NeONATAL epilepsies

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It is estimated that worldwide 10.5 million children under 15 years have active epilepsy (Guerrini, 2006) and clearly its incidence is higher during the first year of life. Thus, it is widely accepted that the maturing brain, for not yet well-understood reasons, is highly excitable as compared to the adult. Neonatal epilepsy constitutes a major problem of public health because it has important impact on cognitive development and social integration of children. Knowledge of the cause and pathophysiology of neonatal epilepsy has considerably improved with modern neuroimaging and molecular genetic studies. However, our understanding of early onset epilepsy is still very limited.

Our project is focused on developmental and epileptic encephalopathies (DEE) and specifically on a particular form of neonatal epilepsy called early onset epileptic encephalopathy with a suppression burst pattern (EESB). This is a very rare form of epilepsy that is characterized by :

- Early onset, before the third month of age,

- Seizure activity characterized by myoclonies, epileptic spasms and focal or multifocal seizures,

- Specific EEG features consisting in discontinuous traces with bursts of generalized spikes and polyspikes lasting 2 to 10 seconds, alternating with periods of silence lasting 1 to 20 seconds (see figure below),

- Encephalopathy with a severe developmental delay, poor neurological outcome and high mortality rate in the first years of life.

This nosological entity has been defined as Ohtahara syndrome, or early onset myoclonic epilepsy, according to the main type of epileptic seizures (epileptic spasms in Ohtahara syndrome, myoclonic jerks in early myoclonic epilepsy), but the distinction between the two entities is often difficult. This electro-clinical entity can be observed in several frequent pathological conditions including :

- Severe and diffuse anoxo-ischemic lesions during the perinatal period,

- Cortical malformations such as hemimegalencephaly, lissencephaly, diffuse polymicrogyria, that are easily recognizable with brain MRI.