Differences between atypical and typical absence seizures
| Features | Atypical absences | Typical absences |
|---|---|---|
| Onset and termination | Usually gradual | Abrupt |
| Responsiveness | Decreased but not abolished | Varies from mild to severe |
| Changes in tone | Usually pronounced | Usually mild |
| Duration | Usually long sometimes minutes | Usually brief; never >30–40 s |
| Postictal recovery | Cognitive impairment may persist | Immediately |
| Interictal EEG | Background often abnormal with frequent discharges of various types | Background usually normal sometimes with typical IGE discharges |
| Ictal EEG | Slow (<2.5 Hz) spike and wave | Fast (>2.5 Hz) spike and slow wave |
| Normal neurological and mental state | Exceptional | As a rule |
| Other types of seizures | Atonic and tonic seizures of symptomatic generalised epilepsies | Depend on IGE syndrome (myoclonic jerks, GTCS or both) |
| Prognosis | Commonly bad | Commonly good |
Adapted from Panayiotopoulos CP. A clinical Guide to Epileptic Syndromes and their treatment 2007.
IGE, idiopathic generalised epilepsy, GTCS, generalised tonic clonic seizures.