Benign myoclonic epilepsy of infancy is among the genetically determined diseases transmitted by the polygenic type of inheritance. Is a little-studied pathology, since it is quite rare.
DMEM is included in the group of idiopathic generalized epilepsy, however, the connection with other nosologies from this group has not been established. At the moment, it is unknown what gene mutation leads to the development of DMEM.
When collecting family history, it turns out that parents of 40% of patients suffer or have suffered from epilepsy or febrile seizures. Pathogenetic development of myoclonic attacks is due to the occurrence of a discharge of rapid generalized spike waves (SV) or polyspike waves (PSV). Their frequency is 3 Hz or more, and the duration is 1-3 seconds.
Waves form in the frontal or parietal areas of the cerebral cortex. The attacks themselves can be spontaneous or occur against certain (sound, tactile, or rhythmic light) stimuli.
Symptoms of DMEM
DMEM is diagnosed at the age of 6 months to 3 years. The development of the child before the appearance of the first myoclonic seizures is normal. Approximately 20% of children show rare convulsions at birth or in the neonatal period. The general condition of the patient suffers rarely, violations of the neurological status are not detected. The first myoclonic attacks strike the upper limbs, neck and head, rarely the legs.
They may have different intensity, including – in the same child during different episodes. Severity ranges from barely noticeable jerks to visible fibrillation.
The frequency of seizures is 2-3 times a day with different time intervals. A long series of attacks is not observed. Possible provocation attack loud sound, tactile or rhythmic light stimulation. After each episode a refractory period of duration from 20 to 120 seconds can be observed. In this time interval, even intense stimulation does not cause a new attack. At the same time muscular atony is often observed. The disease is characterized by increased myoclonic attacks when falling asleep (drowsiness) and their disappearance in the phase of slow sleep.
There are reflex and spontaneous variants of DMEM. In the first case, myoclonic seizures develop after exposure to triggers. The spontaneous form arises without any predictors. In the early stages of the disease and when myoclonus are low in intensity, parents and pediatricians may take attacks for the child’s normal motor responses. Relatively marked myoclonic seizures may be accompanied by an inclination of the head forwards, a diverting and leading movement, flexion of the arms, and rarely a smooth rotation of the eyeballs.
Often parents note the characteristic “nodding” of a head lasting from 1 to 3 seconds, rarely up to 10 seconds. (in older children). In some cases, the only clinical manifestation of DMEM is prolonged occlusion.
In severe forms, generalization of seizures is possible, accompanied by loss of balance, sudden loss of objects from the hands, and rarely – disorders of consciousness. The intercostal muscles, the anterior abdominal wall and the diaphragm are sometimes involved in the process, due to which breathing is disturbed and expiratory noise can be heard. DMEM is characterized by an increase in the intensity of clinical manifestations up to a certain age and their subsequent complete disappearance. With a long course of the disease, it is possible to lag in psychomotor development. Transformation into other forms of seizures, including absences, does not occur even against the background of the absence of specific treatment.
Diagnosis of benign myoclonic epilepsy of infancy consists in collecting anamnestic data and conducting instrumental methods of research. Physical examination of the child in the interictal period is not informative. Laboratory tests do not reveal any deviations from the age norm. Repeated polygraphic video electroencephalography (video-EEG), which can detect spike waves and prove the presence of myoclonic seizures, has the greatest diagnostic value. If necessary, a provocative test with rhythmic light or tactile stimulation is carried out.
Outside seizures (and occasionally during them), EEG data remain within the normal range, spontaneous spike waves rarely occur. During slow sleep it is possible to enhance discharges in the cerebral cortex while maintaining their normal structure, the occurrence of fast rhythms or formal changes. In the fast phase (REM-sleep), generalized spike-wave discharges can be recorded. In order to exclude organic pathology, neurosonography, computed and magnetic resonance imaging can be prescribed. In the presence of clinical symptoms over a long period, psychomotor development is assessed.
Differential diagnosis of DMEM is carried out with cryptogenic children’s convulsions, benign non-epileptic myoclonus, Lennox-Gastaut syndrome and early childhood myoclonic-astatic epilepsy.
Treatment for DMEM is usually performed on an outpatient basis, with the exception of frequent and severe myoclonic attacks that require constant monitoring. Drug therapy with antiepileptic drugs has been shown. The first line consists of drugs from the group of valproate (sodium valproate). An important role is played by maintaining a stable concentration of the active substance in the blood.
Irregular administration of prescribed drugs provokes new attacks and the formation of resistance to further therapy with this medication. With insufficient efficacy of valproate, drugs from the group of benzodiazepines (nitrazepam) or succinimide derivatives (ethosuximide) are indicated. The therapeutic course involves treatment for 3-4 years from the moment of the first seizures.
When expressed sensitivity to rhythmic light stimuli, the duration of the course increases. With minimal activity of the attacks or their exclusively reflex nature, treatment can be carried out in a shorter period or not prescribed at all. In case of recurrence of myoclonic attacks at an older age after the treatment, a simplified version of the same therapeutic course is recommended. A mandatory point is the psychological support of the family, directly affecting the effectiveness of treatment and aimed at eliminating triggers for the child.
Prevention of DMEM
Specific prophylaxis for benign myoclonic epilepsy of infancy is not developed. The prognosis in most cases is favorable, the disease usually ends in complete recovery of the child. Myoclonic attacks arising on the background of sound or tactile stimulation are prognostically more favorable than spontaneous ones. Transition to other forms of epilepsy is uncharacteristic.
The acute period in which severe seizures are observed, on average lasts less than 12 months. More than 53% of children aged 6 years, all the symptoms of DMEM completely disappear. Approximately 14% further have mental retardation or behavioral disorders, which is why patients are forced to receive education in specialized educational institutions. The frequency of complications directly depends on the timeliness of diagnosis, the effectiveness of the treatment and the psychological climate in the family, first of all, the relationship between the child and the mother.
Benign infantile myoclonic epilepsy (DMEM) is an age-dependent form of idiopathic epilepsy characterized by generalized myoclonic seizures. Etiology has not been studied in detail. Pathology is manifested by muscle contractions of the upper limbs, neck and head lasting 1-3 seconds. with a frequency of 2-3 times a day.
The general condition of the child and his psychophysical development is rarely disturbed. Diagnostics is aimed at determining spike or polyspike waves on an EEG. The main treatment is drug monotherapy. Drugs of choice are valproate, with their ineffectiveness benzodiazepines or succinimide derivatives are used.
Benign myoclonic epilepsy of infancy (DMEM) is a rare form of pediatric epilepsy. Characteristic only for a certain age category. For the first time, the disease was isolated as a separate nosological form in 1981 by Darwe and Bior. Pathology is less than 1% of all forms of epilepsy and about 2% of its idiopathic generalized forms. Currently, about 100-130 cases of this disease are described in the literature.
DMEM is observed in children from 6 months to 3 years, in rare cases it occurs before the age of 5 years. Male representatives are sick 1.5-2 times more often. Pathology, as a rule, responds well to treatment and is completely stopped at an older age (mostly after 6 years). Complications in the form of psychomotor retardation are rare and only in the absence of therapy.