Epilepsy Classification

-Summary:

Epilepsy is made up of a heterogeneous set of diseases with a high prevalence and is one of the most frequent causes of consultation in a Neurology service.

It can be defined as an alteration of the brain characterized by the sustained predisposition to generate seizures, epileptic seizures (CE) and by the neurobiological, cognitive, psychological and social consequences of this alteration, and requiring at least the existence of one CE.

It is one of the diseases that most affect the quality of life of the patient.

-Development:

The last classification after 2017 defines and modifies several types:

-Partial is replaced by focal, awareness is used as a classifier for focal seizures; the terms discognitive, simple partial, complex partial, psychic, and secondarily generalized are dropped.

New types of focal seizures include automatisms, behavioral arrest, hyperkinetic, autonomic, cognitive, and emotional; atonic, clonic, epileptic spasm, myoclonic, and tonic seizures may be focal or generalized in onset.

Focal to bilateral tonic-clonic seizures replace secondarily generalized seizures.
The new types of generalized seizures are: absence with palpebral myoclonus, absence myoclonic, myoclonic-atonic, myoclonic-tonic-clonic; and seizures of unknown onset may have features that still allow them to be classified.

Gastaut, proposed a modern classification in 1964.

Lennox-Gastaut syndrome is a form of severe epilepsy that begins in childhood between 3 and 5 years of age. It is characterized by multiple types of seizures and by intellectual disability.

Common seizure types are tonic seizures (in which muscles stiffen and twitch uncontrollably) and atypical absence seizures (very brief partial or complete loss of consciousness).

In addition, many affected individuals can sustain sudden falls that can cause serious or life-threatening injury due to sudden loss of muscle tone (described as «atonic») or abnormal muscle contraction (described as «tonic»).

Most seizures are brief, but in more than two-thirds of cases there are prolonged periods of seizure activity (known as status epilepticus) or episodes of many seizures occurring together.

Most children with Lennox-Gastaut syndrome have intellectual disabilities or learning problems that get worse over time. There may be additional neurological abnormalities, and behavioral problems and delayed development of motor skills.

Orgasm-induced seizures are a very rare epileptic phenomenon characterized by complex partial seizures with or without secondary generalization, or by primarily generalized idiopathic epilepsy, triggered by sexual orgasm. Seizures usually begin immediately, shortly after or a few hours after reaching orgasm, last a few seconds or minutes, and are followed, in very rare cases, by an intense migraine.

The principle of the Types of Crisis Working Group was a reference from Albert Einstein, “to make things as simple as possible, but not simpler”.

The motivations for revising the 1981 Crisis Classification are listed below:

1. Some types of seizures, for example tonic seizures or epileptic spasms, may have a focal or generalized onset.

2. The lack of knowledge about the start of a crisis makes it unclassifiable and difficult to discuss with the 1981 system.

3. Retrospective seizure descriptions often do not specify level of consciousness or whether consciousness is preserved or impaired, although paramount to many seizures, it is a tricky concept.

4. Some terms in current use do not have high levels of community acceptance or public understanding, such as: “psychic”, “partial”, “simple partial”, “complex partial”, and “discognitive”.

5. Some important types of crises are not included.

The 2017 classification allows for the addition of a limited number of qualifiers for seizures of unknown onset in order to better characterize them.

Seizures of unknown onset may be referred to by the single word “not classified” or with additional features, including motor, non-motor, tonic-clonic, epileptic spasm, behavioral arrest.

A seizure type of unknown onset may be further classified as focal or generalized onset, but any associated manifestations (eg, tonic-clonic) of the previously unclassified seizure will continue to apply.

In this sense, the term «unknown start» is a way of locating the crisis due to unknown behavior and is not a characteristic of it.

The basic crisis classification framework used since 1981 has been maintained. Focal Versus Partial In 1981, the Commission declined to designate a crisis that might involve an entire hemisphere as «focal,» so the term «partial» was preferred.

The terminology places some modern emphasis on networks, yet the term «partial» conveys a sense of part of a crisis, rather than a location or anatomical system.

The term «focal» is more understandable in terms of the location of the onset of a seizure.

Focal was defined as “originating in networks limited to one hemisphere.

These networks may be discretely located or more widely distributed.

Focal seizures can originate in subcortical structures. Widespread crises from the outset were defined as “originating at some point, and rapidly involving bilaterally distributed networks.”

Classifying a seizure as apparently of generalized onset does not rule out an undocumented focal onset due to the limitations of our current clinical methods, but this is more a matter of correcting the diagnosis than one of classification.

In addition, focal seizures can quickly involve bilateral networks, while classification is based on unilateral onset.
For some types of seizures, for example epileptic spasms, the distinction of focal versus generalized onset may require careful study of video-EEG monitoring, or the type of onset may be unknown.

A distinction between focal and generalized onset is practical, and may change with advances in the ability to characterize seizure onset.

The focality of seizure onset can be inferred from the pattern of coincidence with known focal-onset seizures, even when the focality is not strictly clear in terms of the observed manifestations.

A seizure is focal, for example, when it begins with déjà vu and then progresses to loss of consciousness and responsiveness, lip smacking, and hand rubbing for a minute.

There is nothing inherently «focal» in the description, but video-EEG monitoring of countless similar seizures has previously demonstrated focal onset.

If the type of epilepsy is known, the onset of the seizure can be presumed even when it is not observed; for example, an absence seizure in a person known to have juvenile absence epilepsy.

