Frontal lobe epilepsy

Conductive Hydrogel Tapes for Tripolar EEG: A Promising Solution to Paste-Related Challenges

Electroencephalography (EEG) remains pivotal in neuroscience for its non-invasive exploration of brain activity, yet traditional electrodes are plagued with artifacts and the application of conductive paste poses practical challenges. Tripolar concentric ring electrode (TCRE) sensors used for EEG (tEEG) attenuate artifacts automatically, improving the signal quality. Hydrogel tapes offer a promising alternative to conductive paste, providing mess-free application and reliable electrode-skin contact in locations without hair. Since the electrodes of the TCRE sensors are only 1.0 mm apart, the impedance of the skin-to-electrode impedance-matching medium is critical. This study evaluates four hydrogel tapes' efficacies in EEG electrode application, comparing impedance and alpha wave characteristics. Healthy adult participants underwent tEEG recordings using different tapes. The results highlight varying impedances and successful alpha wave detection despite increased tape-induced impedance. MATLAB's EEGLab facilitated signal processing. This study underscores hydrogel tapes' potential as a convenient and effective alternative to traditional paste, enriching tEEG research methodologies. Two of the conductive hydrogel tapes had significantly higher alpha wave power than the other tapes, but were never significantly lower.

Brain language networks and cognitive outcomes in children with frontotemporal lobe epilepsy

Introduction

Pediatric frontal and temporal lobe epilepsies (FLE, TLE) have been associated with language impairments and structural and functional brain alterations. However, there is no clear consensus regarding the specific patterns of cerebral reorganization of language networks in these patients. The current study aims at characterizing the cerebral language networks in children with FLE or TLE, and the association between brain network characteristics and cognitive abilities.

Methods

Twenty (20) children with FLE or TLE aged between 6 and 18 years and 29 age- and sex-matched healthy controls underwent a neuropsychological evaluation and a simultaneous functional near-infrared spectroscopy and electroencephalography (fNIRS-EEG) recording at rest and during a receptive language task. EEG was used to identify potential subclinical seizures in patients. We removed these time intervals from the fNIRS signal to investigate language brain networks and not epileptogenic networks. Functional connectivity matrices on fNIRS oxy-hemoglobin concentration changes were computed using cross-correlations between all channels.

Results and discussion

Group comparisons of residual matrices (=individual task-based matrix minus individual resting-state matrix) revealed significantly reduced connectivity within the left and between hemispheres, increased connectivity within the right hemisphere and higher right hemispheric local efficiency for the epilepsy group compared to the control group. The epilepsy group had significantly lower cognitive performance in all domains compared to their healthy peers. Epilepsy patients' local network efficiency in the left hemisphere was negatively associated with the estimated IQ (p = 0.014), suggesting that brain reorganization in response to FLE and TLE does not allow for an optimal cognitive development.

Stereo-EEG localization of midline onset seizures on scalp EEG

PURPOSE

The objective of this study was to describe the sEEG-defined seizure onset zone (SOZ), seizure semiology, presurgical evaluations, surgical intervention and outcome in patients with midline onset noninvasive phase I monitoring.

METHODS

A single center sEEG database was reviewed to identify patients with seizures onset predominantly involving midline electrodes (FZ, CZ, PZ, OZ) on scalp EEG. Data abstracted included clinical factors, seizure semiology graded into lobar segmentation, imaging and electrographic findings, sEEG plan, interventions, and outcome.

RESULTS

Twelve patients were identified (8 males, median age of sEEG 28 years) out of 100 cases of sEEG performed from January 2015-September 2019. "Frontal lobe" seizure semiology was the most common. sEEG-defined SOZ were frontal (5), diffuse (1), multifocal (1), frontal and insular (1), frontal and cingulate (1), insular (1), cingulate (1), and mesial temporal (1). CZ and/or FZ scalp EEG changes were present for all patients with SOZ involving the frontal, cingulate, and insular regions. PZ/OZ scalp involvement was present in one patient with mesial temporal SOZ. Four patients underwent a definitive resective or ablative surgery, and the remaining patients underwent a palliative intervention. Of those with follow-up information available, 8/11 had seizure reduction by ≥ 50%, including 4 with an Engel I outcome. No clinical factors were associated with outcome.

CONCLUSIONS

SOZ for midline onset seizures from noninvasive phase I monitoring was most commonly in the frontal, cingulate, and insular regions. A complex cortical network between these regions may explain overlap in semiology and scalp EEG findings. While the number rendered seizure-free was limited, a significant proportion experienced a reasonably favorable outcome justifying use of sEEG to identify surgical options in these patients.

Topological abnormality of structural covariance network in MRI-negative frontal lobe epilepsy

Background

Frontal lobe epilepsy (FLE) is the second most common type of focal epilepsy, however, imaging studies of FLE have been far less than Temporal lobe epilepsy (TLE) and the structural findings were not consistent in previous literature.

Object

Investigate the changes in cortical thickness in patients with FLE and the alteration of the structural covariance networks (SCNs) of cortical thickness with graph-theory.

Method

Thirty patients with FLE (18 males/12 females; 28.33 ± 11.81 years) and 27 demographically matched controls (15 males/12 females; 29.22 ± 9.73 years) were included in this study with high-resolution structural brain MRI scans. The cortical thickness was calculated, and structural covariance network (SCN) of cortical thickness were reconstructed using 68 × 68 matrix and analyzed with graph-theory approach.

Result

Cortical thickness was not significantly different between two groups, but path length and node betweenness were significantly increased in patients with FLE, and the regional network alterations were significantly changed in right precentral gyrus and right temporal pole (FDR corrected, p < 0.05). Comparing to HC group, network hubs were decreased and shifted away from frontal lobe.

Conclusion

The topological properties of cortical thickness covariance network were significantly altered in patients with FLE, even without obvious surface-based morphological damage. Graph-theory based SCN analysis may provide sensitive neuroanatomical biomarkers for FLE.

Deep phenotyping of frontal lobe epilepsy compared to other epilepsy syndromes

AIMS

Frontal lobe epilepsy (FLE) is understudied and often misdiagnosed. We sought to comprehensively phenotype FLE and to differentiate FLE from other focal and generalised epilepsy syndromes.

