scholarly journals The Connectivity Index: An Effective Metric for Grading Epileptogenicity

2019 ◽  
Author(s):  
Qi Yan ◽  
Nicolas Gaspard ◽  
Hitten P Zaveri ◽  
Hal Blumenfeld ◽  
Lawrence J. Hirsch ◽  
...  
Keyword(s):  
Average Distance ◽  
Single Pulse ◽  
Brain Regions ◽  
Control Site ◽  
Connectivity Index ◽  
Evoked Responses ◽  
Seizure Onset ◽  
Seizure Onset Zone ◽  
Site Of Stimulation ◽  
Stimulation Of

AbstractObjectiveTo investigate the performance of a metric of functional connectivity to classify and grade the excitability of brain regions based on evoked potentials to single pulse electrical stimulation (SPES).MethodsPatients who received 1-Hz frequency stimulation between 2003 and 2014 at Yale at prospectively selected contacts were included. The stimulated contacts were classified as seizure onset zone (SOZ), highly irritative zone (IZp) or control. Response contacts were classified as seizure onset zone (SOZ), active interictal (IZp), quiet or other. The normalized number of responses was defined as the number of contacts with any evoked responses divided by the total number of recorded contacts, and the normalized distance is the ratio of the average distance between the site of stimulation and sites of evoked responses to the average distances between the site of stimulation and all other recording contacts. A new metric we labeled the connectivity index (CI) is defined as the product of the two values.Results57 stimulation-sessions in 22-patients were analyzed. The connectivity index (CI) of the SOZ was higher than control (median CI of 0.74 vs. 0.16, p = 0.0002). The evoked responses after stimulation of SOZ were seen at further distance compared to control (median normalized distance 0.96 vs. 0.62, p = 0.0005). It was 1.8 times more likely to record a response at SOZ than in non-epileptic contacts after stimulation of a control site. Habitual seizures were triggered in 27% of patients and 35 % of SOZ contacts (median stimulation intensity 4 mA) but in none of the control or IZp contacts. Non-SOZ contacts in multifocal or poor surgical outcome cases had a higher CI than non-SOZ contacts in those with localizable onsets (medians CI of 0.5 vs. 0.12, p = 0.04). There was a correlation between the stimulation current intensity and the normalized number of evoked responses (r = + 0.49, p 0.01) but not with distance (r = + 0.1, p 0.64)ConclusionsWe found enhanced connectivity when stimulating the SOZ compared to stimulating control contacts; responses were more distant as well. Habitual auras and seizures provoked by SPES were highly predictive of brain sites involved in seizure generation.

scholarly journals The connectivity index: an effective metric for grading epileptogenicity

2020 ◽  
Vol 133 (4) ◽  
pp. 971-978
Author(s):  
Qi Yan ◽  
Nicolas Gaspard ◽  
Hitten P. Zaveri ◽  
Hal Blumenfeld ◽  
Lawrence J. Hirsch ◽  
...  
Keyword(s):  
Average Distance ◽  
Single Pulse ◽  
Brain Regions ◽  
Epileptic Activity ◽  
Control Site ◽  
Connectivity Index ◽  
Evoked Responses ◽  
Stimulation Current ◽  
Site Of Stimulation ◽  
Stimulation Of

OBJECTIVEThe aim of this study was to investigate the performance of a metric of functional connectivity to classify and grade the excitability of brain regions based on evoked potentials in response to single-pulse electrical stimulation (SPES).METHODSPatients who underwent 1-Hz frequency stimulation at prospectively selected contacts between 2003 and 2014 at the Yale Comprehensive Epilepsy Center were included. The stimulated contacts were classified as the seizure onset zone (SOZ), highly irritative zone (possibly epileptogenic irritative zone [IZp]), and control contacts not involved in the epileptic activity. Response contacts were classified as SOZ, active interictal irritative zone (IZ), quiet, or other. The normalized number of responses was defined as the number of contacts with any evoked responses divided by the total number of recorded contacts, and the normalized distance is the ratio of the average distance between the site of stimulation and sites of evoked responses to the average distances between the site of stimulation and all other recording contacts. A new metric that the authors labeled the connectivity index (CI) is defined as the product of the 2 values.RESULTSA total of 57 stimulation sessions in 22 patients were analyzed. The CI of the SOZ was higher than for control contacts (median CI of 0.74 vs 0.16, p = 0.0002). The evoked responses after stimulation of SOZ were seen at further distances compared to control (median normalized distance 0.96 vs 0.62, p = 0.0005). It was 1.8 times more likely that a response would be recorded at the SOZ than in nonepileptic contacts after stimulation of a control site. Habitual seizures were triggered in 27% of patients and 35% of SOZ contacts (median stimulation intensity 4 mA) but in none of the control or IZp contacts. Non-SOZ contacts in multifocal or poor surgical outcome cases had a higher CI than non-SOZ contacts in patients with localizable onsets (median CI of 0.5 vs 0.12, p = 0.04). There was a correlation between the stimulation current intensity and the normalized number of evoked responses (r = + 0.49, p = 0.01) but not with distance (r = + 0.1, p = 0.64).CONCLUSIONSThe authors found enhanced connectivity when stimulating the SOZ compared to stimulating control contacts; responses were more distant as well. Habitual auras and seizures provoked by SPES were highly predictive of brain sites involved in seizure generation.

