The role of the orbitofrontal cortex and insula for prognosis of mesial temporal lobe epilepsy.

ABSTRACT

OBJECTIVE: We investigated the network between the medial temporal lobe (MTL) and extratemporal structures in patients with mesial temporal lobe epilepsy (MTLE) in order to explain the recurrence of MTLE after surgery. This study contributes to our current understanding of MTLE with stereotactic electroencephalography (SEEG). METHODS: We conducted a retrospective study of SEEG in 20 patients with MTLE in order to observe and analyze the intensity of interictal high-frequency oscillations (HFOs), as well as the dynamic course of coherence connectivity values of the MTL and extratemporal structures during the initial phase of the seizure. The results correlated with the patient prognosis. RESULTS: First, the presence of HFOs was observed during the interictal period in all 20 patients; these were localized to the MTL in 17 patients and the orbitofrontal cortex in seven patients and the insula in six patients. The better the prognosis, the greater the localization of the HFOs concentration in the MTL structures (p < 0.05). Second, significantly enhanced connectivity of MTL structures with the orbitofrontal cortex and insula was observed in most patients with MTLE, before and after the seizure onset (p < 0.05). Finally, the connectivity between extratemporal structures, such as the orbitofrontal cortex and insula, and MTL structures was significantly stronger in patients who had a worse prognosis than in other patients, before and after seizure onset (p < 0.05). INTERPRETATION: The epileptogenic network in recurrent MTLE is not limited to MTL structures but is also associated with the orbitofrontal cortex and insula. This can be used as a potential indicator for predicting the prognosis of patients after surgery, providing an important avenue for future clinical evaluation.