Types of generalized onset seizures
| Seizure Type | Semiology | EEG |
|---|---|---|
| Absence | Sudden behavioral arrest, staring, may have some automatisms. No aura, no postictal confusion. | Generalized 3-Hz spike-and-wave discharges, exacerbated by hyperventilation. Background usually normal. |
| Atypical absence | Sudden behavioral arrest and staring, but more prolonged with more prominent automatisms than absence. | Generalized 1.5-2.5-Hz spike-and-wave discharges. Often less regular and less symmetric than absence. Background usually abnormal. |
| Atonic | Sudden loss of tone in postural muscles, resulting in drop attacks. Usually with brief impairment of consciousness. Minimal postictal state. | Low-voltage fast activity, polyspike and wave, or electrodecrement. |
| Tonic | Generalized or occasionally asymmetric hypertonia. May have sudden or gradual onset. Seldom lasts more than 1 minute. Respiratory muscle contraction—“ictal cry.” | Often associated with generalized 10-Hz or faster activity. |
| Tonic–clonic | Loss of consciousness with initially generalized tonic contractions, followed by rhythmic generalized jerking of all four extremities. | Initially generalized 10-Hz activity in the tonic phase, followed by rhythmic spike-wave, slow-wave, or sharp-slow-wave activity. |