scholarly journals Spatial variation in high-frequency oscillation rates and amplitudes in intracranial EEG

Neurology ◽  
2018 ◽  
Vol 90 (8) ◽  
pp. e639-e646 ◽  
Author(s):  
Hari Guragain ◽  
Jan Cimbalnik ◽  
Matt Stead ◽  
David M. Groppe ◽  
Brent M. Berry ◽  
...  
Keyword(s):  
High Frequency ◽  
Anatomic Variation ◽  
Brain Regions ◽  
Brain Atlas ◽  
Reproducible Research ◽  
High Frequency Oscillation ◽  
Seizure Onset ◽  
Frequency Oscillation ◽  
Intracranial Eeg ◽  
Seizure Onset Zone

ObjectiveTo assess the variation in baseline and seizure onset zone interictal high-frequency oscillation (HFO) rates and amplitudes across different anatomic brain regions in a large cohort of patients.MethodsSeventy patients who had wide-bandwidth (5 kHz) intracranial EEG (iEEG) recordings during surgical evaluation for drug-resistant epilepsy between 2005 and 2014 who had high-resolution MRI and CT imaging were identified. Discrete HFOs were identified in 2-hour segments of high-quality interictal iEEG data with an automated detector. Electrode locations were determined by coregistering the patient's preoperative MRI with an X-ray CT scan acquired immediately after electrode implantation and correcting electrode locations for postimplant brain shift. The anatomic locations of electrodes were determined using the Desikan-Killiany brain atlas via FreeSurfer. HFO rates and mean amplitudes were measured in seizure onset zone (SOZ) and non-SOZ electrodes, as determined by the clinical iEEG seizure recordings. To promote reproducible research, imaging and iEEG data are made freely available (msel.mayo.edu).ResultsBaseline (non-SOZ) HFO rates and amplitudes vary significantly in different brain structures, and between homologous structures in left and right hemispheres. While HFO rates and amplitudes were significantly higher in SOZ than non-SOZ electrodes when analyzed regardless of contact location, SOZ and non-SOZ HFO rates and amplitudes were not separable in some lobes and structures (e.g., frontal and temporal neocortex).ConclusionsThe anatomic variation in SOZ and non-SOZ HFO rates and amplitudes suggests the need to assess interictal HFO activity relative to anatomically accurate normative standards when using HFOs for presurgical planning.

scholarly journals Weighted and directed interactions in evolving large-scale epileptic brain networks

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Henning Dickten ◽  
Stephan Porz ◽  
Christian E. Elger ◽  
Klaus Lehnertz
Keyword(s):  
Large Scale ◽  
Complex Dynamics ◽  
Brain Networks ◽  
Population Sample ◽  
Brain Regions ◽  
Seizure Onset ◽  
Dynamical Disease ◽  
Seizure Onset Zone ◽  
Promising Line ◽  
And Function

Abstract Epilepsy can be regarded as a network phenomenon with functionally and/or structurally aberrant connections in the brain. Over the past years, concepts and methods from network theory substantially contributed to improve the characterization of structure and function of these epileptic networks and thus to advance understanding of the dynamical disease epilepsy. We extend this promising line of research and assess—with high spatial and temporal resolution and using complementary analysis approaches that capture different characteristics of the complex dynamics—both strength and direction of interactions in evolving large-scale epileptic brain networks of 35 patients that suffered from drug-resistant focal seizures with different anatomical onset locations. Despite this heterogeneity, we find that even during the seizure-free interval the seizure onset zone is a brain region that, when averaged over time, exerts strongest directed influences over other brain regions being part of a large-scale network. This crucial role, however, manifested by averaging on the population-sample level only – in more than one third of patients, strongest directed interactions can be observed between brain regions far off the seizure onset zone. This may guide new developments for individualized diagnosis, treatment and control.