METHODS

This was a retrospective, observational cohort study of 1078 cases of confirmed epilepsy in a tertiary neurology centre in London. Data sources were electronic health records, investigation reports and clinical letters.

RESULTS

166 patients had FLE based on clinical findings and investigations-97 with identifiable electroencephalography (EEG) foci in frontal areas (definite FLE), while 69 had no frontal EEG foci (probable FLE). Apart from EEG findings, probable and definite FLE did not differ in other features. FLE was distinct from generalized epilepsy, which tended to present with tonic-clonic seizures and be due to genetic causes. FLE and temporal lobe epilepsy (TLE) both featured focal unaware seizures and underlying structural or metabolic aetiology. FLE, TLE and generalized epilepsy differed in their EEG (P = 0.0003) and MRI (P = 0.002) findings, where FLE had a higher rate of normal EEG and abnormal MRI findings compared to TLE.

CONCLUSIONS

EEG is often normal for FLE, and abnormalities are commonly identified with MRI. There was no difference in the clinical features of definite and probable FLE, suggesting they represent the same clinical entity. The diagnosis of FLE can be made even when scalp EEG is normal. This large medical cohort provides hallmark features of FLE that differentiate it from TLE and other epilepsy syndromes.

Clinical Impacts of Stereotactic Electroencephalography on Epilepsy Surgery and Associated Issues in the Current Situation in Japan

Stereotactic electroencephalography (SEEG) is receiving increasing attention as a safe and effective technique in the invasive evaluation for epileptogenic zone (EZ) detection. The main clinical question is whether the use of SEEG truly improves outcomes. Herein, we compared outcomes in our patients after three types of intracranial EEG (iEEG): SEEG, the subdural electrode (SDE), and a combined method using depth and strip electrodes. We present here our preliminary results from two demonstrative cases. Several international reports from large epilepsy centers found the following clinical advantages of SEEG: 1) three-dimensional analysis of structures, including bilateral and multilobar structures; 2) low rate of complications; 3) less pneumoencephalopathy and less patient burden during postoperative course, which allows the initiation of video-EEG monitoring immediately after implantation and does not require resection to be performed in the same hospitalization; and 4) a higher rate of good seizure control after resection. In other words, SEEG more accurately identified the EZ than the SDE method. We obtained similar results in our preliminary experiences under limited conditions. In Japan, as of August 2022, dedicated electrodes and SEEG accessories have not been approved and the use of the robot arm is not widespread. The Japanese medical community is hopeful that these issues will soon be resolved and that the experience with SEEG in Japan will align with that of large epilepsy centers internationally.

Safety and efficacy of bihemispheric sampling via transmidline stereoelectroencephalography

OBJECTIVE

Stereoelectroencephalography (SEEG) is designed to target distributed cortical networks responsible for electroclinical seizure syndrome and to enable localization of the site of seizure onset in patients with intractable epilepsy. When the preimplantation hypothesis invokes the bilateral mesial frontal lobes, sampling of several deep-seated cortical sites in both hemispheres is required. In this study, the authors have demonstrated the feasibility of sampling bihemispheric areas with intentional implantation of an SEEG electrode crossing the midline (SECM) for sampling the cortex on both sides of the interhemispheric fissure.

METHODS

An analysis of 231 consecutive SEEG procedures over 8 years was used to identify instances of bihemispheric sampling by using the transmidline SEEG technique.

RESULTS

The authors identified 53 SEEG cases, with a total of 126 electrodes that crossed the interhemispheric fissure; all were in the frontal lobes. Eighty-three electrodes targeted the cingulate gyrus (18 rostral, 43 anterior, and 22 middle), 31 targeted the posterior orbitofrontal region, 8 sampled the medial prefrontal cortex, and 4 targeted nodular heterotopia around the frontal horns. The ictal onset zone was localized to the frontal lobe in 16 cases. SECM isolated interictal and ictal activity in the contralateral hemisphere in 6 cases and independent bihemispheric seizure activity in 2 cases. No hemorrhagic or infectious complications were noted in any of these cases.

CONCLUSIONS

Based on this extensive experience of bihemispheric sampling, the authors concluded that this technique is safe and effective. In this series, SECM showed contralateral interictal and/or ictal epileptiform activity in 8 (15%) cases, and 9 (16%) cases (with unilateral implantation) had sufficient data to discard contralateral involvement, contributing to support of the epileptogenic network. SECM may reduce the number of electrodes used to sample bilateral mesial frontal or orbitofrontal cortices, and such an approach may lower the risk of hemorrhage and costs.

Visceral and emotional responses to direct electrical stimulations of the cortex

OBJECTIVE

Visceral sensations are bodily symptoms which are component manifestations of emotions frequently reported during epileptic seizures. Nowadays, the underlying mechanism and location of brain areas involved in the processing of these sensations remain unclear. Our objectives were to characterize the type and frequency of visceral and emotional responses evoked by electrical stimulations, to produce a mapping of brain structures involved in their processing, and to assess the link between visceral sensations and emotional feelings.

METHODS

We reviewed 12,088 bipolar stimulations performed in 203 patients during the presurgical evaluation of drug refractory epilepsy. Responses to stimulation were divided into viscero-sensitive, viscero-vegetative, and emotional sensations. Univariate analysis and conditional logistic regression were used to assess the association between visceral and emotional sensations and localization of the stimulated contacts.

RESULTS

In total, 543 stimulations evoked visceral and emotional sensations. Stimulations of operculo-insulolimbic structures (amygdala, anterior and posterior insula, anterior and mid-cingulate cortex, hippocampus, parahippocampus, temporal pole, frontal and parietal operculum) were significantly more associated with visceral and emotional sensations than all other cortical regions. Preferential implication of certain brain structures, depending on the type of visceral responses was evidenced: temporo-mesial structures, insula, and frontoparietal operculum for viscero-sensitive sensations; amygdala, insula, anterior and mid-cingulate cortex, and temporal pole for viscero-vegetative sensations; temporo-mesial structures, anterior cingulate cortex, and frontal operculum for emotional sensations.

