Absense 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. To detect organic changes in brain structures, cerebral MRI is shown. Treatment is carried out by an epileptologist, based on mono- or polytherapy with anticonvulsants, selected individually.
G40.3 Generalized idiopathic epilepsy and epileptic syndromes
The first mention of absense dates back to 1705. The term was introduced into wide use in 1824. Absense in French means “absense”, 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, absense is combined with other types of epileptic seizures. With its predominance in the clinical picture of the disease, they speak of absentee epilepsy.
Causes for absense
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 absense is divided into:
- Secondary. The factors causing changes in bioelectric activity are various organic lesions: encephalitis, cerebral abscess, brain tumor. In this case, absense is a consequence of the underlying disease, refers to symptomatic epilepsy.
- Idiopathic. It is not possible to establish the etiology. The genetic nature of the disorders is assumed, which is confirmed by family cases of epilepsy. Risk factors for the development of the disease are the age period of 4-10 years, episodes of febrile seizures in the anamnesis, the presence of relatives with epileptic seizures.
Triggers provoking absense 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 absense 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 absense 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 absense 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.
Absense can have a different character, accompanied by muscular and motor disorders. This formed the basis of the generally accepted division of absentee episodes into:
- Typical (simple) – there is a blackout of consciousness, lasting up to 30 seconds. There are no other symptoms. A flash of light, a loud sound can stop the attack. With mild forms, the patient can continue the activity started before the paroxysm (action, conversation), but does it slowly. A typical absense is characteristic of idiopathic epilepsy.
- Atypical (complex) — turning off consciousness is accompanied by changes in muscle tone, motor activity. The average duration is 5-20 seconds. Seizures are typical for symptomatic epilepsy. Depending on the type of musculoskeletal component, there are atonic, myoclonic, tonic, and automatic absense.
Symptoms of absense
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 absense 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 absense often occur unnoticed by the patient and others.
Complex absense 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 an increase in 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.
Absense 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 absense have the character of repetitive simple movements: chewing, rubbing hands, muttering, unbuttoning buttons.
The frequency of absense 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 absense 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 absense 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 absense 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:
- Neurologist’s examination. In cases of idiopathic epilepsy, the neurological status remains normal. It is possible to identify mental retardation, disorders of cognitive functions (memory, attention, thinking). With the secondary genesis of paroxysms, focal and general neurological symptoms are determined.
- Electroencephalography. EEG is the main diagnostic method. It is preferable to conduct an ictal video EEG. It is possible to register bioelectric activity during paroxysm by means of a provocative hyperventilation test. During the study, the patient counts the number of breaths aloud, which allows you to accurately determine the beginning of the absense. A typical EEG pattern is the presence of diffuse high-amplitude spikes and polyspikes with a frequency of >2.5 Hz.
- MRI of the brain. The study is necessary to identify/refute the presence of organic pathology provoking epileptic activity. It allows you to diagnose cerebral tuberculosis, encephalitis, tumors, brain development abnormalities.
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.
Treatment of absense
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 absense, 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 absense 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 absense and myoclonic and tonic-clonic seizures. With a combination of absense and tonic-clonic convulsive paroxysms, lamotrigine is effective.
- Monotherapy of atypical absense 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 absense 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.
Prognosis and prevention
The success of antiepileptic treatment depends on the disease. In the vast majority of cases, children’s idiopathic absense pass by the age of 20. Juvenile absense 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.