Myoclonic epilepsy in infancy (MEI) is a rare disorder characterized by myoclonic onset. MEI was formerly known as benign myoclonic epilepsy in infants, but is now considered not necessarily a benign prognosis. Onset ranges from 6 months to 3 years of age, peaks at 6 to 12 months, and about one-third of children have a history or family history of febrile seizures. There is currently no known genetic cause.
Clinical manifestations
Myoclonic seizures mainly affect the upper extremities and head, and occasionally the lower extremities. Seizures are characterized by nodding, sometimes with bilateral shoulder shaking and upper extremity abduction and upward movement, lower extremity flexion, or eye movements. Most episodes are single, and a few occur several times in a row. Consciousness is difficult to judge at a single episode, but it generally does not interrupt activities and rarely causes falls. Some myoclonic seizures may have transient loss of tone, but this is not easily observed clinically. Mild impairment of consciousness may occur during 3~5 consecutive attacks. In some children, seizures are precipitated primarily by sudden acoustic, light, or tactile stimuli, known as reflex myoclonus epilepsy. The initial onset may be so mild that parents and doctors are not aware of these abnormal pathological movements. Myoclonic seizures in infants can also be accompanied by other seizure types, including partial and generalized seizures. Neurologic examination is normal.
Pre-seizure development is usually normal, and psychomotor development remains normal for some time after onset. If seizures are frequent and not effectively controlled, they can lead to mild psychomotor development or behavioral abnormalities.
Electroencephalogram (EEG) findings
Background activity of EEG during the interictal phase is normal. Abnormal discharge is rare when awake, and if there is discharge, it is often accompanied by myoclonic seizures. Some children may have slow-wave activity in the central area. During myoclonic seizures, it is a generalized 3.5~5Hz irregular fast spinous slow composite wave, multi-spinous slow compound wave burst, lasting 1~3 seconds, and the front head is obvious. Multi-guide recordings confirm a strong relationship between myoclonic seizures and spike-and-slow complex bursts. Spike-slow complex wave emission and myoclonic seizures often increase during sleepiness and light sleep. Spike-slow and multi-spinous slow-wave bursts may also be seen during REM sleep, but are not accompanied by clinical episodes. Normal sleep structure. In some cases, intermittent flash stimulation can induce multispinous and slow complex wave emission and myoclonic seizures (reflex myoclonic epilepsy), which is now considered a subtype of infantile myoclonic epilepsy.
diagnosis
Diagnostic criteria for MEI require myoclonic seizures and normal neurologic examination. EEG is essential to confirm that myoclonus is epileptic. Epileptic myoclonus must be distinguished from other epileptic and nonepileptic conditions, including infantile spasms, ankylosing epilepsy, normal physiologic sleep myoclonus (sleep onset seizures), and benign startle responses.
treat
Seizures are treated with broad-spectrum anticonvulsant drugs, such as levetiracetam and sodium valproate.
prognosis
Myoclonic seizures usually resolve spontaneously within 6 months to 10 years of the onset of MEI, and most children are able to stop anticonvulsants. Other epilepsy may follow, most commonly juvenile myoclonic epilepsy. Most patients have normal neurodevelopmental outcomes, but some develop intellectual disability, learning disability, or attention problems.
Reference source:
- Liu Xiaoyan, Clinical Electroencephalography, Second Edition, People's Medical Publishing House
- Chinese Anti-epilepsy Association Guidelines for Epilepsy 2022 Edition