INTERPRETATION

Our data can help to guide SEEG explorations when visceral or emotional symptoms are part of the ictal semiology. They also bring some insights into the mechanisms of visceroception and the functional significance of the co-localization of visceral and emotional representations in the human brain.

Frontal Lobe Epilepsy in a Pediatric Population: Characterization of Clinical Manifestations and Semiology

Purpose: Frontal lobe epilepsy (FLE) has various clinical presentations depending on the anatomy involved. Seizures are brief and can mimic psychiatric conditions, and patients often cannot describe the aura. Therefore, it is difficult to characterize the semiology, especially in pediatric patients. This study investigated the characteristics of pediatric FLE.Methods: We retrospectively reviewed the data of pediatric patients with FLE who underwent long-term video-electroencephalography (EEG) monitoring between January 2010 and June 2020. Patients’ demographic data, seizure-related clinical presentations, semiology, brain magnetic resonance imaging (MRI), and EEG data were analyzed.Results: Fifty-six patients were included (31 males, 25 females). The age of seizure onset varied from 1 month to 14 years (mean±standard deviation, 6.1±4.4 years). Seizures were classified into nine categories, including focal tonic (30/56), aura (22/56), hypermotor (17/56), focal clonic (15/56), versive (13/56), and bilateral asymmetric tonic (4/56). Seventeen patients (30.4%) had abnormal MRI results, including focal cortical dysplasia, heterotopic gray matter, and neuroepithelial tumors. Ictal EEG changes were commonly observed in the dorsolateral premotor and central cortices. In focal tonic seizures, EEG changes often originated in the premotor cortex. The location of the lesions on MRI and EEG coincided in six cases.Conclusion: In pediatric FLE, various seizure types occur depending on the ictal anatomic origin, and individual patients had multiple semiologies. Brain MRI was normal in two-thirds of patients, and interictal EEG did not reveal epileptiform discharges in approximately 25%. Semiology reported on the basis of home videos and interictal EEG will help localize the ictal onset zone.

A Combination of Curcuma longa and Diazepam Attenuates Seizures and Subsequent Hippocampal Neurodegeneration

Epilepsy is one of the most common neurological disorders, which occurs due to the instability in the inhibitory and excitatory synaptic transmissions in the brain. However, many patients develop resistance to the available drugs, which results in cell degeneration caused due to inadequate control of the seizures. Curcumin, Curcuma longa, is known to be effective for the treatment of organic disorders and may prevent seizures, reduce oxidative stress, and decrease brain damage. Given this, the present study evaluated the antiepileptic effects of C. longa in comparison with both the diazepam and the combined application of these two substances, in terms of their effects on the brain activity and the potential histopathological changes in the hippocampus. This study used male Wistar rats (age: 10–12 weeks; weight: 260 ± 20 g), which were pretreated for 4 days with either saline, C. longa, diazepam, or C. longa + diazepam; and on the fifth day, pentylenetetrazol (PTZ) was administered to induce the seizure. In the C. longa group, a significant increase was observed in the latency of the onset of seizure-related behavior. Surprisingly, however, the combined treatment resulted in the best control of the seizure-related behavior, with the greatest latency of the onset of spasms and isolated clonic seizures. This group also obtained the best results in the electroencephalographic trace and seizure control, with a reduction in the frequency and amplitude of the spike-waves. In the saline group, PTZ significantly reduced the number of cells present in the CA1 and CA3 regions of the hippocampus, while the combined treatment obtained the best results in terms of the preservation of the neuron-like cells. These findings indicate that C. longa may contribute to the control of both seizures and the cell damage induced by PTZ, and that its association with diazepam may be a potentially effective option for the treatment of epilepsy in the future.

Visualization of ictal networks using gamma oscillation regularity correlation analysis in focal motor epilepsy: Illustrative cases

Background

Focal motor epilepsy is difficult to localize within the epileptogenic zone because ictal activity quickly spreads to the motor cortex through ictal networks. We previously reported the usefulness of gamma oscillation (30-70 Hz) regularity (GOR) correlation analysis using interictal electrocorticographic (ECoG) data to depict epileptogenic networks. We conducted GOR correlation analysis using ictal ECoG data to visualize the ictal networks originating from the epileptogenic zone in two cases - a 26-year-old woman with negative motor seizures and a 53-year-old man with supplementary motor area (SMA) seizures.

Case Description

In both cases, we captured several habitual seizures during monitoring after subdural electrode implantation and performed GOR correlation analysis using ictal ECoG data. A significantly high GOR suggestive of epileptogenicity was identified in the SMA ipsilateral to the lesions, which were connected to the motor cortex through supposed ictal networks. We resected the high GOR locations in the SMA and the patients' previously identified tumors were removed. The patients were seizure-free without any neurological deficits after surgery.

Conclusion

The GOR correlation analysis using ictal ECoG data could be a powerful tool for visualizing ictal networks in focal motor epilepsy.

Variations in Seizure Frequency During Pregnancy and Postpartum by Epilepsy Type

BACKGROUND AND OBJECTIVES

To assess whether increased seizure frequency during pregnancy and postpartum is influenced by epilepsy type, seizure location, and antiseizure medications.

METHODS

Clinical data were collected in a longitudinal prospective database of pregnant women with epilepsy at Brigham and Women's Hospital. Within each individual participant, baseline seizure frequency was calculated for the 9 months before conception, and whether seizure frequency increased during pregnancy or the postpartum period was determined. Seizure frequency was calculated for each 4-week interval during pregnancy. Generalized estimating equations for logistic regression were applied.

RESULTS

Ninety-nine patients contributing 114 pregnancies were included from 2013 to 2018. Increased seizure frequency occurred more often during pregnancies of women with focal vs generalized epilepsy (21.1% vs 5.3%, odds ratio [OR] 4.70, 95% confidence interval [CI] 1.00-22.00; p = 0.0497). Among women with focal epilepsy, increased seizure frequency occurred more often in those with frontal lobe epilepsy (OR 8.00, 95% CI 2.19-29.21; p = 0.0017). There was no difference in seizure worsening in the postpartum period between the focal and generalized (11.1% vs 9.1%; p = 0.4478) or frontal and other focal (18.8% vs 6.0%; p = 0.1478) epilepsy groups. Pregnancies on polytherapy had higher odds of seizure worsening compared to monotherapy (OR 8.36, 95% CI 2.07-33.84; p = 0.0029), regardless of the medication or epilepsy type. A lack of preconception seizure freedom was also associated with increased seizure frequency during pregnancy (OR 6.418; p = 0.0076).

