MRI volumetric measurement of amygdala and hippocampus in temporal lobe epilepsy

Intensity-Based Assessment of Hippocampal Segmentation Algorithms Using Paired Precontrast and Postcontrast MRI

Hippocampal segmentation is essential in neuroimaging for evaluating conditions like Alzheimer's dementia and mesial temporal sclerosis, where small volume changes can significantly impact normative percentiles. However, inaccurate segmentation is common due to the inclusion of non-hippocampal structures such as choroid plexus and cerebrospinal fluid (CSF), leading to volumetric overestimation and confounding of functional analyses. Current methods of assessment largely rely on virtual or manual ground truth labels, which can fail to capture these inaccuracies. To address this shortcoming, this study introduces a more direct voxel intensity-based method of segmentation assessment. Using paired precontrast and postcontrast T1-weighted MRIs, hippocampal segmentations were refined by adding marginal gray matter and removing marginal CSF and enhancement to determine a total required correction volume. Six segmentation algorithms-e2dhipseg, HippMapp3r, hippodeep, AssemblyNet, FastSurfer, and QuickNat-were implemented and compared. HippMapp3r and e2dhipseg, followed closely by hippodeep, exhibited the least total correction volumes, indicating superior accuracy. Dedicated hippocampal segmentation algorithms outperformed whole-brain methods.

Trigonelline as an anticonvulsant agent: mechanistic insights into NMDA receptor expression and oxidative stress balance

Glutamatergic neurotransmission and oxidative stress are involved in the pathophysiology of seizures. Some anticonvulsants exert their effects through modulation of these pathways. Trigonelline (TRG) has been shown to possess various pharmacological effects like neuroprotection. Therefore, this study was performed to determine TRG's anticonvulsant effects, focusing on its potential effects on N-methyl-D-aspartate (NMDA) receptors, a type of glutamate receptor, and oxidative stress state in the prefrontal cortex (PFC) in PTZ-induced seizure in mice. Seventy-two male mice were randomly divided into nine groups. The groups included mice that received normal saline, TRG at doses of 10, 50, and 100 mg/kg, diazepam, NMDA (an agonist), ketamine (an antagonist), the effective dose of TRG with NMDA, as well as sub-effective dose of TRG with ketamine, respectively. All agents were administrated intraperitoneally 60 min before induction of seizures by PTZ. Latency to seizure, total antioxidant capacity (TAC), and malondialdehyde (MDA) levels in serum and PFC were measured. Furthermore, the gene expression of NR2A and NR2B, subunits of NMDA receptors, was measured in the PFC. TRG administration increased the latency to seizure onset and enhanced TAC while reducing MDA levels in both the PFC and serum. TRG also decreased the gene expression of NR2B in the PFC. Unexpectedly, the findings revealed that the concurrent administration of ketamine amplified, whereas NMDA mitigated, the impact of TRG on latency to seizure. Furthermore, NMDA diminished the positive effects of TRG on antioxidant capacity and oxidative stress, while ketamine amplified these beneficial effects, indicating a complex interaction between TRG and NMDA receptor modulation. In the gene expression of NMDA receptors, results showed that ketamine significantly decreased the gene expression of NR2B when co-administrated with a sub-effective dose of TRG. It was found that, at least partially, the anticonvulsant effect of TRG in PTZ-induced seizures in male mice was mediated by the attenuation of glutamatergic neurotransmission as well as the reduction of oxidative stress.

DMCA-GAN: Dual Multilevel Constrained Attention GAN for MRI-Based Hippocampus Segmentation

Precise segmentation of the hippocampus is essential for various human brain activity and neurological disorder studies. To overcome the small size of the hippocampus and the low contrast of MR images, a dual multilevel constrained attention GAN for MRI-based hippocampus segmentation is proposed in this paper, which is used to provide a relatively effective balance between suppressing noise interference and enhancing feature learning. First, we design the dual-GAN backbone to effectively compensate for the spatial information damage caused by multiple pooling operations in the feature generation stage. Specifically, dual-GAN performs joint adversarial learning on the multiscale feature maps at the end of the generator, which yields an average Dice coefficient (DSC) gain of 5.95% over the baseline. Next, to suppress MRI high-frequency noise interference, a multilayer information constraint unit is introduced before feature decoding, which improves the sensitivity of the decoder to forecast features by 5.39% and effectively alleviates the network overfitting problem. Then, to refine the boundary segmentation effects, we construct a multiscale feature attention restraint mechanism, which forces the network to concentrate more on effective multiscale details, thus improving the robustness. Furthermore, the dual discriminators D1 and D2 also effectively prevent the negative migration phenomenon. The proposed DMCA-GAN obtained a DSC of 90.53% on the Medical Segmentation Decathlon (MSD) dataset with tenfold cross-validation, which is superior to the backbone by 3.78%.

Quantitative susceptibility mapping identifies hippocampal and other subcortical grey matter tissue composition changes in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is associated with widespread brain alterations. Using quantitative susceptibility mapping (QSM) alongside transverse relaxation rate (R 2 * ), we investigated regional brain susceptibility changes in 36 patients with left-sided (LTLE) or right-sided TLE (RTLE) secondary to hippocampal sclerosis, and 27 healthy controls (HC). We compared three susceptibility calculation methods to ensure image quality. Correlations of susceptibility andR 2 * with age of epilepsy onset, frequency of focal-to-bilateral tonic-clonic seizures (FBTCS), and neuropsychological test scores were examined. Weak-harmonic QSM (WH-QSM) successfully reduced noise and removed residual background field artefacts. Significant susceptibility increases were identified in the left putamen in the RTLE group compared to the LTLE group, the right putamen and right thalamus in the RTLE group compared to HC, and a significant susceptibility decrease in the left hippocampus in LTLE versus HC. LTLE patients who underwent epilepsy surgery showed significantly lower left-versus-right hippocampal susceptibility. SignificantR 2 * changes were found between TLE and HC groups in the amygdala, putamen, thalamus, and in the hippocampus. Specifically, decreased R2 * was found in the left and right hippocampus in LTLE and RTLE, respectively, compared to HC. Susceptibility andR 2 * were significantly correlated with cognitive test scores in the hippocampus, globus pallidus, and thalamus. FBTCS frequency correlated positively with ipsilateral thalamic and contralateral putamen susceptibility and withR 2 * in bilateral globi pallidi. Age of onset was correlated with susceptibility in the hippocampus and putamen, and withR 2 * in the caudate. Susceptibility andR 2 * changes observed in TLE groups suggest selective loss of low-myelinated neurons alongside iron redistribution in the hippocampi, predominantly ipsilaterally, indicating QSM's sensitivity to local pathology. Increased susceptibility andR 2 * in the thalamus and putamen suggest increased iron content and reflect disease severity.

An automated, geometry-based method for hippocampal shape and thickness analysis

The hippocampus is one of the most studied neuroanatomical structures due to its involvement in attention, learning, and memory as well as its atrophy in ageing, neurological, and psychiatric diseases. Hippocampal shape changes, however, are complex and cannot be fully characterized by a single summary metric such as hippocampal volume as determined from MR images. In this work, we propose an automated, geometry-based approach for the unfolding, point-wise correspondence, and local analysis of hippocampal shape features such as thickness and curvature. Starting from an automated segmentation of hippocampal subfields, we create a 3D tetrahedral mesh model as well as a 3D intrinsic coordinate system of the hippocampal body. From this coordinate system, we derive local curvature and thickness estimates as well as a 2D sheet for hippocampal unfolding. We evaluate the performance of our algorithm with a series of experiments to quantify neurodegenerative changes in Mild Cognitive Impairment and Alzheimer's disease dementia. We find that hippocampal thickness estimates detect known differences between clinical groups and can determine the location of these effects on the hippocampal sheet. Further, thickness estimates improve classification of clinical groups and cognitively unimpaired controls when added as an additional predictor. Comparable results are obtained with different datasets and segmentation algorithms. Taken together, we replicate canonical findings on hippocampal volume/shape changes in dementia, extend them by gaining insight into their spatial localization on the hippocampal sheet, and provide additional, complementary information beyond traditional measures. We provide a new set of sensitive processing and analysis tools for the analysis of hippocampal geometry that allows comparisons across studies without relying on image registration or requiring manual intervention.

Alteration of Excitation/Inhibition Imbalance in the Hippocampus and Amygdala of Drug-Resistant Epilepsy Patients Treated with Acute Vagus Nerve Stimulation

An imbalance between excitation (E) and inhibition (I) in the brain has been identified as a key pathophysiology of epilepsy over the years. The hippocampus and amygdala in the limbic system play a crucial role in the initiation and conduction of epileptic seizures and are often referred to as the transfer station and amplifier of seizure activities. Existing animal and imaging studies reveal that the hippocampus and amygdala, which are significant parts of the vagal afferent network, can be modulated in order to generate an antiepileptic effect. Using stereo-electroencephalography (SEEG) data, we examined the E/I imbalance in the hippocampus and amygdala of ten drug-resistant epilepsy children treated with acute vagus nerve stimulation (VNS) by estimating the 1/f power slope of hippocampal and amygdala signals in the range of 1-80 Hz. While the change in the 1/f power slope from VNS-BASE varied between different stimulation amplitudes and brain regions, it was more prominent in the hippocampal region. In the hippocampal region, we found a flatter 1/f power slope during VNS-ON in patients with good responsiveness to VNS under the optimal stimulation amplitude, indicating that the E/I imbalance in the region was improved. There was no obvious change in 1/f power slope for VNS poor responders. For VNS non-responders, the 1/f power slope slightly increased when the stimulation was applied. Overall, this study implies that the regulation of E/I imbalance in the epileptic brain, especially in the hippocampal region, may be an acute intracranial effect of VNS.

