Abstracts

Rationale: The patterns of post-operative seizure control in gliomas are poorly understood. A better understanding of treatment response and seizure control in tumour associated epilepsy (TAE) is essential for the formulation of rational treatment strategies and design of prospective treatment trials. Our aim is to document patterns of seizure control and response to anti-epileptic drugs (AED) in patients with supratentorial gliomas. Methods: This was a retrospective analysis of 186 patients with supratentorial gliomas. Seizure patterns were classified into 4 groups: A - no post-operative seizure; B ?" early post-operative seizure control within 6 months; C - fluctuating seizure control; D ?" never seizure-free. Clinico-pathological predictors of seizure outcome pattern were examined in univariate and multivariate analyses. Rates and duration of seizure freedom, subsequent seizure relapse and response to antiepileptic drugs (AED) were analysed. Results: Among the patients included, 49 had (26.3%) grade II, 28 (15.1%) had grade III and 109 (58.6%) had grade IV glioma. Outcome pattern A was observed in 95 (51.1%), B in 22 (11.8%), C in 45 (24.2%) and D in 24 (12.9%). 119 patients had at least one seizure and were classified as having tumour associated epilepsy (TAE). Compared to pattern A, pattern B was predicted by histological progression (OR 4.30, CI 1.53-12.06, p = 0.006); pattern C by tumour grade (OR 0.58, CI 0.35-0.95, p = 0.03), pre-operative seizure (OR 2.29, CI 1.01-5.19, p = 0.047) and histological progression (OR 2.42, CI 1.07-5.45, p = 0.033); and pattern D by pre-operative seizure (OR 5.33, CI 1.87-15.21, p = 0.002) and gross total resection (OR 0.20, CI 0.06-0.63, p = 0.007). Among patients with TAE, 57.5% of grade II, 68.2% of grade III and 26.3% of grade IV experienced a period of 12-month seizure freedom. After first 12-month seizure remission, 39.1%, 60.0%, 13.3% of grade II, III, IV glioma patients respectively experienced subsequent seizure. Median duration of seizure freedom was 45.4 months (range 12.0 ?" 186.0 months) in grade II, 39.0 months (range 12.0 ?" 120.0 months) in grade III and 24.7 months (range 13.0 ?" 112.4 months) in grade IV glioma patients. 18.1% of those with TAE reached terminal seizure freedom of at least 12 months on their first post-operative AED regimen, 5.2% on their second regimen and 4.3% on subsequent regimens. Conclusions: Distinct patterns of post-operative seizure control exist in gliomas, they have specific risk factor profiles and we hypothesize that these correspond to unique pathogenic mechanisms of TAE. 12-month seizure freedom with subsequent relapse is frequent in grade II-III gliomas. Response to AEDs is markedly poorer than the general epilepsy population which highlights the complex epileptogenicity of gliomas. These findings have implications for the timing of AED withdrawal and add insights into the neurobiology of TAE. Funding: Andrew Neal was supported by an Australian Postgraduate Award Scholarship (University of Melbourne), Epilepsy Society Australia UCB Clinical Pharma Scholarship and the RMH Neuroscience Foundation