P.189 Unruptured Posterior Cerebral Artery aneurysm causing temporal lobe epilepsy

Background: Cerebral aneurysms are an unusal cause of epilepsy. To date, several groups have reported temporal lobe seizures caused by aneurysms projecting into the parahippocampal gyrus. Given the low incidence of posterior cerebral artery aneurysms, they are a very rare cause of temporal lobe seizures. Methods: Here, we report a rare case of temporal lobe epilepsy caused by an unruptured aneurysm. We also present a review of the literature yielding two similar cases. Results: A previosuly well 56 year old male presented to a neurologist with symptoms consistent with temporal lobe epilepsy. He was started on carbamzepine and underwent imaging and neuropsychological assessments. An MRI suggested the existance of a 7mm posterior cerebral artery aneurysm arising from the P2 segment of the posterior cerebral artery and projecting into the parahippocampal gyrus. This was also confirmed with CT angiography and the patient elected to have the aneurysm clipped. Conclusions: Temporal lobe epilepsy is an uncommon presentation for unruptured cerebral aneurysms. We report a rare case wherein a laterally pointing PCA aneurysm was buried in the posterior parahippocampal gyrus. This aneurysm had caused perifocal gliosis leading to stereotyped seizures. Post-operatively, the patient has been seizure free.

The comparative study of invasive electroencephalography modalities in temporal lobe epilepsy

Introduction. Invasive video-EEG monitoring (invasive EEG) is indicated in patients with refractory focal epilepsy while localization of the epileptogenic zone is unclear. Methods of invasive EEG in different groups of patients demonstrate variable results.Objective: to analyse the results of invasive EEG via subdural and depth electrodes in patients with refractory temporal lobe epilepsy with mesial temporal lobe seizures.Materials and methods. The series of 37 patients who underwent invasive EEG from 2013 to 2020 was retrospectively analysed. The study includes primary adult patients with structural refractory focal epilepsy with mesial temporal lobe seizures without tumor and vascular pathology. Patients were divided onto 3 groups: 1) with foramen ovale electrodes 2) subdural strip electrodes and 3) combination of subdural strips and depths electrodes. The results of anteromedial temporal lobectomy after 6 months were classified according to Engel scale.Results. A group with foramen ovale electrodes included 7 patients, subdural strips – 23, combination – 7. The seizure onset zone was detected in 36 (97 %) cases. Serious complications were observed in 2 (29 %) cases in the group with foramen ovale electrodes. The mean follow-up in 23 (76 %) patients after resective surgery was 28.3 months. Favourable results (Engel I, II) were observed in 4 (80 %) patients with foramen ovale electrodes, in 8 (67 %) patients with subdural electrodes, in 6 (100 %) with combination. Unfavourable results (Engel III, IV) were noted in 1 (20 %) patient with foramen ovale electrode, in 4 (33 %) patients with subdural strips.Conclusion. All the presented modalities of invasive EEG are effective for localizing of seizure onset zone in this category of patients. Foramen ovale electrode using may be limited due to increased risk of complications.