scholarly journals The seizure onset zone drives state-dependent epileptiform activity in susceptible brain regions

2019 ◽  
Vol 130 (9) ◽  
pp. 1628-1641 ◽  
Author(s):  
Joshua M. Diamond ◽  
Julio I. Chapeton ◽  
William H. Theodore ◽  
Sara K. Inati ◽  
Kareem A. Zaghloul
Keyword(s):  
Epileptiform Activity ◽  
Brain Regions ◽  
Seizure Onset ◽  
State Dependent ◽  
Seizure Onset Zone

scholarly journals Stable high frequency background EEG activity distinguishes epileptic from healthy brain regions

2020 ◽  
Vol 2 (2) ◽  
Author(s):  
Annika Minthe ◽  
Wibke G Janzarik ◽  
Daniel Lachner-Piza ◽  
Peter Reinacher ◽  
Andreas Schulze-Bonhage ◽  
...  
Keyword(s):  
High Frequency ◽  
Background Activity ◽  
Sleep Stage ◽  
Strong Association ◽  
Brain Regions ◽  
High Frequency Oscillation ◽  
Seizure Onset ◽  
High Frequency Oscillations ◽  
Seizure Onset Zone ◽  
Low Entropy

Abstract High-frequency oscillations are markers of epileptic tissue. Recently, different patterns of EEG background activity were described from which high-frequency oscillations occur: high-frequency oscillations with continuously oscillating background were found to be primarily physiological, those from quiet background were linked to epileptic tissue. It is unclear, whether these interactions remain stable over several days and during different sleep-wake stages. High-frequency oscillation patterns (oscillatory vs. quiet background) were analysed in 23 patients implanted with depth and subdural grid electrodes. Pattern scoring was performed on every channel in 10 s intervals in three separate day- and night-time EEG segments. An entropy value, measuring variability of patterns per channel, was calculated. A low entropy value indicated a stable occurrence of the same pattern in one channel, whereas a high value indicated pattern instability. Differences in pattern distribution and entropy were analysed for 143 280 10 s intervals with allocated patterns from inside and outside the seizure onset zone, different electrode types and brain regions. We found a strong association between high-frequency oscillations out of quiet background activity, and channels of the seizure onset zone (35.2% inside versus 9.7% outside the seizure onset zone, P < 0.001), no association was found for high-frequency oscillations from continuous oscillatory background (P = 0.563). The type of background activity remained stable over the same brain region over several days and was independent of sleep stage and recording technique. Stability of background activity was significantly higher in channels of the seizure onset zone (entropy mean value 0.56 ± 0.39 versus 0.64 ± 0.41; P < 0.001). This was especially true for the presumed epileptic high-frequency oscillations out of quiet background (0.57 ± 0.39 inside versus 0.72 ± 0.37 outside the seizure onset zone; P < 0.001). In contrast, presumed physiological high-frequency oscillations from continuous oscillatory backgrounds were significantly more stable outside the seizure onset zone (0.72 ± 0.45 versus 0.48 ± 0.53; P < 0.001). The overall low entropy values suggest that interactions between high-frequency oscillations and background activity are a stable phenomenon specific to the function of brain regions. High-frequency oscillations occurring from a quiet background are strongly linked to the seizure onset zone whereas high-frequency oscillations from an oscillatory background are not. Pattern stability suggests distinct underlying mechanisms. Analysing short time segments of high-frequency oscillations and background activity could help distinguishing epileptic from physiologically active brain regions.

scholarly journals Transfer Function Models for the Localization of Seizure Onset Zone From Cortico-Cortical Evoked Potentials

2020 ◽  
Vol 11 ◽  
Author(s):  
Golnoosh Kamali ◽  
Rachel June Smith ◽  
Mark Hays ◽  
Christopher Coogan ◽  
Nathan E. Crone ◽  
...  
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Patient Specific ◽  
Seizure Freedom ◽  
Evoked Responses ◽  
Seizure Onset ◽  
Seizure Onset Zone ◽  
Function Models ◽  
Peak Gain ◽  
Transfer Function Models

