Authors :
Presenting Author: Sakhi Bhansali, MD – Neurological Institute
Balu Krishnan, PhD – Cleveland Clinic Foundation
Spencer Morris, MS – Epilepsy Center, Neurological Institute, Cleveland Clinic
Juan Bulacio, MD – Cleveland Clinic
Andreas V. Alexopoulos, MD – Epilepsy Center, Neurological Institute, Cleveland Clinic
Rationale: Insular-Opercular Epilepsy (IOE) is a challenging condition to diagnose and treat due to the deep localization and extensive connectivity of the insular cortex. Patterns of ictal SPECT hyperperfusion are consistent with expected seizure propagation and are relevant to SEEG hypothesis planning and interpretation. Patterns of hypoperfusion may implicate deactivation of networks that are not directly involved in seizure generation & propagation. We aim to utilize Ictal SPECT as a non-invasive functional imaging modality to identify reproducible ictal perfusion patterns in IOE seizures.
Methods:
We enrolled patients diagnosed with IOE with SEEG, who underwent a presurgical ictal SPECT examination.
We utilized Freesurfer©3 to reconstruct the cortical surface from patient MRIs and parcellated the surface into regions of interest (ROIs) using the Virtual Epileptic Patient (VEP)4 brain atlas.
We co-register the interictal and ictal SPECT images to the patient’s MRI and generated a subtraction image by subtracting the interictal study from the ictal SPECT.
We determined the average perfusion z-score and the percentage of hyperperfused and hypoperfused voxels within each ROI.
Results:
Ictal and interictal SPECT data from 19 patients with SEEG-confirmed IOE seen at CCF from 2012-2022 were analysed. (Table 1).
The Anterior Insula (AI) epilepsy had the following perfusion patterns: The left AI group, had a greater incidence of bilateral frontal region hyperperfusion (2 of 2 at pars orbitalis and opercularis), and contralateral insular hyperperfusion (2 of 2). The right AI group, showed less frequent contralateral insula hyperperfusion. Both showed bilateral hyperperfusion in deep grey matter and bilateral occipital hypoperfusion. The right AI group showing more pronounced contralateral frontal hypoperfusion (3 of 3 at left frontal pole, gyrus rectus, and pars orbitalis).
The Posterior Insula (PI) group had the following perfusion patterns: The Left PI group had bilateral hyperperfusion in subcortical structures (4 of 4 at putamen, pallidum ipsilaterally, and 3 of 4 contralaterally) and more common contralateral central (3 of 4) and pre-central (4 of 4) involvement. The right PI group showed a similar pattern of ipsilateral deep grey hyperperfusion (5 of 5), but less contralateral deep grey (3 of 5), indicating right-sided dominance. The hypoperfusion pattern for the PI onset group was again bilateral and posteriorly focused for the left insular patients, whereas the right insular patients exhibited less contralateral hypoperfusion.
Conclusions:
Our study demonstrates that SPECT is localizing & encompasses the ipsilateral insula in most case of IOE
Insular seizures activate bilateral deep grey matter with more prominent connections observed in left anterior insula onset patients.
Bilateral Insular hyperperfusion should be expected in the majority of IOE, especially in the Anterior Insula cases (Left >Right).
Clinicians should consider the possibility of false lateralization in patients with IOE when relying only on ictal SPECT findings.
We expect to identify novel perfusion-based biomarkers specific to IOE, leading to better diagnostic and targeted treatment options
Funding: -