Clinicians have long been aware that so-called generalized seizures, for example an absence seizure with generalized spike-wave activity on the EEG, do not manifest equally in all parts of the brain.

The Task Force emphasized the concept of bilateral, rather than generalized, involving some seizures, since seizures can be bilateral without compromising all brain networks.

Bilateral manifestations are not necessarily symmetrical. The term “focal to bilateral tonic-clonic” replaced “secondarily generalized”.

The term “generalized” stuck to generalized crises from the start. Unknown Onset Clinicians often hear about the unobserved onset of tonic-clonic seizures.

Perhaps the patient was asleep, alone, or the observers were too distracted by the seizure manifestations to notice the focal features.

There should be an opportunity to tentatively classify these seizures, even in the absence of knowledge about their origin.

The Task Force therefore suggested a more detailed description of seizures of unknown onset, when key features are observed during the course of the seizure, such as tonic-clonic activity or behavioral arrest.

The Task Force recommends classifying a seizure as focal-onset or generalized only when there is a high degree of confidence (eg, ≥ 80%, arbitrarily chosen to match the usually allowable beta error) in the accuracy of the determination, of Otherwise, the crisis should remain unclassified until the information is available.

It may be impossible to classify a seizure, either because of incomplete information or because of the unusual nature of the seizure, in which case it is called an unclassified seizure.

The unclassified categorization should be used only for the exceptional situation in which the clinician is confident that the event is a seizure, but cannot classify it.

Consciousness and reactivity The 1981 classification and the 2010 revision suggested a fundamental distinction between seizures with loss or alteration of consciousness and those without alteration of it.

Focal, autonomic, behavioral arrest, cognitive, emotional, and hyperkinetic automatisms are new types of seizures. Focal to bilateral tonic-clonic seizures is a new type that replaces the term secondarily generalized focal seizure.

New Generalized Seizure Types Relative to the 1981 classification, the new generalized seizure type scheme includes: absence with eyelid myoclonus, atonic myoclonic, and myoclonic-tonic-clonic (although clonic onset of tonic-clonic seizures was mentioned in the publication of 1981).

Seizures with eyelid myoclonus could logically have been placed in the motor category, but since eyelid myoclonus is more significant as a feature of absence seizures, it was placed in the nonmotor/absence category.

Frequently, seizures with eyelid myoclonus may show focal features.45 Similarly, myoclonic absence seizures potentially have both absence and motor features, and could have been placed in either group.

Epileptic spasms are seizures represented in the category of focal, generalized, and unknown onset, and the distinction may require video-EEG recording.

The term «epileptic» is implied for each type of seizure, but explicitly stated for epileptic spasms, due to the ambiguity of the word «spasm» in neurological language.

For seizures, lorazepan, midazolam, propofol, thiopental, or pentobarbital is recommended.

-Absence seizures:

Absence seizures, also known as petit mal or typical absences, are a type of generalized seizure characterized by brief episodes of altered consciousness or «absences» and abnormal activity on the electroencephalogram.
The first to use the term petit mal (in Spanish: small evil) to name these episodes was the French psychiatrist Jean Étienne Dominique Esquirol.

Epidemiology
Absence seizures occur in 25% of patients with epilepsy and can occur alone or more frequently in combination with other types of seizures.

They are typical of young people, generally under 20 years of age, although they present mainly during childhood, which is why they can be confused with inattention and affect school performance.
Signs and symptoms

The main and characteristic symptom is the sudden deterioration of consciousness, which is usually brief and lasts only a few seconds.

During the episode, the person interrupts their activities and remains static and with a fixed gaze, and may occasionally present small gesticulations or blinks.

Normally, at the end of the crisis they continue with what they were doing without remembering what happened. They tend to be repetitive and occur several times throughout the day.

Diagnosis
The suspicion is mainly clinical, the presence of sudden episodes of interruption of activities, conversation or gait, accompanied by fixed gaze, blinking and absence of movement, among others, guides towards the diagnostic possibility.

Although nuclear magnetic resonance scans can be useful to rule out other pathologies, the only confirmatory diagnostic test is the electroencephalogram, where spikes and slow wave complexes appear.

Treatment:

Ethosuximide(zarontin), valporic acid(depakine), lamotrigine(lamictal), Lacosamide(vimpac), Topiramate(topamax).

The drug of first choice for isolated absence seizures is ethosuximide, but it is not recommended in the case of combined tonic-clonic seizures, as it can aggravate them.

In the case of combined crises, magnesium valproate, which has a broad spectrum, is more effective.

-References:

-Berg AT, Berkovic SF, Brodie MJ, et al. Revised terminology and concepts for organization of seizures and epilepsies: report of the ILAE Commission on Classification and Terminology, 2005–2009. Epilepsy 2010;51:676–685. 2. Engel J Jr. Report of the ILAE classification core group. Epilepsy 2006;47:1558–1568.

-Gastaut H, Magnus O, Caveness W, et al. A proposed international classification of epileptic seizures. Epilepsy 1964;5:297–306. 4. Gastaut H. Classification of the epilepsies. Proposal for an international classification. Epilepsy 1969;10(Suppl.):14–21.

-keywords:

Classification of epilepsy, absence seizures, focal seizures, generalized seizures, tonic-clonic seizures, sexual dysfunction and epilepsy, treatment of seizures, treatment of absence seizures.
Epilepsy and MRI, epilepsy and EEG