Classification of epileptic seizures
Since seizures are classified mainly on the basis of a terminology agreement developed by an expert committee, and not on the basis of any fundamental provisions, the classification scheme will undoubtedly change as knowledge about epilepsy grows.
Epileptic seizures are divided into two broad categories: partial (focal) and generalized. Partial epileptic seizures are generated in a limited area of the brain, which leads to the appearance of focal symptoms, for example, twitching in the limbs or face, sensitivity disorder and even memory changes (as, for example, in temporal seizures). Generalized seizures result from the involvement of the entire brain. Although some experts believe that these seizures are generated in deep brain structures that are widely projected onto the cortical surface and as a result of the manifestation of dysfunction of different parts of the brain occur almost simultaneously, the true mechanisms of development of generalized seizures remain unknown.
Partial epileptic seizures are divided into simple partial (without loss of consciousness or memory) and complex partial (with loss of consciousness or memory). Simple partial epileptic seizures can be manifested by twitching, pathological sensations, visual images, sounds, smells, distortion of perception. If epileptic activity extends to the autonomic structures, there is a sensation of tidal or nausea. With all types of simple partial seizures, the patient remains conscious and remembers everything that happens to him. If the patient is confused or he can not remember what happened to him during the seizure, then the fit is defined as a complex partial.
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International classification of epileptic seizures (simplified version)
Partial epileptic seizures (generated in a restricted area of the brain)
- Simple (without disturbance of consciousness or memory):
- mental (pathological ideas or altered perception)
- vegetative (sensation of warmth, nausea, tidal, etc.)
- Complex (with a violation of consciousness or memory)
- with aura (forerunners) or without aura
- with automatisms or without automatisms
- Secondary generalized
Generalized epileptic seizures (generated by an extensive brain area)
- Absenses (petit mal)
- Tonic-clonic (grand-mall
- Atonic (drop-fits)
Unclassified epileptic seizures
Complex partial epileptic seizures were previously referred to as psychomotor, temporal or limbic seizures. Complex partial seizures can begin with an aura, a harbinger of a seizure, which is often manifested by the sensations of "already seen" (deja vu), nausea, warmth, crawling, or distorted perception. However, about half of patients with complex partial seizures do not remember the aura. During a complex partial seizure, patients often perform automated actions - they fumigate around themselves, lick their lips, take off their clothes, aimlessly hang around, repeat pointless phrases. Such senseless actions are called automatisms - they are observed in 75% of patients with complex partial seizures.
Generalized epileptic seizures are divided into several categories. Absensives, formerly referred to as petit mal (small seizures), usually begin in childhood. They are short-term bouts of loss of consciousness, accompanied by a stiff look, twitching of the eyelids or a nod of the head. Absenses can be difficult to distinguish from complex partial seizures, which are also accompanied by stasis, but absences usually last a shorter time than complex partial seizures, and are characterized by a faster recovery of consciousness. In the differential diagnosis of these types of seizures, EEG is useful (see below).
Generalized tonic-clonic epileptic seizures, formerly known as grand mal, begin with a sudden loss of consciousness and tonic tension of the trunk and limbs, followed by rhythmic clonic twitching of the limbs. The patient produces a cry, caused by contraction of the respiratory muscles with closed vocal cords. Fit (ictus) typically lasts 1 to 3 minutes, followed by a postictal (postictal) condition characterized by lethargy, drowsiness, confusion, which can last for hours. The postictal period can occur after any seizure.
Epileptic activity, arising in a certain zone, can spread to the entire brain, causing a generalized tonic-clonic seizure. It is important to distinguish between true (primarily generalized) large convulsive seizures from partial seizures with secondary generalization, since these two types of seizures may require the use of different antiepileptic drugs. Moreover, with secondary generalized tonic-clonic seizures, surgical treatment is possible, while in primary generalized tonic-clonic seizures it is not performed, since there is no explicit source (epileptic focus) that could be removed.
Atonic epileptic seizures usually occur after brain damage. When the atonic seizure suddenly decreases muscle tone and the patient can fall to the ground. In some cases, patients are forced to wear a helmet, which prevents serious damage to the head.
Myoclonic seizure is characterized by a short-term rapid twitching or a series of twitchings, usually less coordinated and organized than with a generalized tonic-clonic seizure.
An epileptic status is a seizure or series of seizures that continue, without interrupting the restoration of consciousness and other functions, for more than 30 minutes. Epileptic status is an urgent condition, as it can lead to damage to neurons and to somatic complications. There are several types of epileptic status, corresponding to different types of epileptic seizures. The status of simple partial seizures is known as epilepsia partialis continua (constant partial epilepsy). The status of complex partial seizures and absences is indicated by several terms, including as an unconvulsive status, peak-wave stupor, status of absences, epileptic twilight state. Recommendations for the diagnosis and treatment of epileptic status have been developed by a special working group on epileptic status.
A patient may have several types of seizures, one of which can go into the other as electrical activity spreads through the brain. Usually, a simple partial fit goes into a complex partial, and that one into a secondary generalized tonic-clonic seizure. In some cases, antiepileptic drugs increase the ability of the brain to limit the spread of epileptic activity.