DISCUSSION

Women with focal epilepsy have higher likelihood of seizure worsening during pregnancy compared to women with generalized epilepsy; frontal lobe epilepsy poses an especially elevated risk. Polytherapy and lack of preconception seizure freedom are additional predictors for an increased likelihood of seizure worsening.

Altered gray matter volume in MRI-negative focal to bilateral tonic-clonic seizures

To investigate cortical changes in MRI-negative patients with focal to bilateral tonic-clonic seizures (FBTCS). High-resolution three-dimensional T1-weighted MRI were collected with a GE 3.0-T MRI scanner from 26 patients with FBTCS and 21 healthy volunteers at Nanjing Brain Hospital. Voxel-based morphometry was performed on T1-weighted MRI of all subjects. A two-sample t test was performed to compare the GMV of two groups. Age and gender were taken as covariables, so that brain regions with significant differences, as compared by two-sample t test, between the two group were obtained. These regions were extracted as the regions of interest (ROIs) used for correlation analysis between ROIs and clinical variables. There is no significant difference in GMF between two groups. In FBTCS, regions with decreased GMV are bilateral thalamus, bilateral orbitofrontal cortex, left medical cingulate gyrus, and right supplementary motor area. GMV is increased within the bilateral para-hippocampal regions (voxel-wise FDR-corrected, P < 0.05). The GMVs are significantly negatively correlated with disease duration in the left thalamus and the left para-hippocampal region (P < 0.05). Seizures may lead to the loss of neurons and the decrease of GMV in FBTCS. The increase of GMV in some regions might be due to inflammatory responses in the early stages of epileptic seizures.

Detrended fluctuation analysis in the presurgical evaluation of parietal lobe epilepsy patients

OBJECTIVE

To examine the usability of long-range temporal correlations (LRTCs) in non-invasive localization of the epileptogenic zone (EZ) in refractory parietal lobe epilepsy (RPLE) patients.

METHODS

We analyzed 10 RPLE patients who had presurgical MEG and underwent epilepsy surgery. We quantified LRTCs with detrended fluctuation analysis (DFA) at four frequency bands for 200 cortical regions estimated using individual source models. We correlated individually the DFA maps to the distance from the resection area and from cortical locations of interictal epileptiform discharges (IEDs). Additionally, three clinical experts inspected the DFA maps to visually assess the most likely EZ locations.

RESULTS

The DFA maps correlated with the distance to resection area in patients with type II focal cortical dysplasia (FCD) (p<0.05), but not in other etiologies. Similarly, the DFA maps correlated with the IED locations only in the FCD II patients. Visual analysis of the DFA maps showed high interobserver agreement and accuracy in FCD patients in assigning the affected hemisphere and lobe.

CONCLUSIONS

Aberrant LRTCs correlate with the resection areas and IED locations.

SIGNIFICANCE

This methodological pilot study demonstrates the feasibility of approximating cortical LRTCs from MEG that may aid in the EZ localization and provide new non-invasive insight into the presurgical evaluation of epilepsy.

Recognition of interictal and ictal discharges on EEG. Focal vs generalized epilepsy

INTRODUCTION

The differentiation between focal and generalized epilepsies based on clinical and electroencephalographic features is difficult and sometimes confusing.

OBJECTIVE

To review the EEG findings in patients with focal epilepsy.

METHODS

An extensive literature review was done. We used the following Pubmed and Medline descriptors alone and in different combinations for database searching: focal, partial, epilepsy, electroencephalographic findings, and EEG. Additional filters included review, original articles, and language limited to Spanish and English. Using the above criteria, a total of 69 articles showed the interictal and ictal EEG findings in focal epilepsy.

DEVELOPMENT

Focal epileptiform discharges and persistence of focal abnormalities, characterize the interictal EEG findings in focal epilepsies. To distinguish SBS from primary generalized spike waves are required to note: (a) a lead-in time of at least 2 s, (b) the morphology of the focal triggering spikes clearly differ from that of the bisynchronous epileptiform paroxysms, and (c) the morphology of triggering spikes resemble that of other focal spikes from the same region. Focal and Generalized Epilepsy can coexist. Delayed Lateralization on EEG with inconclusive onset and bizarre semiology confusing semiology should not be confused with generalized onset seizures with focal evolution.

CONCLUSIONS

A close attention to localization and morphology of epileptiform discharges, the correct interpretation of secondary bilateral synchrony, and provocative maneuvers help to correctly identify the EEG findings leading to diagnose focal epilepsies. The presence of generalized epileptiform activity does not rule out the existence of a focal epilepsy.

Morphological Description of Frontal EEG Interictal and Ictal Discharges in an Adult Cohort of 175 Patients

Clinical and electroencephalogram (EEG) features in frontal lobe epilepsy (FLE) vary considerably among patients, making the diagnosis a challenge. The objective of this study was to describe interictal and ictal EEG activity, identifying variables that could help to differentiate and diagnose frontal lobe epilepsy cases. A prospective cross-sectional study from patients with frontal interictal epileptiform discharges (IED) referred to the Vall d’Hebron University Hospital (Barcelona, Spain) after a clinical event compatible with epileptic seizures was designed. The interictal and ictal activity were analyzed to provide a detailed EEG description of the cases, using different statistical analyses. The morphological seizure pattern at the ictal onset remained globally unchanged over time in seizures arising from the frontal lobe for each patient. Isolated sharp waves were the most frequent waveforms in the expression of IED. Frontal lobe seizures are frequently short and sometimes appear grouped in clusters within the same recording. Often the ictal expression of the electrical activity in frontal lobe seizure is subtle and challenging to interpret. A description of the main findings is summarized to identify seizures arising from the frontal lobe and avoid false negatives findings in EEG interpretations.

