Surgery for amygdala enlargement with mesial temporal lobe epilepsy: pathological findings and seizure outcome

Quantitative cellular pathology of the amygdala in temporal lobe epilepsy and correlation with magnetic resonance imaging volumetry, tissue microstructure, and sudden unexpected death in epilepsy risk factors

OBJECTIVE

Amygdala enlargement can occur in temporal lobe epilepsy, and increased amygdala volume is also reported in sudden unexpected death in epilepsy (SUDEP). Apnea can be induced by amygdala stimulation, and postconvulsive central apnea (PCCA) and generalized seizures are both known SUDEP risk factors. Neurite orientation dispersion and density imaging (NODDI) has recently provided additional information on altered amygdala microstructure in SUDEP. In a series of 24 surgical temporal lobe epilepsy cases, our aim was to quantify amygdala cellular pathology parameters that could predict enlargement, NODDI changes, and ictal respiratory dysfunction.

METHODS

Using whole slide scanning automated quantitative image analysis methods, parallel evaluation of myelin, axons, dendrites, oligodendroglia, microglia, astroglia, neurons, serotonergic networks, mTOR-pathway activation (pS6) and phosphorylated tau (pTau; AT8, AT100, PHF) in amygdala, periamygdala cortex, and white matter regions of interest were compared with preoperative magnetic resonance imaging data on amygdala size, and in 13 cases with NODDI and evidence of ictal-associated apnea.

RESULTS

We observed significantly higher glial labeling (Iba1, glial fibrillary acidic protein, Olig2) in amygdala regions compared to cortex and a strong positive correlation between Olig2 and Iba1 in the amygdala. Larger amygdala volumes correlated with lower microtubule-associated protein (MAP2), whereas higher NODDI orientation dispersion index correlated with lower Olig2 cell densities. In the three cases with recorded PCCA, higher MAP2 and pS6-235 expression was noted than in those without. pTau did not correlate with SUDEP risk factors, including seizure frequency.

SIGNIFICANCE

Histological quantitation of amygdala microstructure can shed light on enlargement and diffusion imaging alterations in epilepsy to explore possible mechanisms of amygdala dysfunction, including mTOR pathway activation, that in turn may increase the risk for SUDEP.

Amygdala enlargement in temporal lobe epilepsy: Histopathology and surgical outcomes

OBJECTIVES

Amygdala enlargement is detected on magnetic resonance imaging (MRI) in some patients with drug-resistant temporal lobe epilepsy (TLE), but its clinical significance remains uncertain We aimed to assess if the presence of amygdala enlargement (1) predicted seizure outcome following anterior temporal lobectomy with amygdalohippocampectomy (ATL-AH) and (2) was associated with specific histopathological changes.

METHODS

This was a case-control study. We included patients with drug-resistant TLE who underwent ATL-AH with and without amygdala enlargement detected on pre-operative MRI. Amygdala volumetry was done using FreeSurfer for patients who had high-resolution T1-weighted images. Mann-Whitney U test was used to compare pre-operative clinical characteristics between the two groups. The amygdala volume on the epileptogenic side was compared to the amygdala volume on the contralateral side among cases and controls. Then, we used a two-sample, independent t test to compare the means of amygdala volume differences between cases and controls. The chi-square test was used to assess the correlation of amygdala enlargement with (1) post-surgical seizure outcomes and (2) histopathological changes.

RESULTS

Nineteen patients with and 19 patients without amygdala enlargement were studied. Their median age at surgery was 38 years for cases and 39 years for controls, and 52.6% were male. There were no statistically significant differences between the two groups in their pre-operative clinical characteristics. There were significant differences in the means of volume difference between cases and controls (Diff = 457.2 mm3, 95% confidence interval [CI] 289.6-624.8; p < .001) and in the means of percentage difference (p < .001). However, there was no significant association between amygdala enlargement and surgical outcome (p = .72) or histopathological changes (p = .63).

SIGNIFICANCE

The presence of amygdala enlargement on the pre-operative brain MRI in patients with TLE does not affect the surgical outcome following ATL-AH, and it does not necessarily suggest abnormal histopathology. These findings suggest that amygdala enlargement might reflect a secondary reactive process to seizures in the epileptogenic temporal lobe.

