Cognitive function in preschool children after epilepsy surgery: rationale for early intervention

PURPOSE: The detrimental effect of frequent early seizures on the cognitive potential of children is a significant clinical issue. Epilepsy surgery in childhood offers a good prognosis for seizure control and improved developmental outcome. We studied the postoperative outcome and the developmental velocity after surgery and analyzed risk factors for developmental delay in 50 consecutive preschool children treated surgically for severe epilepsy at ages 3 to 7 years. METHODS: Pre- and postoperative developmental quotients (DQs) were analyzed with analysis of variance; stepwise linear regressions were performed on preoperative DQs and on a difference score between post- and preoperative DQs to determine risk factors for preoperative development and factors influencing postoperative development. RESULTS: Of the 50 patients, 70% were retarded, with IQ < 70; 16% were of average intelligence, with IQ ranging from 85 to 115. Age at seizure onset and extent of lesion were predictive variables for preoperative cognitive development. Six to 12 months after surgery (early postoperative phase), 66% were seizure free (Engel outcome class I), 26% had substantial to worthwhile seizure reduction (classes II and III), and 8% were unchanged (class IV). Forty-one (82%) children showed stable velocity of development; three children showed gains of >/=15 IQ points; three had developmental decline (loss of >/=10 IQ points), which was transient in two children; and three children moved from not assessable to assessable. At last follow-up (6 months to 10 years after surgery), 11 children showed IQ/DQ gains of >/=15 IQ points. Gains in IQ were observed only in seizure-free children and were stable over time. Shorter duration of epilepsy was significantly associated with a postoperative increase in DQ. CONCLUSIONS: (a) Substantial global mental delay is common in young children treated for epilepsy with surgery; (b) In most patients, postoperative development proceeded at a stable velocity; (c) Catch-up development may occur but only in seizure-free patients; (d) Substantial cognitive losses were noted in only one child. and (e) Early seizure control stabilized developmental velocity in this patient cohort.