Hippocampal volumetry to determine the resection side in patients with intractable non-lesional bilateral temporal lobe epilepsy

Bilateral Temporal lobe epilepsy (BTLE) cases may result in poor surgical outcomes due to the difficulty in determining/localizing the epileptogenic zone. In this study, we investigated whether hippocampal volume (HV) would be useful for the determination of the best resection side in BTLE. Eighteen cases of BTLE determined by a scalp video electroencephalogram (SVEEG) underwent resection via intracranial electroencephalography (IVEEG). Patients with lesions or semiologically determined focus lateralization were excluded. In addition to SVEEG, an epilepsy protocol magnetic resonance imaging (MRI) including hippocampus fluid-attenuated inversion recovery (FLAIR) and HV, 18F-fluorodeoxyglucose positron emission tomography (FDG-PET), single-photon emission computed tomography with 123I-iomazenil (IMZ-SPECT), and magnetoencephalography (MEG) were performed for the preoperative evaluation of the lateralization. The resection side was determined based on the IVEEG results, and the seizure outcome at two years postoperatively was classified as either a well-controlled seizure outcome (Engel class I), or residual (classes II-V). We used a Fisher's exact test to compare the concordance between the determination of the epileptic focus by each modality and the resected side where patients achieved a well-controlled seizure outcome. Seizures were well controlled in 9/18 patients after surgery. Eight out of 11 patients (72.7%), in whom the HV results (strongly atrophic side) and the resection side were matched, had well-controlled seizure outcomes (P = 0.0498). The concordance of other presurgical evaluations with the resection side was not significantly related to a well-controlled seizure outcome. HV may be a useful method to determine the optimal resection side of the epileptic focus/foci in cases of suspected BTLE.

Temporal lobe epilepsy in cats

In recent years there has been increased attention to the proposed entity of feline temporal lobe epilepsy (TLE). Epileptic discharges in certain parts of the temporal lobe elicit very similar semiology, which justifies grouping these epilepsies under one name. Furthermore, feline TLE patients tend to have histopathological changes within the temporal lobe, usually in the hippocampus. The initial aetiology is likely to be different but may result in hippocampal necrosis and later hippocampal sclerosis. The aim of this article was not only to summarise the clinical features and the possible aetiology, but also being work to place TLE within the veterinary epilepsy classification. Epilepsies in cats, similar to dogs, are classified based on the aetiology into idiopathic epilepsy, structural epilepsy and unknown cause. TLE seems to be outside of this classification, as it is not an aetiologic category, but a syndrome, associated with a topographic affiliation to a certain anatomical brain structure. Magnetic resonance imaging, histopathologic aspects and current medical therapeutic considerations will be summarised, and emerging surgical options are discussed.

Gene expression profile suggests different mechanisms underlying sporadic and familial mesial temporal lobe epilepsy

Most patients with pharmacoresistant mesial temporal lobe epilepsy (MTLE) have hippocampal sclerosis on the postoperative histopathological examination. Although most patients with MTLE do not refer to a family history of the disease, familial forms of MTLE have been reported. We studied surgical specimens from patients with MTLE who had epilepsy surgery for medically intractable seizures. We assessed and compared gene expression profiles of the tissue lesion found in patients with familial MTLE (n = 3) and sporadic MTLE (n = 5). In addition, we used data from control hippocampi obtained from a public database (n = 7). We obtained expression profiles using the Human Genome U133 Plus 2.0 (Affymetrix) microarray platform. Overall, the molecular profile identified in familial MTLE differed from that in sporadic MTLE. In the tissue of patients with familial MTLE, we found an over-representation of the biological pathways related to protein response, mRNA processing, and synaptic plasticity and function. In sporadic MTLE, the gene expression profile suggests that the inflammatory response is highly activated. In addition, we found enrichment of gene sets involved in inflammatory cytokines and mediators and chemokine receptor pathways in both groups. However, in sporadic MTLE, we also found enrichment of epidermal growth factor signaling, prostaglandin synthesis and regulation, and microglia pathogen phagocytosis pathways. Furthermore, based on the gene expression signatures, we identified different potential compounds to treat patients with familial and sporadic MTLE. To our knowledge, this is the first study assessing the mRNA profile in surgical tissue obtained from patients with familial MTLE and comparing it with sporadic MTLE. Our results clearly show that, despite phenotypic similarities, both forms of MTLE present distinct molecular signatures, thus suggesting different underlying molecular mechanisms that may require distinct therapeutic approaches.

Mammillary Body Atrophy in Temporal Lobe Epilepsy With Hippocampal Sclerosis

BACKGROUND AND PURPOSE

We aimed to determine 1) the frequency of mammillary body (MB) atrophy in patients with temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS), 2) the clinical significance of MB atrophy, and 3) the association between MB atrophy and volume changes in other subcortical limbic structures.

METHODS

We enrolled 69 patients with pathologically confirmed TLE with HS, who underwent a standard anterior temporal lobectomy, as well as 40 healthy controls. We used the FreeSurfer deep-learning tool of U-Net to obtain the volumes of the subcortical limbic structures, including the MB, hypothalamus, basal forebrain, septal nuclei, fornix, and nucleus accumbens. MB atrophy was considered to be present when the MB volume was decreased relative to the healthy controls.

RESULTS

MB atrophy was present in 18 (26.1%) of the 69 patients with TLE and HS. Among the clinical characteristics, the mean age at seizure onset was higher (25.5 vs. 15.9 years, p=0.027) and the median duration of epilepsy was shorter (149 vs. 295 months, p=0.003) in patients with than without MB atrophy. The basal forebrain (0.0185% vs. 0.0221%, p=0.004) and septal nuclei (0.0062% vs. 0.0075%, p=0.003) in the ipsilateral hemisphere of HS were smaller in the patients with MB atrophy.

CONCLUSIONS

We observed ipsilateral MB atrophy in about one-quarter of patients with TLE and HS. The severity of subcortical limbic structure abnormalities was greater in patients without MB atrophy. These findings suggest that MB atrophy in TLE with HS is not rare, but it has little clinical significance.

Amygdala subnuclear volumes in temporal lobe epilepsy with hippocampal sclerosis and in non-lesional patients

Together with hippocampus, the amygdala is important in the epileptogenic network of patients with temporal lobe epilepsy. Recently, an increase in amygdala volumes (i.e. amygdala enlargement) has been proposed as morphological biomarker of a subtype of temporal lobe epilepsy patients without MRI abnormalities, although other data suggest that this finding might be unspecific and not exclusive to temporal lobe epilepsy. In these studies, the amygdala is treated as a single entity, while instead it is composed of different nuclei, each with peculiar function and connection. By adopting a recently developed methodology of amygdala's subnuclei parcellation based of high-resolution T1-weighted image, this study aims to map specific amygdalar subnuclei participation in temporal lobe epilepsy due to hippocampal sclerosis (n = 24) and non-lesional temporal lobe epilepsy (n = 24) with respect to patients with focal extratemporal lobe epilepsies (n = 20) and healthy controls (n = 30). The volumes of amygdala subnuclei were compared between groups adopting multivariate analyses of covariance and correlated with clinical variables. Additionally, a logistic regression analysis on the nuclei resulting statistically different across groups was performed. Compared with other populations, temporal lobe epilepsy with hippocampal sclerosis showed a significant atrophy of the whole amygdala (p Bonferroni = 0.040), particularly the basolateral complex (p Bonferroni = 0.033), while the non-lesional temporal lobe epilepsy group demonstrated an isolated hypertrophy of the medial nucleus (p Bonferroni = 0.012). In both scenarios, the involved amygdala was ipsilateral to the epileptic focus. The medial nucleus demonstrated a volume increase even in extratemporal lobe epilepsies although contralateral to the seizure onset hemisphere (p Bonferroni = 0.037). Non-lesional patients with psychiatric comorbidities showed a larger ipsilateral lateral nucleus compared with those without psychiatric disorders. This exploratory study corroborates the involvement of the amygdala in temporal lobe epilepsy, particularly in mesial temporal lobe epilepsy and suggests a different amygdala subnuclei engagement depending on the aetiology and lateralization of epilepsy. Furthermore, the logistic regression analysis indicated that the basolateral complex and the medial nucleus of amygdala can be helpful to differentiate temporal lobe epilepsy with hippocampal sclerosis and with MRI negative, respectively, versus controls with a consequent potential clinical yield. Finally, the present results contribute to the literature about the amygdala enlargement in temporal lobe epilepsy, suggesting that the increased volume of amygdala can be regarded as epilepsy-related structural changes common across different syndromes whose meaning should be clarified.

Statistical asymmetry analysis of volumetric MRI and FDG PET in temporal lobe epilepsy

PURPOSE

To analyze statistically derived threshold values of volumetric MRI and 18F fluorodeoxyglucose (FDG) PET asymmetry, independent of normative data, for non-invasive detection/exclusion of temporal lobe epilepsy (TLE).