In adults, most often (more than 40% of cases) there are complex partial seizures. Simple partial ones are detected in 20% of cases, primary generalized tonic-clonic seizures - in 20% of cases, absences in 10% of cases, and other types of seizures - in 10% of cases. In children, absences are more common than in adults.
Classification of epileptic syndromes
Classification of epileptic seizures does not carry information about the patient's condition, causes, severity, prognosis of the disease. Hence the need for an additional classification scheme that allows to qualify epileptic syndromes. This is a more voluminous classification, which includes not only a description of the type of seizures, but also information about other clinical features of the disease. Some of these epileptic syndromes are described below.
Infantile spasms / Vest syndrome
Infantile spasms occur in children aged 3 months to 3 years and are characterized by sudden flexion spasms and a high risk of mental retardation. During flexion cramps, the child suddenly unbend limbs, the body tilts forward, a scream is issued. The episode lasts a few seconds, but can be repeated several times per hour. With EEG, gypsarhythmia with high-amplitude peaks and disorganized high-amplitude background activity is revealed. Early active treatment can reduce the risk of developing persistent mental retardation. Although valproic acid and benzodiazepines are considered drugs of choice, their effectiveness is low. Of the new drugs, the most promising results were obtained with the use of vigabatrin and felbamate, as well as lamotrigine and topiramate.
The Lennox-Gasto syndrome is a relatively rare condition (with the exception of epileptological centers, where it constitutes a significant proportion of patients with treatment-resistant seizures). It manifests itself in the following characteristic features:
- polymorphic seizures, usually including atonic and tonic seizures;
- variable mental retardation;
- EEG changes, including slow peak-wave activity.
Although the syndrome usually begins in childhood, adults can suffer from it. The Lennox-Gastaut syndrome is very difficult to treat, only 10-20% of patients have satisfactory results. Since seizures are almost always multifocal, surgical treatment with this disease is ineffective, although collosotomy can reduce the degree of suddenness of a seizure and prevent injuries. In spite of the fact that valproic acid, benzodiazepines, lamotrigine, vigabatrin, topiramate and felbamate can be useful in this condition, the results of treatment are often unsatisfactory.
Febrile epileptic seizures
Febrile epileptic seizures are provoked by fever and are usually manifested in children between the ages of 6 months and 5 years of tonic-clonic seizures. Febrile seizures should be distinguished from seizures caused by more serious diseases, such as meningitis. Febrile epileptic seizures often frighten parents very much, but usually have a benign character. Although they are considered as a risk factor for the subsequent development of complex partial seizures, there is no conclusive evidence that preventing febrile seizures reduces this risk. In most children with febrile seizures, epilepsy does not subsequently develop. In this regard, the advisability of prescribing antiepileptic drugs that can have an adverse effect on the child's learning and personality is being questioned. To prevent febrile seizures, phenobarbital is usually used. But it is effective only with daily intake, as the seizure usually occurs immediately after the body temperature rises. Prolonged daily intake of phenobarbital leads to hyperactivity, behavioral disorders and learning in a significant percentage of children. Many pediatric neurologists believe that treating febrile seizures is more adversely affected than episodic seizures that may never recur, and are advised to refrain from treatment. Several trials with febrile seizures of other antiepileptic drugs did not yield encouraging results. Thus, the problem of treating febrile seizures remains controversial.
Benign epilepsy of childhood with central-temporal peaks
Benign epilepsy of childhood with central-temporal peaks (benign Rolandic epilepsy) is a genetically determined disease, usually manifested in childhood or adolescence (from 6 years to 21 years). Rolandova is called the area in the brain, located in front of the border of the frontal and parietal lobes. Seizures that are generated in this zone are manifested by twitches and paresthesias in the face or hands, sometimes turning into secondary generalized tonic-clonic epileptic seizures. In this condition, the EEG usually reveals pronounced peaks in the central and temporal regions. Seizures often occur when falling asleep. The term "benign" is used not because seizures may manifest as minimal symptoms, but because of a very favorable long-term prognosis. With age, seizures almost always regress. The use of antiepileptic drugs is not necessary, but with frequent or severe seizures use means effective for partial seizures (most often carbamazepine).
Juvenile myoclonic epilepsy
Juvenile myoclonic epilepsy (JME) is the most common cause of generalized seizures at a young age. In contrast to benign epilepsy with central-temporal peaks, there is no age-related regression of these seizures. UME is a genetically determined epileptic syndrome, usually starting in older children and adolescents. In some family cases, a pathological gene was found on chromosome 6. With JME, morning myoclonus (twitching of limbs or head) and episodic generalized tonic-clonic convulsions are usually observed. EEG with JUME usually reveals generalized complexes "peak-wave" frequency of 3-6 / s. High efficacy of antiepileptic agents, including valproic acid and benzodiazepines, is characteristic. If these funds are intolerant, lamotrigine and topiramate can be used.
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