Practical microscopic neuroanatomy of the limbic system and basal forebrain identifiable on clinical 3T MRI

Microscopic neuroanatomy of limbic system and basal forebrain on MRI is complex and is a terra incognita for many radiologists, clinicians, and neuroscientists. Interestingly, most of the important structures/at least anatomical regions containing these structures demonstrable on cadaveric and surgical dissections can be identified on clinical MRI, with 3T being much better than 1.5T. This article teaches the practical MRI identification of these structures which will greatly help in evaluating complex ailments like temporal lobe epilepsy, Alzheimer dementia, and other neuropsychiatric disorders. This knowledge will also aid in accurate reporting of tumor spread along the white matter fasciculi in the temporal stem/basal forebrain region. Limbic system includes the mesial temporal structures and their connections, piriform cortex including "area tempestas," and the septal area comprising of subcallosal area and paraterminal gyrus. Basal forebrain includes structures like substantia innominata with basal nucleus of Meynert, diagonal gyrus/diagonal band of Broca, and nucleus accumbens lying in between the anterior perforated substance inferiorly and the anterior commissure superiorly.

Mesial temporal lobe epilepsy with amygdalar hamartoma-like lesion: Is it a distinct syndrome?

INTRODUCTION

We examined the clinical, semiological, scalp electroencephalographic (EEG), and neuropsychological features of patients with amygdalar hamartoma-like lesion (AHL) without hippocampal sclerosis (HS).

METHODS

This retrospective study included 9 patients with mesial temporal lobe epilepsy (MTLE) who had an amygdalar lesion on preoperative MRI; underwent mesial temporal resection; were diagnosed with amygdalar hamartoma-like lesion (AHL) without hippocampal sclerosis (HS); were followed up for at least 2 years after surgery; and had a favourable postoperative seizure outcome (Engel Class I). There were 5 women and 4 men, and age at surgery ranged from 19 to 54 (mean, 36.6) years. Clinical characteristics, auras, video-recorded seizure semiology, interictal and ictal EEG, and preoperative neuropsychological data were reviewed. Twenty patients with MTLE with HS who had favourable postoperative seizure outcomes (Engel Class I) were selected as controls.

RESULTS

Age at seizure onset was significantly higher in patients with AHL without HS than in those with HS. Fear was more frequently seen in patients with AHL (44 %) than in those with HS (5 %) (P = 0.022). There were no significant differences in interictal epileptiform discharges or ictal EEG pattern. Preoperative full-scale IQ score was significantly higher in the AHL group than in the HS group (mean, 92.9 v. 74.8, P = 0.004), as was preoperative memory quotient score (mean 100.7 v. 85.1, P = 0.028).

CONCLUSION

We clarified the clinical, semiological, and neuropsychological features of patients with MTLE-AHL. These findings may be useful for preoperative evaluation, especially of patients with suspected MTLE but without apparent HS on preoperative MRI.

Ablation of apparent diffusion coefficient hyperintensity clusters in mesial temporal lobe epilepsy improves seizure outcomes after laser interstitial thermal therapy

OBJECTIVE

Laser interstitial thermal therapy (LiTT) is a minimally invasive surgical procedure for intractable mesial temporal epilepsy (mTLE). LiTT is safe and effective, but seizure outcomes are highly variable due to patient variability, suboptimal targeting, and incomplete ablation of the epileptogenic zone. Apparent diffusion coefficient (ADC) is a magnetic resonance imaging (MRI) sequence that can identify potential epileptogenic foci in the mesial temporal lobe to improve ablation and seizure outcomes. The objective of this study was to investigate whether ablation of tissue clusters with high ADC values in the mesial temporal structures is associated with seizure outcome in mTLE after LiTT.

METHODS

Twenty-seven patients with mTLE who underwent LiTT at our institution were analyzed. One-year seizure outcome was categorized as complete seizure freedom (International League Against Epilepsy [ILAE] Class I) and residual seizures (ILAE Class II-VI). Volumes of hippocampus and amygdala were segmented from the preoperative T1 MRI sequence. Spatially distinct hyperintensity clusters were identified in the preoperative ADC map. Proportion of cluster volume and number ablated were associated with seizure outcomes.

