiology is found on imaging and metabolic studies, and genetic factors are important. Myoclonic-astatic epilepsy (MAE) and severe myoclonic epilepsy in infancy (SMEI), also known as Dravet syndrome, are epileptic encephalopathies where multiple seizure types begin in the first few years of life associated with developmental slowing. Clinical and molecular genetic studies of the families of probands with MAE and SMEI suggest a genetic basis. MAE was originally identified as part of the genetic epilepsy syndrome generalized epilepsy with febrile seizures plus (GEFS(+)). Recent clinical genetic studies suggest that SMEI forms the most severe end of the spectrum of the GEFS(+). GEFS(+) has now been associated with molecular defects in three sodium channel subunit genes and a GABA subunit gene. Molecular defects of these genes have been identified in patients with MAE and SMEI. Interestingly, the molecular defects in MAE have been found in the setting of large GEFS(+) pedigrees, whereas, more severe truncation mutations arising de novo have been identified in patients with SMEI. It is likely that future molecular studies will shed light on the interaction of a number of genes, possibly related to the same or different ion channels, which result in a severe phenotype such as MAE and SMEI.     

Clinical spectrum of mutations in SCN1A gene: severe myoclonic epilepsy in infancy and related epilepsies

Severe myoclonic epilepsy in infancy (SMEI) manifests very frequent generalized tonic-clonic seizures (GTC), accompanied by myoclonic seizures, absences and partial seizures [Dravet, C., 1978. Les épilepsie grave de l'enfant. Vie Méd. 8, 543-548; Dravet, C., Roger, J., Bureau, M., Dalla Bernardina, B., 1982. Myoclonic epilepsies in childhood. In: Akimoto, H., Kazamatsuri, H., Seino, M., Ward, A. (Eds.), Advances in Epileptology. Raven Press, New York, pp. 135-140; Dravet, C., Bureau, M., Oguni, H., Fukuyama, Y., Cokar, O., 2002. Severe myoclonic epilepsy of infancy (Dravet syndrome). In: Roger, J., Bureau, M., Dravet, C., Genton, P., Tassinari, C.A., Wolf, P. (Eds.), Epileptic Syndromes in Infancy, Childhood and Adolescence, third ed. John Libbey, London, pp. 81-103]. However, there is a group of severe epilepsy that has many characteristics common to SMEI except for myoclonic seizures. We reported this group of epilepsy as intractable childhood epilepsy with GTC (ICEGTC) [Watanabe, M., Fujiwara, T., Yagi, K., Seino, M., Higashi, T., 1989b. Intractable childhood epilepsy with generalized tonic-clonic seizures. J. Jpn. Epil. Soc. 7, 96-105 (in Japanese); Fujiwara, T., Watanabe, M., Takahashi, Y., Higashi, T., Yagi, K., Seino, M., 1992. Long-term course of childhood epilepsy with intractable grand mal seizures. Jpn. J. Psychiatr. Neurol. 46, 297-302]. Recently, mutations of the neuronal voltage-gated sodium channel alphasubunit type 1 gene (SCN1A) have been found in SMEI [Claes, L., Del-Favero, J., Ceulemans, B., Lagae, L., Van Broeckhoven, C., De Jonghe, P., 2001, De novo mutations in the sodium-channel gene SCN1A cause severe myoclonic epilepsy of infancy. Am. J. Hum. Genet. 68, 327-1332]. Mutations in SCN1A are found in both SMEI and ICEGTC at high rates of 70-81%. The loci of the mutations seen in ICEGTC are quite similar to those found in SMEI, suggesting a genotypic continuity between these entities. The clinical spectrum of epilepsies harboring SCN1A mutations may be consisted of various phenotypes with GEFS+ on the mildest end and SMEI on the severest end of the spectrum.     

