Abstracts

Rationale: The identification of distinct subgroups of patients with epilepsy has become possible due to advances in neuroimaging and refinement of surgical techniques. More patients are now undergoing evaluations with invasive electrodes and resective surgery. We present a distinct group of patients with surgically-remediable frontal lobe epilepsy. All patients had an ictal onset zone confined along the superior frontal sulcus (SFS) as defined by invasive recordings. Methods: In this retrospective study we identified patients in our database from 1997 to 2007, who had undergone an invasive evaluation for resective surgery, and whose seizure onset zone was found to be confined within the superior frontal sulcus. We reviewed medical charts and report on eleven patients, who presented with seizures arising from the SFS (n=11). Results: Our patients (23.4 ± 11.7 years) consisted of seven women and four men with an average follow-up period of 26.3 ± 23.6 months after epilepsy surgery. All underwent resection of the superior and the middle frontal gyri, six from the right and five from the left hemisphere. In addition two patients had the inferior frontal gyrus resected. The average age of onset of seizures was 5.2 ± 4.2 years. Six reported an aura, although only four had a lateralizing somatosensory aura. All seizures had a prominent motor component with five patients’ seizures being classified as complex motor, four tonic bilateral asymmetric tonic and two dialeptic seizures. Lateralizing semiology was noted in six patients only. Small subtle areas of hyperintesity on MR imaging with FLAIR were identified within the SFS in nine patients, the other two showed no MRI abnormalities. All underwent an invasive evaluation with combined subdural and depth electrodes, which yielded an overlap of inter-ictal spiking and ictal onset zone within the SFS in all patients. Histopathology of the resected tissue confirmed the diagnosis of focal cortical dysplasia (FCD) in all patients. Seizure frequency, as reported by patients, before resective surgery was 75.1 ± 79.2 seizures per month, ten patients were classified as seizure-free after surgery (Engel I), one patient was classified Engel III post-resection. Conclusions: There are many interesting factors to this group’s clinical presentation, that show similarities amongst the group, e.g. somatosensory aura, complex motor and bilateral asymmetric tonic seizures. Location and extent of the dysplastic area along the SFS and corresponding propagation patterns account for the reported differences. This group of SFS-FCD patients exemplifies that careful invasive electrode placement (with combined subdural and depth electrodes) allows for tailored and successful topectomies in this subgroup of patients with frontal lobe epilepsy.