Abstract
Objective
To determine if an ictal EEG recording as part of pre-surgical evaluation of children with a demarcated single unilateral MRI lesion is indispensable for surgical decision making, we investigated the relationship between interictal/ ictal EEG and seizure semiology with seizure-free outcome.
Methods
Data were obtained retrospectively from consecutive patients (≤ 18 years) undergoing epilepsy surgery with a single unilateral MRI lesion at our institution over a 6-year period. Video-telemetry EEG (VT-EEG) was classified as concordant or non-concordant/non-informative in relation to the MRI lesion location. The odds of seizure-free outcome associated with non-concordant versus concordant for ‘semiology’, ‘interictal’ and ‘ictal’ EEG were compared separately. Multivariable logistic regression was conducted to correct for confounding variables.
Results
After a median follow-up of 26 months (IQR 17-37.5) 73 (69%) of 117 children enrolled were seizure free. Histopathological diagnoses included: low-grade epilepsy associated tumours 46 (39%), Focal Cortical Dysplasia (FCD) 33 (28%), mesial temporal sclerosis (MTS) 23 (20%), polymicrogyria 3, 3%) and non-diagnostic findings/gliosis 12 (10%). The odds of seizure freedom was lower with a non-concordant interictal EEG (OR=0.227, 95% CI 0.079 to 0.646, p=0.006) and non-concordant ictal EEG (OR=0.359, 95%CI 0.15 – 0.878, p=0.035). In the multivariable logistic regression model, factors predicting lower odds for seizure free outcome were developmental delay/intellectual disability, higher number of anti-seizure medications tried and a non-significant trend for ‘non-concordant interictal EEG’.
In the combined subgroup of patients with FCD and tumours (n=79) there was no significant relationship of VT-EEG factors and seizure outcomes, whilst in children with MTS and acquired lesions (n=25) a non- concordant EEG was associated with poorer seizure outcomes) p =0.003).
Significance
An ictal EEG may not be mandatory for pre-surgical evaluation, particularly when a well-defined single unilateral MRI lesion has been identified and the interictal EEG is concordant.
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