METHODS

We retrospectively analyzed amygdalohippocampal volumetry and temporal FDG PET metabolism in 33 patients (age: 29.27 ± 8.56 years) who underwent surgery following Stereo-EEG implantation and had postsurgical seizure freedom lasting >12 months. The temporal lobe epilepsy group and the extratemporal lobe epilepsy (ETLE) group were compared. Percentage volume loss (PVL) was calculated from manually traced amygdalohippocampal volumetry whereas percentage metabolic loss (PML) was calculated from PET using amygdalohippocampal trace and temporal neocortical Brodmann areas (BA) template.

RESULTS

Receiver operating characteristic (ROC) curve analysis identified a cutoff hippocampal PVL of 4.21% as the minimum indicating probable hippocampal involvement in seizure onset, with sensitivity of 88.89% and the specificity of 100% (p < 0.001). Region of interest (ROI)-based PML values in PET imaging showed a significant correlation with the presence of TLE in the TLE group of patients and its absence in the ETLE group of patients. Region of interest curve analysis yielded PML cutoffs of 5.77% and 8.36%, respectively, for the hippocampus and BA 38 (temporopolar neocortex) to detect TLE with the sensitivity of 72.7% and specificity of 77.8%.

CONCLUSION

We describe statistical thresholds for asymmetry analysis of hippocampal volumetry and FDG PET to improve detection of TLE. These threshold parameters warrant further validation in prospective studies.

Clinical and radiomic features for predicting the treatment response of repetitive transcranial magnetic stimulation in major neurocognitive disorder: Results from a randomized controlled trial

Image-guided repetitive transcranial magnetic stimulation (rTMS) has shown clinical effectiveness in senior adults with co-occurring depression and cognitive impairment, yet the imaging markers for predicting the treatment response are less investigated. In this clinical trial, we examined the efficacy and sustainability of 10 Hz rTMS for the treatment of depression and cognitive impairment in major neurocognitive disorder (NCD) patients and tested the predictive values of imaging-informed radiomic features in response to rTMS treatment. Fifty-five major NCD patients with depression were randomly assigned to receive a 3-week rTMS treatment of either active 10 Hz rTMS (n = 27) or sham rTMS (n = 28). Left dorsolateral prefrontal cortex (DLPFC) was the predefined treatment target. Based on individual structural magnetic resonance imaging scans, surface-based analysis was conducted to quantitatively measure the baseline radiomic features of left DLPFC. Severity of depression, global cognition and the serum brain-derived neurotrophic factor (BDNF) level were evaluated at baseline, 3-, 6- and 12-week follow-ups. Logistic regression analysis revealed that advanced age, higher baseline cognition and randomized group were associated with the remission of depression. Increased cortical thickness and gyrification in left DLPFC were the significant predictors of clinical remission and cognitive enhancement. A 3-week course of 10 Hz rTMS is an effective adjuvant treatment for rapid ameliorating depressive symptoms and enhancing cognitive function. Pre-treatment radiomic features of the stimulation target can predict the response to rTMS treatment in major NCD. Cortical thickness and folding of treatment target may serve as imaging markers to detect the responders. ChiCTR-IOR-16008191, registered on March 30, 2016.

Mechanisms for Cognitive Impairment in Epilepsy: Moving Beyond Seizures

There has been a major emphasis on defining the role of seizures in the causation of cognitive impairments like memory deficits in epilepsy. Here we focus on an alternative hypothesis behind these deficits, emphasizing the mechanisms of information processing underlying healthy cognition characterized as rate, temporal and population coding. We discuss the role of the underlying etiology of epilepsy in altering neural networks thereby leading to both the propensity for seizures and the associated cognitive impairments. In addition, we address potential treatments that can recover the network function in the context of a diseased brain, thereby improving both seizure and cognitive outcomes simultaneously. This review shows the importance of moving beyond seizures and approaching the deficits from a system-level perspective with the guidance of network neuroscience.

Differences in Evolution of Epileptic Seizures and Topographical Distribution of Tissue Damage in Selected Limbic Structures Between Male and Female Rats Submitted to the Pilocarpine Model

Epidemiological evidence shows that clinical features and comorbidities in temporal lobe epilepsy (TLE) may have different manifestations depending on the sex of patients. However, little is known about how sex-related mechanisms can interfere with the processes underlying the epileptic phenomenon. The findings of this study show that male rats with epilepsy in the pilocarpine model have longer-lasting and more severe epileptic seizures, while female rats have a higher frequency of epileptic seizures and a greater number of seizure clusters. Significant sex-linked pathological changes were also observed: epileptic brains of male and female rats showed differences in mass reduction of 41.8% in the amygdala and 18.2% in the olfactory bulb, while loss of neuronal cells was present in the hippocampus (12.3%), amygdala (18.1%), and olfactory bulb (7.5%). Another important sex-related finding was the changes in non-neuronal cells with increments for the hippocampus (36.1%), amygdala (14.7%), and olfactory bulb (37%). Taken together, our study suggests that these neuropathological changes may underlie the differences in the clinical features of epileptic seizures observed in male and female rats.

Using magnetic resonance fingerprinting to characterize periventricular nodular heterotopias in pharmacoresistant epilepsy

OBJECTIVE

We aimed to use a novel magnetic resonance fingerprinting (MRF) technique to examine in vivo tissue property characteristics of periventricular nodular heterotopia (PVNH). These characteristics were further correlated with stereotactic-electroencephalographic (SEEG) ictal onset findings.

METHODS

We included five patients with PVNH who had SEEG-guided surgery and at least 1 year of seizure freedom or substantial seizure reduction. High-resolution MRF scans were acquired at 3 T, generating three-dimensional quantitative T₁ and T₂  maps. We assessed the differences between T₁ and T₂  values from the voxels in the nodules located in the SEEG-defined seizure onset zone (SOZ) and non-SOZ, on -individual and group levels. Receiver operating characteristic analyses were performed to obtain the optimal classification performance. Quantification of SEEG ictal onset signals from the nodules was performed by calculating power spectrum density (PSD). The association between PSD and T₁ /T₂  values was further assessed at different frequency bands.

RESULTS

Individual-level analysis showed T₁ was significantly higher in SOZ voxels than non-SOZ voxels (p < .05), with an average 73% classification accuracy. Group-level analysis also showed higher T₁ was significantly associated with SOZ voxels (p < .001). At the optimal cutoff (normalized T₁ of 1.1), a 76% accuracy for classifying SOZ nodules from non-SOZ nodules was achieved. T₁  values were significantly associated with ictal onset PSD at the ultraslow, θ, β, γ, and ripple bands (p < .05). T₂  values were significantly associated with PSD only at the ultraslow band (p < .05).

SIGNIFICANCE

Quantitative MRF measures, especially T₁ , can provide additional noninvasive information to separate nodules in SOZ and non-SOZ. The T₁ and T₂ tissue property changes carry electrophysiological underpinnings relevant to the epilepsy, as shown by their significant positive associations with power changes during the SEEG seizure onset. The use of MRF as a supplementary noninvasive tool may improve presurgical evaluation for patients with PVNH and pharmacoresistant epilepsy.

Quantification of brain age using high-resolution 7 tesla MR imaging and implications for patients with epilepsy

Purpose

Epilepsy patients exhibit morphological differences on neuroimaging compared to age-matched healthy controls, including cortical and sub-cortical volume loss and altered gray-white matter ratios. The objective was to develop a model of normal aging using the 7T MRIs of healthy controls. This model can then be used to determine if the changes in epilepsy patients resemble the changes seen in aging, and potentially give a marker for the severity of those changes.

Methods

Sixty-nine healthy controls (24F/45M, mean age 36.5 ± 10.5 years) and forty-four epilepsy patients (24F/20M, 33.2 ± 9.9 years) non-lesional at 3T were scanned with volumetric T1-MPRAGE at 7T. These images were segmented and quantified using FreeSurfer. A linear regression-based model trained on healthy controls was developed to predict ages using derived imaging features among the epilepsy patient cohort. The model used 114 features with significant linear correlation with age.

Results

The regression-based model estimated brain age with mean absolute error (MAE) of 6.6 years among controls. Comparable prediction accuracy of 6.9 years MAE was seen epilepsy patients. T-test of mean absolute error showed no difference in the prediction accuracy with controls and epilepsy patients (p = 0.68). However, average signed error showed elevated (+5.0 years, p = 0.0007) predicted age differences (PAD; brain-PAD=, predicted minus biological age) among epilepsy patients. Morphological metrics in the medial temporal lobe were major contributors to PAD. Additionally, patients with seizure frequency greater than once a week showed significantly elevated brain-PAD (+8.2 ± 5.3 years, n = 13) compared to patients with lower seizure frequency (3.7 ± 6.5 years, n = 31, p = 0.033).

Major conclusions

Morphological patterns suggestive of premature aging were observed in non-lesional epilepsy patients vs. controls and in high seizure frequency patients vs. low frequency patients. Modeling brain age with 7T MRI may provide a sensitive imaging marker to assess the differential effects of the aging process in diseases such as epilepsy.

