Spindle density relates to cognitive outcomes in infantile epileptic spasms syndrome with unknown etiology: A retrospective cohort study

OBJECTIVE: Developmental arrest or regression that results in intellectual disability (ID) is a common neurological sequela of infantile epileptic spasms syndrome. Spindles are the hallmark of non-rapid eye movement sleep, and their density correlates with cognitive performance. Recent evidence suggests that ictal and interictal epileptic activities hijack the thalamocortical network. Therefore, we aimed to investigate whether thalamocortical dysfunction, as represented by reduced spindle density, is related to cognitive outcomes. METHODS: We retrospectively recruited patients diagnosed with infantile epileptic spasms syndrome who were treated at Saitama Children's Hospital. Specifically, we included patients with an unknown etiology to minimize the effects of preceding thalamocortical dysfunction induced by various etiologies before the onset of infantile epileptic spasms syndrome. These cohorts were separated into two groups based on the presence or absence of ID, defined as an intelligence quotient (IQ) or developmental quotient (DQ) of