Authors :
Presenting Author: VASILEIOS KOKKINOS, CNIM, NA-CLTM, PhD, PhD, PhD, FACNS – Northwestern Memorial Hospital
Helweh Hussein, MD – Trident Medical Center; Danai-Georgia Sakelliadou, MD – Massachusetts General Hospital; R. Mark Richardson, MD, PhD – Massachusetts General Hospital; Anto Bagic, MD, PhD – University of Pittsburgh Medical Center; Alexandra Urban, MD – University of Pittsburgh Medical Center
Rationale:
This study investigates the variations in frequency of occurrence of hippocampal barques during sleep and compares findings to respective variations of their scalp manifestation, the 14&6/sec positive spikes variant.Methods:
From a pool of 145 epilepsy patients who underwent investigative surgical procedures at the University of Pittsburgh Comprehensive Epilepsy Program, we identified eleven (11) patients matching the following criteria: 1. They had sEEG that included unilateral (4/11) or bilateral (7/11) coverage of the hippocampus, 2. They had concurrent scalp EEG, 3. At least one of the implanted hippocampi was non-epileptogenic (not involved or secondarily involved in the seizure onset), and 4. Barques were identified in at least one of the electrode contacts residing in hippocampal parenchyma. This resulted in 12 non-epileptogenic hippocampi (5 left, 7 right) with barques for this study. We used the first seizure-free whole night sleep recording of their EMU stay. Sleep staging was performed at 60 sec intervals, including 60 minutes of wakefulness before sleep onset and 60 minutes after the morning arousal. The occurrence of barques and the 14&6/sec positive spikes variant was measured in the intracranial hippocampal and scalp EEG signals, respectively.Results:
The sleep architecture pattern of our patients was within normal limits (total sleep time 445.9 ± 42.3 min; awake time during sleep 13.1 ± 10.4 min; NREM I 24.4 ± 10.4 min [5.53%]; NREM II 217.3 ± 21.5 min [48.8%]; SWS 95.0 ± 29.2 min [21.1%]; REM 107.1 ± 22.8 min [23.9%]). The mean hippocampal barque count was 765.2 ± 251.2 per record (total count: 9,183). Hippocampal barques occurred predominantly during NREM II (total: 5,744; mean: 478.6 ± 176.1; 62.2 ± 6.0%) and SWS (total: 2,950; mean: 245.83 ± 92.9; 32.0 ± 6.2%), with rare to occasional occurrence in NREM I (total: 85; mean: 7.0 ± 2.8; 0.9 ± 0.4%), REM (total: 153; mean: 12.75 ± 4.0; 1.7 ± 0.6]) and wakefulness (total: 251; mean: 20.9 ± 6.3; 2.9 ± 0.9%). Barque density was increased during SWS (mean: 2.7 ± 1.0 per min) compared to NREM II (2.2 ± 1.0 per min) and other states (wakefulness: 0.1 ± 0.0 per min; NREM I: 0.3 ± 0.1 per min; REM: 0.1 ± 0.0 per min).
Concordant with the literature, the 14&6/sec positive spikes variant (total count: 2,406; mean: 343.7 ± 106.7) was found present in NREM II (total: 2,059; mean: 249.1 ± 100.2, 84.9 ± 3.6%) and SWS (total: 347; mean: 49.5 ± 12.8, 15.0 ± 3.6%) stages, and completely absent from the rest of sleep and wakefulness. While all 14&6/sec positive spikes correlated with barques, only 44.7 ± 6.1% of barque occurrences were accompanied by 14&6/sec positive spike variant manifestation.
Conclusions:
Hippocampal barques are predominant in, although not exclusive to, NREM II and SWS stages of sleep and tend to increase their presence during deep sleep intervals. Their scalp 14&6/sec positive spikes manifestation is confounded by the emergence of wakefulness, REM and NREM I stages, as well as the co-occurrence of intermittent and continuous slow waves of NREM II and SWS respectively.
Funding: None