NMDA Receptor Mediates the Anticonvulsant Effect of Hydroalcoholic Extract of Artemisia persica in PTZ-Induced Seizure in Mice

It is necessary to seek more effective sources to design new drug against epilepsy. This study aimed to evaluate the effect of hydroalcoholic extract of Artemisia persica on pentylenetetrazole- (PTZ-) induced seizure in male mice by investigating the possible role of the NMDA receptor and antioxidative stress effect. The phenolic profile of A. persica extract was determined by HPLC-DAD analysis. Mice were treated with normal saline or A. persica extract or pentobarbital or a subeffective dose of extract plus ketamine (NMDA receptor antagonist) and/or effective dose of extract plus NMDA. PTZ (90 mg/kg) was injected intravenously for induction of seizure. The seizure threshold was measured. Then mice were euthanized and the antioxidant capacity and the level of malondialdehyde (MDA) of the prefrontal cortex and serum were measured. The gene expression of NMDA receptor subunits (Nr2a and Nr2b) was determined by real-time PCR. Findings showed that A. persica extract increased the seizure threshold, increased antioxidant capacity, and decreased MDA levels in the serum and brain samples. A. persica extract reduced the expression of NMDA receptor subunits. The result showed that ketamine potentiated the effect of the subeffective dose of extract. HPLC analysis showed that quercetin had the highest flavonoid content and also caffeic acid had the highest content of the phenolic acids. A. persica extract probably via NMDA receptor exerts anticonvulsant properties.

Amygdaloid theta-band power increases during conflict processing in humans

The amygdala is a medial temporal lobe structure known to be involved in processing emotional conflict. However, its role in processing non-emotional conflict is not well understood. Previous studies have utilized the Stroop Task to examine brain modulation of humans under the color-word conflict scenario, which is non-emotional conflict processing, and found hippocampal theta-band (4-7 Hz) modulation. This study aims to survey amygdaloid theta power changes during non-emotional conflict processing using intracranial depth electrodes in nine epileptic patients (3 female; age 20-62). All patients were asked to perform a modified Stroop task. During task performance, local field potential (LFP) data was recorded from macro contacts sampled at 2 K Hz and used for analysis. Mean theta power change from baseline was compared between the incongruent and congruent task condition groups using a paired sample t-test. Seven patients were available for analysis after artifact exclusion. In five out of seven patients, statistically significant increases in theta-band power from baseline were noted during the incongruent task condition (paired sample t-test p < 0.001), including one patient exhibiting theta power increases in both task conditions. Average response time was 1.07 s (failure trials) and 1.04 s (success trials). No speed-accuracy tradeoff was noted in this analysis. These findings indicate that human amygdaloid theta-band modulation may play a role in processing non-emotional conflict. It builds directly upon work suggesting that the amygdala processes emotional conflict and provides a neurophysiological mechanism for non-emotional conflict processing as well.

Gamma-band modulation in the human amygdala during reaching movements

OBJECTIVE

Motor brain-computer interface (BCI) represents a new frontier in neurological surgery that could provide significant benefits for patients living with motor deficits. Both the primary motor cortex and posterior parietal cortex have successfully been used as a neural source for human motor BCI, leading to interest in exploring other brain areas involved in motor control. The amygdala is one area that has been shown to have functional connectivity to the motor system; however, its role in movement execution is not well studied. Gamma oscillations (30-200 Hz) are known to be prokinetic in the human cortex, but their role is poorly understood in subcortical structures. Here, the authors use direct electrophysiological recordings and the classic "center-out" direct-reach experiment to study amygdaloid gamma-band modulation in 8 patients with medically refractory epilepsy.

METHODS

The study population consisted of 8 epilepsy patients (2 men; age range 21-62 years) who underwent implantation of micro-macro depth electrodes for seizure localization and EEG monitoring. Data from the macro contacts sampled at 2000 Hz were used for analysis. The classic center-out direct-reach experiment was used, which consists of an intertrial interval phase, a fixation phase, and a response phase. The authors assessed the statistical significance of neural modulation by inspecting for nonoverlapping areas in the 95% confidence intervals of spectral power for the response and fixation phases.

RESULTS

In 5 of the 8 patients, power spectral analysis showed a statistically significant increase in power within regions of the gamma band during the response phase compared with the fixation phase. In these 5 patients, the 95% bootstrapped confidence intervals of trial-averaged power in contiguous frequencies of the gamma band during the response phase were above, and did not overlap with, the confidence intervals of trial-averaged power during the fixation phase.

CONCLUSIONS

To the authors' knowledge, this is the first time that direct neural recordings have been used to show gamma-band modulation in the human amygdala during the execution of voluntary movement. This work indicates that gamma-band modulation in the amygdala could be a contributing source of neural signals for use in a motor BCI system.

Impact of Mesial Temporal Lobe Resection on Brain Structure in Medically Refractory Epilepsy

OBJECTIVE

Surgical resection can decrease seizure frequency in medically intractable temporal lobe epilepsy. However, the functional and structural consequences of this intervention on brain circuitry are poorly understood. We investigated structural changes that occur in brain circuits after mesial temporal lobe resection for refractory epilepsy. Specifically, we used neuroimaging techniques to evaluate changes in 1) contralesional hippocampal and bilateral mammillary body volume and 2) brain-wide cortical thickness.

METHODS

Serial T1-weighted brain magnetic resonance images were acquired before and after surgery (1.6 ± 0.5 year interval) in 21 patients with temporal lobe epilepsy (9 women, 12 men; mean age, 39.4 ± 11.5 years) who had undergone unilateral temporal lobe resection (14 anterior temporal lobectomy; 7 selective amygdalohippocampectomy). Blinded manual segmentation of the unresected hippocampal formation and bilateral mammillary bodies was performed using the Pruessner and Copenhaver protocols, respectively. Brain-wide cortical thickness estimates were computed using the CIVET pipeline.

RESULTS

Surgical resection was associated with a 5% reduction in contralesional hippocampal volume (P < 0.01) and a 9.5% reduction in mammillary body volume (P = 0.03). In addition, significant changes in cortical thickness were observed in contralesional anterior and middle cingulate gyrus and insula (P_{false discovery rate} < 0.01) as well as in other temporal, frontal, and occipital regions (P_{false discovery rate} < 0.05). Postoperative verbal memory function was significantly associated with cortical thickness change in contralesional inferior temporal gyrus (R² = 0.39; P = 0.03).

CONCLUSIONS

These results indicate that mesial temporal lobe resection is associated with both volume loss in spared Papez circuitry and changes in cortical thickness across the brain.

Quantifying Age-Associated Cortical Complexity of Left Dorsolateral Prefrontal Cortex with Multiscale Measurements

BACKGROUND

Cortical complexity plays a central role in the diagnosis and prognosis of age-related diseases. However, little is known about the regional cortical complexity in the context of brain atrophy.

OBJECTIVE

We aimed to systematically examine the age-related changes of the cortical complexity of left dorsolateral prefrontal cortex (DLPFC) and its subregions.

METHODS

Two hundred and fourteen cognitively normal adults drawn from the Open Access Series of Imaging Studies (OASIS) were divided into four age groups: young, middle-aged, young-old, and old-old. Based on structural magnetic resonance imaging (sMRI) scans, the multiscale measures of cortical complexity included cortical thickness (mm), surface area (mm2), grey matter volume (mm3), density, gyrification index (GI), and fractal dimension (FD).

RESULTS

Advancing age was associated with reduced grey matter volume, pial surface area, density, and FD of left DLPFC, but correlated with increased cortical thickness and GI. Volumetric measures, cerebrospinal fluid volume in particular, showed better performance to discriminate young-old adults from old-old adults, while FD was more sensitive than the volumetric measures to discriminate young adults and middle-aged adults.

CONCLUSION

This is the first demonstration that chronological age has a pronounced and differential effect on the cortical complexity of left DLPFC. Our findings suggest that surface-based measures of cortical region, thickness, and gyrification in particular, could be considered as valuable imaging markers for the studies of aging brain and neurodegenerative diseases.

Hippocampal size did not differ between epileptic and non-epileptic dogs using volumetric and subjective methods

Hippocampal changes in epilepsy may manifest as hippocampal atrophy/sclerosis. A recent human study suggests that the demonstration of hippocampal volume loss is more reliable using quantitative evaluation methods. The aim of the present study was to obtain volumetric data in both epileptic and healthy dogs, to compare hippocampal volumes in both groups, and to compare subjective and volumetric assessment. Volumetric measurements of the hippocampi, lateral ventricles and hemispheria were performed in 31 epileptic and 15 control dogs. There was a positive association between the body weight and the hemispheric volume, as well as between the hemispheric volume and the ipsilateral hippocampal volume. There was no significant correlation between age and the volume of any measured brain structures. There was no statistically significant difference between the hippocampal volumes of the control group and the epileptic group. A statistically significant difference between the two groups for hippocampus/hemispherium ratio or hippocampal asymmetric ratio was not identified. An extrapolated hippocampal volume based on body weight was not possible in this study population.

Pentylenetetrazol and Morphine Interaction in a State-dependent Memory Model: Role of CREB Signaling

Introduction:

State-dependent (STD) memory is a process, in which the learned information can be optimally retrieved only when the subject is in the state similar to the encoding phase. This phenomenon has been widely studied with morphine. Several studies have reported that Pentylenetetrazole (PTZ) impairs memory in experimental animal models. Due to certain mechanistic interactions between morphine and PTZ, it is hypothesized that PTZ may interfere with the morphine-STD. The cyclic adenosine monophosphate Response Element-Binding (CREB) is considered as the main downstream marker for long-term memory. This study was designed to determine the possible interaction between PTZ and morphine STD and the presumable changes in CREB mRNA.

Methods:

In an Inhibitory Avoidance (IA) model, posttraining morphine (2.5, 5, and 7.5 mg/ kg-i.p.) was used. The pre-test morphine was evaluated for morphine-induced STD memory. Moreover, the effect of a pre-test PTZ (60 mg/kg-i.p.) was studied along with morphine STD. Locomotion testing was carried out using open-field. Eventually, using real-time-PCR, the CREB mRNA changes in the hippocampus were evaluated.

