A tiered strategy for investigating status epilepticus

In status epilepticus the imperative to start anti-seizure therapy, initially subjugates the need to investigate the cause. Once treatment is initiated this balance shifts in favour of identifying: the causes and consequences of the seizure; the factors that predetermined the occurrence of status epilepticus; and finally the prognosis of this acute episode. Just as there are multiple causes of seizures and epilepsy, there are a vast number of causes of status epilepticus. We discuss the more common and the more important to identify as they may dictate a change in therapy or a certain prognosis. Acknowledging that the burden of epilepsy and status epilepticus is preferentially felt in lower and middle income countries, we have tried to rationalise the investigation of status epilepticus. Basic laboratory studies are necessary in all patients with status epilepticus as systemic complications can occur early and can involve every organ system. Aetiology is important, however the morbidity from treatment does not discriminate when treatment resistant status epilepticus is due to dissociative seizures. Seven percent of epilepsy hospitalisations are for status epilepticus and epilepsy is a prior diagnosis half the time; awareness of prior history is invaluable. EEG is critical for diagnosis in the anaesthetised patient or those in non-convulsive status epilepticus. There is poor correlation of EEG with aetiology except in rare circumstances. Currently quantitative EEG methods should best be viewed as screening tool to reduce EEG reviewing time. MRI is clearly superior for identifying cytotoxic change and the networks that are or were involved in the episode of status epilepticus. Sequential imaging changes may give an estimate of recovery but there is insufficient detail to use MRI as a prognostication tool. We suggest the following model: 1) immediate investigations; 2) investigations targeted by the clinical scenario; 3) investigations targeted following results from bloods, imaging or EEG; 4) investigations targeted for rarer causes and super-refractory status epilepticus.