This syndrome, also termed Dravet syndrome, begins during the first year of life. The first seizure (frequently febrile) is either generalized or unilateral. The febrile seizures tend to be long and recurrent. When the children are between 1 and 4 years of age, either generalized or partial myoclonic seizures develop. Partial seizures often occur as well.
Retardation in psychomotor development is evident from the second year of life, including:
- corticospinal tract dysfunction
- nonictal myoclonus
This type of epilepsy is very resistant to all forms of treatment, and all affected children are mentally retarded.
De novo truncating mutations of the SCN1A gene on 2p24 encoding for the neuronal voltage-gated sodium channel alpha1 subunit have been found in this syndrome.73 Interestingly, inherited missense mutations of the same gene will result in generalized epilepsy, febrile seizures plus (GEFS+).
At the time of the first febrile seizure, the EEG is usually normal and without any paroxysmal abnormalities. Between ages 1 and 2 years, generalized spike-and-wave or polyspike-and-wave activity is seen during the seizures. When absence seizures occur, they are also associated with generalized spike-and-wave activity. Focal and multifocal spikes and sharp waves are also seen.
Adapted from: Holmes GL. Classification of seizures and the epilepsies. In: Schachter SC, Schomer DL, eds. The comprehensive evaluation and treatment of epilepsy. San Diego, CA: Academic Press; 1997. p. 1-36.
With permission from Elsevier (www.elsevier.com)