Refractory epilepsy: one size does not fit all.

A unifying definition of refractory epilepsy has been hotly debated but, to date, has not been agreed upon. Evidence from clinical trials indicates that some patients actually are not refractory, as many will partially respond to add-on treatment or will worsen when antiepileptic drugs (AEDs) are removed. There are several important issues relating to the assessment of AED response that routinely have not been addressed in the determination of treatment responsiveness, such as incorporating baseline seizure severity, including partial response rather than solely an all-or-none response, and the consideration of variability in response over time.