Bases physiopathologiques des états de mal épileptiques

The mechanisms that induce epileptic activity and make it durable, leading to status epilepticus (SE), are poorly known. They probably result from an imbalance between the activating systems of neuronal depolarisation (excitatory amino acids release with postsynaptic N-methyl-d-aspartate [NMDA] receptor activation, spreading depolarisation following abnormal progression) and the inhibiting systems (GABAergic synapses). Status epilepticus leads to many direct and indirect cerebral disorders, as well as systemic disorders, with intertwined mechanisms and consequences. These disorders are more frequent in case of convulsive SE with generalized tonic-clonic seizures. Direct neuronal damage (selective neuronal loss and epileptogenesis) results mostly from excitotoxicity, which arises from enhanced and extended neuronal activation. Indirect neuronal damage results from the inability of the circulatory system to supply sufficient oxygen and glucose contribution compared to the high metabolism level of the highly depolarized and synchronized neurons. This energetic deficit is usually patent after 30 minutes of SE, when systemic compensation mechanisms (cardiac output increase) are exhausted. Understanding these pathophysiologic aspects is essential for effective treatment of SE.