Results:

Posttraining MOR (7.5 mg/kg-i.p.) impaired IA memory (P<0.001). The pre-test injection of similar doses of morphine recovered the morphine-induced memory impairment (P<0.001). The pre-test PTZ impaired the IA memory recall (P<0.001); however, the pre-test PTZ along with morphine STD potentiated the morphine-induced STD (P<0.001). Alterations in CREB mRNA were observed in all groups. No difference was seen in the locomotor activity.

Conclusion:

Presumably, the certain interactive effect of PTZ on morphine-induced STD is mediated through gamma-aminobutyric acid and opioid systems via CREB signaling.

Diagnostic Performance of MRI Volumetry in Epilepsy Patients With Hippocampal Sclerosis Supported Through a Random Forest Automatic Classification Algorithm

Introduction: Several methods offer free volumetry services for MR data that adequately quantify volume differences in the hippocampus and its subregions. These methods are frequently used to assist in clinical diagnosis of suspected hippocampal sclerosis in temporal lobe epilepsy. A strong association between severity of histopathological anomalies and hippocampal volumes was reported using MR volumetry with a higher diagnostic yield than visual examination alone. Interpretation of volumetry results is challenging due to inherent methodological differences and to the reported variability of hippocampal volume. Furthermore, normal morphometric differences are recognized in diverse populations that may need consideration. To address this concern, we highlighted procedural discrepancies including atlas definition and computation of total intracranial volume that may impact volumetry results. We aimed to quantify diagnostic performance and to propose reference values for hippocampal volume from two well-established techniques: FreeSurfer v.06 and volBrain-HIPS.

Methods: Volumetry measures were calculated using clinical T1 MRI from a local population of 61 healthy controls and 57 epilepsy patients with confirmed unilateral hippocampal sclerosis. We further validated the results by a state-of-the-art machine learning classification algorithm (Random Forest) computing accuracy and feature relevance to distinguish between patients and controls. This validation process was performed using the FreeSurfer dataset alone, considering morphometric values not only from the hippocampus but also from additional non-hippocampal brain regions that could be potentially relevant for group classification. Mean reference values and 95% confidence intervals were calculated for left and right hippocampi along with hippocampal asymmetry degree to test diagnostic accuracy.

Results: Both methods showed excellent classification performance (AUC:> 0.914) with noticeable differences in absolute (cm³) and normalized volumes. Hippocampal asymmetry was the most accurate discriminator from all estimates (AUC:1~0.97). Similar results were achieved in the validation test with an automatic classifier (AUC:>0.960), disclosing hippocampal structures as the most relevant features for group differentiation among other brain regions.

Conclusion: We calculated reference volumetry values from two commonly used methods to accurately identify patients with temporal epilepsy and hippocampal sclerosis. Validation with an automatic classifier confirmed the principal role of the hippocampus and its subregions for diagnosis.

Effective connectivity among the hippocampus, amygdala, and temporal neocortex in epilepsy patients: A cortico-cortical evoked potential study

OBJECTIVE

Mesial temporal lobe epilepsy (MTLE) is one of the most common types of intractable epilepsy. The hippocampus and amygdala are two crucial structures of the mesial temporal lobe and play important roles in the epileptogenic network of MTLE. This study aimed to explore the effective connectivity among the hippocampus, amygdala, and temporal neocortex and to determine whether differences in effective connectivity exist between MTLE patients and non-MTLE patients.

METHODS

This study recruited 20 patients from a large cohort of drug-resistant epilepsy patients, of whom 14 were MTLE patients. Single-pulse electrical stimulation (SPES) was performed to acquire cortico-cortical evoked potentials (CCEPs). The root mean square (RMS) was used as the metric of the magnitude of CCEP to represent the effective connectivity. We then conducted paired and independent sample t-tests to assess the directionality of the effective connectivity.

RESULTS

In both MTLE patients and non-MTLE patients, the directional connectivity from the amygdala to the hippocampus was stronger than that from the hippocampus to the amygdala (P < 0.01); the outward connectivity from the amygdala to the cortex was stronger than the inward connectivity from the cortex to the amygdala (P < 0.01); the amygdala had stronger connectivity to the neocortex than the hippocampus (P < 0.01). In MTLE patients, the neocortex had stronger connectivity to the hippocampus than to the amygdala (P < 0.01). No significant differences in directional connectivity were noted between the two groups.

CONCLUSIONS

A unique effective connectivity pattern among the hippocampus, amygdala, and temporal neocortex was identified through CCEPs analysis. This study may aid in our understanding of physiological and pathological networks in the brain and inspire neurostimulation protocols for neurological and psychiatric disorders.

Dynamic changes of region-specific cortical features and scalp-to-cortex distance: implications for transcranial current stimulation modeling

BACKGROUND

Transcranial current stimulation in rehabilitation is a fast-growing field featured with computational and biophysical modeling. Cortical features and scalp-to-cortex distance (SCD) are key variables for determining the strength and distribution of the electric field, yet longitudinal studies able to capture these dynamic changes are missing. We sought to investigate and quantify the ageing effect on the morphometry and SCD of left primary motor cortex (M1) and dorsolateral prefrontal cortex (DLPFC) in normal ageing adults and mild cognitive impairment (MCI) converters.

METHODS

Baseline, 1-year and 3-year follow-up structural magnetic resonance imaging scans from normal ageing adults (n = 32), and MCI converters (n = 22) were drawn from the Open Access Series of Imaging Studies. We quantified the changes of the cortical features and SCDs of left M1 and DLPFC, including grey matter volume, white matter volume, cortical thickness, and folding. Head model was developed to simulate the impact of SCD on the electric field induced by transcranial current stimulation.

RESULTS

Pronounced ageing effect was found on the SCD of left DLPFC in MCI converters. The SCD change of left DLPFC from baseline to 3-year follow-up demonstrated better performance to discriminate MCI converters from normal ageing adults than the other morphometric measures. The strength of electric field was consequently decreased with SCD in MCI converters.

CONCLUSION

Ageing has a prominent, but differential effect on the region-specific SCD and cortical features in older adults with cognitive impairments. Our findings suggest that SCD, cortical thickness, and folding of the targeted regions could be used as valuable imaging markers when conducting transcranial brain stimulation in individuals with brain atrophy.

Radiomics features of hippocampal regions in magnetic resonance imaging can differentiate medial temporal lobe epilepsy patients from healthy controls

To investigative whether radiomics features in bilateral hippocampi from MRI can identify temporal lobe epilepsy (TLE). A total of 131 subjects with MRI (66 TLE patients [35 right and 31 left TLE] and 65 healthy controls [HC]) were allocated to training (n = 90) and test (n = 41) sets. Radiomics features (n = 186) from the bilateral hippocampi were extracted from T1-weighted images. After feature selection, machine learning models were trained. The performance of the classifier was validated in the test set to differentiate TLE from HC and ipsilateral TLE from HC. Identical processes were performed to differentiate right TLE from HC (training set, n = 69; test set; n = 31) and left TLE from HC (training set, n = 66; test set, n = 30). The best-performing model for identifying TLE showed an AUC, accuracy, sensitivity, and specificity of 0.848, 84.8%, 76.2%, and 75.0% in the test set, respectively. The best-performing radiomics models for identifying right TLE and left TLE subgroups showed AUCs of 0.845 and 0.840 in the test set, respectively. In addition, multiple radiomics features significantly correlated with neuropsychological test scores (false discovery rate-corrected p-values < 0.05). The radiomics model from hippocampus can be a potential biomarker for identifying TLE.

Interictal Single-Voxel Proton Magnetic Resonance Spectroscopy of the Temporal Lobe in Dogs With Idiopathic Epilepsy

Proton magnetic resonance spectroscopy (H1-MRS) could provide insight into the metabolic pathophysiology of the temporal lobe of canine brain after seizure. Currently, there is no evidence-based data available on MRS of temporal lobe in dogs with idiopathic epilepsy (IE). The aim of this prospective, cross-sectional study was to evaluate the interictal metabolic activity of the temporal lobe in IE dogs compared to a control group with the use of H1-MRS. Ten healthy dogs and 27 client-owned dogs with IE underwent 1.5-Tesla magnetic resonance imaging (MRI) and single-voxel H1-MRS. The MRS studies were acquired as spin echoes with a repetition time (TR) of 2,000 ms and an echo time (TE) of 144 ms. A cubic voxel (10 ×10 ×10 mm) was positioned bilaterally into the region of the left and right temporal lobe, including a middle part of the hippocampus and the amygdala. The N-acetylaspartate (NAA)-to-creatine (NAA/Cr), NAA-to-choline (NAA/Cho), choline-to-creatine (Cho/Cr), and choline-to-NAA (Cho/NAA) ratios were determined in both hemispheres and compared to controls. No significant differences in all metabolite ratios between epileptic dogs and the control group could be found. A time-dependent decrease in the NAA/Cho ratio as well as an increase in the Cho/NAA ratio was found with proximity in time to the last seizure. We found no correlation between metabolite ratios and age or sex in this animal group. Time span from the last seizure to the acquisition of MRS significantly correlated with NAA/Cho and Cho/NAA ratio. We conclude that without a time relation, metabolite ratios in dogs with IE do not differ from those of the control group.

