Focal autonomic seizures are characterized by alterations in systems controlled by the autonomic nervous system at seizure onset. These may occur with or without objective clinical signs of a seizure evident to the observer. Focal autonomic seizures can be further described using the following descriptors:
CAUTION Ictal asystole of sufficient duration (> 5 seconds) to cause reduced brain perfusion may result in loss of body tone, stiffening and/or tonic-clonic movements.
NOTE If the focal seizure is not characterized by this feature at the very outset of the seizure, it is not used to classify the seizure, it is instead used as a seizure descriptor, after the seizure is classified according to its onset feature.
NOTE Focal autonomic seizures with predominantly subjectively experienced phenomena are one type of epileptic 'aura'. An 'aura' is an subjective experience (which may be sensory, emotional, autonomic or cognitive) felt by the individual having a seizure. The 'aura' reflects the initial seizure discharge in the brain. It may be an isolated phenomenon or progress to a focal motor seizure, to a focal impaired awareness seizure or to a focal to bilateral tonic-clonic seizure. An aura is also known as a "warning".