Presurgical Evaluation Of Patients Research Articles

Multiscale neuro-inspired models for interpretation of EEG signals in patients with epilepsy

ObjectiveThe aim is to gain insight into the pathophysiological mechanisms underlying interictal epileptiform discharges observed in electroencephalographic (EEG) and stereo-EEG (SEEG, depth electrodes) recordings performed during pre-surgical evaluation of patients with drug-resistant epilepsy. MethodsWe developed novel neuro-inspired computational models of the human cerebral cortex at three different levels of description: i) microscale (detailed neuron models), ii) mesoscale (neuronal mass models) and iii) macroscale (whole brain models). Although conceptually different, micro- and mesoscale models share some similar features, such as the typology of neurons (pyramidal cells and three types of interneurons), their spatial arrangement in cortical layers, and their synaptic connectivity (excitatory and inhibitory). The whole brain model consists of a large-scale network of interconnected neuronal masses, with connectivity based on the human connectome. ResultsFor these three levels of description, the fine-tuning of free parameters and the quantitative comparison with real data allowed us to reproduce interictal epileptiform discharges with a high degree of fidelity and to formulate hypotheses about the cell- and network-related mechanisms underlying the generation of fast ripples and SEEG-recorded epileptic spikes and spike-waves. ConclusionsThe proposed models provide valuable insights into the pathophysiological mechanisms underlying the generation of epileptic events. The knowledge gained from these models effectively complements the clinical analysis of SEEG data collected during the evaluation of patients with epilepsy. SignificanceThese models are likely to play a key role in the mechanistic interpretation of epileptiform activity.

Comparison of Ictal SPECT with 99mTc-HMPAO versus MRI for the Epileptic Seizure Onset Zone Detection in Saudi Patients

Background: In the presurgical evaluation of patients with drug-resistant epilepsy, magnetic resonance imaging (MRI) and ictal brain perfusion SPECT with the chemical microspheres 99mTc-HMPAO are widely used for diagnosing the seizure onset zone (SOZ). For both modalities, there is theoretical controversy over favoring one over the other. This study aimed to compare the performance of 99mTc-HMPAO SPECT with MRI for SOZ identification in EEG-proved epileptic Saudi patients. Methods and Results: For this observational retrospective study, the database of the nuclear medicine departments at the Prince Sultan Military Medical City (PSMMC) and King Abdullah bin Abdulaziz University Hospital (KAAUH) were searched for male and female patients with suspected unifocal epilepsy in whom ictal brain perfusion SPECT and MRI had been performed for presurgical evaluation. A total of 14 adult epileptic patients above 18 years were included who have undergone SPECT scans using 99mTc-HMPAO and MRI between Jan 2014 and Dec 2021. 99mTc-HMPAO SPECT and MRI scans were performed simultaneously for each patient, and there was almost general agreement that 99mTc-HMPAO SPECT accurately localized and detected the SOZ in 12/14 patients (sensitivity 85.71%). It was superior to MRI, which detected and localized the SOZ in only 7/14 patients (sensitivity 50.0%). Unfortunately, the specificity of ictal brain perfusion SPECT, by using 99mTc-HMPAO in seizure localization in epileptic patients, was not detected due to the shortage of data that led to all the EEG findings being 100% positive. Conclusion: This study reported that ictal SPECT using 99mTc-HMPAO provides more valuable information about SOZ localization than MRI. However, future studies with a larger sample size are needed to assess the specificity of 99mTc-HMPAO SPECT in detecting the SOZ.

PSMA PET/CT and mpMRI discrepancies in prostate cancer detection with whole-mount histopathology gold standard.

