Severe myoclonic epilepsy of infancy

Severe Myoclonic Epilepsy of Infancy
Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Seizures, developmental delay
Complications	N/A
Onset	Infancy
Duration	Lifelong
Types	N/A
Causes	Genetic mutations
Risks	Family history
Diagnosis	Clinical evaluation, genetic testing
Differential diagnosis	N/A
Prevention	N/A
Treatment	Antiepileptic drugs, ketogenic diet
Medication	N/A
Prognosis	Variable
Frequency	N/A
Deaths	N/A

Severe Myoclonic Epilepsy of Infancy (SMEI), also known as Dravet syndrome, is a rare and severe form of epilepsy that begins in infancy. It is characterized by febrile seizures, developmental delay, and a variety of seizure types that are often resistant to treatment.

Epidemiology

SMEI is a rare condition, with an estimated incidence of 1 in 20,000 to 1 in 40,000 live births. It affects both males and females, although some studies suggest a slight male predominance.

Etiology

The majority of cases of SMEI are caused by mutations in the SCN1A gene, which encodes a subunit of the voltage-gated sodium channel. These mutations lead to dysfunctional sodium channels, which are crucial for the proper functioning of neurons.

Clinical Presentation

Seizure Types

The hallmark of SMEI is the presence of multiple types of seizures, including:

• Febrile seizures: These are often the first type of seizure to appear, typically occurring in the first year of life.
• Myoclonic seizures: Characterized by brief, shock-like muscle jerks.
• Generalized tonic-clonic seizures: These involve loss of consciousness and convulsive movements.
• Atypical absence seizures: Brief lapses in awareness.
• Focal seizures: Seizures that originate in one part of the brain.

Developmental Delay

Children with SMEI often experience developmental delays, particularly in language and motor skills. Cognitive impairment is common, and some children may develop autism spectrum disorder features.

Diagnosis

The diagnosis of SMEI is primarily clinical, based on the characteristic seizure types and developmental history. Genetic testing can confirm the diagnosis by identifying mutations in the SCN1A gene. Electroencephalogram (EEG) findings may show generalized spike-and-wave or polyspike activity.

Management

Pharmacological Treatment

Treatment of SMEI is challenging due to the drug-resistant nature of the seizures. Commonly used antiepileptic drugs include:

• Valproate
• Clobazam
• Stiripentol

Dietary Therapy

The ketogenic diet, a high-fat, low-carbohydrate diet, has been shown to reduce seizure frequency in some patients with SMEI.

Other Therapies

• Cannabidiol (CBD) has been approved for use in Dravet syndrome and may help reduce seizure frequency.
• Vagus nerve stimulation (VNS) is sometimes considered for patients who do not respond to medication.

Prognosis

The prognosis for individuals with SMEI is variable. While some children may experience a reduction in seizure frequency with age, others continue to have frequent seizures and significant developmental challenges. Lifelong management and support are often necessary.

See Also

• Epilepsy
• SCN1A
• Ketogenic diet

External Links

• Dravet Syndrome Foundation