The Natural History of Myoclonic Astatic Epilepsy (Doose Syndrome) and Lennox-Gastaut Syndrome

Summary:  The purpose of this article is to present a short review of the natural history of myoclonic astatic epilepsy (MAE; Doose syndrome) and the Lennox-Gastaut syndrome (LGS). In the 1989 classification of the International League Against Epilepsy (ILAE, 1989), MAE and LGS were initially included in group 2.2: "Cryptogenic or symptomatic generalized epilepsies and syndromes." The subsequent classification of the Proposed Diagnostic Scheme for People with Epileptic Seizures and with Epilepsy (see Ref. 8 ) placed MAE in axis 3 in the "generalized epilepsy" group and LGS, severe myoclonic epilepsy of infancy (SMEI or Dravet syndrome) and atypical benign partial epilepsy/pseudo-Lennox syndrome (ABPE/PLS) in the "epileptic encephalopathy" group. The semiology of MAE and LGS and their differential diagnosis from SMEI and ABPE/PLS are described. Before the onset of SMEI, MAE, and ABPE/PLS, the development of the child is usually normal. In contrast, in LGS, development is frequently retarded at the onset, depending on the etiopathogenesis of the underlying brain disease. The course of MAE is highly variable with regard to seizure outcome (complete remission in some cases, persistent epilepsy in others) and cognitive development (normal or delayed). The course of LGS and SMEI is generally poor, both with regard to the epilepsy and to the cognitive development whereas the course and seizure outcome of ABPE/PLS is favorable; the patients will be seizure-free at puberty. However, the neuropsychological outcome is less favorable; most patients remain mentally retarded.     

Early diagnosis of severe myoclonic epilepsy in infancy.

Of 329 epileptic patients referred in a six year period with the first seizure occurring in the first year of life, 20 met the following criteria: generalized seizures excluding infantile spasms, myoclonic, tonic or absence seizures, at least one afebrile seizure, normal development prior to the first seizure, normal CT scan, and no etiology. Seventeen of these 20 patients developed the full pattern of severe myoclonic epilepsy in infancy (SMEI). This syndrome was recognizable from the second or third seizure in the first year of life, although epileptiform EEG abnormalities were lacking until the age of 11 to over 30 months. Therefore, based on the clinical pattern, the diagnosis of SMEI can be made with quite good reliability by the end of the first year of life.     

Dravet syndrome and deep brain stimulation: Seizure control after 10 years of treatment

Dravet syndrome is a genetically determined severe epilepsy associated with cognitive decline and ataxia. The many types of seizures seen in these patients are typically pharmacoresistant. Here we describe two adults with Dravet syndrome who were treated with thalamic deep brain stimulation (DBS) and followed for 10 years. One patient with partial onset seizures received DBS at age 19 and showed a marked improvement in seizure control after DBS insertion and stimulation. The other patient with generalized onset seizures received DBS at age 34 and did not show any immediate benefit. No side effects or changes in cognition were observed in either of the patients. This is the first report of (short‐ and) long‐term results in Dravet patients treated with thalamic DBS. We speculate that the results of DBS for epilepsy in patients with Dravet syndrome may be related to age at initiation of DBS treatment and seizure type.     

Dravet syndrome history

Severe myoclonic epilepsy of infancy (SMEI) is a complex form of epilepsy that was first described in France in 1978. Because the myoclonic component of this epilepsy is not always present and because some variability has been observed in the symptomatology, the name was changed to Dravet syndrome in 1989. The genetic aetiology of this epilepsy was discovered in 2001, and since then numerous studies have contributed to a better knowledge of the disease. Around 70% of affected patients are carriers of a mutation on the alpha subunit of the SCN1A gene. An accurate analysis of the clinical features leads to the distinction between typical and atypical forms, both with the same unfavourable prognosis and the same genetic background. However, many studies are being conducted in order to establish correlations between phenotypes and genotypes, and to understand the factors underlying the cognitive impairment of the affected patients.     

Dravet syndrome: a technologist's perspective

Dravet Syndrome (DS), also known as Severe Myoclonic Epilepsy in Infancy (SMEI) is a rare, primarily genetic disorder which develops in infancy. The characteristics of DS are frequent, prolonged, primarily generalized seizures which occur initially with fever and eventually evolve to multiple afebrile seizure types such as myoclonic, atypical absence, and complex partial seizures. Patients, who are initially developmentally normal, will experience concomitant developmental regression as the syndrome progresses. Because it is a childhood disorder, DS is not well known outside the realm of pediatrics. An astute EEG technologist should be able to recognize key factors both clinically and electrographically which point suspicion to the diagnosis of Dravet Syndrome.     

