PREDICTORS OF POST-SURGICAL SEIZURE FREEDOM IN CHILDREN WITH NORMAL MRI AND INTRACTABLE EPILEPSY

Objectives: To identify the predictors of seizure freedom in children with refractory epilepsy and normal or non-lateralised MRI findings.

Methods: We analyzed 22 children (M10:F12) under 18 years with normal, subtle (isolated sulcal, gyral or white matter abnormality) or non-lateralised (eg- diffuse atrophy, bilateral white matter changes) MRI findings, who underwent surgery for intractable epilepsy following intracranial EEG. Clinical profiles, neurophysiological data (video scalp EEG, magnetoencephalography and video intracranial EEG) and surgical data (type, location, extent and completeness) were compared to post-operative seizure outcome (good seizure outcome defined as seizure freedom and >90% seizure control).

Results: We performed combined lobectomy and corticectomy (10), corticectomy (9), lobectomy (2) and multiple subpial transaction (1). Surgical resections included combined temporal-extratemporal (13), extratemporal (8) and temporal (1) areas. Seventeen children (77%) had good seizure outcome; 8 (36%) seizure free and additional 9 (41%) with >90% seizure control (mean follow up 2.1 years). Ictal onset confined to <5 adjacent intracranial electrodes (5/5) predicted seizure freedom (p=0.02). Children with more than one type of seizure (5/5) (p=0.07) and children with both generalized spike and wave and extra-resection site epileptic discharge (3/3) did not become seizure free. Complete resection of preoperatively localized epileptogenic zone resulted in seizure freedom in 63% (5/8) and incomplete resections in 21% (3/14) (p=0.06). Age of onset, duration of epilepsy, presence of developmental delay (14), number of lobes involved in resection (single, 5; two, 8; >three, 9) or pathology (cortical dysplasia-9, dysembryoplastic neuroepithelial tumor-1, mesial temporal sclerosis-1, non-specific gliosis-6, no pathological lesion-4) did not correlate with seizure freedom.

Conclusion: Surgery for intractable partial epilepsy in children with normal MRI findings can provide good seizure outcome in majority of children. Restricted localized ictal onset zone predicted postoperative seizure freedom. Seizure freedom less likely occurred in multiple seizure types and incomplete resection of the proposed epileptogenic zone.