A 7-year-old girl presents with frequent episodes of brief staring spells occurring 20–30 times daily at school. Each episode lasts 5–15 seconds with abrupt onset and offset, subtle eyelid fluttering at 3 per second, and no postictal confusion. Hyperventilation in the clinic triggers a typical spell. EEG during hyperventilation shows the pattern marked **A** in the diagram. Which of the following is the most appropriate first-line antiepileptic drug for this diagnosis?

Why Ethosuximide is right

The pattern marked A—bilaterally synchronous, symmetric generalized 3 Hz spike-and-wave discharge provoked by hyperventilation—is the pathognomonic ictal EEG signature of childhood absence epilepsy (CAE). This electrographic pattern, combined with the clinical semiology (brief staring spells, eyelid clonus, no postictal state, normal background rhythm, and excellent prognosis), establishes the diagnosis. Ethosuximide is the first-line agent specifically for absence seizures without generalized tonic-clonic seizures because it selectively blocks T-type calcium channels in the thalamus, interrupting the thalamocortical oscillations that generate the 3 Hz spike-and-wave discharge. Pearl PL (2018) emphasizes that ethosuximide achieves seizure freedom in approximately 65–70% of CAE patients and remains the preferred initial therapy when generalized tonic-clonic seizures are absent.

Why each distractor is wrong

Pearl PL. Epilepsy Syndromes in Childhood. Continuum (Minneap Minn). 2018;24(1):186-209.