Abstracts

RATIONALE: Orbitofrontal seizures are often clinically indistinguishable from complex partial seizures of temporal lobe origin. We review an approach to presurgical evaluation of three patients with orbitofrontal lesions and partial seizures with uncertain noninvasive localization.
METHODS: We reviewed charts of three patients (A, B, C) with orbitofrontal lesions(hamartoma, cortical dysplasia, trauma). All patients had gross lesions on MRI with normal-appearing temporal lobes. Patient A had a history of partial seizures and had been seizure-free after removal of a left orbitofrontal hamartoma; five years after the surgery, she developed seizures of a different semiology with non-localizing scalp frontotemporal changes ipsilateral to the lesion. Patient B had partial seizures of two distinct semiologies and MRI evidence of right orbitofrontal cortical dysplasia, with scalp recordings showing ipsilateral, non-localizing frontotemporal changes. Patient C had a history of multiple seizure types following head trauma, with MRI evidence of right orbitofrontal encephalomalacia; surface recording revealed seizures that appeared to arise from the right temporal lobe. However, invasive monitoring was pursued in light of the orbitofrontal lesion.
All patients underwent invasive electrophysiological monitoring. In cases A and B recordings were obtained using: a 6-contact depth electrode placed in the superior frontal gyrus directed inferiorly into the lesion, a lateral frontal 6-contact strip electrode inserted from the same burr hole, and two depth electrodes directed orthogonally into the amygdala and pes hippocampus. In case C, recordings were made using two medial and lateral frontal strip electrodes placed via a superior approach, and one laterally-placed subtemporal strip electrode with distal contacts approximating mesial temporal structures.
RESULTS: 1. An independent temporal focus was found in all cases. In addition, there were coexisting orbitofrontal seizures in two of the three (B, C); patient A had distant orbitofrontal seizures based on the previous evaluation and outcome from frontal resection.
2. Following surgical intervention (selective amygdalohippocampectomy in case A, orbitofrontal resection in case B targeting the predominant seizure type, multilobar resection in case C), there was complete seizure control in cases A & B and a significant reduction (Engel 2) in case C. Of note, the recurrent seizures in case C were mainly simple partial seizures, all of extratemporal semiology.
3. The pathology was mesiotemporal sclerosis in case A, cortical dysplasia in case B, and old hemorrhage (orbitofrontal) with normal temporal lobe in case C.
CONCLUSIONS: 1. In patients with independent orbitofrontal and temporal lobe seizures, multilobar resection can effectively control seizures without significant adverse neuropsychological consequences.
2. Invasive video/EEG telemetry was necessary in the evaluation of our patients with orbitofrontal lesions and partial seizures of unclear localization. This was especially helpful in the case where recurrence was shown to be from a focus independent of the orbitofrontal lesion.