Unilateral prefrontal lobotomy for epilepsy: technique and surgical anatomy

OBJECTIVE

Surgery for frontal lobe epilepsy remains a challenge because of the variable seizure outcomes after surgery. Disconnective procedures are increasingly applied to isolate the epileptogenic focus and avoid complications related to extensive brain resection. Previously, the authors described the anterior quadrant disconnection procedure to treat large frontal lobe lesions extending up to but not involving the primary motor cortex. In this article, they describe a surgical technique for unilateral disconnection of the prefrontal cortex, while providing an accurate description of the surgical and functional anatomy of this disconnective procedure.

METHODS

The authors report the surgical treatment of a 5-month-old boy who presented with refractory epilepsy due to extensive cortical dysplasia of the left prefrontal lobe. In addition, with the aim of both describing the subcortical intrinsic anatomy and illustrating the different connections between the prefrontal lobe and the rest of the brain, the authors dissected six human cadaveric brain hemispheres. These dissections were performed from lateral to medial and from medial to lateral to reveal the various tracts sectioned during the three different steps in the surgery, namely the intrafrontal disconnection, anterior callosotomy, and frontobasal disconnection.

RESULTS

The first step of the dissection involves cutting the U-fibers. During the anterior intrafrontal disconnection, the superior longitudinal fasciculus in the depth of the middle frontal gyrus, the uncinate fasciculus, and the inferior frontooccipital fasciculus in the depth of the inferior frontal gyrus at the level of the anterior insular point are visualized and sectioned, followed by sectioning of the anterior limb of the internal capsule. Once the frontal horn is reached, the anterior callosotomy can be performed to disconnect the genu and the rostrum of the corpus callosum. The intrafrontal disconnection is deepened toward the falx, and at the medial surface, the cingulum is sectioned. The frontobasal disconnection involves cutting the anterior limb of the anterior commissure.

CONCLUSIONS

This technique allows selective isolation of the epileptogenic focus located in the prefrontal lobe to avoid secondary propagation. Understanding the surface and white matter fiber anatomy is essential to safely perform the procedure and obtain a favorable seizure outcome.

Different faces of frontal lobe epilepsy: The clinical, electrophysiologic, and imaging experience of a tertiary center

OBJECTIVE

Frontal lobe epilepsy (FLE) is the second most common epilepsy among drug-resistant focal epilepsies. Semiologic and electrophysiologic features of FLE present some difficulties because frontal lobe seizures are brief, accompanied by complex motor activities and emotional signs. The rich connectivity of the frontal lobe with other areas leads to the rapid and widespread propagation of seizure activity, which contribute to the difficulty of evaluating the semiologic and EEG patterns of the seizure. In this study, we investigated semiologic, interictal, ictal, and postictal EEG characteristics; the imaging data of patients with FLE and the possible contribution of these data to localization and lateralization of seizures.

MATERIALS AND METHODS

The medical records of patients who were diagnosed as having FLE between 2010 and 2019 in our clinic were evaluated retrospectively. The diagnosis of FLE was considered either when patients had a structural lesion in the frontal region or seizure semiology and EEG characteristics were compatible with FLE. Clinical, electrophysiologic, and imaging features were investigated in these patients.

RESULTS

We have evaluated 146 seizures in 36 patients (17 lesional and 19 non-lesional according to MRI). There were 110 focal motor or nonmotor seizures, 18 bilateral tonic-clonic seizures, and 18 subclinical seizures. There were 16 patients with aura. The most common semiologic feature was hyperkinetic movements. Among the interictal EEGs, 30.5 % included focal anomalies. Among the ictal EEGs, 69.1 % were non-localizing or lateralizing. The most common ictal pattern was rhythmic theta activity (21.2 %). In four patients, who had non-localizing or lateralizing EEG, the postictal EEG was informative. Our study showed a low percentage of localized FDG-PET, which, however, involved visual analysis.

CONCLUSION

Our results support the previously known difficulties in the determination of the epileptogenic zone of FLE. Semiologic and electrophysiologic correlation studies, longer postictal records, and quantitative analysis of FDG-PET may contribute to a better characterization of the disease.

Changes in resting-state cerebral blood flow and its connectivity in patients with focal to bilateral tonic-clonic seizures

Arterial spin labeling (ASL) is an important tool for understanding cerebral perfusion in epilepsy patients. The aim of this study was to explore patterns of change in cerebral blood flow (CBF) and CBF connectivity in patients with focal to bilateral tonic-clonic seizures (FBTCS). High-resolution three-dimensional (3-D) T1-weighted and 3-D pseudo-continuous ASL magnetic resonance imaging (MRI) was collected from 32 patients with FBTCS and 16 healthy volunteers using a 3.0 T MRI scanner. Cerebral blood flow and its connectivity were compared between the FBTCS and control group. Correlation analysis was used to explore relationships of CBF and its connectivity changes with clinical parameters. Cerebral blood flow data of spatial standardization and normalization were used to improve statistical power. Patients with FBTCS exhibited increased CBF in the bilateral thalamus, caudate nucleus, olfactory cortex, and gyrus rectus, but decreased CBF in the bilateral supplementary motor areas (SMA) and middle cingulate cortex (MCC). Patients with FBTCS showed significant positive correlation between CBF and gray matter volume (GMV) in bilateral SMA and MCC. No significant correlations between CBF and clinical parameters were found among FBTCS patients. The anterior cingulate cortex (ACC) showed positive CBF connectivity with the bilateral SMA and MCC, and these CBF connectivity measures differed significantly between groups (cluster-level, FWE-corrected, P < 0.001). These findings suggest that patients with FBTCS have changes in cerebral CBF and CBF connectivity, which may relate to the underlying neuropathology of FBTCS.

Heart rate variability in frontal lobe epilepsy: Association with SUDEP risk

OBJECTIVES

Frontal lobe epilepsy (FLE) may impair autonomic heart rate modulation. Decreased heart rate variability (HRV) may enhance risk of sudden death. Our objective was to describe whole day and wakefulness/sleep HRV parameters from FLE patients in comparison with those of healthy controls and correlate HRV parameters to SUDEP-7 scores.

