What is the primary feature of the EEG during a seizure?

The primary feature of the EEG during a seizure is high amplitude rhythmic activity. During a seizure, there is a sudden and excessive electrical discharge of neurons in the brain. This leads to the generation of abnormal brain wave patterns that are characterized by high amplitude spikes or sharp waves, which can be rhythmic in nature. This rhythmic activity is typically observed in bursts and indicates a state of hyper-excitability in the brain's electrical activity.

High amplitude rhythmic activity is a key signature that distinguishes various types of seizures, whether they are focal or generalized. Observing this pattern on an EEG can assist clinicians in diagnosing the type and origin of the seizure, enabling appropriate management and treatment options. The presence of such pronounced activity stands in stark contrast to other potential EEG patterns that might occur under different circumstances.