Intelligence outcomes in 17 patients with developmental and/or epileptic encephalopathy with spike-wave activation in sleep ((D)EE-SWAS) after remission of SWAS

Developmental and/or Epileptic encephalopathy with spike-wave activation in sleep ((D)EE-SWAS) is an age related epilepsy syndrome that is associated with, often profound, cognitive deterioration in childhood. Although the EEG pattern in (D)EE-SWAS resolves, cognitive deficits persist during adulthood. Studies assessing objective cognitive outcomes after resolution of the EEG SWAS pattern are scarce. In this study we assessed intelligence quotient (IQ) scores after remission of SWAS in seventeen patients with a history of (D)EE-SWAS. In all patients with IQ data available before the onset of SWAS there was a profound decline in IQ during (D)EE-SWAS (mean decline -22.1 IQ points, sd 9.3). When we plotted change in IQ over time we observed two different developmental trajectories: in 8 children there was a further decrease of IQ after remission of SWAS (mean decrease of 8.1 IQ points, sd 4.8) and in 9 children an increase (mean increase of 15.9 IQ points, sd 11.0). The group with a decrease of IQ had a significantly earlier first assessment of SWAS. Our results reinforce the classification of (D)EE-SWAS as a true epileptic encephalopathy and suggest that an earlier onset of SWAS is related to poorer neurodevelopmental outcome.