METHODS

Ten patients with FLE and 15 healthy controls underwent a 24-hour electrocardiogram holter. The SUDEP-7 score was calculated for patients. Subgroups were identified according to active epilepsy, number of generalized seizures, cognitive deficit, medication load, and time-length of epilepsy. Time-domain SDNN, SDNNi, SDANN, rMSDD, and pNN50 and frequency-domain LF, HF, and LF/HF parameters were analyzed. Wilcoxon and Spearman correlation tests were used. A P < .05 was considered significant.

RESULTS

Patients SDNN, SDNNi, rMSSD, and pNN50 were decreased in 24-hour recordings. Although a tendency for a protective effect of sleep was seen for both patients and controls, intragroup comparisons of sleeping/waking states revealed a significant increase in sleep rMSSD (P = .046) and pNN50 (P = .041) only for controls. All 24-hour time-domain parameters and LF were inversely and significantly correlated to SUDEP-7, particularly SDANN (ρ = -0.896, P = .00019), known to deteriorate with diminished physical activity and decreased in patients with more generalized seizures. Wakefulness parameters did not correlate to SUDEP-7, whereas correlations to sleep parameters were very strong, particularly with rMSSD (ρ = -0.945, P = .00012). Cognitive deficit was associated with decreased pNN50, sleep pNN50, and LH.

CONCLUSION

HRV is impaired in patients with FLE. Low HRV scores are associated with increased risk for SUDEP as measured by the SUDEP-7 score.

Electroencephalography in Epilepsy Evaluation

PURPOSE OF REVIEW

Epilepsy is a heterogeneous disorder that is often associated with abnormal electroencephalogram (EEG) findings. This article provides an overview of common EEG findings in epileptic disorders. The physiologic basis of EEG and intracranial EEG studies is also discussed.

RECENT FINDINGS

EEG is widely used in clinical practice. Because of the paroxysmal nature of seizure disorders, interictal epileptiform discharges, such as spikes and sharp waves, are often used to support the diagnosis of epilepsy when a habitual seizure is not captured by EEG. Interictal and ictal EEG findings also underlie the classification of seizures and epilepsy. Continuous critical care EEG monitoring has become an invaluable study in the diagnosis and treatment of subclinical seizures and nonconvulsive status epilepticus. Intracranial EEG with subdural or intraparenchymal electrodes is warranted when localization of the seizure focus and mapping of eloquent brain areas are required to plan epilepsy surgery.

SUMMARY

The EEG is a key tool in the diagnosis of epilepsy. Interictal and ictal EEG findings are crucial for the confirmation and classification of seizure disorders. Intracranial EEG monitoring is also indispensable for planning surgery for some patients.

Altered intrinsic brain activity associated with outcome in frontal lobe epilepsy

Frontal lobe epilepsy (FLE) is the second most common type of the focal epilepsies. Our understanding of this disease has been revolutionized over the past decade, but variable treatment outcomes persist and the underlying functional mechanisms responsible for this have yet to be deciphered. This study was designed to determine how intrinsic brain connectivity related to treatment response in patients with FLE. 50 patients with FLE and 28 healthy controls were enrolled in this study and underwent functional MRI at baseline. At the end of 12-month follow up period, all patients with FLE were classified, based on their responses to AEDs treatment, into drug-responsive and drug-refractory groups. The amplitude of low-frequency fluctuation (ALFF) was calculated amongst the three groups in order to detect regional neural function integration. The responsive group showed decreased ALFF only in the left ventromedial prefrontal cortex (vmPFC), while the refractory group showed decreased ALFF in the left vmPFC, right superior frontal gyrus (SFG), and supramarginal gyrus (SMG) relative to healthy controls. In addition, both the responsive and refractory groups showed increased ALFF in the precuneus and postcentral gyrus when compared to the healthy controls. Furthermore, the refractory group exhibited significantly decreased ALFF in the left vmPFC, right SFG and SMG, relative to the responsive group. Focal spontaneous activity, as assessed by ALFF, was associated with response to antiepileptic treatment in patients with FLE. Patients with refractory frontal lobe epilepsy exhibited decreased intrinsic brain activity. Our findings provide novel neuroimaging evidence into the mechanisms of medically-intractable FLE at the brain level.

Focal epilepsies and focal disorders

Electroencephalographic (EEG) investigations are crucial in the diagnosis and management of patients with focal epilepsies. EEG may reveal different interictal epileptiform discharges (IEDs: abnormal spikes, sharp waves). The EEG visibility of a spike depends on the surface area of cortex involved (>10cm²) and the brain localization of cortical generators. Regions generating IEDs (defining the "irritative zone") are not necessarily equivalent to the seizure onset zone. Focal seizures are dynamic processes originating from one or several brain regions (that generate fast oscillations and are called the epileptogenic zone) before spreading to other structures (that generate lower frequency oscillations and are called the propagation zone). Several factors limit the expression of seizures on scalp EEG, such as the area involved, degree of synchronization, and depth of the cortical generators. Different scalp EEG seizure onset patterns may be observed: fast discharge, background flattening, rhythmic spikes, sinusoidal discharge, or sharp activity. However, to a large extent EEG changes are linked to seizure propagation. Finally, in the context of presurgical evaluation, the combination of interictal and ictal EEG features is crucial to provide an optimal hypothesis concerning the epileptogenic zone.

Seizure manifesting as a reaching/grasping movement in a patient with post-traumatic epilepsy

Electrical stimulation (ES) of the pre-supplementary or cingulate motor area can cause reaching/grasping (R/G) movements with the hand contralateral to the side of the brain receiving the ES. We report this phenomenon occurring in a 23-year-old right-handed man during spontaneous epileptic seizure, which developed after traumatic brain injury.

