Generalized epilepsy is a clinical concept that unites all forms of epilepsy, which are based on primary generalized epilepsy: absences, generalized myoclonic and tonic-clonic paroxysms. In most cases, it is idiopathic in nature. The basis of the diagnosis is the analysis of clinical data and EEG results. Additionally, an MRI or CT scan of the brain is performed. Treatment of generalized epilepsy consists in monotherapy with anticonvulsants (volproates, topiramate, lamotrigine, etc.), in rare cases, combination therapy is required.
Generalized epilepsy (GE) is a type of epilepsy in which epileptic paroxysms are accompanied by clinical and electroencephalographic signs of primary diffuse involvement of cerebral tissues in the process of epileptiform excitation. The basis of the clinical picture of this form of epilepsy is generalized epilepsy: absences, myoclonic and tonic-clonic paroxysms. Secondary generalized epilepsy does not belong to generalized epilepsy. However, since the beginning of the 21st century, some authors have begun to question the accuracy of the division into generalized and focal epilepsy.
Nevertheless, so far the concept of “generalized epilepsy” is widely used in practical neurology. Depending on the etiology, idiopathic and symptomatic GE are distinguished. The first is hereditary and occupies about a third of all cases of epilepsy, the second is secondary, occurs against the background of organic brain damage, and is less common than idiopathic forms.
Idiopathic generalized epilepsy (IGE) has no other causes than genetic determinism. Its main pathogenetic factor is usually channelopathy, which causes membrane instability of neurons, leading to diffuse epileptiform activity. The probability of having a child with epilepsy in the presence of the disease in one of the parents does not exceed 10%. About 3% are monogenic forms of IGE (frontal epilepsy inherited by autosomal dominant principle, benign family convulsions of newborns, etc.), in which the disease is determined by a defect in one gene, and polygenic forms (for example, juvenile myoclonic epilepsy, childhood absentee epilepsy) caused by mutations of several genes.
The etiofactors of the occurrence of symptomatic GE can be traumatic brain injuries, neurointoxications, infectious diseases (encephalitis, meningitis), tumors (brain gliomas, lymphomas, multiple metastatic brain tumors), dysmetabolic conditions (hypoxia, hypoglycemia, lipidosis, phenylketonuria), fever, hereditary pathology (for example, tuberous sclerosis). Symptomatic generalized epilepsy in children may occur due to fetal hypoxia, intrauterine infection, birth trauma of a newborn, brain development abnormalities. Among symptomatic epilepsy, the majority of cases occur in the focal form, the generalized variant is quite rare.
Idiopathic generalized epilepsy manifests in childhood and adolescence (mainly up to 21 years). It is not accompanied by other clinical symptoms, except for epileptic paroxysms of a primary generalized nature. In the neurological status, in some cases, scattered symptoms are observed, extremely rarely — focal. Cognitive functions are not impaired; in some cases, intellectual disorders may be of a transient nature, which sometimes affects the academic performance of schoolchildren. Recent studies have shown the presence of mild intellectual decline in 3-10% of patients with IGE, the possibility of some affective and personal changes.
Symptomatic generalized epilepsy occurs at any age period against the background of the underlying disease, with hereditary pathology and congenital malformations — more often in early childhood. Generalized epiprimes are only part of its clinical picture. Depending on the underlying disease, there are cerebral and focal manifestations. Intellectual decline often develops, and children have oligophrenia.
Typical absences are paroxysms of short—term loss of consciousness lasting up to 30 seconds. Clinically, the attack looks like a patient fading with an absent look. A vegetative component is possible in the form of hyperemia or pallor of the face, hypersalivation. Absenteeism can be accompanied by unconscious movements: twitching of individual facial muscles, licking of lips, rolling of eyes, etc. In the presence of such a motor component, absenteeism belongs to the category of complex, in its absence — to the category of simple. Ictal (during the epiprime) The EEG registers generalized peak-wave complexes having a frequency of 3 Hz. Typically, the frequency of peaks drops from the beginning of the attack (3-4 Hz) to its end (2-2.5 Hz). Atypical absences have a slightly different EEG pattern: irregular peak waves whose frequency does not exceed 2.5 Hz. Despite diffuse EEG changes, the primary generalized nature of atypical absences is currently being questioned.