284 Background: Multiparametric MRI (mpMRI) and PSMA-PET are complementary imaging modalities used in the pre-surgical evaluation of patients with prostate cancer (PCa). The aim of this study was to evaluate the imaging and pathology parameters associated with PSMA-PET and mpMRI disagreement with each other and with gold standard histopathology. Methods: Patients undergoing radical prostatectomy (RP) with pre-surgical PSMA-PET and mpMRI were screened for inclusion in this retrospective analysis. Patients had the imaging scans done <3 months from each other, and whole mount histopathology (WMHP) slides available. Two nuclear medicine physicians and 2 radiologists independently contoured PCa lesions on PSMA-PET and mpMRI, respectively. A consensus read was done with a third reader for each modality, and a majority rule was applied (2:1). Quantitative measures were extracted on a lesion-basis (SUVmean, SUVmax, tumor volume). A PET/MRI fusion was obtained, and agreement/disagreement was assessed visually, based on the overlapping lesion contours. WMHP slides were used to establish the disagreement of imaging-identified lesions with the gold standard pathology. Independent samples t-test and one-way ANOVA were used to assess group differences. Univariable and multivariable logistic regression models were used to assess the association of clinical, pathological, and imaging variables with PSMA-PET and mpMRI agreement/disagreement with each other and with pathology. Results: The cohort included 114 patients, and 175 pathology lesions were identified (ISUP 3, n=22; ISUP>3, n=153). mpMRI and PSMA PET identified 138 and 170 lesions, respectively. Sensitivity for ISUP>3 lesions was 79% and 87% for mpMRI and PSMA-PET, respectively. 115/153 (76%) ISUP> 3 lesions were correctly identified, and 14/153 (9%) were missed by both imaging modalities, respectively. 5/153 (3%) were correctly identified by mpMRI and missed by PSMA-PET, 17/153 (11%) were correctly identified by PSMA-PET and missed by mpMRI. Lesion’s ISUP grade group and size on pathology were significantly lower in mpMRI- compared to mpMRI+ and in PET- compared to PET+ lesions. SUVmax and SUVmean were significantly higher in PET+/MRI+ than PET+/MRI- lesions. Lesion’s ISUP grade group and size were significantly correlated to PSMA-PET and mpMRI agreement, whereas PSMA-PET metrics were not. Logistic regression model showed that lesions with lower ISUP, smaller size, and lack of aggressive prostate cancer features on pathology (cribriform pattern and intraductal carcinoma) have higher likelihood of being missed by PET and mpMRI and of PET/MRI disagreement. Conclusions: Higher SUVmax, SUVmean, and tumor volume on PSMA-PET were associated with a TP finding on PSMA-PET, higher ISUP grade group and size on pathology were associated with a TP finding on both PSMA-PET and mpMRI, and with agreement between PSMA-PET and mpMRI.

The role of magnetoencephalography in preoperative localization and postoperative outcome prediction in patients with posterior cortical epilepsy.

We aimed to explore the value of magnetoencephalography in the presurgical evaluation of patients with posterior cortex epilepsy. A total of 39 patients with posterior cortex epilepsy (PCE) and intact magnetoencephalography (MEG) images were reviewed from August 2019 to July 2022. MEG dipole clusters were classified into single clusters, multiple clusters, and scatter dipoles based on tightness criteria. The association of the surgical outcome with MEG dipole classifications was evaluated using Fisher's exact tests. Among the 39 cases, there were 24 cases of single clusters (61.5%), nine cases of multiple clusters (23.1%), and six cases of scattered dipoles (15.4%). Patients with single dipole clusters were more likely to become seizure-free. Among single dipole cluster cases (n = 24), complete MEG dipole resection yielded a more favorable surgical outcome than incomplete resection (83.3% vs. 16.7%, p = 0.007). Patients with concordant MRI and MEG findings achieved a significantly more favorable surgical outcome than discordant patients (66.7% vs. 33.3%, p = 0.044), especially in single dipole cluster patients (87.5% vs. 25.0%, p = 0.005). MEG can provide additional valuable information regarding surgical candidate selection, epileptogenic zone localization, electrode implantation schedule, and final surgical planning in patients with posterior cortex epilepsy.

