A 7-year-old girl is brought to the paediatric neurology clinic by her mother, who reports that the child has been having multiple brief episodes of unresponsiveness throughout the day, often mistaken for "daydreaming" or inattention at school. During the clinical examination, hyperventilation for 4 minutes is performed, and the child experiences a clinical absence seizure with a vacant stare. The EEG during this episode shows the pattern marked **A** in the diagram. Which of the following is the most appropriate first-line antiepileptic drug for this patient?

Why Ethosuximide is right

The EEG pattern marked A — generalized, bilaterally synchronous 3 Hz spike-and-wave discharges provoked by hyperventilation — is the pathognomonic hallmark of childhood absence epilepsy (CAE). The clinical presentation (brief unresponsiveness, vacant stare, multiple daily episodes, school-age onset) combined with this EEG finding confirms CAE. Ethosuximide is the first-line drug for CAE, particularly when seizures are limited to absences. The landmark NEJM 2010 CAE Trial demonstrated that ethosuximide achieved absence-freedom in 62% of patients, superior to lamotrigine (58%) and more effective than valproate (29%) for absence control alone, while causing fewer attentional adverse effects than valproate. Ethosuximide works by blocking T-type calcium channels in the thalamocortical circuit, directly addressing the pathophysiology underlying the 3 Hz spike-and-wave pattern (Nelson 21e Ch 611; NEJM 2010;362:790).

Why each distractor is wrong

Nelson 21e Ch 611; NEJM 2010;362:790 (CAE Trial)