Background/Purpose: Drug-resistant focal epilepsy in children is often accompanied by developmental delay.
It is incompletely understood how epileptic activity interferes with normal psychomotor
development. We hypothesized that sleep spindles in mesial temporal structures and
in the neocortex are reduced in children with focal epilepsy and developmental delay.
Methods: Intracranial EEG, recorded with depth electrodes or subdural grid electrodes, was
retrospectively analyzed in consecutive pediatric patients (≤12 years) with drug-resistant
focal epilepsy. Children with severe developmental delay (group 1) were compared to
subjects with mild or no developmental delay (group 2). A representative 30-minute
interval of NREM sleep was selected for analysis. Sleep spindles were visually identified
in a referential montage. Interictal spikes and ripple oscillations (80–256 Hz) were
detected using the Delphos algorithm.
Results: Sixteen patients (age: 2–12 years) were included, and intracranial EEG from 740 electrode
contacts was analyzed. The median rate of sleep spindles was lower in children with
epilepsy and severe developmental delay (group 1, n = 8 patients) than in patients with mild or no developmental delay (group 2, n = 8 patients), although there was considerable variance within the two groups. A
reduction of spindles was found both for mesial temporal structures and the neocortex,
and both inside the seizure onset zone (SOZ) and in non-SOZ contacts. The proportion
of ripples associated with interictal spikes was higher in children with epilepsy
and severe developmental delay (group 1) than in patients with mild or no developmental
delay (group 2). Patient age and the number of contacts per patient did not differ
significantly between the two groups.
Conclusion: In children with drug-resistant focal epilepsy, developmental delay was associated
with a reduction of mesial temporal and neocortical sleep spindles. This suggests
that disruption of local sleep in both regions might contribute to developmental delay.
