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Benign Myoclonus of Early Infancy (Benign Infantile Spasms)

Benign myoclonus of early infancy (BMEI) is characterized by episodes of myoclonic spasms involving flexion of the trunk, neck, and extremities in a manner resembling the infantile spasms of West syndrome.[7,][8] The myoclonic spasms typically occur in clusters. In some cases they involve a shuddering movement of the head and shoulders, and in others the movements of the trunk and limbs are extensor.[9] There is no change in consciousness during the spells. Unlike benign neonatal sleep myoclonus, the movements in BMEI only occur in the waking state. The onset of these spells is usually between ages 3 and 9 months, but they may begin in the first month of life. The spells usually cease within 2 weeks to 8 months of onset,[10] but may persist for 1 to 2 years.[7] Both ictal and interictal EEGs are normal, distinguishing this entity from infantile spasms. Treatment is not required. Development and neurologic outcome are normal.