O156 A functional connectivity analysis of patients with temporal lobe epilepsy with different propagation patterns

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Abstracts / Clinical Neurophysiology 128 (2017) e178–e303

Patients and method: We included 13 patients with HFS and 13 healthy subjects. Baseline BR, BR recovery at ISI of 300 ms and BRPPI at ISI of 100 ms were performed on the right sides of healthy subjects and on the asymptomatic and symptomatic sides of patients. Latency, amplitude and area of R1 and R2 were measured in all tests and compared among two groups using Mann-Whitney U test and ttest for paired groups when appropriate. Results: Baseline values of R1 and R2 were normal and similar among groups. The mean recovery of R2 area was the higher on both symptomatic side of HFS (77.5%) compared to asymptomatic side of HFS (46.5%) and compared to healthy subjects (27.2%, p = 0.007). All groups had inhibition during BR-PPI. However, PPI was low on both sides of HFS compared to healthy subjects (p = 0.010). There was no correlation between disease duration and recovery of BR or BR-PPI. Conclusions: HFS patients in this study had increased recovery of BR indicating increased excitability of BR circuit which was bilateral but more prominent on the symptomatic side. Similarly, inhibitory control upon BR circuit was prominently reduced on bilateral sides in HFS group. Significance: This study discloses the central changes in HFS. Keywords: Hemifacial spasm, Prepulse inhibition of blink reflex, Blink reflex recovery doi:10.1016/j.clinph.2017.07.164

O154 Deactivation of default mode network in focal epilepsy, inferred by single pulse electrical stimulation—Mihai Dragos Maliia 1, Cristian Donos 2, Andrei Barborica 3, Ioana Mindruta 4, Irina Popa 4, Mirela Ene 3, Sandor Beniczky 1 (1 Danish Epilepsy Center, Department of Clinical Neurophysiology, Dianalund, Denmark, 2 University of Texas Health Science Center at Houston, Department of Neurosurgery, Houston, USA, 3 University of Bucharest, Physics Department, Bucharest, Romania, 4 University Emergency Hospital, Department of Neurology, Bucharest, Romania) Objective: To investigate default-mode network (DMN) deactivation in different types of focal epilepsy by single pulse electric stimulation (SPES). Method: We analyzed 18 patients with focal epilepsy (8 frontal, 8 temporal, 2 posterior), implanted with depth electrodes. SPES was applied to each pair of adjacent contacts in seiwure onset zone (SOZ), and responses were recorded from the 10 different DMNhubs; The responses to SPES in Gamma, Ripple (R) and Fast-Ripple (FR) bands were quantified in a 60–250 ms time-window following each stimulation pulse and compared to baseline. Time of propagation was determined based on N1 latency. These responses were compared across the three epilepsy types. Results: Overall, we observed a significant deactivation of the DMN in the upper frequency ranges for all epilepsies (75% drop from baseline for gamma and 93% for R and FR). In the gamma band, the stimulation of frontal SOZs deactivated the ipsilateral posterior cingulate and precuneus significantly more than in the other epilepsytypes, with shorter general latencies of 22, 25 and 23 ms, respectively. Discussion: Our results might explain why in prefrontal focal epilepsies and in generalized epilepsies, thought to have a frontal generator, the consciousness is preferentially and significantly impaired. Significance: This is a promising method for quantifying the engagement of the consciousness processing areas by the epileptic focus. Detailed illustrations and tables for all 10 DMN-hubs, in all 3 high-frequency bands are provided.

Keywords: Single pulse electrical stimulation, Default mode network, Drug resistant epilepsy, SEEG doi:10.1016/j.clinph.2017.07.165

