Last week we learned how epilepsy is defined and classified. Let's continue this week into the subcategories. Focal onset seizures can be subcategorized into aware and impaired awareness (describing the person’s level of consciousness) then further divided into motor or non-motor (describing clinical manifestations or semiology) during an event. The onset features can allow identification of the area of the brain, lobe or hemisphere that is involved in seizure onset and propagation.
Focal seizures can spread widely in the brain to engage bilateral networks, including cortical and subcortical structures, resulting in a tonic-clonic seizure with loss of consciousness. This seizure type is known as a focal to bilateral tonic clonic seizure.
This type of seizure has other symptoms that occur first, such as changes in sensation, emotions, thinking, or experiences.
Focal sensory seizure involves a sensation being experienced at seizure onset, without objective clinical signs of a seizure evident to the observer.
Focal cognitive seizure involves an alteration in a cognitive function (which can be a deficit or a positive phenomenon such as forced thought), which occurs at seizure onset.
Focal autonomic seizures are characterized by alterations in systems controlled by the autonomic nervous system at seizure onset.
Focal emotional seizures are characterized by alterations in mood or emotion, or the appearance of altered emotion without the subjective emotion, at seizure onset.