Abstracts

Seizure freedom after extra-temporal epilepsy surgery has been noted to be lower than after temporal lobectomy. Proximity to functional areas of the cortex and the diffuse nature of the abnormalities may reduce success. Accurate prognostication will assist pre-operative counselling of patients and selection of appropriate surgical candidates. Here, we investigate outcome for 76 patients who underwent extra-temporal surgery (1991 to 2003) at Austin Health, Australia., Procedures included lesionectomy (n=22), corticectomy (n=39) and lobectomy (n=15); sites were: frontal (n=46), parietal (n=16), occipital (n=7), multi-lobar (n=7). Survival analysis calculated the probabilities of post-operative seizure freedom after surgery., Median follow-up was 6 years (1.7-11.6). Seven patients had discontinued their anti-epileptic drugs. Eight patients had deceased, 4 deaths were a result of epilepsy or tumor progression. Histopathology comprised: dysplasia (53%), lesions (24%), previous injury (15%), and non-specific pathology (7%). The dysplasia group was comprised of balloon cell dysplasia (60%) and non-balloon cell dysplasia (40%).
Post-operatively, the probabilities of seizure freedom were: 42.1% (95%CI 30.9-52.9) at three months, 31.6% (95%CI 21.5- 42.1) at one year and 29.0% (95%CI 19.3- 39.3) at two years. Patients with previous injuries had a better seizure outcome (58% (95%CI 27-80) compared to other pathologies although this was not significant (p=0.33). Those with lesions did not have a seizure free advantage. Data at three months post surgery indicated that patients with non-balloon dysplasia had a low seizure free probability (13%, 95%CI 0.2-32) compared to those with balloon cell dysplasia (54%; 32-71) p = 0.00. Further analysis of the completeness of resection of pathology is in progress. Compared to our temporal lobectomy cohort, extra-temporal patients have a significantly lower seizure free outcome (p=0.00). However, preliminary data indicates that assessment of seizure improvement may be a more informative approach to the measurement of post-operative outcome amongst the extra-temporal cohort., Using strict measures of seizure-freedom, one third of patients are seizure free after extra-temporal resection. This group appear to differ from the temporal lobectomy cohort in terms of outcome and risk factors for recurrence. This information will improve the accuracy of pre-operative patient counselling., (Supported by University of Melbourne Early Career Researcher grant, Australian NHMRC, Austin Hospital Medical Research Foundation.)