Abstracts

There is almost no information regarding clinical and seizure features or results of resective epilepsy surgery in nonlesional orbitofrontal epilepsy.
Case series collected from 95 patients undergoing intracranial EEG recording prior to resective epilepsy surgery. Patients included if 1) high quality MRI showed no lesions; 2) intracranial electrode array sampled temporal neocortical (TN), temporal mesiobasal (MB), orbitofrontal (OF) and lateral frontal regions; and 3) ictal EEG onset preceded clinical onset and involved OF cortex in most seizures. Clinical features and surgical outcome determined from medical record review and phone followup. Intracranial EEG reviewed.
Six patients (3 males) identified. Mean age at seizure onset was 9 years. Two had nonspecific auras. All had complex partial seizures; in 4 automatisms suggested frontal lobe involvement, in 2 temporal lobe involvement. None had tonic-clonic seizures. Four had at least weekly seizures and two had daily seizures at presentation. With scalp interictal EEG, 4 of 6 had inferior frontal-anterior temporal, 5/6 sphenoidal and 1/6 midtemporal discharges. Intracarotid amytal test found evidence of hippocampal dysfunction in 4/6. Thirty five seizures were recorded with intracranial EEG (4-12/case). Sixteen emerged from OF regions alone (4/6 cases), 9 from OF and TN regions simultaneously (4/6 cases), 4 from OF and MB regions simultaneously (2/6 cases), 5 from TN alone (3/6 cases), and 1 from MB regions. EEG onset preceded clinical onset by 2-154 seconds (median 7 seconds) in 33/35 seizures. In seizures with OF onset, propagation to TN occurred in 1-23 seconds (median 5 seconds), always before spread to MB regions. One patient could not have surgery because seizure onset area overlapped with language cortex. One patient underwent OF resection, 4 had multilobar resections including OF, TN and MB regions based on extent of seizure onset area. Four have been seizure free since surgery, one has rare seizures (mean duration followup 20 months, range 2 [ndash] 57 months). The patient with persistent seizures had OF resection alone. No complications or neurological sequellae.
Patients with nonlesional OF epilepsy often have seizure onset areas involving both OF and TN regions either individually or simultaneously. Seizure onset areas and other features indicate that the epileptogenic lesion involves both OF and TN areas. Nontheless aggressive intracranial recording can define seizure onset areas adequately. Multilobar resection is safe and very effective.
[Supported by: MINCEP[reg] Epilepsy Care]