Surgical resection of the seizure onset zone (SOZ) could potentially lead to seizure-freedom in medically refractory epilepsy patients. However, localizing the SOZ can be a time consuming and tedious process involving visual inspection of intracranial electroencephalographic (iEEG) recordings captured during passive patient monitoring. Cortical stimulation is currently performed on patients undergoing invasive EEG monitoring for the main purpose of mapping functional brain networks such as language and motor networks. We hypothesized that evoked responses from single pulse electrical stimulation (SPES) can also be used to localize the SOZ as they may express the natural frequencies and connectivity of the iEEG network. To test our hypothesis, we constructed patient specific transfer function models from the evoked responses recorded from 22 epilepsy patients that underwent SPES evaluation and iEEG monitoring. We then computed the frequency and connectivity dependent “peak gain” of the system as measured by the norm from systems theory. We found that in cases for which clinicians had high confidence in localizing the SOZ, the highest peak gain transfer functions with the smallest “floor gain” (gain at which the dipped 3dB below DC gain) corresponded to when the clinically annotated SOZ and early spread regions were stimulated. In more complex cases, there was a large spread of the peak-to-floor (PF) ratios when the clinically annotated SOZ was stimulated. Interestingly for patients who had successful surgeries, our ratio of gains, agreed with clinical localization, no matter the complexity of the case. For patients with failed surgeries, the PF ratio did not match clinical annotations. Our findings suggest that transfer function gains and their corresponding frequency responses computed from SPES evoked responses may improve SOZ localization and thus surgical outcomes.

A Novel Method of Seizure Onset Zone Localization by Serial Tc-99m ECD Brain Perfusion SPECT Clearance Patterns

2021 ◽  
Author(s):  
Chanan Sukprakun ◽  
Chusak Limotai ◽  
Kitiwat Khamwan ◽  
Panya Pasawang ◽  
Supatporn Tepmongkol
Keyword(s):  
Brain Perfusion ◽  
Brain Regions ◽  
Diagnostic Tools ◽  
Seizure Onset ◽  
Visual Grading ◽  
Seizure Onset Zone ◽  
Significant Difference ◽  
Perfusion Spect ◽  
Novel Method ◽  
Drug Resistant Epilepsy

Abstract In this prospective study, we postulate that there is a difference between clearance of [99mTc]Tc- ethyl cysteinate dimer (ECD) in the seizure onset zone (SOZ) and other brain areas and thus SOZ localization by clearance patterns might become a potential novel method for SOZ localization in epilepsy. The parametric images of brain ECD clearance were generated by linear regression model analysis from serial brain SPECT scans from 30 minutes to 240 minutes after ECD injection (7-times point) in 7 patients with drug-resistant epilepsy and 3 normal volunteers. Clearance patterns of the SOZ confirmed by good surgical outcome or consensus with other investigations were analyzed quantitatively and semi-quantitatively by visual grading (slower or faster washout than contralateral brain regions). The average [99mTc]Tc-ECD clearance rates of SOZs were + 1.08 % ± 2.57 %/hr (wash in), -7.02 % ± 2.56 %/hr (washout), and − 5.37% ± 1.71 %/hr (washout) in ictal, aura and interictal states, respectively. Paired t-tests between the SOZ and contralateral regions showed statistically significant difference (p = 0.039 in interictal state). Clearance patterns that can define the SOZs were 1) wash in and slow washout on ictal slope, 2) fast washout on aura slope and interictal slope with 100% (6/6), 100% (2/2) and 75% (6/8) localization using ictal, aura, and interictal slope maps, respectively. Our study provided the evidence that clearance pattern methods are potential additive diagnostic tools for SOZ localization when routine one-time point SPECT are unable to define the SOZ.

scholarly journals Awake perimetry testing for occipital epilepsy surgery

2018 ◽  
Vol 129 (5) ◽  
pp. 1195-1199 ◽  
Author(s):  
Holger Joswig ◽  
John P. Girvin ◽  
Warren T. Blume ◽  
Jorge G. Burneo ◽  
David A. Steven
Keyword(s):  
Visual Field ◽  
Occipital Lobe ◽  
Technical Note ◽  
Laser Pointer ◽  
Seizure Onset ◽  
Resective Surgery ◽  
Seizure Onset Zone ◽  
Visual Field Impairment ◽  
Stimulation Of

In the literature, there are few reports that provide a detailed account on the technique of visual electrocortical stimulation in the setting of resective surgery for occipital epilepsy. In this technical note, the authors describe how a 26-year-old male with long-standing occipital epilepsy underwent resective surgery under awake conditions, using electrocortical stimulation of the occipital lobe, with the aid of a laser pointer and a perimetry chart on a stand within his visual field. The eloquent primary visual cortex was found to overlap with the seizure onset zone that was previously determined with subdural electrodes. A maximum functionally safe resection was performed, rendering the patient seizure free as of his last follow-up at 20 months, with no visual field impairment.

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