Abstracts

Rationale:
Despite advances in localization techniques, long term outcomes after frontal lobe epilepsy (FLE) resections remain disappointing. Reasons for unfavorable surgical outcome in FLE include potential proximity to motor and eloquent cortex as well as rapid propagation of epileptiform activity making localization difficult even with invasive monitoring.The superior frontal sulcus and gyrus (SFS/G) is one of the commonest sites of cortical dysplasia. The superior frontal sulcus (SFS) is one of the deepest sulci in the brain and hence not surprisingly a common site for bottom of the sulcus dysplasia. Giving its extensive connections, seizures arising from the SFS/G, particularly anteriorly can have variable clinical manifestations mimicking temporal lobe or generalized epilepsies while seizures arising from the posterior part tend to present predominantly with elementary motor signs. The variability in semiology makes identification of SFS/G cortical dysplasia difficult particularly in patients with normal MRI. In this study we examined the clinical characteristics and role of multimodal neuroimaging in the evaluation of SFS/G cortical dysplasia in the context of a cohort of surgically-treated frontal lobe epilepsy
Method:
We identified patients with FLE who underwent epilepsy surgery at our institution. We included patients with SFS/G cortical dysplasia if they met any of the following criteria: Cortical dysplasia seen in the SFS/G on conventional or post processing MRI, Frontal resection or laser ablation involving predominantly SFS/G with good surgical outcome or depth electrode recordings demonstrating seizures arising from the SFS/G. All patients underwent comprehensive presurgical evaluation including 3T MRI, interictal positron emission tomography (PET) and ictal Single Photon Emission Computed Tomography SPECT and when available Magnetoencephalography (MEG). MRI post processing was performed retrospectively using morphometric analysis software (MAP). Clinical characteristics, imaging findings and surgical outcomes were reviewed
Results:
Eight patients were included. Age of seizure onset ranged from 18 months to 11 years. Asymmetric elementary motor signs were the predominant seizure semiology in 6 patients and were absent in 2 patients. Seven patients had history of seizures with impaired awareness, including one with absence seizures. Four patients had history of generalized tonic-clonic seizures. MRI was initially reported as normal in all patients. MRI post processing was positive in three patients. MEG was localizing in four out of five patients. SPECT was positive in three patients and was unsuccessful in another four and PET was localizing in two out of eight patients. Re review of MRI based on presurgical workup identified possible cortical dysplasia in five patients. Invasive monitoring was performed via stereotactic EEG in four patients and subdural electrodes in another four. Seven patients underwent surgical resections, limited to the SFG in only two and extending to the medial frontal cortex in the other five. One patient had laser ablation of the SFG. Cortical dysplasia IIA was detected in four patients, II B in one and gliosis and cortical delamination in another two. Engel class I was achieved in five patients and II in the other three
Conclusion:
SFS/G cortical dysplasia presents mostly during childhood or early adolescence with variable semiology. Dysplasia in the SFS might be more favorable for detection using MRI post processing and the tangential fields generated by neurons in the sulcal walls can be detected using MEG. Good surgical outcome can be achieved in most patients, sometimes with limited resections
Funding:
:The study was funded through KPRI Children's of Alabama grant