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- | Severe myoclonic epilepsy in infancy (SME) was described by Charlotte Dravet in 1978. In the Revised ILAE classification of epilepsies, the SMEI is named " | + | Severe myoclonic epilepsy in infancy (SME) was described by Charlotte Dravet in 1978. In the Revised ILAE classification of epilepsies, the SMEI is named " |
===== Epidemiology ===== | ===== Epidemiology ===== | ||
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* **Eye closure:** The eye closure may facilitate the occurrence of localized and generalized abnormalities. | * **Eye closure:** The eye closure may facilitate the occurrence of localized and generalized abnormalities. | ||
* **Sleep:** Sleep is usually well structured with physiological patterns and cyclic organization, | * **Sleep:** Sleep is usually well structured with physiological patterns and cyclic organization, | ||
- | * **Photosensitivity: | + | * **Photosensitivity: |
* **Fever Sensitivity: | * **Fever Sensitivity: | ||
* Epileptic seizures in SME are very sensitive to body temperature elevation itself, regardless of etiology, either due to infection, hot baths, or even physical exercise. In the Japanese population, frequent seizures triggered by fever and Japanese style hot-water immersion have been reported. The convulsive seizures are often prolonged and develop into status during such episodes. | * Epileptic seizures in SME are very sensitive to body temperature elevation itself, regardless of etiology, either due to infection, hot baths, or even physical exercise. In the Japanese population, frequent seizures triggered by fever and Japanese style hot-water immersion have been reported. The convulsive seizures are often prolonged and develop into status during such episodes. | ||
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===== Genetics ===== | ===== Genetics ===== | ||
* Between 70% and 80% of patients carry sodium channel α1 subunit gene ([[https:// | * Between 70% and 80% of patients carry sodium channel α1 subunit gene ([[https:// | ||
- | * truncating mutations account for about 40% and have a significant correlation with an earlier age of seizures onset[(: | + | * truncating mutations account for about 40% and have a significant correlation with an earlier age of seizures onset[(: |
* remaining SCN1A mutations comprise [[splice_site_mutation|splice-site]] and [[https:// | * remaining SCN1A mutations comprise [[splice_site_mutation|splice-site]] and [[https:// | ||
* mutations are randomly distributed across the SCN1A protein | * mutations are randomly distributed across the SCN1A protein | ||
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* A majority of cases have a family history of epilepsy or febrile seizures (FS). | * A majority of cases have a family history of epilepsy or febrile seizures (FS). | ||
===== Pathophysiology ===== | ===== Pathophysiology ===== | ||
- | * The voltage-gated sodium channel is responsible for the initiation of action potentials and, therefore, is involved in neuronal excitability[(: | + | * The voltage-gated sodium channel is responsible for the initiation of action potentials and, therefore, is involved in neuronal excitability[(: |
* The α subunit has 4 homologous domains, with 6 transmembrane segments each, that form the voltage sensor and ion-conducting pore[(: | * The α subunit has 4 homologous domains, with 6 transmembrane segments each, that form the voltage sensor and ion-conducting pore[(: | ||
* Mutations cause either a gain or a loss of function[(: | * Mutations cause either a gain or a loss of function[(: | ||
- | * A mouse model of DS showed selective loss of sodium current in the hippocampal γ-aminobutyric acid(GABA)–mediated inhibitory interneurons. Failure of inhibition leading to excitation is hence a potential pathogenetic mechanism in this mutation causing DS[(: | + | * A mouse model of DS showed selective loss of sodium current in the hippocampal γ-aminobutyric acid(GABA)–mediated inhibitory interneurons. Failure of inhibition leading to excitation is hence a potential pathogenetic mechanism in this mutation causing DS[(: |
===== Outcome ===== | ===== Outcome ===== | ||
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Stiripentol -The use of Stiripentol, | Stiripentol -The use of Stiripentol, | ||
- | A ketogenic diet may be helpful in some cases and has recently shown to be beneficial in children receiving a combination of Stiripentol, | + | A ketogenic diet may be helpful in some cases and has recently shown to be beneficial in children receiving a combination of Stiripentol, |
