The development of a seizure severity scale as an outcome measure in epilepsy.

In controlled trials of antiepileptic drugs (AEDs) seizure frequency is often the only variable considered. With little prospect of improving assessment of AEDs, using seizure counts as the only end-point, there is a need for the development of new outcome measures. Clinical experience indicates that seizure severity is equally important to the patient and, by preventing seizure spread, AEDs can influence seizure severity without necessarily reducing seizure frequency. A scale capable of measuring seizure severity and change of severity attributable to treatment could be a useful additional outcome measure. Such a scale should exhibit the basic properties of validity and reliability. An easily administrable 16-point scale, containing 2 subscales--perception of control and ictal/post-ictal effects--has been developed. This scale has been tested on a patient population (n = 159) representative of that seen in trials of novel AEDs. Using standardised statistical methods, the scale has been shown to be both reliable and valid.