What are the diagnostic criteria for Dravet (Epilepsy, Severe Myoclonic) syndrome?

From the Guidelines

Dravet syndrome is diagnosed based on several key clinical criteria, including multiple seizure types beginning in the first year of life, developmental delay, and genetic mutations, particularly in the SCN1A gene 1. The diagnostic criteria for Dravet syndrome involve a combination of clinical features and genetic testing.

• The presence of multiple seizure types, including febrile, myoclonic, focal, and atypical absence seizures, is a key diagnostic criterion.
• Normal early development followed by developmental delay and regression, particularly affecting speech, motor skills, and cognition, is also characteristic of Dravet syndrome.
• Genetic testing is crucial for confirmation, with approximately 80-90% of cases showing mutations in the SCN1A gene, which encodes a sodium channel essential for neuronal function 1.
• Additional features supporting the diagnosis include a family history of epilepsy or febrile seizures, normal initial EEG and brain imaging, and the development of gait abnormalities or ataxia.
• Early diagnosis is important for appropriate management, which often includes medications like stiripentol, valproate, clobazam, and dietary therapies such as the ketogenic diet, while avoiding sodium channel blockers like carbamazepine and lamotrigine which can worsen seizures in these patients 1. The International League Against Epilepsy (ILAE) defines epilepsy as having at least two unprovoked seizures occurring more than 24 hours apart, one unprovoked seizure and a probability of further seizures similar to the general recurrence risk after two unprovoked seizures, or diagnosis of an epilepsy syndrome 1.
• Seizures are classified as focal onset, generalized onset, or unknown onset, and Dravet syndrome is characterized by multiple seizure types, including generalized and focal seizures 1. The diagnosis of Dravet syndrome requires a comprehensive evaluation of clinical features, genetic testing, and EEG and brain imaging results, with a focus on early diagnosis and appropriate management to improve outcomes 1.

From the Research

Diagnostic Criteria for Dravet Syndrome

The diagnostic criteria for Dravet syndrome, also known as severe myoclonic epilepsy in infancy, include:

• Prolonged seizures in the first year of life, often triggered by fever or illness 2, 3
• Initial seizures are frequently categorized as febrile seizures, but later develop into more complex seizure types, including myoclonic seizures 2, 3
• Normal EEG at onset, with no structural lesions on neuroimaging 2
• Early normal development, followed by signs of regression in the second year of life, including convulsive status epilepticus, alternating hemiconvulsions, and myoclonic seizures 2, 3
• Genetic testing can confirm the diagnosis, with mutations in the SCN1A gene being a common cause of Dravet syndrome 2, 3, 4, 5, 6

Clinical Presentation

The clinical presentation of Dravet syndrome includes:

• Complex febrile seizures in infancy, which can progress to refractory epilepsy with psychomotor regression 3
• High frequency of complex febrile seizures associated with recurrent febrile status epilepticus 3
• Developmental regression, including moderate to severe intellectual impairment, motor impairment, and behavioral abnormalities 4, 5, 6
• Characteristic crouching gait in later stages of the disease 4

Diagnosis and Confirmation

Diagnosis of Dravet syndrome can be confirmed by:

• Genetic testing, which can detect mutations in the SCN1A gene 2, 3, 4, 5, 6
• Clinical evaluation, including assessment of seizure types, developmental regression, and other clinical features 2, 3, 4, 5, 6