Comparing the efficacy of awake and sedated MEG to TMS in mapping hand sensorimotor cortex in a clinical cohort

Non-invasive methods such as Transcranial Magnetic Stimulation (TMS) and magnetoencephalography (MEG) aid in the pre-surgical evaluation of patients with epilepsy or brain tumor to identify sensorimotor cortices. MEG requires sedation in children or patients with developmental delay. However, TMS can be applied to awake patients of all ages with any cognitive abilities. In this study, we compared the efficacy of TMS with MEG (in awake and sedated states) in identifying the hand sensorimotor areas in patients with epilepsy or brain tumors. We identified 153 patients who underwent awake- (n = 98) or sedated-MEG (n = 55), along with awake TMS for hand sensorimotor mapping as part of their pre-surgical evaluation. TMS involved stimulating the precentral gyrus and recording electromyography responses, while MEG identified the somatosensory cortex during median nerve stimulation. Awake-MEG had a success rate of 92.35 % and TMS had 99.49 % (p-value = 0.5517). However, in the sedated-MEG cohort, TMS success rate of 95.61 % was significantly higher compared to MEG’s 58.77 % (p-value = 0.0001). Factors affecting mapping success were analyzed. Logistic regression across the entire cohort identified patient sedation as the lone significant predictor, contrary to age, lesion, metal, and number of antiseizure medications (ASMs). A subsequent analysis replaced sedation with anesthetic drug dosage, revealing no significant predictors impacting somatosensory mapping success under sedation. This study yields insights into the utility of TMS and MEG in mapping hand sensorimotor cortices and underscores the importance of considering factors that influence eloquent cortex mapping limitations during sedation.

Role of short term Video EEG monitoring and MRI in refractory Epilepsy

Introduction: Inpatient video EEG monitoring is widely used for the diagnosis, seizure classification and pre surgical evaluation of patients with epilepsy. Only few studies have highlighted the role of short term video EEG in the diagnosis of paroxysmal events. The present study was undertaken to identify the role of short term video EEG in refractory epilepsy. Materials & Methods: Forty patients, attending neurology outpatient department in our institution, during the study period, fulfilling the criteria for refractory epilepsy were included. Short term video EEG and MRI Brain were done for all of them. Outcomes measured were 1) Video recording of epileptic seizures with concurrent ictal pattern or psychogenic non epileptic seizure. 2) Identification of new interictal epileptiform discharges, which were not there in the previous routine EEG. 3) Observation of congruency between EEG and MRI Brain. Results: Clinical events were recorded in 12.5% of patients - 7.5% had epileptic seizures and 5% had psychogenic non epileptic seizures recorded. Short term video EEG was abnormal in 70% of the patients, whereas previous routine EEG was abnormal in only 30% and these observations were statistically significant. Short term video EEG was useful in diagnostic classification in 70% of the cases. MRI Brain was abnormal in 35% and among them, 30% had lateralized epiletiform discharges and the congruency between them is not statistically significant. Conclusions: Short term video EEG monitoring could be an initial investigation to sort our more frequent seizure group and proceed to long term VEEG if short term VEEG is inconclusive.

Role of Pre-Operative High-Resolution Computed Tomography for Surgical Planning in Patients Undergoing Cochlear Implantation - An Observational Study.

Currently preoperative magnetic resonance imaging (MRI) brain and High-Resolution Computed Tomography (HRCT) scanning of temporal bones form part of routine Cochlear implantation (CI) assessment. Pre- operative imaging demonstrates anatomic details or anomalies if any, that prove essential in pre-surgical evaluation of patients. These form a road map for the surgeon to anticipate any difficulty during surgery, to aid in decision making to implant the most appropriate ear, plan surgical technique, or select electrode arrays. A descriptive observational pilot study was conducted at tertiary care hospital involving 51 paediatric patients worked-up for CI. Patients after detailed clinical evaluation and MRI Brain, a tentative surgical plan was formulated by a candidacy CI screening committee. Patients selected for surgery underwent HRCT temporal bones and surgical plan was modified after analysing the same. Percentage of cases in which surgical plan changed (in terms of laterality of surgery) after correlating with HRCT findings were determined and data analysed. A total of 51 patients worked up for CI were included in the study. In 37.3% cases, there were unfavourable MRI findings. HRCT scan was used to aid the surgical road map in these patients, which based on MRI findings would have had suboptimal outcome. With this understanding, we recommend that, MRI with precise interpretation would be sufficient to furnish all necessary information in preoperative assessment of CI patients, and a HRCT temporal bones maybe indicated only in difficult cases or those with unfavourable MRI findings, may aid predict surgical events.