RESULTS

The mean age at surgery was 37.5 years and the mean follow-up duration was 1.9 years. Proportions of hippocampal cluster volume (p = .013) and number (p = .03) ablated were significantly higher in patients with seizure freedom. For amygdala clusters, the proportion of cluster number ablated was significantly associated with seizure outcome (p = .026). In the combined amygdalohippocampal complex, ablation of amygdalohippocampal clusters reliably predicted seizure outcome by their volume ablated (area under the curve [AUC] = 0.7670, p = .02).

SIGNIFICANCE

Seizure outcome after LiTT in patients with mTLE was associated significantly with the extent of cluster ablation in the amygdalohippocampal complex. The results suggest that preoperative ADC analysis may help identify high-yield pathological tissue clusters that represent epileptogenic foci. ADC-based cluster analysis can potentially assist ablation targeting and improve seizure outcome after LiTT in mTLE.

Diagnostic value of an algorithm for autoimmune epilepsy in a retrospective cohort

Purpose

This study aims to propose a diagnostic algorithm for autoimmune epilepsy in a retrospective cohort and investigate its clinical utility.

Methods

We reviewed 60 patients with focal epilepsy with a suspected autoimmune etiology according to board-certified neurologists and epileptologists. To assess the involvement of the autoimmune etiology, we used the patients' sera or cerebrospinal fluid (CSF) samples to screen for antineuronal antibodies using rat brain immunohistochemistry. Positive samples were analyzed for known antineuronal antibodies. The algorithm applied to assess the data of all patients consisted of two steps: evaluation of clinical features suggesting autoimmune epilepsy and evaluation using laboratory and imaging findings (abnormal CSF findings, hypermetabolism on fluorodeoxyglucose-positron emission tomography, magnetic resonance imaging abnormalities, and bilateral epileptiform discharges on electroencephalography). Patients were screened during the first step and classified into five groups according to the number of abnormal laboratory findings. The significant cutoff point of the algorithm was assessed using a receiver-operating characteristic curve analysis.

Results

Fourteen of the 60 patients (23.3%) were seropositive for antineuronal antibodies using rat brain immunohistochemistry. Ten patients had antibodies related to autoimmune epilepsy/encephalitis. The cutoff analysis of the number of abnormal laboratory and imaging findings showed that the best cutoff point was two abnormal findings, which yielded a sensitivity of 78.6%, a specificity of 76.1%, and an area under the curve of 0.81.

Conclusion

The proposed algorithm could help predict the underlying autoimmune etiology of epilepsy before antineuronal antibody test results are available.

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.

Multiple hippocampal transection for mesial temporal lobe epilepsy: A systematic review

PURPOSE

Multiple hippocampal transection (MHT) is a surgical technique that offers adequate seizure control with minimal perioperative morbidity. However, there is little evidence available to guide neurosurgeons in selecting this technique for use in appropriate patients. This systematic review analyzes patient-level data associated with MHT for intractable epilepsy, focusing on postoperative seizure control and memory outcomes.

METHODS

The systematic review was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Relevant articles were identified from 3 databases (PubMed, Medline, Embase) up to August 1, 2021. Inclusion criteria were that the majority of patients had received a diagnosis of intractable epilepsy, the article was written in English, MHT was the primary procedure, and patient-level metadata were included.

RESULTS

Fifty-nine unique patients who underwent MHT were identified across 11 studies. Ten (17%) of 59 patients underwent MHT alone. Forty-three (75%) of 57 patients who had a follow-up 12 months or longer were seizure free at last follow-up. With respect to postoperative verbal memory retention, 9 of 38 (24%) patient test scores did not change, 14 (37%) decreased, and 16 (42%) increased. With respect to postoperative nonverbal memory retention, 12 of 38 (34%) patient test scores did not change, 13 (34%) decreased, and 13 (33%) increased.

CONCLUSION

There are few reported patients analyzed after MHT. Although the neurocognitive benefits of MHT are unproven, this relatively novel technique has shown promise in the management of seizures in patients with intractable epilepsy. However, structured trials assessing MHT in isolation are warranted.

The Dorsal Bed Nucleus of the Stria Terminalis in Depressed and Non-Depressed Temporal Lobe Epilepsy Patients

OBJECTIVES

Temporal lobe epilepsy (TLE) and depression are common comorbid disorders whose underlying shared neural network has yet to be determined. While animal studies demonstrate a role for the dorsal bed nucleus of the stria terminalis (dBNST) in both seizures and depression, and humans clinical studies demonstrate a therapeutic effect of stimulating this region on treatment-resistant depression, the role for the dBNST in depressed and non-depressed TLE patients is still unclear. Here, we tested the hypothesis that this structure is morphologically abnormal in these epilepsy patients, with an increased abnormality in TLE patients with comorbid depression.

