For the first time in almost three decades, the classification for epileptic seizures has been updated. The new system formally recognizes some seizure types, provides additional information on causes, and replaces obscure or questionable words and terms with more meaningful ones, the authors say.
Three articles related to the new classification, developed through a process initiated by the International League Against Epilepsy (ILAE) in 2010, were published online March 9 in Epilepsia. Preliminary information on the new classification system was presented at the American Epilepsy Society meeting in December of 2016, and reported by Medscape Medical News at that time.
Huge scientific advances have occurred since the last epilepsy classification was developed in 1989, Ingrid E. Scheffer, MBBS, PhD, professor, Departments of Medicine and Pediatrics, University of Melbourne, Australia, and lead author of one of the articles, told Medscape Medical News.
For example, no epilepsy genes had been discovered back in the 1980s, but now 300 to 400 have been identified, with more to come. Furthermore, imaging technology has “completely revolutionized our ability to understand the structure and networks of the brain,” said Dr Scheffer.
Although the previous seizure classification was partially updated several times over the years, “it did not cover several important seizure types,” said Robert S. Fisher, MD, PhD, professor, Stanford Department of Neurology & Neurological Sciences, California. In addition, he added, “the terminology was obscure to nonphysicians — and even many physicians.”
Dr Fisher chaired the Task Force on Seizure Classification and was lead author of the other two of the three articles, one a practical manual describing how to apply the new seizure classification, the other a position paper on classification and terminology.
In an interview, he summarized the important aspects of the new system. Seizures, he said, 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.
“This is the first classification where you’re allowed to say the word ‘unknown’,” noted Dr Scheffer. “With the previous classification, we had this dreadful word — ‘cryptogenic’ — and that was cryptogenic to the world because nobody knew what it meant.”
Focal seizures can now be subdivided into those with awareness (formerly called “simple partial seizures”) and with impaired awareness (formerly called “complex partial seizures”), said Dr Fisher.
Seizures can be subcategorized into focal motor onset and focal nonmotor onset. Several seizure types previously listed only in the generalized category, such as tonic, atonic, clonic, myoclonic, and infantile spasms (now epileptic spasms), now can also have focal onset, said Dr Fisher.
Other seizure types, such as autonomic, behavior arrest, automatisms, emotional, cognitive, and sensory, are more clearly defined than in the past classification, he said.
In addition to the terms “simple partial” and “complex partial” being eliminated, so, too, are the terms “dyscognitive,” “psychic,” and “secondarily generalized,” he added.
In their second paper, Dr Fisher and colleagues emphasized that the new classification system is operational (or practical) and not based on fundamental mechanisms. Current knowledge is insufficient to form a scientifically based classification, he said.
In her paper, Dr Scheffer elaborated on the multilevel framework for the new classifications.
Determining seizure type (focal, generalized, or unknown onset) may be the maximum possible level of diagnosis, said Dr Scheffer. This may be the case, for example, where there’s no access to electroencephalography (EEG) or video or imaging studies of if the patient has had only a single seizure.
Another level of diagnosis is determining epilepsy type. In addition to focal, generalized, and unknown, there’s a new category of “combined generalized and focal.” Examples of this are Dravet and Lennox-Gastaut syndromes, said Dr Scheffer.
Clinicians may also be able to determine the epilepsy syndrome, a cluster of features incorporating seizure types, EEG, and imaging features that tend to occur together. Some well-recognized syndromes include childhood absence epilepsy, benign epilepsy with centro-temporal spikes, and West and Dravet syndromes.
Dr Scheffer noted, however, that there has never been a formal classification of syndromes by the ILAE.
The Task Force determined that a subgroup of “generalized epilepsies” called idiopathic generalized epilepsies (IGEs) is an acceptable classification for four well-established epilepsy syndromes: childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and generalized tonic-clonic seizures alone (formerly known as “generalized tonic-clonic seizures on awakening” but modified in recognition that seizures can occur at any time of day).
Along with other experts, Dr Scheffer, whose research centers on the genetics of epilepsy, preferred the term “genetic generalized epilepsy.” But this suggestion “was highly controversial,” with “explosive feedback” from different parts of the world, she said. In some countries, there is still a concerning stigma associated with a condition being called genetic.
“We left ‘IGE’ to use for those four syndromes that people really held on to, but where physicians are comfortable, they can use the term ‘genetic generalized epilepsy’.”
Causes, said Dr Scheffer, can be grouped into structural, genetic, infectious (the most common in some regions of the world), metabolic, immune, and unknown. “An etiological diagnosis should be considered from when the patient first presents and at each step along the diagnostic pathway.”
Determining comorbidities is another important step in the classification system. “There’s increasing awareness that many of the epilepsies are associated with comorbidities such as learning, psychological, and behavioral problems,” said Dr Scheffer.
These range in type and severity and can include subtle learning difficulties, intellectual disability, psychiatric features (such as autism spectrum disorder and depression), and psychosocial concerns.
“Like etiology, it is important that the presence of comorbidities be considered for every patient with epilepsy at each stage of classification, enabling earlier identification, diagnosis and appropriate management,” said Dr Scheffer.
The paper for which she was lead author elaborated on some new terminology and definitions. For example, the term “epileptic encephalopathy” refers to situations where the epileptic activity itself contributes to severe cognitive and behavioral impairment above and beyond what might be expected form the underlying pathology (eg, cortical malformations).
The concept of “epileptic encephalopathy” can be used more widely than just for the severe epilepsies with onset in infancy and childhood, said Dr Scheffer. It can be applied to single gene disorders, but a single gene may cause an epileptic encephalopathy in some patients and in others an epilepsy that is self-limited (referring to the likely spontaneous resolution).
A “key component” of the epileptic encephalopathy concept is that amelioration of the epileptiform activity may improve the developmental consequences of the disorder, Dr Scheffer and colleagues write. “This is a critical issue from a clinical perspective and one often mirrored in the observation of families and clinicians.”
Because some severe genetic disorders have developmental consequences in addition to the epileptic component — for example, Dravet syndrome — the term “developmental and epileptic encephalopathy” may be used where appropriate.
Also where appropriate, the word “benign” should be replaced with “self-limited” or “pharmaco-responsive” (meaning it will likely be controlled with appropriate therapy) in describing an epilepsy syndrome, said Dr Scheffer.
“The word ‘benign’ means it’s fine, you’ll grow out of it; there will be no problem, but the reality is that epilepsy is not really benign.”
Even though some childhood epilepsies might be self-limited, there’s increasing research pointing to psychosocial fallout with, for example, subtle learning problems or sleep issues.
The terms “malignant” and “catastrophic” will be removed from the epilepsy lexicon because of their “serious and devastating connotations,” said Dr Scheffer.
For an extensive teaching resource about seizure types and epilepsy syndromes, Dr Scheffer recommends that clinicians and other healthcare professionals visit www.epilepsydiagnosis.org, which is operated by the ILAE.
Source: Medscape, article by P. Anderson