Juvenile myoclonic epilepsy is a form of generalized epilepsy, the clinical picture of which is based on myoclonic seizures — asynchronous muscle contractions that occur briefly in symmetrical areas of the body, mainly in the arms and shoulder girdle. Along with myoclonic episodes, absences and clonic-tonic generalized epiprimes may be observed in the clinic. Juvenile myoclonic epilepsy is diagnosed on the basis of the clinic of the disease and the results of electroencephalography, with the exclusion of organic cerebral pathology according to neurological examination and MRI. Treatment is carried out mainly with valproic acid preparations. As a rule, lifelong supervision of an epileptologist is necessary.
G40.3 Generalized idiopathic epilepsy and epileptic syndromes
Juvenile myoclonic epilepsy (JME) accounts for up to 12% of all forms of this disease and about 23% of cases of idiopathic generalized epilepsy. JME is one of the varieties of myoclonic epilepsy — generalized epilepsy occurring with myoclonic seizures. This group of diseases also includes: children’s benign myoclonia, West syndrome (myoclonic encephalopathy of childhood with cerebral hypsarrhythmia), Lafora’s disease, etc.
The first description of JME is dated 1867. However, as a separate nosological unit, juvenile myoclonic epilepsy was isolated only in 1955 at the suggestion of a group of German doctors led by Janz, after which it became referred to as Janz syndrome. In the scientific literature on neurology and epileptology, the term “impulsive petit mal” can also be found.
Juvenile myoclonic epilepsy is hereditary. Cases of the development of this form of epilepsy due to organic brain damage have not been recorded. Half of the patients in the family history have relatives of the 1st or 2nd line, who have various types of epiprimes. The genes responsible for the development of the disease have not yet been precisely established. Several possible variants are assumed – chromosome 15q, one of the loci of the short arm of chromosome 6, genes C6orf33 and BRD2, etc. Most geneticists tend to think about the polygenic mechanism of inheritance of myoclonic epilepsy. The specific pathogenesis of JME has not been identified.
Juvenile myoclonic epilepsy manifests at the age of 8 to 24 years. Most often, the onset of the disease occurs in the age range of 12-18 years. The pathognomonic symptom of UME is myoclonic seizures — short, sudden, involuntary muscle contractions that have an asynchronous character.
As a rule, at the beginning of the disease, paroxysms are noted in the morning hours when the patient wakes up. Muscle contractions occur symmetrically in both halves of the body, more often they cover only the shoulder girdle and arms, less often they extend to the lower extremities or the entire body. During a paroxysm, patients can automatically drop or drop objects held in their hands, when the lower extremities are involved, a fall occurs.
Paroxysms of JME can have a single character or occur in clusters. In rare cases, the so-called myoclonic epileptic status is observed. A distinctive feature is the complete preservation of the patient’s consciousness during myoclonic paroxysm, even in cases when it comes to myoclonic status.
In 3-5% of cases, juvenile myoclonic epilepsy occurs with the presence of only myoclonic paroxysms. In the vast majority of cases (about 90%), some time after the onset of the disease (on average after 3 years), the patient has generalized tonic-clonic epiprimes. They can begin with a series of increasing myoclonic twitches, then turning into clonic-tonic convulsions. Approximately 40% of patients have absences — short-term episodes of “turning off” consciousness.
It is very difficult to establish a diagnosis of JME in its initial period. Often, myoclonic episodes that occur against the background of awakening are regarded as a child’s nervousness, and the children themselves usually do not pay attention to such minor symptoms. As a rule, parents turn to a neurologist when a child has tonic-clonic seizures. The study of the neurological status does not determine any disorders. Instrumental methods include:
- MRI of the brain. It is carried out to exclude cerebral pathology (intracerebral tumor, brain abscess, cerebral cyst, encephalitis, intracerebral hematoma) and the organic origin of epiprimes. If it is necessary to exclude aneurysms of cerebral vessels, the patient is referred for MR angiography.
- Electroencephalography. In 75%, the EEG reveals the presence of interictal epileptiform patterns. Bilaterally symmetrical paroxysmal discharges consisting of polyspike-wave complexes with a frequency of 4-6 Hz are recorded. In 17% of cases, complexes with a frequency of 3 Hz are observed. Ictal EEG detects high and medium amplitude spikes with a frequency of 10-16 Hz, after which slow waves of an irregular nature are recorded. The number of spikes of one paroxysm varies from 5 to 20 and depends rather not on the duration, but on the intensity of the attack. For early diagnosis of UME, it may be necessary to conduct an EEG upon awakening, daily EEG video monitoring, provoking tests (sleep deprivation, photostimulation).
Massiveness and bilateral synchronicity distinguishes JME paroxysms from non-epileptic myoclonus, whose episodes are sporadic and focal. Juvenile myoclonic epilepsy also requires differentiation from other forms of epilepsy occurring with myoclonic episodes. So, unlike JME, with epilepsy with generalized convulsive paroxysms of awakening or with youthful absentee epilepsy, myoclonic paroxysms are not dominant in the clinical picture of the disease.
Epilepsy with myoclonic-astatic paroxysms, Lennox-Gastaut syndrome and epilepsy with myoclonic absences make their debut in earlier childhood and are accompanied by a delay in mental development. The latter is characterized by seizures in which myoclonic convulsions are combined with absences, while JME paroxysms proceed without disturbing consciousness.
Important is not only the pharmacotherapy of epilepsy, but also the patient’s compliance with certain vital norms that allow avoiding provoking seizures. As with other types of epilepsy, with JME, seizures can be caused by a violation of the regime, mental and physical overload, stress, lack of sleep, taking alcoholic beverages. Therefore, the patient should avoid such provoking factors. A calm, simple and unhurried lifestyle, staying in nature, away from the hustle and bustle of the city, has a positive effect on the course of the disease. In this regard, some families where the child is diagnosed with JME, move and live in rural areas.
Drug therapy of JME is carried out with valproates. Monotherapy with these drugs proved to be effective against all types of seizures accompanying the JME clinic — myoclonic, tonic-clonic and absences. If monotherapy is insufficient, combined treatment is possible. The relief of resistant absences is achieved by combining valproates with ethosuximide, resistant clonic-tonic seizures — by combining valproates with primidone or phenobarbital.
Clonazepam is effective for the control of myoclonic paroxysms, but its effect does not apply to tonic-clonic generalized seizures. At the same time, complete relief of myoclonic seizures deprives the patient of the opportunity to know in advance about the approaching tonic-clonic attack by the myoclonic manifestations that arise before him. Therefore, the appointment of clonazepam is justified only with persistent myoclonic paroxysms and should be combined with a valproic acid preparation.
The results of treatment of JME with new generation antiepileptic drugs (levetiracetam, lamotrigine, topiramate) are still being tested in clinical conditions. The high prospects of levetiracetam were noted.
Juvenile myoclonic epilepsy is considered a chronic disease that continues throughout the patient’s life. Cases of spontaneous remission are rare. In 90% of patients who interrupted treatment with an antiepileptic drug for various reasons, the resumption of epiprimes was noted. However, there are indications that in some cases, long-term remission was observed in patients after discontinuation of the drug.
In general, with the right therapy, seizures are controlled in most patients, although half of them may experience separate paroxysms during treatment. Relatively resistant to therapy is rarely observed, mainly in cases when the patient has all 3 types of paroxysms of JME.