METHODS

In this case-controlled study, three Tesla structural magnetic resonance imaging scans were obtained from TLE patients with no depression (TLEonly), with depression (TLEdep) and healthy comparison subjects (HC). TLE subjects were recruited from the Yale University Comprehensive Epilepsy Center, diagnosed with the International League Against Epilepsy 2014 Diagnostic Guidelines, and confirmed by video electroencephalography. Diagnosis of major depressive disorder was confirmed by a trained neuropsychologist through a Mini International Neuropsychiatric Interview based on the DSM-IV. The dBNST was delineated manually by reliable raters using Bioimage Suite software.

RESULTS

The number of patients and subjects included 35 TLEonly patients, 20 TLEdep patients, and 102 HC subjects. Both TLEonly and TLEdep patients had higher dBNST volumes compared to HC subjects, unilaterally in the left hemisphere in the TLEonly patients (p=0.003), and bilaterally in the TLEdep patients (p<0·0001). Furthermore, the TLEdep patients had a higher dBNST volume than the TLEonly patients in the right hemisphere (p=0.02).

SIGNIFICANCE

Here we demonstrate an abnormality of the dBNST in TLE patients, both without depression (left enlargement) and with depression (bilateral enlargement). Our results demonstrate this region to underlie both temporal lobe epilepsy with and without depression, implicating it as a target to treat the comorbidity between these two disorders.

Emotional Recognition in Patients With Mesial Temporal Epilepsy Associated With Enlarged Amygdala

BACKGROUND

Amygdalae play a central role in emotional processing by interconnecting frontal cortex and other brain structures. Unilateral amygdala enlargement (AE) is associated with mesial temporal lobe epilepsy (mTLE). In a relatively large sample of patients with mTLE and AE, we aimed to evaluate functional integration of AE in emotion processing and to determine possible associations between fMRI activation patterns in amygdala and deficits in emotion recognition as assessed by neuropsychological testing.

METHODS

Twenty-two patients with drug resistant unilateral mTLE due to ipsilateral AE were prospectively recruited in a large epilepsy unit and compared with 17 healthy control subjects in terms of amygdala volume, fMRI activation patterns and performance in emotion recognition as assessed by comprehensive affect testing system (CATS) and Ekman faces. All patients underwent structural and functional 1.5 Tesla MRI, electro-clinical assessment and neuropsychological testing.

RESULTS

We observed BOLD signal ipsilateral to AE (n = 7; group PAT1); contralateral to AE (n = 6; group PAT2) and no activation (n = 9; group PAT3). In the region of interest (ROI) analysis, beta estimates for fearful face > landscape contrast in the left amygdala region did not differ significantly in patients with left TLE vs. patients with right TLE [T (16) = -1.481; p = 0.158]. However, beta estimates for fearful face > landscape contrast in the right amygdala region were significantly reduced in patients with right TLE vs. patients with left TLE [T (16) = -2,922; p = 0.010]. Patients showed significantly lower total scores in CATS and Ekman faces compared to healthy controls.

CONCLUSION

In our cohort, patients with unilateral mesial TLE and ipsilateral AE, an amygdala could display either functional integration in emotion recognition or dysfunction as demonstrated by fMRI. Perception and recognition of emotions were impaired more in right-sided mTLE as compared to left-sided mTLE. Neuropsychological tests showed deficits in emotion recognition in patients as compared to healthy controls.

Epileptogenic networks in drug-resistant epilepsy with amygdala enlargement: Assessment with stereo-EEG and 7 T MRI

OBJECTIVE

Amygdala enlargement is increasingly described in association with temporal lobe epilepsies. Its significance, however, remains uncertain both in terms of etiology and its link with psychiatric disorders and of its involvement in the epileptogenic zone. We assessed the epileptogenic networks underlying drug-resistant epilepsy with amygdala enlargement and investigated correlations between clinical features, epileptogenicity and morphovolumetric amygdala characteristics.

