What EEG pattern characterizes simple absence seizures?

The characteristic EEG pattern for simple absence seizures is a 3/second generalized spike-and-wave rhythm. This pattern is identifiable by its specific frequency and morphology, consisting of a burst of spikes followed by a slow wave, occurring at a rate of approximately 3 Hz. During an absence seizure, this rhythmic activity reflects a disruption in the normal electrical activity of the brain associated with the temporary loss of awareness or consciousness that defines the seizure. The presence of this 3 Hz spike-and-wave pattern signifies a generalized seizure originating from the thalamocortical connections, uniquely associating it with the absence seizure phenomenon.

In contrast, fast beta activity typically pertains to alert and engaged brain states and does not characterize absence seizures. Slow theta activity is often linked with drowsiness or sleep stages rather than seizures. Rolandic spikes are related to focal seizures originating in the central region of the brain, particularly in children, and do not represent absence seizures. Therefore, the identification of the 3/second generalized spike-and-wave pattern is crucial for diagnosing simple absence seizures.