Non-linear ICA Analysis of Resting-State fMRI in Mild Cognitive Impairment

Compared to linear independent component analysis (ICA), non-linear ICA is more suitable for the decomposition of mixed components. Existing studies of functional magnetic resonance imaging (fMRI) data by using linear ICA assume that the brain's mixed signals, which are caused by the activity of brain, are formed through the linear combination of source signals. But the application of the non-linear combination of source signals is more suitable for the mixed signals of brain. For this reason, we investigated statistical differences in resting state networks (RSNs) on 32 healthy controls (HC) and 38 mild cognitive impairment (MCI) patients using post-nonlinear ICA. Post-nonlinear ICA is one of the non-linear ICA methods. Firstly, the fMRI data of all subjects was preprocessed. The second step was to extract independent components (ICs) of fMRI data of all subjects. In the third step, we calculated the correlation coefficient between ICs and RSN templates, and selected ICs of the largest spatial correlation coefficient. The ICs represent the corresponding RSNs. After finding out the eight RSNs of MCI group and HC group, one sample t-tests were performed. Finally, in order to compare the differences of RSNs between MCI and HC groups, the two-sample t-tests were carried out. We found that the functional connectivity (FC) of RSNs in MCI patients was abnormal. Compared with HC, MCI patients showed the increased and decreased FC in default mode network (DMN), central executive network (CEN), dorsal attention network (DAN), somato-motor network (SMN), visual network(VN), MCI patients displayed the specifically decreased FC in auditory network (AN), self-referential network (SRN). The FC of core network (CN) did not reveal significant group difference. The results indicate that the abnormal FC in RSNs is selective in MCI patients.

Three phase-ictal scalp EEG patterns in patients with seizures arising from the cortex facing the interhemispheric fissure

OBJECTIVE

Ictal scalp EEG patterns have been reported to vary across onset regions. We assessed the sequential EEG changes during seizure events on scalp EEG, and tested our hypothesis that patients with focal seizures arising from the cortex facing the interhemispheric fissure (IHF cortex) would be specifically characterized by 3 phase-EEG patterns (3Ph-EEG).

METHODS

Patient inclusion criteria were: 1) focal epilepsy and 2) ictal onset records on scalp and intracranial video-EEG. Patients were classified into one of the three groups: the IHF group, mesial temporal (MT) group, or lateral convexity (LC) group, based on the localization of the ictal onset zone (IOZ) on intracranial video-EEG. We defined 3Ph-EEG on ictal scalp EEG as follows: phase 1, brief spike/fast wave burst; phase 2, diffuse attenuation; and phase 3, focal rhythmic activity with evolution. We determined if the occurrence ratios of 3Ph-EEG and each of the three phases differed between the groups (IHF and others).

RESULTS

We studied 36 patients aged 8-59 years (mean, 30 years). Ten patients were classified as IHF, 16 as MT, and 10 as LC group from 303 ictal events on intracranial EEG. 193 seizures on scalp EEG consisted of 79 seizures in IHF; 58 in MT; 56 in LC group. Sixty-nine seizures (92%) in nine patients (90%) in IHF group showed 3Ph-EEG, whereas none of the seizures in MT and LC groups showed the 3Ph-EEG. Multivariate logistic regression analysis suggested that the presence of 3Ph-EEG (p < 0.01) and phase 2 (p = 0.03) components were predictive of IHF scalp EEG onset.

SIGNIFICANCE

The 3Ph-EEG may be observed preferentially in patients with focal seizures from IHF cortex. Observation of the ictal phases on scalp EEG may warrant consideration of intracranial EEG sampling for the presurgical evaluation.

Long-term surgical results of supplementary motor area epilepsy surgery

OBJECTIVE Supplementary motor area (SMA) epilepsy is a well-known clinical condition; however, long-term surgical outcome reports are scarce and correspond to small series or isolated case reports. The aim of this study is to present the surgical results of SMA epilepsy patients treated at 2 reference centers in Mexico City. METHODS For this retrospective descriptive study (1999-2014), 52 patients underwent lesionectomy and/or corticectomy of the SMA that was guided by electrocorticography (ECoG). The clinical, neurophysiological, neuroimaging, and pathological findings are described. The Engel scale was used to classify surgical outcome. Descriptive statistics, Student t-test, and Friedman, Kruskal-Wallis, and chi-square tests were used. RESULTS Of these 52 patients, the mean age at epilepsy onset was 26.3 years, and the mean preoperative seizure frequency was 14 seizures per month. Etiologies included low-grade tumors in 28 (53.8%) patients, cortical dysplasia in 17 (32.7%) patients, and cavernomas in 7 (13.5%) patients. At a mean follow-up of 5.7 years (range 1-10 years), 32 patients (61%) were classified as Engel Class I, 16 patients (31%) were classified as Engel Class II, and 4 (8%) patients were classified as Engel Class III. Overall seizure reduction was significant (p = 0.001). The absence of early postsurgical seizures and lesional etiology were associated with the outcome of Engel Class I (p = 0.05). Twenty-six (50%) patients had complications in the immediate postoperative period, all of which resolved completely with no residual neurological deficits. CONCLUSIONS Surgery for SMA epilepsy guided by ECoG using a multidisciplinary and multimodality approach is a safe, feasible procedure that shows good seizure control, moderate morbidity, and no mortality.

Normalized power variance change between pre-ictal and ictal phase of an epilepsy patient using NAT analysis: a case study

Variance of state variables shifts due to phase-instability and may serve as an early-warning signal of phase transition of complex systems such as an epileptic seizure of brain cortical activity. Neuronal Activity Topology (NAT) analysis calculates a normalized-power-variance (NPV) of electroencephalogram (EEG) data in each frequency band to obtain relative values comparable among different power states.

Thought suppression predicts task switching deficits in patients with frontal lobe epilepsy

OBJECTIVE

To examine the relationship between task switching and thought suppression in connection with frontal lobe epilepsy (FLE).

METHODS

This experimental study included 30 patients with FLE admitted to the Services and Jinnah Hospital, Lahore, Pakistan between February and November 2013, and 30 healthy individuals from the local community. Participants performed a task switching experiment where they switched between emotion and age categorizations among faces. In addition, they completed a thought suppression questionnaire.

RESULTS

There were 3 important results: (i) Patients with FLE showed weaker task switching abilities than healthy individuals. This result is attributed toward executive dysfunctions in patients with FLE. (ii) Contrary to the control group, patients with FLE showed larger switch cost for the age than the emotion categorization. This result can be seen in the context of social cognition deficits and poor inhibitory control in patients with FLE. In addition, larger switch costs reflected a binding effect with facial emotion as compared to age. The integration might represent emotion as an intrusive facial dimension that interrupted task switching performance. (iii) Patients with FLE had more recurrent suppression of thoughts than controls. Thought suppression was a significant predictor for switch costs. High scores on thought suppression were correlated with task switching deficits.