835 Ictal Central Apneic Events Detected on Polysomnogram: An Educational Case Report

Introduction Ictal central apneas (ICA) are frequently observed in focal epilepsy, mostly with temporal lobe seizures, and have been considered as potential biomarkers of sudden unexpected death in epilepsy (SUDEP), particularly when they are prolonged and associated with significant hypoxemia. We present an interesting educational case report of occurrence of such ictal apneic events as recorded during a nocturnal diagnostic polysomnogram (PSG). Report of case(s) A 39-year-old woman with history of left focal epilepsy, hypertension, and headaches was referred to the sleep clinic for loud snoring, witnessed apneic events, and excessive daytime sleepiness. She subsequently underwent a diagnostic (PSG) that demonstrated severe obstructive sleep apnea (apnea-hypopnea index of 63.1) associated with significant hypoxemia (nadir SpO2 of 58%). In addition, the patient had one ictal discharge detected on the PSG’s limited electroencephalogram that occurred in N2 sleep and lasted for almost three minutes with a focal onset and progression in the left hemisphere. The ictal discharge was briefly preceded by central apneic events that continued to occur during and shortly after the termination of the ictal discharge. These ICA events were associated with severe oxygen desaturations down to an SpO2 of 62%. The only time during the PSG recording that the patient had central apneic events was around the ictal event. There were no behavior changes on the video during the seizure, but the ictal discharge was associated with a sustained increase in the mentalis muscles activity and a brief tachycardia. The patient’s neurologist was alerted about the above findings on PSG. The patient was taking a lower dose then prescribed of her anti-epileptic medication (topiramate) that was adjusted, and the patient was counseled on the risks associated with the above findings and positive airway pressure therapy was recommended for her severe sleep apnea. Conclusion The above case report illustrates the importance of polysomnography (specifically the recording of respiratory variables rarely performed in epilepsy monitoring units) in the evaluation of patients with epilepsy given that central apneic events (ICA and post-convulsive central apneas) potentially underlie SUDEP, the most common cause of mortality in refractory epilepsy patients and usually occurring during sleep. Support (if any) None

Atrioventricular Conduction in Mesial Temporal Lobe Seizures

Purpose: Asymmetric cerebral representation of autonomic function could help to stratify cardiac complications in people with epilepsy, as some seizures are associated with potentially deleterious arrhythmias including bradycardia and atrioventricular (AV) conduction block. We investigated seizure-related changes in AV conduction and ascertained whether these alterations depend on the hemisphere in mesial temporal lobe epilepsy (mTLE).Methods: EEG and ECG data of people with pharmacoresistant mTLE undergoing pre-surgical video-EEG telemetry with seizures independently arising from both hippocampi, as determined by intracranial depths electrodes were reviewed. RR and PR intervals were measured using one-lead ECG. Statistics were done with paired student's t-tests and linear regression analysis. Data are given as mean ± SD.Results: Fifty-six seizures of 14 patients (5 men, age 34.7 ± 9.8 years) were included (2 seizures per hemisphere and patient). There were no differences of absolute PR intervals and HR before and during unilateral ictal activity between left- and right-sided hippocampal seizures. Peri-ictal modulation of AV conduction, however, appeared greater with left-sided seizures, as the slope of the PR/HR correlations was significantly steeper with seizures originating in the left hippocampus. PR lengthening >200 ms or full block did not occur in any seizure.Conclusions: Our data show that on average, PR intervals shortens with mesial temporal lobe seizures with more prominent effects in seizures with left-sided onset, supporting the notion of lateralized cerebral control of cardiac function. The clinical relevance of this subtle finding is unclear but may indicate a lateralized susceptibility to seizure-related AV node dysfunction in mTLE.

Heart rate variability analysis for the identification of the preictal interval in patients with drug-resistant epilepsy

Electrocardiogram (ECG) recordings, lasting hours before epileptic seizures, have been studied in the search for evidence of the existence of a preictal interval that follows a normal ECG trace and precedes the seizure’s clinical manifestation. The preictal interval has not yet been clinically parametrized. Furthermore, the duration of this interval varies for seizures both among patients and from the same patient. In this study, we performed a heart rate variability (HRV) analysis to investigate the discriminative power of the features of HRV in the identification of the preictal interval. HRV information extracted from the linear time and frequency domains as well as from nonlinear dynamics were analysed. We inspected data from 238 temporal lobe seizures recorded from 41 patients with drug-resistant epilepsy from the EPILEPSIAE database. Unsupervised methods were applied to the HRV feature dataset, thus leading to a new perspective in preictal interval characterization. Distinguishable preictal behaviour was exhibited by 41% of the seizures and 90% of the patients. Half of the preictal intervals were identified in the 40 min before seizure onset. The results demonstrate the potential of applying clustering methods to HRV features to deepen the current understanding of the preictal state.