Lack of spontaneous typical seizures during intracranial monitoring with stereo-electroencephalography.

In the presurgical evaluation of patients with drug-resistant epilepsy (DRE), occasionally, patients do not experience spontaneous typical seizures (STS) during a stereo-electroencephalography (SEEG) study, which limits its effectiveness. We sought to identify risk factors for patients who did not have STS during SEEG and to analyze the clinical outcomes for this particular set of patients. We conducted a retrospective analysis of all patients with DRE who underwent depth electrode implantation and SEEG recordings between January 2013 and December 2018. SEEG was performed in 155 cases during this period. Eleven (7.2%) did not experience any clinical seizures (non-STS group), while 143 experienced at least one patient-typical seizure during admission (STS group). No significant differences were found between STS and non-STS groups in terms of patient demographics, lesional/non-lesional epilepsy ratio, pre-SEEG seizure frequency, number of ASMs used, electrographic seizures or postoperative seizure outcome in those who underwent resective surgery. Statistically significant differences were found in the average number of electrodes implanted (7.0 in the non-STS group vs. 10.2 in STS), days in Epilepsy Monitoring Unit (21.8 vs. 12.8 days) and the number of cases that underwent resective surgery following SEEG (27.3% vs 60.8%), respectively. The three non-STS patients (30%) who underwent surgery, all had their typical seizures triggered during ECS studies. Three cases were found to have psychogenic non-epileptic seizures. None of the patients in the non-STS group were offered neurostimulation devices. Five of the non-STS patients experienced transient seizure improvement following SEEG. We were unable to identify any factors that predicted lack of seizures during SEEG recordings. Resective surgery was only offered in cases where ECS studies replicated patient-typical seizures. Larger data sets are required to be able to identify factors that predict which patients will fail to develop seizures during SEEG.

18F]DPA-714 PET Imaging in the Presurgical Evaluation of Patients With Drug-Resistant Focal Epilepsy.

Translocator protein 18 kDa (TSPO) PET imaging is used to monitor glial activation. Recent studies have proposed TSPO PET as a marker of the epileptogenic zone (EZ) in drug-resistant focal epilepsy (DRFE). This study aims to assess the contributions of TSPO imaging using [18F]DPA-714 PET and [18F]FDG PET for localizing the EZ during presurgical assessment of DRFE, when phase 1 presurgical assessment does not provide enough information. We compared [18F]FDG and [18F]DPA-714 PET images of 23 patients who had undergone a phase 1 presurgical assessment, using qualitative visual analysis and quantitative analysis, at both the voxel and the regional levels. PET abnormalities (increase in binding for [18F]DPA-714 vs decrease in binding for [18F]FDG) were compared with clinical hypotheses concerning the localization of the EZ based on phase 1 presurgical assessment. The additional value of [18F]DPA-714 PET imaging to [18F]FDG for refining the localization of the EZ was assessed. To strengthen the visual analysis, [18F]DPA-714 PET imaging was also reviewed by 2 experienced clinicians blind to the EZ location. The study included 23 patients. Visual analysis of [18F]DPA-714 PET was significantly more accurate than [18F]FDG PET to both, show anomalies (95.7% vs 56.5%, p = 0.022), and provide additional information to refine the EZ localization (65.2% vs 17.4%, p = 0.019). All 10 patients with normal [18F]FDG PET had anomalies when using [18F]DPA-714 PET. The additional value of [18F]DPA-714 PET seemed to be greater in patients with normal brain MRI or with neocortical EZ (especially if insula is involved). Regional analysis of [18F]DPA-714 and [18F]FDG PET provided similar results. However, using voxel-wise analysis, [18F]DPA-714 was more effective than [18F]FDG for unveiling clusters whose localization was more often consistent with the EZ hypothesis (87.0% vs 39.1%, p = 0.019). Nonrelevant bindings were seen in 14 of 23 patients in visual analysis and 9 patients of 23 patients in voxel-wise analysis. [18F]DPA-714 PET imaging provides valuable information for presurgical assessments of patients with DRFE. TSPO PET could become an additional tool to help to the localization of the EZ, especially in patients with negative [18F]FDG PET. Eudract 2017-003381-27. Inclusion of the first patient: September 24, 2018. This study provides Class IV evidence on the utility of [18F]DPA-714 PET compared with [18F]FDG PET in identifying the epileptic zone in patients undergoing phase 1 presurgical evaluation for intractable epilepsy.