O155 Pre-seizure brain networks architecture as index of prediction in epileptic seizure—Francesca Miraglia 1, Fabrizio Vecchio 1, Catello Vollomo 2, Filomena Fuggetta 3, Beatrice Cioni 3, Paolo Maria Rossini 2 (1 IRCCS San Raffaele Pisana, Brain Connectivity Laboratory, Rome, Italy, 2 Università Cattolica del Sacro Cuore, Department of Neurology, Rome, Italy, 3 Università Cattolica del Sacro Cuore, Department of Neurosurgery, Rome, Italy) Objective: Epilepsy is a neurological disorder characterized by sudden and unpredictable occurrence of paroxysmal neuronal firing and sometimes evolving in clinically evident seizure. To predict seizure event, small-world characteristic in nine minutes before seizure, divided in three 3-min periods (T0, T1, T2) were investigated. Methods: Intracerebral recordings were obtained from 10 patients with drug resistant focal epilepsy examined by means of stereotactically implanted electrodes; analysis was focused in a period of low spiking (Baseline) and during two seizures for each subject. Weighted and undirected networks were built. Network vertices are electrodes’ contacts close to epileptic focus, edges are weighted by mscohere (magnitude squared coherence). Results: Differences were observed between Baseline and T1 and between Baseline and T2 in Theta band; and between Baseline and T1, Baseline and T2, and near-significant difference between T0 and T2 in Alpha 2 band. Moreover, an intra-band index was computed for small worldness as difference between Theta and Alpha 2. It was found a growing index trend from Baseline to T2. Discussion: Results of this study suggest that cortical network features significantly modify their configuration up to about 10 min before seizure onset. Significance: Identifying connectivity alterations could provide valuable informations at individual level on transient factors that influence the clinical manifestations of the disease. Conclusions: Cortical network shows a specific pre-seizure architecture which could predict the incoming epileptic seizure. This study opens interesting avenues for future researches investigating brain connectivity modifications approximating a clinical seizure also in order to address a preventive therapy. Keywords: Epilepsy, Graph theory, EEG doi:10.1016/j.clinph.2017.07.166

O156 A functional connectivity analysis of patients with temporal lobe epilepsy with different propagation patterns—Nermin Gorkem Sirin 1, Elif Kurt 2, Cigdem Ulasoglu Yıldız 2, Ani Kicik 3, Zerrin Karaaslan 1, Ali Bayram 2, Tamer Demiralp 4, Candan _ _ University, Istanbul Faculty of Medicine, Gurses 1 (1 Istanbul Department of Neurology, Istanbul, Turkey, 2 Istanbul University, Hulusi Behcet Life Sciences Research Laboratory, Istanbul, Turkey, 3 Istanbul University, Aziz Sancar Institute of Experimental Medicine, Department of Neuroscience, Istanbul, _ _ University, Istanbul Faculty of Medicine, Turkey, 4 Istanbul Department of Physiology, Istanbul, Turkey) Objective: To analyze the functional connectivity (FC) of temporal lobe and related areas in patients with temporal lobe epilepsy (TLE)

Abstracts / Clinical Neurophysiology 128 (2017) e178–e303

showing unilateral lateralized ictal discharges (uniTLE) and unusual ictal propagation patterns (UiP) defined as ‘switch-of lateralization’ and ‘bilateral asynchrony’ in scalp EEG. Methods: Twelve TLE patients with UiP (6 with left and 6 with right seizure-onset) and 13 patients with uniTLE (7 with left and 6 with right seizure-onset) and 13 healthy controls (HC) underwent resting state functional MRI. ROI-to-ROI FC analyses were carried out between homologous insula, hippocampi, parahippocampal gyri, amygdala, superior temporal and middle temporal gyri. Results: All TLE patients showed reduced overall FC compared to HC, where univariate comparisons revealed that the connectivities were significantly reduced between right and left insula, parahippocampal and superior temporal gyri. MANOVA among the 3 groups revealed that the uniTLE patients displayed a lower FC between the homologous parahippocampal gyri, while patients with UiP had lower FC between the homologous insula, parahippocampal and superior temporal gyri when compared with the HC. Furthermore, TLE patients with UiP showed significantly lower FC between the bilateral insula when compared with uniTLE patients. Discussion: While the reduction level of the resting-state FC between the homologous temporal lobe structures may depend on neural loss, a network change to protect contralateral temporal areas might also play role in further reduced FC in TLE with UiP. This might support the presence of independent epileptogenic zones bilaterally rather than a propagation from the contralateral hemisphere. Keywords: Temporal lobe epilepsy, Unusual propagation patterns, Functional connectivity doi:10.1016/j.clinph.2017.07.167

