The role of SEEG in the presurgical decision-making process in MRI-normal mesial temporal lobe epilepsy.

OBJECTIVES: In patients with mesial temporal lobe epilepsy (mTLE) and normal MRI, anterior temporal lobectomy sparing the hippocampus might be considered because of the risk of post-operative memory deficit. However, it is unclear whether some patients with normal MRI and non-invasive EEG and semiological pattern highly suggestive of mesial temporal seizures demonstrate a seizure onset network sparing the hippocampus, potentially warranting surgery. METHODS: A retrospective study of 17 patients with mTLE epilepsy and normal MRI who underwent SEEG. Only patients whose non-invasive presurgical data suggested an unilateral mesial temporal epileptogenic zone (EZ), as defined by combination of ictal semiology and ictal EEG during scalp video-EEG, were included. SEEG data were analyzed using both visual and quantitative approaches. Two EZ organization were defined: (i) EZ involved the hippocampus at the onset of the ictal discharge (HIP group): (ii) patients in whom a delay>1sec was observed between the seizure onset and the involvement of the hippocampus (nHIP group). Non-invasive clinical and functional imaging data, as well as post-operative outcomes, were compared across groups. RESULTS: Eleven patients were included in HIP group and 6 in the nHIP group. In the nHIP group, the maximal epileptogenicity was in the amygdala in five patients and in the entorhinal cortex in one. The hippocampus normalized interictal spiking activity was not different between groups. None of the patients characteristics collected during the non-invasive presurgical workup was associated with the SEEG-based organization of the EZ. Twelve patients underwent a surgical resection, including temporal cortectomy sparing hippocampus in six. Seizure and neuropsychological post-operative outcomes were similar. CONCLUSION: In patients with MRI-normal mTLE, SEEG should be included in the surgical decision-making process because seizure organization cannot be predicted from non-invasive investigations. When hippocampus is not included in the EZ, temporal resection sparing the hippocampus can be considered.

Single and paired-pulse electrical stimulation during invasive EEG recordings.

Invasive EEG recordings are frequently required during the presurgical exploration of patients with drug-resistant focal epilepsy in order to clarify the epileptic zone location. Intracranial direct electrical stimulations (DES) induce EEG and/or clinical responses that participate in this evaluation. Clinical DES protocols (1Hz and/or 50Hz) trigger massive cortical activation that can elicit seizures, after-discharges or complex clinical signs. In contrast, low-energy (<1Hz) protocols activate more localized cortical regions using single-pulse electrical stimulations (SPES). SPES can elicit two main types of responses. Cortico-cortical evoked potentials (CCEPs) correspond to highly consistent early responses, appearing before 100ms after stimulation, with fixed latency; they are considered physiological and assess the effective connectivity between the recorded regions. Late responses appear after 100ms; they are rare, inconsistent with variable latency and are suggestive of an underlying epileptogenic cortex. Paired-pulse stimulation paradigm associates a conditioning and a test stimulation to induce intracortical inhibition or facilitation by modifying the response amplitude. Largely used in transcranial magnetic stimulation, it has rarely been applied to CCEP although the mechanisms put in place seem highly similar. Low frequency intracerebral stimulations allow analysing brain connectivity and cortical excitability with a high temporal and spatial resolution. The development of new stimulation protocols and the combination with imaging or statistical techniques recently offered promising results.

[Sequential MRI imaging of progressive bilateral rostro-caudal medullary infarction]. / Infarctus bulbaire paramédian bilatéral d'évolution progressive: à propos de deux cas documentés en imagerie par résonance magnétique séquentielle.

Bilateral medial medullary infarction is exceptional. Initial symptoms can be misleading, even for a trained neurologist. We report two patients who presented progressive quadriplegia, anarthia and dysphagia. Sequential MRI showed progressive constitution of the characteristic "heart appearance" sign.

Structural enhancement and video endoscopy: results of a large prospective comparative study.

INTRODUCTION: The structural-enhancement (SE) function electronically improves the video-endoscopic signal of Olympus processors (EXERA CV-160 or greater), enabling an increase in relief that may help in the detection of flat or ulcerated and raised lesions, especially those of small size. We assessed the diagnostic impact of this technique in the screening of lesions during basic video colonoscopy. METHODS: Maximum-level SE was programmed into processors on alternate weeks, and endoscopy dates were planned by an assistant unaware of the SE schedule, thus ensuring randomization. The endoscopists-senior practitioners with 3-29 years of digestive endoscopy practice-were informed of the experiment >3 weeks before it began and were not told about it again either before or during the study. This was to ensure that endoscopy examinations were performed without over-awareness of the technical conditions. GIF-100 to -160 Olympus endoscopes were used. RESULTS: During the study, 606 patients underwent upper digestive video-endoscopy, 305 with and 301 without the use of the SE function. Of 645 patients who underwent video colonoscopy, 593 were included in the study and 52 were excluded due to poor cleansing (8%); of those included, 330 were analyzed with and 263 without the SE function. We observed no differences in the detection of lesions (small or large) by either upper digestive endoscopy or video colonoscopy. CONCLUSION: This is the first study comparing video-endoscopy diagnosis with or without SE during upper digestive endoscopy and colonoscopy. The SE function available on Olympus video-endoscopy processors had no impact on the detection of lesions, not even on those of very small size.

Diagnostic accuracy of quantitative EEG to detect delayed cerebral ischemia after subarachnoid hemorrhage: A preliminary study.

OBJECTIVE: Delayed cerebral ischemia (DCI) is the most important and preventable morbidity cause after subarachnoid hemorrhage (SAH). Therefore, DCI early detection is a major challenge. Yet, neurological examination can be unreliable in poor grade SAH patients. EEG provides information from most superficial cortical area, with ischemia-related changes. This study aims at defining an alpha-theta/delta (AT/D) ratio decrease thresholds to detect DCI. METHODS: We used EEG with a montage matching vascular territories (right and left anterior central and posterior) and compared them to follow-up brain imaging. RESULTS: 15 SAH patients (Fischer ≥ 3, World Federation of Neurological Surgeons scale ≥4, 9 DCI) were monitored during 6.4 [4-8] days (min = 2d, max = 13d). AT/D changes could follow three different patterns: (1) prolonged or (2) transient decrease and (3) no decrease or progressive increase. A regional 30% decrease outlasting 3.7 h reached 100% sensitivity and 88.9% specificity to detect DCI. Only 22.6% were in a zone of uncertain diagnosis (3.7-8.04 h). These prolonged decreases, with a loss of transient changes, started in cortical areas evolving toward DCI, and preceded intracranial changes when available. CONCLUSION: Although this study has a small sample size, prolonged AT/D decrease seems to be a reliable biomarker of DCI. SIGNIFICANCE: cEEG changes are likely to precede cerebral infarction and could be useful at the bedside to detect DCI before irreversible damage.