Generalized tonic-clonic seizures are characterized by a change in tonic tension of all muscle groups (tonic phase) and intermittent muscle contractions (clonic phase) against the background of complete loss of consciousness. During the paroxysm, the patient falls, at the beginning for 30-40 seconds. there is a tonic phase, then a clonic phase lasting up to 5 minutes. At the end of the attack, involuntary urination occurs, then complete muscle relaxation and the patient usually falls asleep. In some cases, isolated clonic or tonic paroxysms are noted.
Generalized myoclonic seizures are diffuse rapid asynchronous muscle twitches caused by involuntary contraction of individual muscle bundles. They may not affect all the muscles of the body, but they are always symmetrical. Often such contractions cause involuntary movements in the limbs, the involvement of the leg muscles leads to a fall. Consciousness during the period of paroxysm is preserved, sometimes deafness is observed. The ictal EEG registers symmetrical polypic wave complexes with a frequency from 3 to 6 Hz.
The diagnostic basis is the assessment of clinical and electroencephalographic data. A normal basic EEG rhythm is typical for IGE, although it may slow down somewhat. In symptomatic forms, the basic rhythm can be changed depending on the disease. In both cases, diffuse peak-wave activity is recorded on the EEG in the inter-approach interval, the distinctive features of which are primary generalized character, symmetry and bilateral synchronicity.
In order to exclude / identify the symptomatic nature of epilepsy, CT or MRI of the brain is used in the diagnosis. With their help, it is possible to visualize organic brain damage. If a primary genetic disease is suspected, a geneticist’s consultation is indicated, a genealogical study is carried out, DNA diagnostics is possible. In cases of exclusion of organic pathology and the presence of other diseases in which epilepsy is secondary, a neurologist diagnoses idiopathic epilepsy.
It is necessary to differentiate GE from focal and secondary generalized forms, drop attacks, somatogenic fainting (with severe arrhythmia, chronic lung pathology), hypoglycemic states, psychogenic paroxysms (with hysterical neurosis, schizophrenia), episodes of transient global amnesia, somnambulism.
Treatment and prognosis
The choice of anticonvulsant therapy depends on the type of epilepsy. In most cases, the first-line drugs are valproates, topiramate, lamotrigine, ethosuximide, levetiracetam. As a rule, idiopathic variants of generalized epilepsy respond well to therapy. In approximately 75% of patients, monotherapy is sufficient. In case of resistance, a combination of valproate and lamotrigine is used. Some forms of IGE (for example, childhood abscess epilepsy, IGE with isolated generalized seizures) are a contraindication for the appointment of carbamazepine, phenobarbital, oxcarbazepine, vigabatrin.
At the beginning of treatment, an individual selection of the anticonvulsant and its dose is carried out. After achieving complete remission (absence of epiprimes) against the background of taking the drug, a gradual reduction in dosage is carried out only after 3 years of its constant intake, provided that there was not a single paroxysm during this period. In symptomatic HE, in parallel with antiepileptic pharmaceuticals, the treatment of the underlying disease is carried out, if possible.
The GE forecast largely depends on its shape. Idiopathic generalized epilepsy is not accompanied by mental retardation and cognitive decline, and has a relatively favorable prognosis. However, it often recurs against the background of dose reduction or complete withdrawal of the anticonvulsant. The outcome of symptomatic GE is closely related to the course of the underlying disease. With anomalies of development and the impossibility of effective treatment of the underlying disease, epiprimes turn out to be resistant to the therapy. In other cases (with TBI, encephalitis), generalized epilepsy may act as a residual consequence of a cerebral lesion.