Neuroplasticity in Cholinergic Projections from the Basal Forebrain to the Basolateral Nucleus of the Amygdala in the Kainic Acid Model of Temporal Lobe Epilepsy

The amygdala is a cerebral region whose function is compromised in temporal lobe epilepsy (TLE). Patients with TLE present cognitive and emotional dysfunctions, of which impairments in recognizing facial expressions have been clearly attributed to amygdala damage. However, damage to the amygdala has been scarcely addressed, with the majority of studies focusing on the hippocampus. The aim of this study was to evaluate epilepsy-related plasticity of cholinergic projections to the basolateral nucleus (BL) of the amygdala. Adult rats received kainic acid (KA) injections and developed status epilepticus. Weeks later, they showed spontaneous recurrent seizures documented by behavioral observations. Changes in cholinergic innervation of the BL were investigated by using an antibody against the vesicular acetylcholine transporter (VAChT). In KA-treated rats, it was found that (i) the BL shrunk to 25% of its original size (p < 0.01 vs. controls, Student’s t-test), (ii) the density of vesicular acetylcholine transporter-immunoreactive (VAChT-IR) varicosities was unchanged, (iii) the volumes of VAChT-IR cell bodies projecting to the BL from the horizontal limb of the diagonal band of Broca, ventral pallidum, and subcommissural part of the substantia innominata were significantly increased (p < 0.05, Bonferroni correction). These results illustrate significant changes in the basal forebrain cholinergic cells projecting to the BL in the presence of spontaneous recurrent seizures.

Investigation of Generalized EEG Paroxysms Accompanying Focal Epilepsies

Interictal focal EEG features were frequently observed in generalized, epilepsies, but there is limited information about interictal, epileptiform/nonepileptiform generalized paroxysms in focal epilepsies. We aimed to report the frequency and associated factors of generalized EEG discharges in focal epilepsy with unknown cause (FEUC) and mesial, temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS). A total of 200 patients (FEUC in 90 patients; MTLE-HS in 110 patients) were included. Generalized epileptiform (spike/sharp waves simultaneously in all regions) and nonspecific generalized discharges (paroxysmal slow waves) were investigated. All clinical and laboratory findings of 2 groups were compared with each other and with remaining control group, without generalized paroxysms, statistically. Generalized EEG features were present in 22 (11%; 4 males) patients; 9 in the FEUC group (10%; 2) and 13 in the MTLE-HS group (11.8%). Female gender (P < .021), febrile seizure (P < .034), precipitant factors (P < .025), and parental consanguinity (P < .033) were significantly higher in the group with generalized EEG findings. Monotherapy rates were lower in the MTLE-HS group (P < .05). The relationship of generalized EEG features with female gender and parental consanguinity may point out to a genetic property among focal epilepsies, while the relationship with febrile seizures and precipitant factors may be a clue about mechanisms with more extensive involvement of the neuronal networks.

Segmentation errors and intertest reliability in automated and manually traced hippocampal volumes

Objective

To rigorously compare automated atlas‐based and manual tracing hippocampal segmentation for accuracy, repeatability, and clinical acceptability given a relevant range of imaging abnormalities in clinical epilepsy.

Methods

Forty‐nine patients with hippocampal asymmetry were identified from our institutional radiology database, including two patients with significant anatomic deformations. Manual hippocampal tracing was performed by experienced technologists on 3T MPRAGE images, measuring hippocampal volume up to the tectal plate, excluding the hippocampal tail. The same images were processed using NeuroQuant and FreeSurfer software. Ten subjects underwent repeated manual hippocampal tracings by two additional technologists blinded to previous results to evaluate consistency. Ten patients with two clinical MRI studies had volume measurements repeated using NeuroQuant and FreeSurfer.

Results

FreeSurfer raw volumes were significantly lower than NeuroQuant (P < 0.001, right and left), and hippocampal asymmetry estimates were lower for both automatic methods than manual tracing (P < 0.0001). Differences remained significant after scaling volumes to age, gender, and scanner matched normative percentiles. Volume reproducibility was fair (0.4–0.59) for manual tracing, and excellent (>0.75) for both automated methods. Asymmetry index reproducibility was excellent (>0.75) for manual tracing and FreeSurfer segmentation and fair (0.4–0.59) for NeuroQuant segmentation. Both automatic segmentation methods failed on the two cases with anatomic deformations. Segmentation errors were visually identified in 25 NeuroQuant and 27 FreeSurfer segmentations, and nine (18%) NeuroQuant and six (12%) FreeSurfer errors were judged clinically significant.

Interpretation

Automated hippocampal volumes are more reproducible than hand‐traced hippocampal volumes. However, these methods fail in some cases, and significant segmentation errors can occur.

Preservation of Memory Despite Unresected Contralateral Hippocampal Volume Loss After Resection of Hippocampal Sclerosis in Seizure-Free Patients

OBJECTIVE

To determine postoperative long-term changes of hippocampal volume (HV) correlating with cognitive functions in patients who underwent surgery for hippocampal sclerosis with postoperative freedom from seizures.

METHODS

We studied 1.5T magnetic resonance imaging before and after surgery in 24 patients (mean ± SD age, 36.9 ± 11.0 years) with hippocampal sclerosis. We performed serial magnetic resonance imaging at 6 months to 1 year, 1-2 years, 2-3 years, and 3-5 years postoperatively. We compared HVs of 24 patients with HVs of 14 age-matched control subjects. We analyzed correlations between consecutive HVs and seizure duration and age at surgery. We compared consecutive changes in HVs between dominant and nondominant hemispheres with concurrent cognitive functions.

RESULTS

Preoperative HVs of unresected contralateral hippocampus were significantly smaller than HVs of control subjects (P < 0.01). Unresected contralateral HV changes compared with preoperative HVs were -3.6% ± 6.9%, -2.3% ± 8.5%, -3.6% ± 10.2% (P < 0.05), and -5.0% ± 9.5% (P < 0.05) at consecutive postoperative periods. Largest change in HVs at 3-5 years was significantly correlated with older age at surgery (P < 0.05). Unresected contralateral dominant 14 HVs remained consistently smaller than nondominant 10 HVs up to 5 years with statistical significance (P < 0.05). Verbal memory was preserved in 14 patients with unresected contralateral smaller dominant hippocampus.

CONCLUSIONS

In seizure-free patients after hippocampal sclerosis resection , unresected contralateral HV significantly declined with older age at surgery. Visual memory was preserved regardless of side and volume loss. Despite significantly reduced HVs, verbal memory was preserved with the unresected contralateral dominant hippocampus. Earlier surgical intervention may have lower potential risk for memory decline secondary to postoperative HV loss.

Manual Hippocampal Subfield Segmentation Using High-Field MRI: Impact of Different Subfields in Hippocampal Volume Loss of Temporal Lobe Epilepsy Patients

In patients with temporal lobe epilepsy (TLE), presurgical magnetic resonance imaging (MRI) often reveals hippocampal atrophy, while neuropathological assessment indicates the different types of hippocampal sclerosis (HS). Different HS types are not discriminated in MRI so far. We aimed to define the volume of each hippocampal subfield on MRI manually and to compare automatic and manual segmentations for the discrimination of HS types. The T2-weighted images from 14 formalin-fixed age-matched control hippocampi were obtained with 4.7T MRI to evaluate the volume of each subfield at the anatomical level of the hippocampal head, body, and tail. Formalin-fixed coronal sections at the level of the body of 14 control cases, as well as tissue samples from 24 TLE patients, were imaged with a similar high-resolution sequence at 3T. Presurgical three-dimensional (3D) T1-weighted images from TLE went through a FreeSurfer 6.0 hippocampal subfield automatic assessment. The manual delineation with the 4.7T MRI was identified using Luxol Fast Blue stained 10-μm-thin microscopy slides, collected at every millimeter. An additional section at the level of the body from controls and TLE cases was submitted to NeuN immunohistochemistry for neuronal density estimation. All TLE cases were classified according to the International League Against Epilepsy's (ILAE's) HS classification. Manual volumetry in controls revealed that the dentate gyrus (DG)+CA4 region, CA1, and subiculum accounted for almost 90% of the hippocampal volume. The manual 3T volumetry showed that all TLE patients with type 1 HS (TLE-HS1) had lower volumes for DG+CA4, CA2, and CA1, whereas those TLE patients with HS type 2 (TLE-HS2) had lower volumes only in CA1 (p ≤ 0.038). Neuronal cell densities always decreased in CA4, CA3, CA2, and CA1 of TLE-HS1 but only in CA1 of TLE-HS2 (p ≤ 0.003). In addition, TLE-HS2 had a higher volume (p = 0.016) and higher neuronal density (p < 0.001) than the TLE-HS1 in DG + CA4. Automatic segmentation failed to match the manual or histological findings and was unable to differentiate TLE-HS1 from TLE-HS2. Total hippocampal volume correlated with DG+CA4 and CA1 volumes and neuronal density. For the first time, we also identified subfield-specific pathology patterns in the manual evaluation of volumetric MRI scans, showing the importance of manual segmentation to assess subfield-specific pathology patterns.

Use of an Automated Quantitative Analysis of Hippocampal Volume, Signal, and Glucose Metabolism to Detect Hippocampal Sclerosis

Purpose: Magnetic resonance imaging (MRI) and positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸FDG) are valuable tools for evaluating hippocampal sclerosis (HS); however, bias may arise during visual analyses. The aim of this study was to evaluate and compare MRI and PET post-processing techniques, automated quantitative hippocampal volume (Q-volume), and fluid-attenuated inversion-recovery (FLAIR) signal (Q-FLAIR) and glucose metabolism (Q-PET) analyses in patients with HS.

