Which diagnostic test is most definitive for diagnosing absence seizures?

• A. CT scan
• B. EEG
• C. MRI
• D. PET

Answer: (B)

Absence seizures are diagnosed most definitively by EEG because they produce a distinctive electrical signature in the brain. During an absence event, the EEG shows generalized, rhythmic 3 Hz spike-and-wave discharges that reflect a brief, widespread disruption of consciousness driven by thalamocortical networks. This pattern is the key feature that confirms the diagnosis and isn’t captured by imaging alone.

Imaging studies like CT or MRI may be useful to rule out structural lesions, and PET can show metabolic information, but neither modality demonstrates the characteristic electrical activity that defines absence seizures. In practice, EEG, often with video monitoring (and sometimes triggered by hyperventilation to provoke the pattern), provides the definitive diagnostic evidence.