New information concerning the treatment of childhood absence epilepsy
Childhood absence epilepsy (CAE) is a common syndrome of early childhood, in which seizures usually begin between the ages of four and nine years. It is seen slightly more often in girls than in boys, and those affected can experience up to several hundred absence seizures per day. An absence seizure is a sudden loss of awareness that normally lasts between five and twenty seconds, and this is commonly mistaken for daydreaming (particularly in the class room).
CAE doesn’t often cause developmental delay, and most children ‘grow out of it’ when they reach puberty (they are said to be in remission). Seizure control is still very important, however, because recurrent absences can affect the child’s learning ability. Ethosuximide and sodium valproate are the anti-epileptic drugs (AEDs) of choice for CAE, but it is not known whether giving one over the other as a first treatment is linked to a higher chance of remission in the longer term. Researchers in Illinois have recently investigated this.
During the study the team recruited 59 children who had just been diagnosed with CAE, and had been prescribed either sodium valproate (this will be known as valproate – 18 children) or ethosuximide (41 children) as a first treatment. The two groups were very similar in terms of their clinical traits; except that a greater proportion of the valproate group had irregular EEG features (the importance of this will be discussed later). Children with convulsive seizures or significant abnormalities on brain imaging were excluded, as these are not typical features of CAE.
After recruitment, the two therapy groups were followed for approximately 10 years. The scientists were particularly interested in 1) the proportion of children in each group that became seizure free soon after treatment, and 2) the proportion in each that, by the end of the study, had been seizure free without medication (known as complete remission) for at least five years.
The initial success rates of the two drugs were found to be very similar (59% for ethosuximide and 56% for valproate). However, while complete remission occurred in 31 children (76%) in the ethosuximide group, only 7 (39%) who were treated with valproate achieved this. It is important to note that children with irregular EEG features were shown to be less likely to enter complete remission than those without irregular EEG features (50% vs 71%). Yet even when the scientists accounted for the greater proportion of irregular EEGs in the valproate group statistically, ethosuximide was still linked to a higher rate of complete remission. By the end of the study, larger proportions of children in the ethosuximide group had achieved five-year and ten-year remission, both with and without continued treatment.
Impact of findings
These findings are important, because they suggest that prescribing ethosuximide (rather than valproate) in the first instance is linked to a better long-term outcome for children with CAE. This information will be very valuable to Paediatric Neurologists in managing their patients.