Introduction: The presence of myoclonus in a patient has different meanings: there exist myoclonus without encephalopathy or epilepsy (sleep myoclonus), encephalopathies with non-epileptic myoclonus (Kinsbourne's syndrome), encephalopathies with epileptic myoclonus (progressive or not), epileptic encephalopathies with myoclonic seizures (the classic West and Lennox-Gastaut syndromes) and myoclonic epilepsies.

Development: Main types of myoclonic epilepsies (benign childhood myoclonic epilepsy, severe-polymorphic-myoclonic epilepsy, juvenile myoclonic epilepsy, childhood familial myoclonic epilepsy, benign reflex myoclonic epilepsy, as well as progressive myoclonic epilepsies, among which progressive myoclonic epilepsy (PME) type 1 (Unverricht-Lundborg's disease) and PME2 (Lafora type) are prominent, whereas other entities, such as those related to neuronal ceroid lipofuscinosis or mitochondrial cytopathies are discussed more briefly) are reviewed, analyzing clinical, EEG and therapeutic issues, while the most recent contributions in the field of genetics are considered.

Conclusions: Myoclonic epilepsies constitute a very heterogeneous type of epilepsy, both in their origin and in their prognosis, with favorable forms of course along with other progressive and refractory forms with an ill-fated prognosis.