Methods: We collected MRI and ¹⁸FDG-PET images from 54 patients with HS and 22 healthy controls and independently performed conventional visual analyses (CVA) of PET (CVA-PET) and MRI (CVA-MRI) images. During the subsequent quantitative analyses, the hippocampus was segmented from the 3D T1 image, and the mean volumetric, FLAIR intensity and standardized uptake value ratio (SUVR) values of the left and right hippocampus were assessed in each subject. Threshold confidence levels calculated from the mean volumetric, FLAIR intensity and SUVR values of the controls were used to identify healthy subjects or subjects with HS. The performance of the three methods was assessed using receiver operating characteristic (ROC) curves, and the detection rates of CVA-MRI, CVA-PET, Q-volume, Q-FLAIR, and Q-PET were statistically compared.

Results: The areas under the curves (AUCs) for the Q-volume, Q-FLAIR, and Q-PET ROC analyses were 0.88, 0.41, and 0.98, which suggested a diagnostic method with moderate, poor, and high accuracy, respectively. Although Q-PET had the highest detection rate among the two CVA methods and three quantitative methods, the difference between Q-volume and Q-PET did not reach statistical significance. Regarding the HS subtypes, CVA-MRI, CVA-PET, Q-volume, and Q-PET had similar detection rates for type 1 HS, and Q-PET was the most sensitive method for detecting types 2 and 3 HS.

Conclusions: In MRI or ¹⁸FDG-PET images that have been visually assessed by experts, the quantification of hippocampal volume or glucose uptake can increase the detection of HS and appear to be additional valuable diagnostic tools for evaluating patients with epilepsy who are suspected of having HS.

Contribution of Quantitative Amygdalar MR FLAIR Signal Analysis for Lateralization of Mesial Temporal Lobe Epilepsy

BACKGROUND AND PURPOSE

This study evaluates the contribution of an automated amygdalar fluid-attenuated inversion recovery (FLAIR) signal analysis for the lateralization of mesial temporal lobe epilepsy (mTLE).

METHODS

Sixty-nine patients (27 M, 42 F) who had undergone surgery and achieved an Engel class Ia postoperative outcome were identified as a pure cohort of mTLE cases. Forty-six nonepileptic subjects comprised the control group. The amygdala was segmented in T1-weighted images using an atlas-based segmentation. The right/left ratios of amygdalar FLAIR mean and standard deviation were calculated for each subject. A linear classifier (ie, discriminator line) was designed for lateralization using the FLAIR features and a boundary domain, within which lateralization was assumed to be less definitive, was established using the same features from control subjects. Hippocampal FLAIR and volume analysis was performed for comparison.

RESULTS

With the boundary domain in place, lateralization accuracy was found to be 70% with hippocampal FLAIR and 67% with hippocampal volume. Taking amygdalar analysis into account, 22% of cases that were found to have uncertain lateralization by hippocampal FLAIR analysis were confidently lateralized by amygdalar FLAIR. No misclassified case was found outside the amygdalar FLAIR boundary domain.

CONCLUSIONS

Amygdalar FLAIR analysis provides an additional metric by which to establish mTLE in those cases where hippocampal FLAIR and volume analysis have failed to provide lateralizing information.

Features of amygdala in patients with mesial temporal lobe epilepsy and hippocampal sclerosis: An MRI volumetric and histopathological study

OBJECTIVE

It is well-known that there is a correlation between the neuropathological grade of hippocampal sclerosis (HS) and neuroradiological atrophy of the hippocampus in mesial temporal lobe epilepsy (mTLE) patients. However, there is no strict definition or criterion regarding neuron loss and atrophy of the amygdala neighboring the hippocampus. We examined the relationship between HS and neuronal loss in the amygdala.

MATERIALS AND METHODS

Nineteen mTLE patients with neuropathological proof of HS were assigned to Group A, while seven mTLE patients without HS were assigned to Group B. We used FreeSurfer software to measure amygdala volume automatically based on pre-operation magnetic resonance images. Neurons observed using Klüver-Barrera (KB) staining in resected amygdala tissue were counted. and the extent of immunostaining with stress marker antibodies was semiquantitatively evaluated.

RESULTS

There was no significant difference in amygdala volume between the two groups (Group A: 1.41±0.24; Group B: 1.41±0.29cm³; p=0.98), nor in the neuron cellularity of resected amygdala specimens (Group A: 3.98±0.97; Group B: 3.67±0.67 10×^-4 number of neurons/μm²; p=0.40). However, the HSP70 level, representing acute stress against epilepsy, in Group A patients was significantly larger than that in Group B. There was no significant difference in the level of Bcl-2, which is known as a protein that inhibits cell death, between the two groups.

CONCLUSIONS

Neuronal loss and volume loss in the amygdala may not necessarily follow hippocampal sclerosis. From the analysis of stress proteins, epileptic attacks are as likely to damage the amygdala as the hippocampus but do not lead to neuronal death in the amygdala.

Beyond a Differential Diagnosis: Cognitive and Morphometric Decoding of Information Processing Speed in Senior Adults with DSM-5 Mild Neurocognitive Disorders

BACKGROUND

Processing speed has been highlighted as a diagnostic item for neurocognitive disorders (NCD) in DSM-5. The utility of information processing speed (IPS) enclosed with multiscale constructs in the diagnosis of NCD warrants exploration.

OBJECTIVE

We aimed to investigate the IPS with two types of measurements in the patients with NCD due to vascular disease (NCD-vascular) and NCD due to Alzheimer's disease (NCD-AD), and examine the associations between IPS measures and morphometric features.

METHODS

The IPS was evaluated using trail making test (TMT) and flanker test (n = 204). Direct scores, derived scores, and reaction time (RT) were used as IPS measures. Further, surface-based morphometry cortical volume was calculated in a subsample (n = 44) with structural MRI data.

RESULTS

All IPS measures showed a significant value to differentiate NCD patients from healthy subjects. Only mean RT could distinguish NCD-AD from NCD-vascular groups. TMT-B score and difference score were correlated with gray matter volume (GMV) of inferior frontal gyrus, precuneus and superior temporal cortex. Mean RT was associated with the GMV of post-central gyrus (r = -0.327, p = 0.035), and executive speed was associated with inferior frontal cortex (r = -0.475, p = 0.001), cingulate gyrus (r = -0.497, p = 0.001), and superior temporal gyrus (r = -0.36, p = 0.019).

CONCLUSION

The cognitive and morphometric correlates of IPS measures indicate that complex IPS might be decomposed into the domain-specific components with corresponding neural underpinnings. Our findings may also provide essential insights into the diagnostic item of NCD.

How Different Are the Patients With Bilateral Hippocampal Sclerosis From the Unilateral Ones Clinically?

PURPOSE

There is a lack of knowledge on consecutive patients with epilepsy associated with bilateral hippocampal sclerosis (BHS). We aimed to investigate the differentiating features of BHS in comparison with unilateral HS (UHS).

METHOD

We investigated our database for patients with epilepsy fulfilling the major magnetic resonance imaging criteria for BHS; namely, presence of bilateral atrophy and high signal changes on T2 and FLAIR series in the hippocampi. UHS patients seen in past 2 years were included as the control group. Clinical, EEG, and other laboratory findings, data on treatment response and epilepsy surgery were investigated from their files.

RESULTS

A total of 124 patients (31 with BHS and 93 with UHS; 49 right-sided and 44 left-sided) were included. We found that 16.1% of the BHS and 18.3% of the UHS groups were not drug-refractory. A binary logistic regression analysis performed with significant clinical features disclosed that history of febrile status epilepticus, mental retardation, and status epilepticus were statistically more common in BHS group. Moreover, diagnosis of psychosis established by an experienced psychiatrist and slowing of the EEG background activity were both found significantly more frequent in BHS. 66.67% of the operated BHS patients showed benefit from epilepsy surgery.

CONCLUSIONS

BHS is a heterogeneous group, showing significant differences such as increased frequencies of mental retardation, status epilepticus, febrile status epilepticus and psychosis, in comparison to UHS. In all, 16.1% of the BHS cases showed a benign course similar to the UHS group and some patients with drug-resistant epilepsy may show benefit from epilepsy surgery.

Automated volumetry for unilateral hippocampal sclerosis detection in patients with temporal lobe epilepsy

Hippocampal sclerosis (HS) is the most common cause of temporal lobe epilepsy (TLE) and can be identified in magnetic resonance imaging as hippocampal atrophy and subsequent volume loss. Detecting this kind of abnormalities through simple radiological assessment could be difficult, even for experienced radiologists. For that reason, hippocampal volumetry is generally used to support this kind of diagnosis. Manual volumetry is the traditional approach but it is time consuming and requires the physician to be familiar with neuroimaging software tools. In this paper, we propose an automated method, written as a script that uses FSL-FIRST, to perform hippocampal segmentation and compute an index to quantify hippocampi asymmetry (HAI). We compared the automated detection of HS (left or right) based on the HAI with the agreement of two experts in a group of 19 patients and 15 controls, achieving 84.2% sensitivity, 86.7% specificity and a Cohen's kappa coefficient of 0.704. The proposed method is integrated in the "Advanced Brain Imaging Lab" (ABrIL) cloud neurocomputing platform. The automated procedure is 77% (on average) faster to compute vs. the manual volumetry segmentation performed by an experienced physician.

