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Updates to a 1980s classification system of epilepsies and seizure types, which identify several types of seizure not captured in the previous version, are expected to allow more fully informed decisions regarding epilepsy diagnosis, treatment, and research, researchers reported.

Applying the right therapy often depends upon knowing the precise type of seizure, according to , of Stanford, the lead author of the and, which was published in Epilepsia.

"This more precise and transparent classification system gives words to patients and families to describe their seizures," Fisher told MedPage Today.

Treatment indications and approvals are predicated on specific seizure types, so it's important that classification "gracefully map to existing indications for drug or device usage," the researchers noted.

Developed over several years by experts from the International League Against Epilepsy, the revised classification "creates a modern, common language that is more accessible to patients, and allows physicians, patients, and families to communicate more clearly with each other," said , of Baylor College of Medicine and President of the American Epilepsy Society. Mizrahi was not involved in the revisions.

"For physicians and researchers, the classification can be used to be more specific about seizure types with the goal of tailoring diagnosis, management and, hopefully, the development of new therapies," Mizrahi told MedPage Today.

Epilepsy is a disease characterized by spontaneously recurrent seizures or one seizure with high chance for another. The classification of the different types of epilepsy is based in part on the type of seizures that a person has, but also on many other clinical factors, such as the neurological exam, brain imaging studies, genetics, immune status, prognosis, and other factors, Fisher explained. "Therefore, the epilepsy classification is much broader than the seizure classification, and considers the whole clinical picture."

"An etiologic diagnosis should be considered from when the patient first presents, and at each step along the diagnostic pathway," wrote , of the University of Melbourne and lead author of , adding that a patient's epilepsy may be classified into more than one etiological category.

Other key changes include replacement of the term "benign" with "self-limited" and "pharmacoresponsive" where appropriate, and use of the term "developmental and epileptic encephalopathy" to be applied in whole or in part where appropriate.

Mention of a seizure type should bring to mind a specific entity, albeit sometimes with subcategories and variations on a theme, the researchers said. The classification chart is columnar, but not hierarchical, meaning that levels can be skipped, they added.

While seizures are still classified by their onset as focal (emerging in one brain hemisphere) or generalized (emerging in both hemispheres), a new category of "unknown onset seizures" permits a limited classification even if the onset is unknown, they noted.

Focal seizures are optionally subdivided into those with retained awareness, i.e. of self and environment, even if patients are immobile (formerly called simple partial seizures), and have impaired awareness (formerly called complex partial seizures), Fisher said. Additional sub-categorization is into focal motor and non-motor onset.

Several seizure types previously listed only in the generalized category, such as tonic, atonic, clonic, myoclonic, infantile spasms (now epileptic spasms) now can also have focal onset. Other seizure types, such as autonomic, behavior arrest, automatisms, emotional, cognitive, sensory, are more clearly defined than in the past classification.

Focal motor seizure descriptions include:

• Automatism: a more or less coordinated, purposeless, repetitive seizure
• Motor activity
• Hyperkinetic: pedaling, thrashing

Focal non-motor seizures descriptions include:

• Autonomic: presents with gastrointestinal sensations, a sense of heat or cold, flushing, goosebumps, palpitations, sexual arousal, respiratory changes
• Behavior arrest: involves cessation of movement and unresponsiveness.
• Cognitive: the patient reports or exhibits deficits in language, thinking or associated higher cortical functions during seizures, which outweigh other manifestations of the seizure
• Emotional: the patient reports or exhibits emotional changes, including fear, anxiety, agitation, anger, paranoia, pleasure, joy, ecstasy, laughing (gelastic), or crying (dacrystic)

While epilepsy is now understood as a disease involving neocortical, thalamocortical, limbic, and brainstem networks rather than simply local brain abnormalities, not enough is currently known to allow seizure classification based on networks, the researchers wrote.

The prior classification of seizures lasted 35 years. It is unknown how long this one will last or how long it will take to be fully adopted, Fisher said.

"The ultimate classification will emerge when we know the underlying science of epilepsy and can explain why there are different seizure types," he said.