Impact of Age on the Diagnostic Yield of Routine EEG in People With Childhood or Juvenile Absence Epilepsy: A Cross-Sectional Study.

BACKGROUND: We aimed to identify the proportion of individuals with a confirmed diagnosis of childhood absence epilepsy (CAE) or juvenile absence epilepsy (JAE) who show a negative routine EEG (rEEG), and to determine the main factors associated with this finding. METHODS: Individuals with CAE or JAE underwent both an rEEG and a 24-h ambulatory EEG (24-h-aEEG). Participants were classified as 'rEEG positive' if generalised spike-wave discharges (GSWs) and/or typical absences (TAs) were observed, and as 'rEEG negative' if no such features were detected. 24-h-aEEG recordings served as the ground truth to confirm the diagnosis in cases with a negative rEEG. RESULTS: Eighty-two individuals [40/82 (48.8%) females; mean age 12.5 ± 5.6 years] were included, of whom 39/82 (47.6%) were not receiving anti-seizure medications (ASMs) at the time of the EEG. Overall, 31/82 (37.8%) had a negative rEEG, including 10/39 (25.6%) in the cohort of ASM-naïve individuals. Compared with rEEG-positive participants, those in the rEEG-negative group had a later age at epilepsy onset (12.1 ± 4.5 years; p < 0.001) and were older at the time of EEG (16.5 ± 5.3 years; p < 0.0001). Older age at EEG emerged as significantly associated with a negative rEEG (OR = 1.23; 95% CI = 1.03-1.46; p = 0.019), independent of age at onset, epilepsy syndrome (CAE or JAE) and ASM exposure. Sensitivity analyses confirmed the association between older age and rEEG negativity across all cohorts: ASM-naïve individuals (OR = 1.41; 95% CI = 1.12-1.78), CAE (OR = 1.27; 95% CI = 1.02-1.58), and JAE (OR = 1.36; 95% CI 1.09-1.69) groups. Youden's exploratory analysis identified ≥ 14 years as the optimal threshold for predicting a rEEG negative. CONCLUSION: Age significantly reduces the diagnostic yield of rEEG in CAE and JAE, regardless of ASM treatment.