Introduction: Seizures are the most common presenting symptom of WHO grade II gliomas (LGGs) and impose significant coststo patients’ quality of life. Prior studies have demonstrated that gross total resection of LGGs is associated with higher rates of seizure control. However, many patients present with diffuse lesions unamenable to gross-total resection and it is unclear whether an extent of resection (EOR) threshold exists for long-term seizure control.

Methods: We reviewed the Barrow Neurological Institute’s experience with low-grade gliomas from 2000-2012. Pre- and post-operative MR imagingwas used to volumetrically calculate tumor volumes and EOR. Univariate analysis of patient characteristics included the chi-squared test and the Mann-Whitney U test. Analysis of post-operative seizure control was performed by applying a Cox Proportional Hazards model to independent pre-operative variables.

Results: One hundred and sixty cases were included for analysis; 109 patients presented with seizure activity (48 simple partial, 12 complex partial, 49 generalized). Temporal lobe involvement and oligodendroglial tumor subtype were associated with seizure presentation (p <.001 and p = 0.029 respectively). Among the cohort of patients presenting with seizures, the Engel class at 3 months immediately after surgery were as follows: Class I 86%, Class II 7%, Class III 3%, Class IV 3%. Among a scatter-plot of patients with seizures, all but one at Engel Class >1 had initial EOR less than 80%. Utilizing a multivariate Cox Proportional Hazards Model, we found an EOR under 80% to be associated with reduced length of post-operative seizure freedom (p = .003).

Conclusions: While recent data suggests a survival benefit associated with subtotal resection of LGGs, the corresponding impact on seizure control – a critical determinant of quality of patient life – remains unclear. Here, we demonstrate that, for newly-diagnosed LGG patients presenting with seizures, an EOR>80% is associated with greater post-operative seizure freedom.

Patient Care: This research attempts to define a threshold of surgical resection for low grade gliomas that will confer seizure control for patients. Such knowledge may be critically important when dealing with surgical planning for diffuse lesions that may not be amenable to gross-total resection, but where operative resection may still offer significant improvements in patient quality of life.

Learning Objectives: 1) Describe the impacts of seizure on quality of life for low grade glioma patients. 2) Describe the factors associated with seizure presentation of low grade gliomas. 3) Discuss the extent of resection threshold for low grade gliomas in order to control seizures.

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