What EEG pattern is often seen in patients with absence seizures?

• A. Generalized theta waves with slowing.
• B. Delta waves only.
• C. 3-Hz spike-and-wave discharges.
• D. Focal sharp waves in temporal lobe.

Answer: (C)

Absence seizures show a generalized, bilateral, synchronous pattern on EEG called 3-Hz spike-and-wave discharges. This rhythm reflects abnormal thalamocortical oscillations that underpin the brief loss of consciousness and subtle automatisms seen in these seizures. The 3-Hz frequency is particularly characteristic for typical absence seizures, and hyperventilation during EEG can often provoke it in susceptible individuals, which helps confirm the diagnosis.

Other patterns don’t fit absence seizures: generalized theta waves with slowing usually indicate diffuse brain dysfunction or drowsiness, not a discrete epileptic discharge; delta waves alone are seen in deep sleep or severe brain dysfunction; focal sharp waves in the temporal lobe point to focal epilepsy rather than a generalized syndrome. Thus, the 3-Hz spike-and-wave discharges best explain the EEG finding in absence seizures.