It is very important to aggressively treat the status episodes and prophylaxis of infections and hyperthermia. Rectal diazepam can prevent the evolution into status in the case prolonged or repeated convulsive seizures. IV Benzodiazepines are best for status particularly Clonazepam (CZP), Midazolam along with Chloral hydrate or barbiturates. | It is very important to aggressively treat the status episodes and prophylaxis of infections and hyperthermia. Rectal diazepam can prevent the evolution into status in the case prolonged or repeated convulsive seizures. IV Benzodiazepines are best for status particularly Clonazepam (CZP), Midazolam along with Chloral hydrate or barbiturates. | ||
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===== Epilepsy surgery ===== | ===== Epilepsy surgery ===== | ||
- | Andrade et al (2010)[(: | + | Andrade et al (2010)[(: |
The presumed topography of the epileptogenic areas involves preferentially the mesial frontal lobe, the central area, sometimes the parietal and, even, the occipital lobes. Few interictal foci are localized in the temporal area. Surprisingly a hippocampal sclerosis has not been shown in the MRI of these patients who had prolonged and repeated severe FS[(: | The presumed topography of the epileptogenic areas involves preferentially the mesial frontal lobe, the central area, sometimes the parietal and, even, the occipital lobes. Few interictal foci are localized in the temporal area. Surprisingly a hippocampal sclerosis has not been shown in the MRI of these patients who had prolonged and repeated severe FS[(: | ||
===== Cannabidiol ===== | ===== Cannabidiol ===== | ||
- | * Clinical trials show that cannabidiol reduces the number of convulsive and non-convulsive seizures when compared with usual care[(: | + | * Clinical trials show that cannabidiol reduces the number of convulsive and non-convulsive seizures when compared with usual care[(: |
* Cannabidiol (CBD) has been shown to cut seizure occurrence by almost 50% in patients with Dravet syndrome in doses of 10 mg/kg per day and 20 mg/kg per day, based on the results of a phase 3 study[(: | * Cannabidiol (CBD) has been shown to cut seizure occurrence by almost 50% in patients with Dravet syndrome in doses of 10 mg/kg per day and 20 mg/kg per day, based on the results of a phase 3 study[(: | ||
- | * In a separate study in Dravet syndrome, the median frequency of convulsive seizures per month declined by -6.5 from 12.4 at baseline for patients treated with cannabidiol. In the placebo group, seizures declined by just 0.8 from baseline. There were 43% of patients achieving a 50% reduction with cannabidiol compared with 27% with placebo (OR, 2.00; P = .08)[(: | + | * In a separate study in Dravet syndrome, the median frequency of convulsive seizures per month declined by -6.5 from 12.4 at baseline for patients treated with cannabidiol. In the placebo group, seizures declined by just 0.8 from baseline. There were 43% of patients achieving a 50% reduction with cannabidiol compared with 27% with placebo (OR, 2.00; P = .08)[(: |
- | * Interim interim analysis of the safety, efficacy, and patient-reported outcomes from GWPCARE5 showed that long-term CBD treatment had an acceptable safety profile and led to sustained, clinically meaningful reductions in seizure frequency in patients with treatment-resistant DS[(: | + | * Interim interim analysis of the safety, efficacy, and patient-reported outcomes from GWPCARE5 showed that long-term CBD treatment had an acceptable safety profile and led to sustained, clinically meaningful reductions in seizure frequency in patients with treatment-resistant DS[(: |
===== Differential Diagnoses ===== | ===== Differential Diagnoses ===== | ||
* [[Febrile Seizures]] (FS) | * [[Febrile Seizures]] (FS) | ||
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| SCN2B | GEFS+ | | | SCN2B | GEFS+ | | ||
- | Catterall et al (2010)[(: | + | Catterall et al (2010)[(: |
Mild impairment of NaV1.1 channel function causes febrile seizures; moderate to severe impairment of NaV1.1 function by missense mutations and/or altered mRNA processing causes the range of phenotypes observed in GEFS+ epilepsy; and very severe to complete loss of function causes SMEI. | Mild impairment of NaV1.1 channel function causes febrile seizures; moderate to severe impairment of NaV1.1 function by missense mutations and/or altered mRNA processing causes the range of phenotypes observed in GEFS+ epilepsy; and very severe to complete loss of function causes SMEI. |