Dravet syndrome: From electroclinical characteristics to molecular biology

The onset of Dravet syndrome typically occurs within the first year, with prolonged, generalized, or unilateral clonic seizures triggered by fever. In the early stages, other types of refractory seizures usually present that include myoclonic seizures, atypical absences, and partial seizures. Electroencephalography (EEG) findings are not pathognomonic, and signs of cognitive arrest or deterioration progressively appear. In contrast, in adults, myoclonic seizures, atypical absences, and focal seizures tend to disappear, and short tonic–clonic seizures, often associating a focal component, persist particularly during sleep. The sensitivity to fever persists into adulthood, and although mental deterioration occurs in infancy, usually leaving patients with severe mental impairment, further deterioration does not occur. The identification of genes associated with Dravet syndrome and related syndromes hints at the complexity of the etiology of such epilepsies. Identifying SCN1A mutations has become useful as a means to support an early diagnosis of Dravet syndrome, to benefit counseling, and to avoid use of antiepileptic drugs (AEDs) that may have adverse effects. However, the defining characteristics of seizure type and EEG patterns initially identified by Dravet remain fundamental to diagnosis.     

"Severe myoclonic epilepsy in infancy". Relevance for the clinician of severe epilepsy starting in infancy

'Severe myoclonic epilepsy in infancy' or Dravet syndrome is a clear example of the impact of severe epilepsy on the developing child. Presenting with febrile seizures in infancy, children later on develop a severe epileptic syndrome with mental retardation. Nearly all children have life-threatening status epilepticus during the first two years of life. The clinical diagnosis can now be confirmed by DNA-analysis in a majority of patients. Most patients have a de novo mutation in the alfa subunit of the neuronal sodium channel SCN1A. In the past few years' treatment of severe myoclonic epilepsy in infancy has changed. Prevention of seizures, avoiding anti-epileptic drugs which only block sodium channels, a simple combination of two major anti-epileptic drugs (sodium valproate and topiramate) and a strict acute seizure treatment significantly improve the quality of life for these patients. Long-term follow up is necessary to evaluate if we can also improve the development possibilities for these children.     

Dravet syndrome: Early clinical manifestations and cognitive outcome in 37 Italian patients

Aims of our study were to describe the early clinical features of Dravet syndrome (SMEI) and the neurological, cognitive and behavioral outcome. The clinical history of 37 patients with clinical diagnosis of SMEI, associated with a point mutation of SCN1A gene in 84% of cases, were reviewed with particular attention to the symptoms of onset. All the patients received at least one formal cognitive and behavior evaluation. Epilepsy started at a mean age of 5.7 months; the onset was marked by isolated seizure in 25 infants, and by status epilepticus in 12; the first seizure had been triggered by fever, mostly of low degree in 22 infants; the first EEG was normal in all cases. During the second year of life difficult-to-treat seizures recurred, mostly triggered by fever, hot bath, and intermittent lights and delay in psychomotor development became evident. At the last evaluation, performed at a mean age of 16 ± 6.9 years, mental retardation was present in 33 patients, associated with behavior disorders in 21. Our data indicate that the most striking features of SMEI are: the early onset of seizures in a previously healthy child, the long duration of the first seizure, the presence of focal ictal symptoms, and sensitivity to low-grade fever. Diagnosis of SMEI may be proposed by the end of the first year of life, and a definite diagnosis can be established during the second year based on the peculiar seizure-favoring factors, EEG photosensitivity and psychomotor slowing. The temporal correlation between high seizure frequency and cognitive impairment support the role of epilepsy in the clinical outcome, even if a role of channelopathy cannot be ruled out.     

Severe Myoclonic Epilepsy of Infancy: Extended Spectrum of GEFS+?

