Nonconvulsive status epilepticus in epileptic encephalopathies in childhood

Epileptic encephalopathies are conditions in which the abundant epileptiform activity itself interferes with development, resulting in cognitive slowing and often regression, psychiatric and behavioral disturbances. Nonconvulsive status epilepticus has been defined as ongoing or nonrecovering nonconvulsive seizures. It has been challenging to differentiate clinical and electroencephalographic patterns in epileptic encephalopathies from those attributed to nonconvulsive status epilepticus, since several different epileptic encephalopathies may show continuous or subcontinuous epileptiform activity. Especially for patients with known epileptic encephalopathy, the new proposal for diagnosis of nonconvulsive status epilepticus suggests an increase in prominence or frequency of specific electroencephalographic features as compared to baseline correlated to clinical and EEG responsiveness to intravenous anti-seizure drugs. This clinical change may be unclear, particularly in patients with pre-existent cognitive or behavioral impairments. This review intends to organize previously published data, with available information in the literature on some of those specific epileptic syndromes and diseases, focusing on two main questions: i. When should specialists suspect of nonconvulsive status epilepticus in epileptic encephalopathies? ii. Could epileptic encephalopathies themselves be nonconvulsive status epilepticus presentations? Lastly, the rationale for definition and treatment in many of the epileptic encephalopathies is the effect of ongoing frequent epileptiform activity on development and cognition, and this will require monitoring with serial clinical, neurophysiological, functional neuroimaging, and neuropsychological assessments. Whether there would be an association or causality between epileptic encephalopathies and nonconvulsive status epilepticus is a key question demanding further research.