Abstracts

Rationale: Medically refractory, focal epileptic seizures are commonly caused by focal cortical dysplasia, which may be managed favourably by epilepsy surgery. Identifying potential epilepsy surgical candidates with focal cortical dysplasia in children is often challenging. Utilizing scalp, EEG signatures of focal polyspikes, fast waves or rhythmic sharp waves as a marker for focal cortical dysplasia may assist the clinical diagnosis, expediting neuroimaging and referral to a comprehensive pediatric epilepsy centre. Methods: A single centre retrospective analysis of the EEG and MRI reports of children with focal epileptic seizures, referred for prolonged scalp video EEG monitoring at McMaster Children's Hospital between 2008 and 2015. Patients with focal epilepsy between 1 month and 18 years were included in the study. Patients with generalized epilepsy syndromes and children with EEG diagnoses of electrographical status epilepticus in sleep (ESES), childhood epilepsy with central temporal spikes (CECTS), multiple independent spike foci (MISF), Lennox Gastaut Syndrome, and non epileptic seizures or MRI diagnosis of tuberous sclerosis complex were excluded. Each patient's EEG's were categorized as with or without focal polyspikes, fast waves or rhythmic sharp waves and MRI's for focal cortical dysplasia. Results: Out of 270 patient's reviewed, 81 were included in the study. EEG was truly positive in 8, falsely positive in 15, falsely negative in 16 and truly negative in 42 cases. The sensitivity of the scalp EEG combination of focal polyspikes, fast waves or rhythmic sharp waves for focal cortical dysplasia was 33%, however the specificity was significant at 73%. The positive predictive value of the test was 34% while the negative predictive value was 72%. The Diagnostic odds ratio was 1.4. The focal EEG findings correctly lateralized the focal cortical dysplasia reported on MRI in 6/8 cases. Conclusions: Focal polyspikes, focal fast waves or rhythmic sharp waves on scalp EEG, is a specific marker of focal cortical dysplasia in children with focal epileptic seizures. Neuroimaging correlation is warranted and in cases of medically refractory epilepsy referral to a comprehensive pediatric epilepsy centre to assess surgical candidacy should be considered. Funding: No funding was received in support of this abstract