Longitudinal cohort studies of the prognosis of epilepsy: contribution of the National General Practice Study of Epilepsy and other studies.

Longitudinal cohort studies of prognosis in epilepsy have been carried out since the late 1970s and these have transformed our understanding of prognosis in epilepsy. This paper reviews the contribution of such studies and focuses particularly on the National General Practice Study of Epilepsy, a prospective population-based cohort study of 1195 patients that was initiated in 1983. The National General Practice Study of Epilepsy and other studies have shown that: (i) epilepsy has an often good prognosis with 65-85% of cases eventually entering long-term remission, and an even higher proportion of cases entering a short-term remission; (ii) the likelihood of long-term remission of seizures is much better in newly diagnosed cases than in patients with chronic epilepsy; (iii) the early response to treatment is a good guide to longer term prognosis (although not inevitably so, as in a minority of cases seizure remission can develop after prolonged activity); (iv) the longer is the remission (and follow-up), the less likely is subsequent recurrence; (v) the longer an epilepsy is active, the poorer is the longer term outlook; (vi) that delaying treatment, even for many years, does not worsen long-term prognosis; (vii) the 'continuous' and 'burst' patterns are more common than the 'intermittent' seizure pattern; (viii) epilepsy has a mortality that is highest in the early years after diagnosis, and in the early years is largely due to the underlying cause, however, higher mortality rates than expected are observed throughout the course of an epilepsy; (ix) the prognosis of febrile seizures is generally good, with ~6-7% developing later epilepsy; and (x) clinical factors associated with outcome have been well studied, and those consistently found to predict a worse outcome include: the presence of neurodeficit, high frequency of seizures before therapy (seizure density), poor response to initial therapy, some epilepsy syndromes.