Focal onset seizures (previously called partial seizures) start in a specific part of the brain in one hemisphere, and may or may not spread to other parts of the brain. Focal seizures are described on the basis of their onset (motor or non-motor) and whether or not the person is aware during the seizure. Focal onset seizures include:
Focal aware seizures
During these seizures the person is aware and may experience feelings such as déjà vu, an unpleasant smell or taste, or sensations such as ‘butterflies’ or nausea. These seizures may also involve motor activity (such as involuntary and brief jerking of an arm or leg) or autonomic behaviours (such as fiddling with clothing or pointing). These seizures used to be called ‘simple partial seizures’.
In some cases, this type of seizure can come before another seizure type (e.g. tonic-clonic seizure). A feeling or movement that indicates a bigger seizure is going to happen is sometimes called an ‘aura’, although they are actually part of the seizure.
Focal impaired awareness seizures
During these seizures the person may appear confused and dazed, and may do strange and repetitive actions (such as fiddling with their clothes, making chewing movements with their mouth or uttering unusual sounds). These seizures used to be called ‘complex partial seizures’.