Developmental stage affects cognition in children with recently-diagnosed symptomatic focal epilepsy

•We studied the effect of developmental stage on cognition after seizure onset.•We administered a range of measures to 3- to 5-year-old and 6- to 8-year-old patients with focal epilepsy.•Skills in a critical period of development at seizure onset were vulnerable.•Skills in a stable developmental phase at seizure onset were more resilient.•Developmental timing affects cognition in this recently-diagnosed cohort.

This study explored the impact of developmental stage on cognitive function in children with recently-diagnosed epilepsy. In keeping with a neurodevelopmental framework, skills in a critical developmental period were expected to be more vulnerable than those stable at the time of seizure onset. We studied children with early-onset (EO) symptomatic focal epilepsy (onset: 3-5 years; n = 18) and compared their performance with that of the group with late-onset (LO) epilepsy (onset: 6-8 years performance of; n = 8) on a range of cognitive tasks. Performance of both groups was compared with normative standards. 'Critical' and 'stable' classifications were based on developmental research. Nonparametric analyses revealed that skills in a critical developmental period for the group with EO epilepsy fell below normative standards (Phonological Processing: p = .007, Design Copying: p = .01, Visuomotor Precision:, p = .02) and fell below the performance of the group with LO epilepsy (Design Copying: p = .03, Visuomotor Precision: p = .03). There were no differences between the group with EO epilepsy and the group with LO epilepsy on measures of receptive vocabulary and memory, which were proposed to be in a stable developmental period across both groups. Auditory span, as measured by Word Order, was reduced for both the group with EO epilepsy (p = .02) and the group with LO epilepsy (p = .02) relative to normative standards, but the groups did not differ from each other. These results are consistent with a prolonged period of critical development for this skill. These findings support the notion that skills in a critical phase of development are particularly vulnerable following the onset of symptomatic focal epilepsy in childhood.