Abstracts

Rationale: Epilepsy surgery outcomes are best when a well demarcated lesion is visible on MRI, enabling a complete resection such as with malformations of cortical development. Although MRI can delineate characteristic structural abnormities in many patients, functional imaging and physiological recordings may indicate a more widespread epileptogenic region than is evident on MRI. Patients with bilateral MRI lesions (with the exception of Tuberous Sclerosis) may not be considered optimal surgery candidates. The purpose of this study was to assess surgical outcomes in children with bilateral lesions and intractable epilepsy. Methods: We describe the history and clinical course of 3 consecutive children with bilateral lesions on MRI who underwent epilepsy surgery at Children's of Alabama between 2010 and 2011. Children with Tuberous Sclerosis were excluded. Results: Patient 1 is an 18 year old female with panhypopituitarism, S/P craniopharyngioma resection at 7 and 11 years old with intractable epilepsy beginning at 16 years old. MRI showed bifrontal encephalomalacia, maximal on the right but EEG was more localizing to the left. After an initial bilateral subdural strip evaluation, left frontal grid evaluation revealed seizure onset from the left anterior mesial frontal and pre-frontal region. Patient 2 is a 14 year old female with congenital right hemiparesis and intractable seizures since 1 year old. She had a known perinatal lesion involving the frontal and parietal lobes, maximal left , with bilateral cystic dilatation of the lateral ventricles and numerous areas of cortical thickening and heterotopia. Scalp and invasive physiologic studies, however, indicated a left frontal epileptogenic zone. Patient 3 is a 5 year old male with intractable seizures since 8 months old. MRI showed multiple areas of mass-like grey matter gyral thickening and asymmetry within the left temporal lobe and right occipital lobe with periventricular heterotopia in bilateral occipital horns of the lateral ventricles. Invasive EEG revealed a right posterior epileptogenic zone. With an average follow up of 1.5 years, all 3 patients are seizure free since epilepsy surgery. Conclusions: Our results show that perinatal or acquired bilateral lesions may be amenable to epilepsy surgery. While the epileptogenic zone may extend beyond the visible margins such as in certain types of cortical dysplasia, our patients' results show that the epileptogenic zone may also be confined to a smaller substrate well within the visible lesion(s) in one hemisphere despite bilateral MRI lesions. Bilateral lesions are not a contraindication to epilepsy surgery. Successful seizure outcomes can safely be achieved in these children with careful pre-surgical evaluation and planning.