Abstracts

Rationale: Low grade gangliogliomas (GG) and dysembryoplastic neuroepithelial tumors (DNT) are well recognized causes of chronic pharmaco-resistant focal epilepsy in children. They are composed of a mixture of neuronal and glial elements and show little or slow growth over time. The optimal management strategy remains controversial. Our practice has traditionally been an initial period of radiological surveillance with surgery being reserved for those with radiological progression or refractory seizures. We planned to review our series of children with low grade GG/DNT presenting with seizures in order to evaluate their clinical course and identify prognostic factors.Methods: We retrospectively reviewed the records of 151 children presenting to Great Ormond Street Hospital between 1995-2014 with seizures secondary to low grade GG/DNT. Analysis of clinical, neuroimaging, neuropsychological, and surgical factors was performed to determine independent predictors of outcome. Seizure outcome was classified as either seizure free (Engel class I), or not seizure free (Engle classes II-IV) for patients with at least 12 months follow up post-surgery. Full scale IQ (FSIQ) was used as a measure of cognitive outcome.Results: 91 males and 60 females were identified. Median age at seizure onset was 3 years (range 15 days-15 years). Tumor location was temporal in 66% of cases. Median pre-surgical FSIQ was 86. 120 patients (79.5%) underwent surgery. Of those who underwent surgery, the rationale was refractory epilepsy in 111 patients (92.5% of cases), and tumor growth in 9 patients (7.5% of cases). Median duration from seizure onset to surgery was 4 years (range 3 months-15 years). Histopathology review identified DNT in 77 (64%), GG in 43 (36%). MRI demonstrated residual tumor in 48% of cases. Median follow up after surgery was 2 years (range 7 months-14 years) with 92 patients (76%) having at least 12 months follow up after surgery. 5 patients had surgical complications (2 patients with transient blurring of vision,1 empyema, and 2 subdural hematomas requiring evacuation . 74 patients (80%) were seizure free, 18 (20%) continued to have seizures. Radiology demonstrated total resection was associated with higher rates of seizure freedom (p=0.026). Duration from seizure onset to surgery (p=0.46), location of tumor (p=0.87), and age at seizure onset (p=0.89) was not related to seizure outcome. Higher pre-surgical FSIQ was related to shorter epilepsy duration until surgery (p=0.014), and to older age at seizure onset (p=0.043).Conclusions: A high proportion of children presenting with epilepsy and low grade GG/DNT undergo surgical tumor resection with excellent post-operative seizure control. Complete resection is associated with increased seizure freedom. Higher pre-surgical cognitive functioning is associated with shorter epilepsy duration prior to surgery, and older age at seizure onset. Given the high rate of eventual surgery, early surgical intervention should be considered in children with continuing seizures associated with low grade GG/DNT.