Purpose: To determine the frequency and determinants of subnormal global cognitive function in a representative, community-based sample of children prospectively identified at the time of initial diagnosis of epilepsy.
Methods: In children enrolled with newly diagnosed epilepsy and followed a median of 10.5 years, level of cognitive function (within normal, borderline, mild, moderate to severe mental retardation (MR), neurologically devastated, and impaired but not further classified (NFC)) was determined based upon neurologists' and school records, repeated parental interviews, and, in over half the participants, standardized neuropsychological testing. For multivariable analyses, subnormal cognitive function was designated as consistent with a full scale IQ < 80.
Results: Global cognitive function was considered within normal, N = 451 (73.6%), borderline, N = 31 (5.1%), mild MR, N = 21 (3.4%), more severe MR, N = 45 (7.3%), devastated, N = 29 (4.7%), and impaired-NFC, N = 36 (5.9%). Age at onset <5 years, symptomatic etiology, epileptic encephalopathy, remission status and current AED treatment were each strongly associated with level of cognitive function (all p-values <0.0001). In a multivariable logistic regression model, all variables except remission status independently contributed to subnormal global cognitive function.
Discussion: Evidence of subnormal global cognitive function is apparent in approximately one of four children with epilepsy. Young age at onset, symptomatic cause, epileptic encephalopathy, and continued treatment, despite their strong intercorrelations, are independently associated with this outcome.