Gammagrafía de perfusión miocárdica en la evaluación del riesgo cardiovascular en el trasplante hepático de adultos

IntroductionThe non-invasive diagnostic study of cardiovascular risk in patients who are going to undergo liver transplantation is not clear, especially in asymptomatic patients. Regarding myocardial perfusion scintigraphy (MPS), it has been thought that the impaired vasodilator reserve in these patients may reduce its performance. The objective is to assess the role of the MPS in the pre-surgical evaluation of patients who are going to undergo liver transplantation. Material and methodsRetrospective, descriptive and observational study was designed. All adult patients undergoing liver transplantation between 2017 and 2021 who had previous MPS were included. The findings of MPS were described and correlated with the findings of invasive angiography and with the appearance or not of peri- and post-transplant cardiovascular events. ResultsThere were a total of 188 transplanted patients (mean age: 57 years, SD: 12), 178 had previous myocardial perfusion, 82 (46%) patients had no cardiovascular risk factors, and 5 (2.8%) had a history of coronary disease.Of the MPS, 177 were with dipyridamole stress performed on average 10 months before transplantation. Only 17/178 (9.5%) studies were abnormal. The mean follow-up was 38 months (SD: 10). Of the patients with normal MPS, only 2 (1.2%) presented cardiovascular events, both with studies performed more than 2years before the procedure. There were no deaths of cardiovascular origin. ConclusionsMPS is a safe and reliable technique for cardiovascular assessment of patients who are candidates for liver transplantation, given the low rate of false negatives during follow-up.

Myocardial perfusion scintigraphy in the assessment of cardiovascular risk in adult liver transplantation

IntroductionThe non-invasive diagnostic study of cardiovascular risk in patients who are going to undergo liver transplantation is not clear, especially in asymptomatic patients. Regarding myocardial perfusion scintigraphy (MPS), it has been thought that the impaired vasodilator reserve in these patients may reduce its performance. The objective is to assess the role of the MPS in the pre-surgical evaluation of patients who are going to undergo liver transplantation. Material and methodsRetrospective, descriptive and observational study was designed. All adult patients undergoing liver transplantation between 2017 and 2021 who had previous MPS were included. The findings of MPS were described and correlated with the findings of invasive angiography and with the appearance or not of peri- and post-transplant cardiovascular events. ResultsThere were a total of 188 transplanted patients (mean age: 57 years, SD: 12), 178 had previous myocardial perfusion, 82 (46%) patients had no cardiovascular risk factors, and 5 (2.8%) had a history of coronary disease.Of the MPS, 177 were with dipyridamole stress performed on average 10 months before transplantation. Only 17/178 (9.5%) studies were abnormal. The mean follow-up was 38 months (SD: 10). Of the patients with normal MPS, only 2 (1.2%) presented cardiovascular events, both with studies performed more than 2 years before the procedure. There were no deaths of cardiovascular origin. ConclusionsMPS is a safe and reliable technique for cardiovascular assessment of patients who are candidates for liver transplantation, given the low rate of false negatives during follow-up.

