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Mysterious epilepsy classification: How does ILAE define different epilepsy types?
In neurology, seizure types are classified based on seizure behavior, symptoms, and diagnostic tests. The epilepsy classification launched by the International League in Epilepsy (ILAE) in 2017 is the international standard for identifying epilepsy types. This classification is a revision of the 1981 ILAE epilepsy classification. It is important to distinguish between different types of epilepsy because different seizures may have different causes, consequences, and treatments.
Historical review
As early as 2500 BC, the Sumerians provided the first written records of epilepsy. Around 1050 BC, Babylonian scholars developed the first classification of epilepsy, inscribing their medical knowledge on stone tablets called Sakikku, or "all diseases." This early classification primarily identified febrile epilepsy, absence epilepsy, generalized tonic-clonic epilepsy, focal epilepsy, confusional epilepsy, and persistent epilepsy. Over time, prominent medical scientists such as Samuel-Auguste Tissot and Jean-Etienne Dominique Esquirol introduced more specific terms for these epileptic seizures.
Henry Gastout led the development of the ILAE epilepsy classification in 1969, further promoting research and progress in this field.
Classification of epilepsy attacks
A seizure is defined as a transient abnormality in symptoms or behavior resulting from an abnormal excess or synchronization of brain neuron activity. Seizures in epilepsy can be classified as either localized or generalized in origin. Specifically, epileptic seizures with localized onset originate from a biological neural network located within one cerebral hemisphere, whereas generalized onset seizures rapidly involve both cerebral hemispheres.
These classification improvements allow physicians to better distinguish between different seizure types based on epilepsy symptoms, behavior, neuroimaging, etiology, electroencephalography (EEG), and video recordings.
Distinction between states of consciousness
ILAE's classification also distinguishes between seizures with partial consciousness and seizures with impaired consciousness. If during an attack, the patient can recall what happened during the attack, it can be said to be awake; however, in an attack with impaired consciousness, the patient cannot clearly recall what happened even if part of the memory is damaged.
Motor and non-motor epilepsy
Motor seizures are characterized by marked movements, including increased or decreased contractions of muscles. Common motor seizures include brief muscle relaxation, sudden jerking of the hands and feet, and generalized tonic-clonic seizures. Non-motor epilepsy, on the other hand, may begin with sensory, cognitive or emotional symptoms, often accompanied by a sudden cessation of activity or impairment of consciousness.
These classifications help doctors better understand the nature of epilepsy and its potential treatment options.
ILAE 2017 classification of epilepsy types
In the ILAE 2017 classification, partial epilepsy can be further subdivided into three categories: awake, impaired consciousness, and undetermined consciousness. Each type can be attached with a more specific description to provide doctors with more complete diagnostic information.
Comparison between the old version and the new version
Compared with the previous 1981 classification, the 2017 version provides clearer divisions in terms of retention of consciousness and behavioral characteristics of attacks. Some terms from the 1981 edition are no longer used in the current classification, such as "simple partial epilepsy" or "complex partial epilepsy".
Persistent and subclinical epilepsy
Persistent epilepsy is a seizure that lasts longer than 30 minutes, or a series of seizures without the ability to return to a normal level of wakefulness. Subclinical epilepsy does not show obvious symptoms, but seizure patterns appear with EEG testing.
Future challenges
With the deepening of epilepsy research, the understanding and classification of epilepsy are also constantly evolving. How can we use these latest classifications for more accurate diagnosis and personalized treatment?
