Abstracts

Rationale: The significance of the extent of the resection of the temporal-lateral neocortex with respect to post-surgical outcome is a source of debate among epileptologists. Most epilepsy centers do standard lobectomies which include a pre-determined resection of temporal lateral neocortex, which typically consist of 3cm along the superior temporal gyrus (STG), 4cm along the medial temporal gyrus (MTG) and 4cm along the inferior temporal gyri (ITG) in the dominant hemisphere and 5-6cm along the MTG and ITG in the non-dominant hemisphere. A minority of centers, however, tailor the extent of the resection according to the EEG data obtained with intracranial recordings and/or intraoperative electrocorticography (ECoG). The purpose of this study is to investigate whether the extent of the resection of the temporal-lateral cortex is related to the seizure outcome following anterior temporal lobectomy.Methods: This was a retrospective study of 111 consecutive patients who underwent an anterior temporal lobectomy (ATL) between 1996 and 2003 at the Rush Epilepsy Center. Every patient underwent a tailored resection of temporal lateral neocortex according to prolonged intracranial V-EEG data or intraoperative pre-resective ECoG data, using a previously published protocol (Kanner et al, Archives of Neurology 1995; 52(2): 173-178). Post-surgical seizure outcome was established with Engel’s classification (Class I –no disabling seizures; Class II-rare seizures(1 -2/year); Class III: >90% reduction in seizure frequency; Class IV < 90% reduction). The postsurgical follow up period was one year. The extent of resection of temporal lateral neocortex was based on the neurosurgeon’s measurements in the OR at the completion of the resection for the STG, MTG and ITG in centimeters (cms). The impact of extent of resection of mesial temporal structures was also investigated. The extent of resection was coded as complete, partial and spared according to the neurosurgeon’s grading at the end of the resection. Patients were grouped by cause of temporal lobe epilepsy (TLE) into: mesial temporal sclerosis, lesional TLE and idiopathic TLE. Statistical analyses included t-test for continuous variables and chi-square statistics for categorical variables. Extent of resection was compared according to outcome and co-variates including cause of TLE and side of resection. Results: There were no significant differences in seizure outcome with respect to the extent of the resection of temporal-lateral neocortex for the entire group. Lack of differences persisted when the analyses factored in the cause of TLE and the side of resection. Extent of resection of mesial structures did not differ with respect to post-surgical seizure outcome, either.Conclusions: The absence of any association between seizure outcome and the extent of the resection of temporal lateral neocortex questions the use of predetermined resections of lateral neocortex in standard lobectomies, particularly in surgeries involving the dominant hemisphere.