PURPOSE: Severe myoclonic epilepsy of infancy (SMEI) is an intractable epilepsy of early childhood of unknown etiology. It is often associated with a family history of seizure disorders, but epilepsy phenotypes have not been well described. We sought to characterize the seizure phenotypes of relatives to better understand to the genetic basis of SMEI. METHODS: Probands with SMEI were identified, and systematic family studies were performed. Epilepsy syndromes were characterized in affected family members. RESULTS: Twelve probands with SMEI were identified. Eleven of the 12 probands with SMEI had a family history of seizures, and the twelfth was the result of a consanguineous marriage. We found that 16.7% of full siblings and 8.3% of parents had definite seizures. A total of 39 affected family members was identified. The most common phenotype was febrile seizures in 14, febrile seizures plus in seven, partial epilepsy in two, and there were single individuals with SMEI, myoclonic-astatic epilepsy, Lennox-Gastaut syndrome, and 13 cases with unclassified or unconfirmed seizures. CONCLUSIONS: The family history of seizures in SMEI is in keeping with the spectrum of seizure phenotypes seen in generalized epilepsy with febrile seizures plus (GEFS+). Our findings suggest that SMEI is the most severe phenotype in the GEFS+ spectrum.     

Absence of mutations in major GEFS+ genes in myoclonic astatic epilepsy

Myoclonic astatic epilepsy (MAE) is a genetically determined condition of childhood onset characterized by multiple generalized types of seizures including myoclonic astatic seizures, generalized spike waves and cognitive deterioration. This condition has been reported in a few patients in generalized epilepsy with febrile seizures plus (GEFS+) families and MAE has been considered, like severe myoclonic epilepsy of infancy (SMEI), to be a severe phenotype within the GEFS+ spectrum. Four genes have been identified in GEFS+ families, but only three (SCN1A, SCNlB, GABRG2) were found in MAE patients within GEFS+ families. We analysed these three genes in a series of 22 sporadic patients with MAE and found no causal mutations. These findings suggest that MAE, unlike SMEI, is not genetically related to GEFS+. Although MAE and SMEI share the same types of seizures, only SMEI patients are sensitive to fever. This is probably its main link to GEFS+. A different family of genes is likely to account for MAE.     

Overall management of patients with Dravet syndrome

Dravet syndrome, or as it was called in the past 'severe myoclonic epilepsy in infancy', is a drug-resistant epilepsy first described by Charlotte Dravet in 1978. Besides the well-known and well-described therapy resistance, Dravet syndrome dramatically impacts the development and behaviour of the affected children. As it is still not a curable disease, families need to be taught how to cope with the disorder and will require assistance from both clinical and non-clinical structures. At the onset of the disease, many questions arise regarding the diagnosis of Dravet syndrome, the severity of the illness and its deleterious effects, and the management of seizures, especially the long-lasting status epilepticus. Once the diagnosis has been established, severe convulsions, often unpredictable and long-lasting, are still a major worry, but developmental and behavioural problems also rapidly become a serious concern. Later on, nearly all parents will have a child who becomes an adult with special needs, requiring specialised attention from professionals.     

Topiramate as add-on drug in severe myoclonic epilepsy in infancy: an Italian multicenter open trial

PURPOSE: This study was to evaluate the efficacy and safety of topiramate (TPM) in patients with severe myoclonic epilepsy in infancy (SMEI) and refractory seizures. METHODS: We performed a prospective multicentric open label add-on study in 18 patients (age 2-21 years, mean 9 years) with SMEI and refractory seizures of different types. TPM was added to one or two other baseline drugs and the efficacy was rated according to seizure type and frequency. RESULTS: TPM was initiated at a daily dose of 0.5-1 mg/kg, followed by a 2-week titration at increments of 1-3 mg/kg/24 h up to a maximum daily dose of 12 mg/kg. After a mean period of 11.9 months (range 2-24 months), three patients (16.7%) had 100% fewer seizures and ten patients (55.5%) had a more than 50% seizure decrease. In no patient there was a seizure worsening. Mild to moderate adverse events were present in four patients (22.2%), represented by weight loss, hypermenorrhoea, renal microlithiasis, nervousness and dysarthric speech. CONCLUSION: TPM may be a useful drug in patients with SMEI, being particularly effective against generalized tonic-clonic seizures. Further studies are needed to evaluate the early use of this drug in such a severe syndrome.     

