Localization of Barques in the Posterior Part of the Human Hippocampus
Abstract number :
3.142
Submission category :
3. Neurophysiology / 3C. Other Clinical EEG
Year :
2021
Submission ID :
1826669
Source :
www.aesnet.org
Presentation date :
12/6/2021 12:00:00 PM
Published date :
Nov 22, 2021, 06:55 AM
Authors :
Vasileios Kokkinos, PhD - Massachusetts General Hospital and Harvard Medical School; Alexandra Urban - University of Pittsburgh; Birgit Frauscher - Montreal Neurological Institute; Mirela Simon - Massachisetts General Hospital and Harvard Medical School; Helweh Hussein - Massachisetts General Hospital; Alan Bush - Massachisetts General Hospital and Harvard Medical School; Anto Bagic - University of Pittsburgh; R. Mark Richardson - Massachisetts General Hospital and Harvard Medical School
Rationale: The hippocampal barque is an epileptiform iEEG entity manifesting as a series of high-amplitude ≈14Hz spikes following a ramping-up—often ramping-down—profile that are sometimes overlaid on lower-amplitude ≈6Hz slow waves, and constitutes the intracranial correlate of the “14&6/sec positive spikes” benign scalp EEG variant. This study investigates the localization of barques along the anterio-posterior axis of the hippocampus in a series of epilepsy surgery candidates.
Methods: Thirty-three patients (17 females, mean age 38.8±12.2) implanted with two depth electrodes in either one (21/33, 13 right) or both hippocampi (12/33)—one in the anterior part and one in the posterior part of the hippocampus—were selected for this study. A total of 45 hippocampi (20 left and 25 right) were implanted with both anterior and posterior coverage, of which 21 were not involved at seizure onset. In turn, 158 8-hour long night-time seizure-free intracranial EEG (iEEG) studies were reviewed for the independent presence of barques in the anterior and posterior hippocampus. Electrode contact locations were determined by either post-implantation MRI or co-registration of pre-operative T1 MRI and post-implantation CT. Fisher’s exact test was used to assess statistical significance at p ≤ 0.05.
Results: 12/33 (36.36%) patients manifested barques, corresponding to 33.33% in the hippocampal group (15/45). In all 12 patients (100%), barques were identified in the posterior part of the hippocampus, while only in 25.00% (3/12) barques were also observed in the anterior part (p = 0.0003). Similarly, at the hippocampal level, all 15 hippocampi (100%) presented with barques in the posterior hippocampus, while only 3 (20.00%) of them showed concurrent and/or independently generated barques in the anterior hippocampus (p < 0.0001). The anterior hippocampus barques manifested exclusively in right hippocampi; a specificity supported by the fact that 2/3 patients had bilateral symmetric hippocampal implantation. There was no significant difference in the manifestation of posterior hippocampus barques between left and right hippocampi (p = 0.75).
Neurophysiology