CONCLUSION

The results suggest that thought suppression causes significant cognitive decline.

Epilepsy surgery in bifrontal injury from prior craniopharyngioma resections

Epilepsy surgery in frontal lobe epilepsy (FLE) has less favorable seizure-free outcomes than temporal lobe epilepsies. Possible contributing factors include fast propagation patterns and large clinically silent areas which are characteristics of the frontal lobes. Bilateral frontal lobe abnormalities on MRI are another relative contraindication to epilepsy surgery. For example, bilateral encephalomalacia may be a presupposition to bilateral or multifocal epilepsy. The possibility of potential disinhibition with already poor reserves may be another deterrent to consideration for resective epilepsy surgery. As such, conventional surgical approaches to intractable epilepsy with bilateral frontal injury may be limited to palliative procedures like vagus nerve stimulation and corpus callosotomy. We present a case in which the epileptogenic zone was a subset of the acquired, bilateral, cystic encephalomalacia. This iatrogenic injury resulted from two prior craniotomies for excision of craniopharyngioma and its recurrence.

Following the initial bilateral and subsequent unilateral, subdural grid- and depth electrode-based localization and resection, our patient has remained seizure-free 2 years after epilepsy surgery with marked improvement in her quality of life, as corroborated by her neuropsychological test scores. Our patient's clinical course is testament to the potential role for resective strategies in selected cases of intractable epilepsy associated with bifrontal injury. Reversal of behavioral deficits with frontal lobe epilepsy surgery such as in this patient provides a unique opportunity to further our understanding of the complex nature of frontal lobe function.

Seizure patterns in childhood

Seizures are alarming and can be life-threatening. It is essential that pediatric providers be able to identify those paroxysmal events most likely to be seizures and to know which require immediate evaluation. Severity can range from childhood syndromes that are controlled relatively easily and usually outgrown to epileptic encephalopathies that are associated with severe developmental delay and sometimes death. Familiarity with seizure semiology can guide early diagnosis and treatment.

Investigation of magnetic resonance imaging texture analysis as an aid tool for characterization of refractory epilepsies

Refractory epilepsies are syndromes for which therapies that employ two or more antiepileptic drugs, separately or in association, do not result in control of crisis. Patients may present focal cortical dysplasia or diffuse dysplasia and/or hippocampal atrophic alterations that may not be detectable by a simple visual analysis in magnetic resonance imaging. The aim of this study was to evaluate MRI texture in regions of interest located in the hippocampi, limbic association cortex and prefrontal cortex of 20 patients with refractory epilepsy and to compare them with the same areas in 20 healthy individuals, in order to find out if the texture parameters could be related to the presence of the disease. Of the 11 texture parameters calculated, three indicated the existence of statistically significant differences between the studied groups. Such findings suggest the possibility of this technique contributing to studies of refractory epilepsies.

Temporal relationship between awakening and seizure onset in nocturnal partial seizures

Clinical awakening can be seen just before or after seizure onsets. In this study we determined the time between onset of seizures and awakening in patients with frontal lobe epilepsy (FLE) and temporal lobe epilepsy (TLE). Sixty-eight patients who underwent video-EEG monitoring with simultaneous PSG were retrospectively examined. TLE or FLE patients having seizures during sleep were included. Seizure onset and awakening onset were marked according to clinical and electrophysiological features. The duration between awakening and seizure onset was compared in patients with TLE and FLE. Twenty-five patients who had been diagnosed with TLE (17) or FLE (8) had a total of 75 seizures during sleep. All seizures except one, occurred during NREM sleep in both TLE and FLE patients. The seizure onsets were before awakening in 49 seizures (FLE: 20, TLE: 29) and the awakening preceded the seizure onsets in 12 seizures (FLE: 3, TLE: 9). The duration between seizure onset and the awakening was shorter in FLE, either in seizures with preceding awakening or not (p=0.014, p=0.015). Awakening was mostly seen after onset of seizures rather than before, especially in TLE. But in patients with FLE the duration between seizure onset and awakening was shorter. The localization of epileptic activity may play a role for the timing of awakening mechanisms during nocturnal partial seizures.

The correlation between ictal semiology and magnetoencephalographic localization in frontal lobe epilepsy

OBJECTIVE

The aim of this study was to investigate the correlation of ictal semiology with localization and/or lateralization by magnetoencephalography (MEG).

METHODS

Seven patients from the Neurology Department of the University Hospital Erlangen who underwent resective surgery for frontal lobe epilepsy (FLE) with an Engel 1a outcome were investigated retrospectively. MEG localizations were classified according to five compartments (separate or combined) of the frontal lobe: frontal basal (FB), frontal lateral (FL), frontal polar (FP), frontal mesial (FM), and frontal precentral (FPr). On the basis of previous studies that investigated the value of ictal semiology in localization and lateralization, we compared the experiential localization and/or lateralization of the epileptogenic region deduced from ictal semiology, that is, both seizure history and ictal video/EEG monitoring, with MEG localization.

RESULTS

It is easier to determine lateralization than localization from ictal semiology because of the variety of signs and fast propagation in FLE. All of the patients had specific MEG localizations according to favorable postoperative outcome. Three patients had MEG foci associated with ictal semiology; in another four, the MEG localization was adjacent to the estimated area suggested by ictal semiology. Head version signs could be observed in all compartments of the frontal lobe: clonic in FB and FP areas; postural in FPr, FL, and FM areas; hypermotor in FB, FP, FPr, and FM areas; sensation aura in FB, FL, and FM areas; and automatisms in FP, FPr, and FL areas. All patients had concordant lateralizing and limited valuable locating information from ictal semiology, but no complete correlation with MEG foci.

CONCLUSION

Ictal semiology may indicate the involvement of a symptomatogenic brain region during a seizure, but extent of seizure onset in central motor or sensorimotor area is not reliable enough to indicate the seizure onset zone and favorable postoperative outcome in FLE. MEG provided specific localization of epileptic activity in a FLE compartment, and indicated the relationship between epileptogenic region and lesion. MEG can complement ictal semiology in establishing a noninvasive focal localization hypothesis.