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.     

Epileptic encephalopathies: a brief overview.

Epileptic encephalopathies are conditions in which neurologic deterioration is attributable entirely or partly to epileptic activity. It can be due to very frequent or severe seizures and/or to subcontinuous paroxysmal interictal activity. The former mainly consists of Dravet syndrome, in which patients have seizures from the middle of the first year of life and repeat episodes of severe febrile status epilepticus and migrating partial epilepsy in infancy, in which from the first trimester of life, partial seizures affect various areas of the cortex randomly and in a subcontinuous fashion. In Rasmussen syndrome, also, epileptic activity contributes at least partly to the neurologic deterioration. Subcontinuous paroxysmal interictal activity affects newborn infants with suppression bursts, thus consisting in either Ohtahara syndrome or neonatal myoclonic encephalopathy. In infants, it is either myoclonic epilepsy of nonprogressive encephalopathy or West syndrome. In school-age children, it consists of various types of generalized seizures combined with slow spike waves of the Lennox-Gastaut syndrome, myoclonic-astatic epilepsy, and continuous spike waves in slow sleep combined with various motor or cognitive deficits including negative myoclonus, orofacial dyspraxia, Landau-Kleffner syndrome, and frontal lobe syndrome. Treatment differs for all of these syndromes. It is important to avoid potential drug-induced worsening, and valproate is preferred when a definitive diagnosis is not reached in children and especially infants.     

Lamotrigine can be beneficial in patients with Dravet syndrome

Dravet syndrome, a severe infantile epilepsy syndrome, is typically resistant to anti‐epileptic drugs (AED). Lamotrigine (LTG), an AED that is effective for both focal and generalized seizures, has been reported to aggravate seizures in Dravet syndrome. Therefore, LTG is usually avoided in Dravet syndrome. We describe two adults and a child with Dravet syndrome in whom LTG resulted in decreased seizure duration and frequency. This benefit was highlighted in each patient when LTG was withdrawn after 6 to 15 years, and resulted in an increased frequency of convulsive seizures together with longer seizure duration. A 25‐year‐old male required hospital admission for frequent seizures for the first time in 7 years, 6 weeks after ceasing LTG. Reintroduction of LTG improved seizure control, suggesting that in some patients with Dravet syndrome, LTG may be beneficial.     

Levetiracetam in patients with generalised epilepsy and myoclonic seizures: an open label study.

PURPOSE: To evaluate the efficacy and tolerability of levetiracetam (LEV) as either 'de novo' (monotherapy) or 'add-on' therapy in patients with different generalised epilepsies characterised by myoclonic seizures from an observational study. METHODS: We evaluated 35 patients (21 female, mean age 24.7 years) with different types of generalised epilepsies (juvenile myoclonic epilepsy (JME), severe myoclonic epilepsy of infancy (SMEI), Lennox-Gastaut syndrome (LGS), myoclonic-astatic epilepsy (MAE), myoclonic absences (MA), benign myoclonic epilepsy in infancy (BMEI) and 4 patients had unspecified epileptic syndromes). Patients received LEV as de novo monotherapy or add-on therapy. Seizure frequency changes and adverse events were observed. Follow-up was conducted for a period of 12 months after treatment. RESULTS: Patients received LEV 2000-3000 mg/day as de novo (n = 8) and as add-on therapy. In total, 29 (82%) of the 35 patients achieved > or = 50% seizure frequency reduction, 15 (42%) patients achieved seizure freedom while a further 14 (40%) patients achieved > or = 50-99% seizure frequency reduction. Six (17%) patients discontinued LEV due to inefficacy or seizure worsening. Not even a single patient discontinued due to adverse effects. CONCLUSIONS: Our results confirm that LEV as de novo (monotherapy) and add-on therapy at doses between 2000 and 3000 mg/day effectively reduces myoclonic seizure frequency in patients with generalised epilepsy. LEV was also well-tolerated.