Independent component analysis: a reliable alternative to general linear model for task-based fMRI.

Functional magnetic resonance imaging (fMRI) is a valuable tool for the presurgical evaluation of patients undergoing neurosurgeries. Although many pre-processing steps have been modified according to advances in recent years, statistical analysis has remained largely the same since the first days of fMRI. In this study, we examined the ability of Independent Component Analysis (ICA) to separate the activation of a language task in fMRI, and we compared it with the results of the General Lineal Model (GLM). Sixty patients undergoing evaluation for brain surgery due to various brain lesions and/or epilepsy and 20 control subjects completed an fMRI language mapping protocol that included three tasks, resulting in 259 fMRI scans. Depending on brain lesion characteristics, patients were allocated to (1) static/chronic not-expanding lesions (Group 1) and (2) progressive/expanding lesions (Group 2). GLM and ICA statistical maps were evaluated by fMRI experts to assess the performance of each technique. In the control group, ICA and GLM maps were similar without any superiority of either technique. In Group 1 and Group 2, ICA performed statistically better than GLM, with a p-value of < 0.01801 and < 0.0237, respectively. This indicated that ICA performs as well as GLM when the subjects are able to cooperate well (less movement, good task performance), but ICA could outperform GLM in the patient groups. When both techniques were combined, 240 out of 259 scans produced reliable results, showing that the sensitivity of task-based fMRI can be increased when both techniques are integrated with the clinical setup. ICA may be slightly more advantageous, compared to GLM, in patients with brain lesions, across the range of pathologies included in our population and independent of symptoms chronicity. Our findings suggest that GLM analysis may be more susceptible to brain activity perturbations induced by a variety of lesions or scanner-induced artifacts due to motion or other factors. In our research, we demonstrated that ICA is able to provide fMRI results that can be used in surgery, taking into account patient and task-wise aspects that differ from those when fMRI is used in research.

Trends in referral patterns to presurgical evaluation at a European reference center

PurposeTo determine if growing evidence for epilepsy surgery as an early treatment option is reflected in the decrease of latencies between epilepsy onset and referral for presurgical evaluation MethodsRetrospective analysis of latencies in 1646 patients (children and adults) from the time of epilepsy diagnosis to first presurgical workup in the period from 1999 to 2019 based on electronic patient charts at a tertiary epilepsy center. Time spans 1999–2009 and 2010–2019, prior to and following the ILAE definition of pharmacoresistance, and the role of etiological factors were assessed. ResultsOver the whole period, the mean latency between diagnosis and a presurgical workup was 15.3 y. There was a significant reduction in the latencies between the periods 1999–2009 (16.9 y) and 2010–2019 (13.4 y), (p < 0.0001). In a linear regression analysis, the latency decreased by 2.6 months/year from 17.4 in 1999 to 13.1 y in 2019 (p < 0.001). Subgroup analyses showed significant decreases in latency to presurgical evaluation in patients with hippocampal sclerosis from 24.4 to 19.5 y, in malformations of cortical development from 16.4 to 13.2 y, and in nonlesional patients from 18.1 to 12.8 y, in contrast to patients with MR evidence for brain tumors with similar latencies across time (10.5 vs. 9.5 y, n.s.). ConclusionThe reduction of the time span to a first presurgical evaluation was highly significant over time, yet moderate in its degree. Overall, the aim of early diagnostic evaluation for epilepsy surgery options after established pharmacoresistance was only achieved for a minority of patients.

Delayed 18F-FDG PET imaging provides better metabolic asymmetry in potential epileptogenic zone in temporal lobe epilepsy.