Hippocampal subfields at ultra high field MRI: An overview of segmentation and measurement methods

The hippocampus is one of the most interesting and studied brain regions because of its involvement in memory functions and its vulnerability in pathological conditions, such as neurodegenerative processes. In the recent years, the increasing availability of Magnetic Resonance Imaging (MRI) scanners that operate at ultra‐high field (UHF), that is, with static magnetic field strength ≥7T, has opened new research perspectives. Compared to conventional high‐field scanners, these systems can provide new contrasts, increased signal‐to‐noise ratio and higher spatial resolution, thus they may improve the visualization of very small structures of the brain, such as the hippocampal subfields. Studying the morphometry of the hippocampus is crucial in neuroimaging research because changes in volume and thickness of hippocampal subregions may be relevant in the early assessment of pathological cognitive decline and Alzheimer's Disease (AD). The present review provides an overview of the manual, semi‐automated and fully automated methods that allow the assessment of hippocampal subfield morphometry at UHF MRI, focusing on the different hippocampal segmentation produced. © 2017 The Authors Hippocampus Published by Wiley Periodicals, Inc.

Abnormality in hippocampal signal intensity predicts atrophy in patients with systemic lupus erythematosus

Objectives

To quantify signal abnormalities in the hippocampus (Hsig) of patients with systemic lupus erythematosus (SLE) and to determine if Hsig predict hippocampal atrophy (HA) in SLE.

Methods

We included all SLE patients and healthy age- and sex-matched individuals with two magnetic resonance imaging (MRI) scans performed with a minimum of 1 year interval. All individuals underwent a standardized neuropsychological evaluation. Individual results were converted into standard scores and compared to normative data. SLE patients were additionally assessed for disease activity (SLE Disease Activity Index (SLEDAI)), damage (Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index (SDI)), and the presence of antiphospholipid antibodies. MRI was performed on an Elscint 2 T scanner and T1 inversion recovery and T2 coronal images were used for analysis. Volumetric (HV) and signal quantification (Hsig) were determined by standardized protocols.

Results

We included 54 SLE patients (48 women; mean age 32.2 ± 10.56 years). Hsig were found at study entry in 15 (45.5%) patients. Hsig in the body and tail of non-atrophic hippocampi correlated with progression of volume loss during the follow-up period ( r = 0.8, p < 0.001). The presence of Hsig in the head of atrophic hippocampi correlated with progression of HA ( r = 0.73, p = 0.005) during the same period. No correlation of Hsig and disease activity or prednisone dose was observed.

Conclusion

HA is frequently observed in SLE patients and volume loss is progressive in a subgroup of patients. The evaluation of Hsig is an easy tool to determine patients that may have progressive hippocampal volume loss and should be followed more closely with MRI and cognitive evaluation.

Comparative Lateralizing Ability of Multimodality MRI in Temporal Lobe Epilepsy

Purpose. The objective is to compare lateralizing ability of three quantitative MR (qMRI) modalities to depict changes of hippocampal architecture with clinical entities in temporal lobe epilepsy. Methods. We evaluated 14 patients with clinical and EEG proven diagnosis of unilateral TLE and 15 healthy volunteers. T1-weighted 3D dataset for volumetry, single-voxel ¹H MR spectroscopy (MRS), and diffusion tensor imaging (DTI) were performed for bilateral hippocampi of all subjects. Results. Individual volumetric measurements provided accurate lateralization in 85% of the patients, spectroscopy in 57%, and DTI in 57%. Higher lateralization ratios were acquired combining volumetry-spectroscopy (85%), spectroscopy-DTI (85%), and volumetry-DTI (100%). Significantly decreased NAA/(Cho+Cr) ratios (p = 0.002) and increased FA (p = 0.001) values were obtained in ipsilateral to epileptogenic hippocampus. Duration of epilepsy and FA values showed a significant negative correlation (p = 0.016, r = −0.847). The history of febrile convulsion associated with ipsilateral increased ADC values (p = 0.015, r = 0.851) and reduced NAA/(Cho+Cr) ratios (p = 0.047, r = −761). Conclusion. Volumetry, MRS, and DTI studies provide complementary information of hippocampal pathology. For lateralization of epileptogenic focus and preoperative examination, volumetry-DTI combination may be indicative of diagnostic accuracy.

The effects of apolipoprotein ε 4 on aging brain in cognitively normal Chinese elderly: a surface-based morphometry study

BACKGROUND

Default mode network (DMN) has been reported to be susceptible to APOE ε 4 genotype. However, the APOE ε 4-related brain changes in young carriers are different from the ones in elderly carriers. The current study aimed to evaluate the cortical morphometry of DMN subregions in cognitively normal elderly with APOE ε 4.

METHOD

11 cognitively normal senior APOE ε 4 carriers and 27 matched healthy controls (HC) participated the neuropsychological tests, genotyping, and magnetic resonance imaging (MRI) scanning. Voxel-based morphometry (VBM) analysis was used to assess the global volumetric changes. Surface-based morphometry (SBM) analysis was performed to measure regional gray matter volume (GMV) and gray matter thickness (GMT).

RESULTS

Advancing age was associated with decreased GMV of DMN subregions. Compared to HC, APOE ε 4 carriers presented cortical atrophy in right cingulate gyrus (R_CG) (GMV: APOE carriers: 8475.23 ± 1940.73 mm3, HC: 9727.34 ± 1311.57 mm3, t = 2.314, p = 0.026, corrected) and left insular (GMT: APOE ε 4 carriers: 3.83 ± 0.37 mm, HC: 4.05 ± 0.25 mm, t = 2.197, p = 0.033, corrected).

CONCLUSIONS

Our results highlight the difference between different cortical measures and suggest that the cortical reduction of CG and insular maybe a potential neuroimaging marker for APOE 4 ε senior carriers, even in the context of relatively intact cognition.

Isolated amygdala enlargement in temporal lobe epilepsy: A systematic review

OBJECTIVE

The objective of this study was to compare the seizure characteristics and treatment outcomes in patient groups with temporal lobe epilepsy (TLE) identified with isolated amygdala enlargement (AE) on magnetic resonance imaging studies.

METHODS

PubMed, Embase, and the Cochrane Library were searched for relevant studies using the keywords 'amygdala enlargement', 'epilepsy', and 'seizures' in April 2015. Human studies, written in English, that investigated cohorts of patients with TLE and AE were included.

RESULTS

Of 204 abstracts initially identified using the search strategy, 14 studies met the inclusion criteria (11 epilepsy studies and 3 psychiatry studies). Ultimately, 8 full studies on AE and TLE involving 107 unique patients were analyzed. Gender distribution consisted of 50 males and 57 females. Right amygdala enlargement was seen in 39 patients, left enlargement in 58 patients, and bilateral enlargement in 7 patients. Surgical resection was performed in 28 patients, with the most common finding being dysplasia/hamartoma or focal cortical dysplasia. Most studies involved small samples of less than 12 patients. There was a wide discrepancy in the methods used to measure amygdala volume, in both patients and controls, hindering comparisons. Most TLE with AE studies observed a later age of seizure onset (mean: 32.2years) compared with studies involving TLE with HS (mean of mid- to late childhood). A higher frequency of complex partial seizures compared with that of convulsive seizures is seen in patients with AE (67-100% vs. 26-47%), and they have an excellent response to antiepileptic drugs (81.8%-100% of seizure-free patients). All studies that included controls also found a significant difference in frequency of seizure types between their cases and controls.

CONCLUSIONS

Reliable assessment of amygdala volume remains a critical issue hindering better understanding of the clinical management and research of this focal epilepsy syndrome. Within these limitations, the literature suggests characteristics of an older age of epilepsy onset, a greater tendency to nonconvulsive seizures, and a good response to antiepileptic drugs in this interesting group of epilepsies.

Neuronal autoantibodies in mesial temporal lobe epilepsy with hippocampal sclerosis

OBJECTIVE

Our aim was to investigate the prevalence of neuronal autoantibodies (NAbs) in a large consecutive series with mesial temporal lobe epilepsy with hippocampal sclerosis (MTLE-HS) and to elucidate the clinical and laboratory clues for detection of NAbs in this prototype of frequent, drug-resistant epilepsy syndrome.

METHODS

Consecutive patients diagnosed with MTLE fulfilling the MRI criteria for HS were enrolled. The sera of patients and various control groups (80 subjects) were tested for eight NAbs after ethical approval and signed consents. Brain tissues obtained from surgical specimens were also investigated by immunohistochemical analysis for the presence of inflammatory infiltrates. The features of seropositive versus seronegative groups were compared and binary logistic regression analysis was performed to explore the differentiating variables.

RESULTS

We found antibodies against antigens, contactin-associated protein-like 2 in 11 patients, uncharacterised voltage-gated potassium channel (VGKC)-complex antigens in four patients, glycine receptor (GLY-R) in 5 patients, N-methyl-d-aspartate receptor in 4 patients and γ-aminobutyric acid receptor A in 1 patient of 111 patients with MTLE-HS and none of the control subjects. The history of status epilepticus, diagnosis of psychosis and positron emission tomography or single-photon emission CT findings in temporal plus extratemporal regions were found significantly more frequently in the seropositive group. Binary logistic regression analysis disclosed that status epilepticus, psychosis and cognitive dysfunction were statistically significant variables to differentiate between the VGKC-complex subgroup versus seronegative group.

CONCLUSIONS

This first systematic screening study of various NAbs showed 22.5% seropositivity belonging mostly to VGKC-complex antibodies in a large consecutive series of patients with MTLE-HS. Our results indicated a VGKC-complex autoimmunity-related subgroup in the syndrome of MTLE-HS.