Seizures with hemiclonic features affecting face and limbs occur, and can alternate sides from seizure to seizure. Seizure features may include tonic features, vocalization, autonomic features and/or automatisms. Focal to bilateral tonic-clonic seizures may also occur. Seizures are brief (up to 3 minutes in duration). Apnoea and cyanosis commonly accompany seizures (seen in one third of seizures). Clusters of individually brief seizures may occur over hours or days, with the child behaving normally between seizures.