To investigate the value of 18F-FDG positron emission tomography/computed tomography (PET/CT) two time point imaging for the identification of the potential epileptogenic zone (EZ) in temporal lobe epilepsy (TLE). Fifty-two patients with TLE were prospectively enrolled in the 18F-FDG PET/CT two time point imaging study. The early imaging was obtained approximately 40 min (43.44 ± 18.04 min) after 18F-FDG injection, and the delayed imaging was obtained about 2 to 3 h (160.46 ± 28.70 min) after the injection. Visual and semi-quantitative analysis of 18F-FDG uptake were performed at the two time points in EZ and contralateral symmetrical region. The mean standardized uptake value (SUVmean) of EZ and contralateral symmetrical region was calculated to determine the asymmetry index (AI) of the early and delayed images, as well as in the MRI positive and negative patient groups. Semi-quantitative analysis demonstrated that AI of the early and delayed 18F-FDG PET/CT images was 13.47 ± 6.10 and 16.43 ± 6.66, respectively. The ΔAI was 2.95 ± 3.05 in 52 TLE patients between the two time points. The AI of the EZ was significantly elevated in delayed images compared to the early images (p < 0.001). The AI of delayed imaging was also significantly elevated compared to the early imaging in both MRI positive (ΔAI = 2.81 ± 2.54, p < 0.001) and MRI negative (ΔAI = 3.21 ± 3.91, p < 0.003) groups, and more pronounced in MRI negative group. Visual analysis also showed that the delayed imaging appeared to be superior to the early imaging for identification of potential EZ. Delayed 18F-FDG PET imaging provided significantly better than the early imaging in the identification of potential EZ, which can be valuable during epilepsy pre-surgical evaluation in patients with TLE.

ID: 203253 Electrochemical Characterization of the First FDA-Cleared Thin-Film Electrodes for Recording and Stimulation of Brain Activity

Introduction: Subdural strip and grid (SDE) and stereoelectroencephalography (sEEG) electrodes are essential tools for pre-surgical evaluation of patients suffering from drug resistant epilepsy (DRE). Both device types are used to precisely localize the origin and spread of seizures and the relationship with eloquent cortex. The electrodes must accurately and reliably record brain activity over a wide frequency band needed for seizure event detection and deliver electrical stimulation within safety limits for brain mapping. The ability of the devices to meet these performance criteria is tested using electrochemical evaluation, which is a critical step in the path to commercialization of implantable medical devices. Driven by a constant need to develop new technologies or improve upon existing ones with potential to enhance the tissue/electrode interaction, here we present a thorough electrochemical characterization of two implantable thin-film SDG and sEEG arrays.??

The impact of the time to last seizure before admission to the epilepsy monitoring unit (EMU) on epilepsy classifications

Introduction and backgroundThe impact of the timing of the last seizure (TTLS) prior to admission to the epilepsy monitoring unit (EMU) on epilepsy classification is unclear for which we conducted this study. MethodsWe reviewed patients with epilepsy admitted to EMU between January 2021 and April 2022 and identified TTLS before EMU admission. We considered EMU yield as whether; it confirmed epilepsy classification, added new knowledge to the classification, or failed to classify epilepsy. ResultsWe studied 156 patients. There were 72 (46%) men, with a mean age of 30. TTLS was divided according to a one- or three-month cutoff. We confirmed the pre-EMU epilepsy classification in 52 (33%) patients, learned new findings on epilepsy classification in 80 (51%) patients, and failed to classify epilepsy in 24 (15%) patients. Patients with “confirmed epilepsy classifications” reported seizures sooner to EMU admission than other groups (0.7 vs. 2.3 months, p-value = 0.02, 95% CI; −1.8, −1.3). Also, the odds of confirming epilepsy classification were more than two times in patients with TTLS within a month compared to those with TTLS of more than a month (OR = 2.4, p-value = 0.04, 95% CI; 1.1, 5.9). The odds were also higher when the 3-month TTLS cutoff was considered (OR = 6.2, p-value = 0.002, 95% CI; 1.6, 40.2). Confirming epilepsy classification was also associated with earlier seizures recorded at one- or three-month cutoff (OR = 2.1 and OR = 2.3, respectively, p-value = 0.05). We did not observe similar findings when we modified the classification or failed to reach a classification. ConclusionsThe timing of the last seizure before EMU admission appeared to influence the yield of EMU and enhanced the confirmation of epilepsy classifications. Such findings can improve the utilization of EMU in the presurgical evaluation of patients with epilepsy.

