DRAVET SYNDROME (DS)

Overview

Dravet syndrome typically presents in the first year of life in a normal child with prolonged, febrile and afebrile, focal (usually hemiclonic) or generalized tonic-clonic seizures. Other seizure types including myoclonic and atypical absence seizures appear between the age of 1 and 4 years. Seizures are usually intractable and from the second year of life children demonstrate cognitive and behaviour impairments. The clinical diagnosis is supported by the presence of abnormalities in the sodium channel gene SCN1A (found in over 80% of cases).

NOTE Dravet syndrome is a syndrome with developmental and epileptic encephalopathy.

Clinical context

Seizure onset is typically between 3-9 months (median 6 months, range 1-20 months). Both sexes are affected. Antecedent, birth and neonatal history is normal. Neurological exam and head size is normal at seizure onset. Seizures are frequently triggered by fever, heat, illness or immunization. Episodes of status epilepticus are common before 5 years of age. Seizures that are drug resistant are expected throughout life. Development is typically normal in the first year of life, with plateauing or regression resulting in impairments seen from 12-60 months of age. Walking may be mildly delayed and gait instability is present. Patients may have attentional disorders, most have intellectual impairment (ranging from mild to severe) in time. A characteristic crouch gait may be seen by adolescence.

CAUTION Anti-seizure medications that have sodium channel blocking properties may aggravate seizures in this syndrome.

CAUTION Tonic seizures and epileptic spasms are not expected, if present consider other epilepsy syndromes.