Absence is a separate form of epileptic paroxysms, occurring with a short-term blackout without visible convulsions. It can be accompanied by disorders of muscle tone (atony, hypertonicity, myoclonia) and simple automatism. It is often combined with other forms of epileptic seizures. The basis of diagnosis is electroencephalography. Cerebral MRI is shown to detect organic changes in brain structures. Treatment is carried out by an epileptologist, based on mono- or polytherapy with anticonvulsants, selected individually.
The first mention of absences dates back to 1705. The term was introduced into wide use in 1824. Absense in French means "absence", which accurately characterizes the main symptom - the disconnection of consciousness. Among specialists in the field of epileptology and neurology, the synonymous name "petit mal" is common - a small seizure. Absense is included in the structure of various forms of idiopathic and symptomatic generalized epilepsy. It is most typical for children. The peak incidence occurs at 4-7 years. In most patients, abscess is combined with other types of epileptic seizures. With its predominance in the clinical picture of the disease, they speak of absentee epilepsy.
The basis of epileptic paroxysms is an imbalance of the processes of inhibition and excitation of neurons of the cerebral cortex. Due to the occurrence of these changes , the absenteeism is divided into:
Triggers provoking absences can be deep, forced breathing (hyperventilation), excessive visual stimulation (flashes of light, flashing of bright dots), mental and physical overload, lack of sleep (sleep deprivation). The development of an attack on the background of hyperventilation is observed in 90% of patients.
The mechanisms of occurrence of absences are not precisely established. The results of the conducted studies indicate the joint role of the cortex and thalamus in the initiation of seizures, the participation of inhibitory and excitatory transmitters. Perhaps the pathogenesis is based on genetically determined abnormal properties of neurons.
Researchers believe that absences are formed against the background of the dominance of inhibitory activity, in contrast to convulsive paroxysms, which are a consequence of hyperexcitation. Excessive inhibitory activity of the cortex can develop compensatorily to suppress previous pathological arousal. The appearance of absences in childhood and their frequent disappearance by the age of 18-20 indicates the connection of the disease with the processes of maturation of the brain.
Absences can have a different character, accompanied by muscular and motor disorders. This formed the basis of the generally accepted division of absentee episodes into:
The paroxysm lasts from several to 30 seconds, during which the patient loses conscious perception. From the outside, you can notice the absent appearance of the patient at the time of the attack, his sudden "shutdown" from activity, a short freezing. Pronounced absenteeism occurs with the cessation of the initiated action, speech; light - with a sharply delayed continuation of the activity preceding the attack.
In the first variant, after the paroxysm, the resumption of movements and speech is noted exactly from the moment where they stopped. Patients describe the absentee state as "an attack of inhibition", "failure", "falling out of reality", "sudden stupor", "trance". In the post-onset period, the state of health is normal, without peculiarities. Short-term typical absences often occur unnoticed by the patient and others.
Complex absences are more noticeable due to the accompanying motor and tonic phenomena. Atonic paroxysms occur with a decrease in muscle tone, which leads to lowering of the arms, tilting of the head, sometimes sliding off the chair. Total atony causes a fall. Tonic episodes are accompanied by increased muscle tone. In accordance with the localization of tonic changes, there is flexion or extension of the limbs, tilting of the head, bending of the body.
Abscess with a myoclonic component is characterized by the presence of myoclonia - low-amplitude muscle contractions in the form of twitching. There is a twitching of the corner of the mouth, chin, one or both eyelids, eyeballs. Myoclonia can be symmetrical and asymmetrical. The automatisms accompanying absences have the character of repetitive simple movements: chewing, rubbing hands, muttering, unbuttoning buttons.
The frequency of absences can vary significantly from 2-3 to several dozen times a day. Absentee episodes may be the only form of epileptic seizures in a patient, which is typical for childhood absentee epilepsy. They can dominate among different types of paroxysms (myoclonia, tonic-clonic convulsions), as in juvenile absentee epilepsy, or enter the structure of the epileptic syndrome, where other forms of seizures predominate.
The epileptic status of absences is observed in 30% of patients. Lasts an average of 2-8 hours, may last several days. It is characterized by varying degrees of confusion from slow thinking to complete disorientation and disturbed behavior. The motor sphere and coordination are preserved. Stereotypical monosyllabic phrases prevail in speech. Automatism is noted in 20% of cases.
The consequences of an atonic abscess are injuries received during a fall (bruises, fractures, dislocations, TBI). Serious complications are the delay and decrease in intellectual development (oligophrenia, dementia). Their occurrence and degree of progression are associated with the underlying disease.
Diagnostic measures are designed to establish the presence of absences and differentiate the disease, of which they are an integral part. A detailed survey about the course of the attack of the patient and his relatives is important. Further diagnostic procedures include:
Differential diagnosis is performed with paroxysms of focal epilepsy. The latter are distinguished by complex motor automatism, complex hallucinations, post-onset symptoms; they are not provoked by hyperventilation.
The difficulties of therapy are associated with the emergence of resistance. In this regard, an important point is a differentiated approach to the appointment of anticonvulsants, according to the type and etiology of paroxysms.
Monotherapy of typical absences, acting as the only type of epiprimes, is carried out by valproic acid, ethosuximide. These drugs are effective in 75% of patients. In resistant cases, it is recommended to combine monotherapy with small doses of lamotrigine.
Monotherapy of combined idiopathic forms of epilepsy, where typical absences are combined with other variants of seizures, requires the appointment of anticonvulsants effective against all types of existing paroxysms. Valproates and levetiracetam are used, which affect both absences and myoclonic and tonic-clonic seizures. With a combination of absences and tonic-clonic convulsive paroxysms, lamotrigine is effective.
Monotherapy of atypical absences is carried out with valproic acid, lamotrigine, phenytoin. Often, a combination with steroid therapy gives a positive effect. Thiagabine, carbamazepine, phenobarbital can aggravate symptoms. Often atypical absences are poorly treated with one drug.
Polytherapy is necessary in cases of weak effectiveness of monotherapy. The selection of a combination of anticonvulsants and dosage is made by an epileptologist individually, depending on the disease.
Gradual reduction of the dose of anticonvulsant and cancellation of antiepileptic therapy are possible against the background of persistent remission for 2-3 years. Secondary cases of epilepsy require therapy of the underlying disease and symptomatic treatment. If the epileptic syndrome proceeds with a decrease or incomplete development of cognitive abilities, classes with a psychologist, neuropsychological correction, complex psychological support are necessary.
The success of antiepileptic treatment depends on the disease. In the vast majority of cases, children's idiopathic absences pass by the age of 20. Juvenile absences persist in adulthood in 30% of patients. The prognosis is worse for Lennox-Gastaut syndrome, characterized by epiprime resistance and progressive cognitive disorder. The prognosis of secondary paroxysms depends entirely on the effectiveness of treatment of causal pathology.
Prevention is reduced to the prevention and timely treatment of organic cerebral diseases, the exclusion of the effects on the fetus of various teratogenic influences that can cause structural brain abnormalities, genetic disorders.