Authors :
Presenting Author: Elena Pasini, MD – IRCCS Istituto delle Scienze Neurologiche di Bologna, Bologna, Italy
Lorenzo Ferri, Dr – Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Italy; Roberto Mai, Dr – Claudio Munari Epilepsy Surgery Center, Niguarda Hospital, Milan, Italy; Roberto Michelucci, MD, PhD – IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy; Francesca Bisulli, Prof. – IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy . Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Italy; Francesco Cardinale, MD – Claudio Munari Epilepsy Surgery Center, Niguarda Hospital, Milan, Italy; Matteo Martinoni, MD – IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy; Giovanni Sighinolfi, Dr – Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Italy; Gianfranco Vornetti, MD – IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy . Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Italy; Caterina Tonon, Prof. – IRCCS Istituto delle Scienze Neurologiche di Bologna, Italy . Department of Biomedical and NeuroMotor Sciences (DIBINEM), University of Bologna, Italy
Rationale:
Identification of the epileptogenic zone (EZ) often requires invasive techniques like stereo-EEG (SEEG) to plan a surgical treatment. Unfortunately, only the 59% of the SEEG-studied patients are seizure free after surgical resection (1). Therefore, complementary methods or techniques may improve results on seizures.
Among the non-invasive preoperative investigations, EEG-fMRI has gained popularity. However even the association of interictal EEG-fMRI and stereo-EEG shows a positive predictive value of about 50%, perhaps due to the lack of information on the early spreading of ictal activity (2).
Methods:
In our center, each SEEG patient also undergoes an EEG-fMRI study, which is then integrated with all available clinical, EEG and neuroimaging data. When an ictal event is recorded, different EEG-fMRI time intervals can be analyzed.
We report here the case of a 23-year-old right-handed patient with drug-resistant focal epilepsy associated with a right temporo-parieto-occipital ulegyria. She underwent prolonged video-EEG (VEEG) monitoring, MRI, fdg-PET, ictal EEG-fMRI, SEEG and is currently awaiting a tailored full temporal lobectomy.
Results:
VEEG findings suggested right temporal lobe involvement, both mesial and basal/lateral. PET showed severe hypometabolism in the right basal/lateral temporal and parieto-occipital lobes and moderate hypometabolism in the right temporo-mesial structures. Temporo-perisylvian SEEG was mandatory to better define the EZ and extent of resection.
SEEG showed a SOZ encompassing the fusiform and parahippocampal gyri, while showing a large epileptogenic network with early involvement of all the other temporal regions and later spread to the other hypometabolic structures.
During EEG fMRI acquisition, we recorded not only interictal abnormalities but also a habitual seizure of the patient. Conventional analysis of interictal spikes showed involvement of the anterior insula and temporal pole, while the ictal activations overlapped with the SOZ defined by the SEEG, especially at the level of the collateral sulcus. Finally, we applied a series of different hemodynamic response function models, peaking at different time intervals from seizure onset, in order to confirm the discharge diffusion throughout the whole brain and validate our surgical plan.
Conclusions:
EEG-fMRI complements SEEG findings because it covers the whole brain. Its advanced analysis, performed at different time intervals when a seizure is recorded, can return the SOZ and spreading pathways.
References
1. Cardinale F, Rizzi M, Vignati E, Cossu M, Castana L, d’Orio P, et al. Stereoelectroencephalography: retrospective analysis of 742 procedures in a single centre. Brain 2019;142:2688–704.
2. Koupparis A, von Ellenrieder N, Khoo HM, Zazubovits N, Nguyen DK, Hall JA, et al. Association of EEG-fMRI Responses and Outcome After Epilepsy Surgery. Neurology 2021 Aug 16;97(15):e1523-e1536.
Funding: None