N°87 – Stereo-EEG in pre-surgical evaluation of patients with drug-resistant focal epilepsy

N°87 – Stereo-EEG in pre-surgical evaluation of patients with drug-resistant focal epilepsy

N°193 – MEG in presurgical evaluation of patients with epilepsy

N°193 – MEG in presurgical evaluation of patients with epilepsy

Lateralization of interictal temporal lobe hypoperfusion in lesional and non-lesional temporal lobe epilepsy using arterial spin labeling MRI

PurposeNon-invasive imaging studies play a critical role in the presurgical evaluation of patients with drug-resistant temporal lobe epilepsy (TLE), particularly in helping to lateralize the seizure focus. Arterial Spin Labeling (ASL) MRI has been widely used to non-invasively study cerebral blood flow (CBF), with somewhat variable interictal alterations reported in TLE. Here, we compare temporal lobe subregional interictal perfusion and symmetry in lesional (MRI+) and non-lesional (MRI-) TLE compared to healthy volunteers (HVs). MethodsTwenty TLE patients (9 MRI+, 11 MRI-) and 14 HVs under went 3 T Pseudo-Continuous ASL MRI through an epilepsy imaging research protocol at the NIH Clinical Center. We compared normalized CBF and absolute asymmetry indices in multiple temporal lobe subregions. ResultsCompared to HVs, both MRI+ and MRI- TLE groups demonstrated significant ipsilateral mesial and lateral temporal hypoperfusion, specifically in the hippocampal and anterior temporal neocortical subregions, with additional hypoperfusion in the ipsilateral parahippocampal gyrus in the MRI+ and contralateral hippocampus in the MRI- TLE groups. Contralateral to the seizure focus, there was significant relative hypoperfusion in multiple subregions in the MRI- compared to the MRI+ TLE groups. The MRI+ group therefore had significantly greater asymmetry across multiple temporal subregions compared to the MRI- TLE and HV groups. No significant differences in asymmetry were found between the MRI- TLE and HV groups. ConclusionWe found a similar extent of interictal ipsilateral temporal hypoperfusion in MRI+ and MRI- TLE. However, significantly increased asymmetries were found only in the MRI+ group due to differences in perfusion contralateral to the seizure focus between the patient groups. The lack of asymmetry in the MRI- group may negatively impact the utility of interictal ASL for seizure focus lateralization in this patient population.

A framework for focal and connectomic mapping of transiently disrupted brain function

The distributed nature of the neural substrate, and the difficulty of establishing necessity from correlative data, combine to render the mapping of brain function a far harder task than it seems. Methods capable of combining connective anatomical information with focal disruption of function are needed to disambiguate local from global neural dependence, and critical from merely coincidental activity. Here we present a comprehensive framework for focal and connective spatial inference based on sparse disruptive data, and demonstrate its application in the context of transient direct electrical stimulation of the human medial frontal wall during the pre-surgical evaluation of patients with focal epilepsy. Our framework formalizes voxel-wise mass-univariate inference on sparsely sampled data within the statistical parametric mapping framework, encompassing the analysis of distributed maps defined by any criterion of connectivity. Applied to the medial frontal wall, this transient dysconnectome approach reveals marked discrepancies between local and distributed associations of major categories of motor and sensory behaviour, revealing differentiation by remote connectivity to which purely local analysis is blind. Our framework enables disruptive mapping of the human brain based on sparsely sampled data with minimal spatial assumptions, good statistical efficiency, flexible model formulation, and explicit comparison of local and distributed effects.