What is status epilepticus and what do we know about its epidemiology?

Epidemiological studies across medical conditions share many similar difficulties relating, for instance, to selection bias, defining a population frame, statistical power and adequate documentation. However, in the case of status epilepticus there are, in addition to these, a variety of specific issues that pose significant hurdles to accurate investigation - not least defining status epilepticus itself and determining whether it is simply a severe manifestation of epilepsy or should be considered a distinct entity in its own right. In this paper, we present a historical overview of how opinions about status epilepticus have changed with time, outline some of the issues unique to the study of status epilepticus and provide personal perspectives on certain controversies within this important area of epileptology. This article focuses on adult status epilepticus as paediatric status epilepticus has been covered in a separate Seizure special edition. With a focus on status epilepticus in adults, we review salient population based studies, exploring their advantages and limitations. While it can be difficult to draw conclusions from these studies, it does seem that status epilepticus is more common in African-Americans, males and in either young children or older adults. Given demographic changes resulting in an ageing population, the incidence of status epilepticus is therefore likely to rise. We illustrate how the majority of work performed to date has been in convulsive status epilepticus and demonstrate that more needs to be done to better understand nonconvulsive status epilepticus as well as to further refine the boundaries of status epilepticus as a whole. Despite status epilepticus being common and associated with significant morbidity, our knowledge of the true epidemiology of this condition remains far from complete.