O157 Mapping the function and connectivity of the cingulate gyrus using stereo-encephalography (SEEG)—Irina Popa 1, Cristian Donos 2, Dragos Mihai Maliia 1, Andrei Barborica 2, Edouard Hirsch 3, Julia Scholly 3, Maria Paola Valenti-Hirsch 3, Anca Arbune 1, Andrei Daneasa 1, Ioana Mindruta 4 (1 Emergency University Hospital Bucharest, Neurology Department, Bucharest, Romania, 2 University of Bucharest, Physics Department, Bucharest, Romania, 3 Strasbourg University Hospital, Neurology Department, Strasbourg, France, 4 ‘‘Carol Davila” University of Medicine and Pharmacy, Neurology Department, Bucharest, Romania) Objectives: We aim to map the function and connectivity of the cingulate gyrus (CG) using cortical direct electrical stimulation. Methods: We selected patients explored by SEEG at the Emergency University Hospital Bucharest and at the Strasbourg University Hospital, that had minimum one electrode sampling the CG (anterior-ACG, middle-MCG or posterior-PCG), outside the epileptogenic zone. We systematically reviewed the functional stimulations (bipolar, 50 Hz, 0.25–3 mA). For 17 patients explored in Bucharest, cortico-cortical evoked potentials (CCEPs) elicited by single pulse electrical stimulations (SPES) were used to obtain the effective connectivity at a group level for each part of the CG. Results: We included 429 bipolar stimulations from 108 patients. From 151 stimulations in the ACG, 24.5% elicited a clinical response like: emotions (19%), vestibular (13.5%), thoracic sensation (13.5%), smile (11%). There are 135 stimulations in the MCG of which 53.3% elicited clinical responses like: elementary motor (24.94%), proprioception (22.22%), elementary somatosensitive (13.2%), compulsive motor (2.77%). There were 143 stimulations in the PCG and only 18.88% were positive, for example: executive function (11.11%), vestibular (7.4%).

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CCEPs analysis revealed that ACG is connected with the prefrontal (frontobasal and frontopolar) regions, anterior insula, mesiotemporal regions. MCG is connected with the primary and supplementary motor areas, insulo-perisylvian region and parietal lobe. PCG is connected with the ACG, MCG, prefrontal, parietal and temporal regions. Discussion: High frequency stimulations elicit clinical responses as a result of a network effect that we have mapped with CCEPs. Conclusions: There is a regional organization of the cingulate gyrus for each part both in function and connectivity. Significance: These findings help us understand the functional organization of the cingulate gyrus with possible implications in epilepsy surgery, depression or other mental disorders.

Keywords: Functional connectivity, Cortical direct electrical stimulations, CCEPs, Cingulate gyrus doi:10.1016/j.clinph.2017.07.168

O158 Excessive inhibitory visuomotor connections in parkinson’s disease with freezing of gait—Gionata Strigaro, Chiara Pizzamiglio, Paolo Barbero, Giacomo Tondo, Luca Magistrelli, Cristina Rovellotti, Cristoforo Comi, Roberto Cantello (University of Piemonte Orientale, Department of Translational Medicine, Section of Neurology, Novara, Italy) Objectives: Freezing of gait (FoG) is an invalidating symptom in patients with Parkinson’s disease (PD); it is defined as a brief, episodic absence or marked reduction of forward progression of the feet despite the intention to walk. The pathophysiology of this phenomenon remains obscure. Visual information are crucial for the initiation and control of movement, therefore an impairment of the visuomotor connections may underlie FoG. We used transcranial magnetic stimulation (TMS) to assess bilateral physiological connections (VMc) between primary visual (V1) and motor (M1) areas in PD with (PD + FoG) and without FoG (PDFoG).We hypothesized that PD+FoG would show an abnormal response in M1. Methods: Twelve PD+FoG were compared with 12 PD-FoG and 12 healthy subjects (HS) of similar age and sex. VMc was assessed bilaterally in resting participants by delivering a conditioning stimulus (CS) over the phosphene hotspot of V1 (intensity 90% phosphene threshold, PT) followed at two random interstimulus intervals (ISIs) (18 and 40 ms) by a test stimulus (TS) over left and right M1 to elicit a motor evoked potential (MEP) of 1 mV from the controlateral first dorsal interosseous (FDI). Results: In HS, the VMc was reproducible with MEP suppression at ISI of 18 and 40 ms. Similar effects occurred in PD-FoG. PD+FoG behaved differently, since the inhibitory VMc was significantly enhanced in the right, non-dominant hemisphere. Conclusions: PD+FoG had an excessive inhibitory response of the right M1 to inputs travelling from V1. Significance: This may represent one core factor for the pathophysiology of FoG.

Keywords: Parkinson’s disease, Freezing of gait, Visuomotor integration, Functional connectivity, Transcranial magnetic stimulation doi:10.1016/j.clinph.2017.07.169