METHODS

We identified 12 consecutive patients suffering from drug-resistant epilepsy with visually suspected amygdala enlargement and available stereoelectroencephalographic recording. The epileptogenic zone was defined using the Connectivity Epileptogenicity Index. Morphovolumetric measurements were performed using automatic segmentation and co-registration on the 7TAMIbrain Amygdala atlas.

RESULTS

The epileptogenic zone involved the enlarged amygdala in all but three cases and corresponded to distributed, temporal-insular, temporal-insular-prefrontal or prefrontal-temporal networks in ten cases, while only two were temporo-mesial networks. Morphovolumetrically, amygdala enlargement was bilateral in 75% of patients. Most patients presented psychiatric comorbidities (anxiety, depression, posttraumatic stress disorder). The level of depression defined by screening questionnaire was positively correlated with the extent of amygdala enlargement.

CONCLUSIONS

Drug-resistant epilepsy with amygdala enlargement is heterogeneous; most cases implied "temporal plus" networks.

SIGNIFICANCE

The enlarged amygdala could reflect an interaction of stress-mediated limbic network alterations and mechanisms of epileptogenesis.

Temporal lobe epilepsy with amygdala enlargement: A systematic review

Temporal lobe epilepsy (TLE) with enlargement of the amygdala (AE) is a distinct clinical entity with contrasting clinical features from TLE with hippocampal sclerosis (HS). The objectives of this systematic analysis were to study the clinical characteristics and treatment outcome of people with TLE with AE. Pubmed, Embase, Cochrane, Web of Science, Scopus, and Medline were searched using the keywords amygdala enlargement, temporal lobe epilepsy, epilepsy, and seizure in November 2020. We found 18 studies that satisfied the inclusion criteria. A total of 361 patients were included in this analysis. The mean age of onset was 36.2 years, and febrile seizure was uncommon compared to TLE with HS subjects. The type of aura and automatism was similar to TLE with HS, though less prevalent. Electroencephalography (EEG) was usually concordant with the side of AE. Anti-seizure medications (ASM), surgical, and immunotherapy were used in different studies. 86 patients underwent surgery with Engel I outcome in 69.7%. Histopathology of the resected samples was predominantly dysplasia and gliosis. A group of patients that responded well to immunotherapy with subsequent reduction of amygdala volume (AMV) purported an autoimmune etiology of AE. Heterogeneity was the main drawback that prevented comparability among the studies. The methods of measurement of AMV also differed widely in the included studies, and standardization of its method is still lacking. This analysis suggests TLE with AE as a distinctive group of patients either due to a developmental anomaly or autoimmune etiology.

Outcomes of hippocampus-sparing lesionectomy for temporal lobe epilepsy and the significance of intraoperative hippocampography

OBJECTIVES

We investigated hippocampal-sparing lesionectomy (HSL) outcomes in temporal lobe epilepsy (TLE) and the significance of high-frequency oscillations (HFOs) detected by hippocampography in HSL.

METHODS

We retrospectively reviewed data from patients who underwent HSL for lesional TLE. Patients were included when MRI confirmed (i) a lesion limited to the temporal lobe with normal hippocampi preoperatively and (ii) hippocampal integrity postoperatively. Factors possibly related to outcomes were collected. Intraoperative hippocampography was reviewed, and spikes, ripples, and fast ripples were marked. Seizure outcomes were tracked ≥ 2 years. Postoperative neuropsychological tests were performed and analyzed.

RESULTS

We included 67 patients (35 males/32 females, median age at surgery 28 years, 57 seizure-free). Complete resection was significantly associated with being seizure-free without aura, an outcome achieved by 32 (69.6%) patients with complete resection vs 1 (12.5%) with incomplete resection (p = 0.004). Spikes/ripples/fast ripples appeared frequently in the hippocampus, occurring in 86.4%/82.4%/75.0% of cases before resection and 76.7%/78.1%/63.0% after resection. The presence and rate were unconnected to seizure outcome. Postoperative neuropsychological outcomes in intelligence and visual memory improved overall.

CONCLUSIONS

HSL in lesional TLE can produce satisfactory seizure and cognitive outcomes. Intraoperative hippocampography-guided resection of apparently normal hippocampi should be performed cautiously and might not be necessary.

SIGNIFICANCE

This study provided evidence in decision making for patients with lesional TLE with a radiologically normal hippocampus.

