Authors :
Presenting Author: Khalid Al Orabi, MD – Schulich School of Medicine and Dentistry, Western University
Amit Persad, MD – Schulich School of Medicine and Dentistry, Western University
Arun Thurairajah, MSc – Schulich School of Medicine and Dentistry, Western University
Greydon Gilmore, PhD – Schulich School of Medicine and Dentistry, Western University
David A Steven, MD, MPH, FRCSC, FACS – Western University
Keith W MacDougall, MD – Western University
Jorge Burneo, MD, MSPH, FAAN, FAES, FRCPC – Western University
Ana Suller-Marti, PhD – Western University
Giovanni Pellegrino, MD, PhD – Western University
Jonathan C Lau, MD, PhD – Western University
Rationale:
Stereoelectroencephalography (SEEG) is the preferred surgical method for identifying the seizure onset zone (SOZ) in patients with focal intractable epilepsy, especially when non-invasive techniques yield inconclusive results. One particularly difficult type to localize is cingulate epilepsy. This study assesses the effectiveness of unilateral orthogonal interhemispheric SEEG (IH-SEEG) placement for investigating bilateral posterior cingulate cortices. Previous studies have documented the use of anterior and mid-cingulate electrodes [refs]; however, to our knowledge, bilateral coverage of the posterior cingulate has not been reported. While PCC epilepsy is uncommon, the PCC is a common site of propagation for temporal lobe epilepsy. Physical impediments, including the falx cerebri and deep cerebral veins, which separates the posterior cingulate regions in some patients, have limited consideration. This report is the first to introduce bilateral posterior cingulate monitoring using a unilateral interhemispheric (IH) / interhemispheric trans-falcine (IH-TF) technique.
Methods:
We describe seven patients who underwent bilateral posterior cingulate coverage using IH-SEEG (4 electrodes) and IH-TF-SEEG (3 electrodes) SEEG lead placement and describe the operative technique. Outcomes from implantation, as well as Euclidean and radial error were computed to assess the safety and accuracy of these trajectories.
Results:
All leads (interhemispheric/IH-transfalcine) were placed without adverse events, mislocalizations, hemorrhages, or any other complications. Postoperative error analysis indicated that euclidean entry error (0.83 mm, SD 0.36 mm ) and radial entry error (0.74 mm, SD 0.42 mm), euclidean target error (1.73 mm, SD 0.72 mm), radial target error (1.35 mm, SD 0.53mm) and less operating room time, saving 7.1 min for each electrode covering both sides. Each patient had successful localization of the seizure onset zone. The criteria for performing IH/IH-TF electrode placement were identified.
Conclusions:
The IH and IH-TF trajectories for PCC SEEG, are both feasible, safe, and cost-effective, owing to the reduced number of electrodes required and the decreased operative time involved. The IH SEEG completes cingulate sampling by using a single electrode sampling bilateral posterior cingulate, thereby facilitating successful localization of the seizure onset zone in challenging varieties of epilepsy cases when the ipsilateral and contralateral cingulate are of interest, but not the contralateral cortical surface. The feasibility and safety of unilateral trans-falcine SEEG open the door for considering the exploration of other midline cortical regions where the falx cerebri separates the two sides.
Funding: none