Brain volume and perfusion asymmetry in temporal lobe epilepsy with and without hippocampal sclerosis

Objectives: To detect and compare the features of interictal perfusion and volume asymmetry between temporal lobe epilepsy (TLE) patients with and without hippocampal sclerosis (HS).Methods: Sixty-one TLE patients (mean age 28.4 ± 9.3 years; 28 female/33 male) with unilateral signs of HS (TLE-HS+) and 25 TLE patients (mean age 29.8 ± 8.0 years; 17 female/8 male) without HS (TLE-HS-) were included. Thirty healthy volunteers served as controls (mean age 26.0 ± 8.7 years; 22 female/8 male). Brain segmentation and volume calculation were performed. Quantitative cerebral blood flow (CBF) values were measured based on arterial spin labeling (ASL). The asymmetry indices (AIs) of volume and perfusion were calculated.Results: TLE-HS+ (adjusted P = 0.001) and TLE-HS- patients (adjusted P = 0.006) had significantly higher hippocampal perfusion AIs than controls. TLE-HS+ and TLE-HS- had similar hippocampal perfusion AIs (adjusted P = 1.00). TLE-HS+ had higher hippocampal volume AIs than TLE-HS- and controls (adjusted P < 0.001). TLE-HS- and controls had similar hippocampal volume AIs (adjusted P = 1.00). All (100%) TLE-HS+ patients had positive hippocampal perfusion or volume AIs. No significant correlation between the AIs of hippocampal perfusion and volume was found in both TLE-HS+(P = 0.894) and TLE-HS- (P = 0.106) patients. TLE-HS+ patients demonstrated more extensive whole-brain asymmetry of both perfusion and volume than TLE-HS- patients.Conclusion: TLE-HS+ and TLE-HS- patients have different patterns of whole-brain perfusion and volume asymmetry. Hippocampal perfusion asymmetry was revealed in both TLE-HS+ and TLE-HS- patients.

Nasal pain as an aura: Amygdala origin?

PURPOSE

Nasal pain, as an epileptic aura, has been poorly recognized. This study aims to demonstrate clinical features of patients with epilepsy who have nasal pain as an aura.

METHODS

We retrospectively investigated consecutive patients who visited the epilepsy clinic of tertiary hospital from April 2000 to September 2019. All included patients underwent epilepsy-dedicated, high-resolution magnetic resonance imaging (MRI) examinations. All MRI studies were analyzed by visual inspection.

RESULTS

Seven patients who presented nasal pain as an aura, were identified. Four patients reported nasal pain as the first aura. Four patients had right amygdala enlargement (isolated amygdala enlargement in three patients; amygdala enlargement in addition to hippocampal sclerosis in one patient), and one patient with compression of an internal carotid-posterior communicating artery aneurysm to right amygdala on brain MRI. Interictal epileptiform or ictal discharges on EEG were found in the right temporal region in five patients. In all four patients with amygdala enlargement, amygdala enlargement was ipsilateral to EEG anomalies. In all patients, nasal pain was accompanied by ictal semiological features, such as autonomic, olfactory, abdominal, or psychic auras, and focal impaired awareness seizures, which are typically associated with mesial temporal lobe epilepsy.

CONCLUSIONS

Our findings suggest that nasal pain can occur as an epileptic aura in patients with temporal lobe epilepsy with probable involvement of the amygdala.

Cerebrocerebellar structural covariance in temporal lobe epilepsy with hippocampal sclerosis

PURPOSE

The purpose of the study was to evaluate cerebral morphological changes in temporal lobe epilepsy with hippocampal sclerosis (TLE-HS) and their relationship to the cerebellum.

METHODS

The study cohort included 21 patients with intractable TLE-HS (14 left-sided, 7 right-sided) and 38 healthy controls (HC). All patients later underwent anteromedial temporal lobe resection. All subjects were examined using a 1.5-T magnetic resonance imaging (MRI). Volumes of distinct cerebral and cerebellar structures were measured using voxel-based morphometry. The structural covariance of temporal lobe structures, insula, and thalamus with cerebellar substructures was examined using partial least squares regression.

RESULTS

Morphological changes were more significant in the group with left TLE-HS when comparing left-sided with right-sided structures as well as when comparing patients with controls. The gray matter volume (GMV) of the temporal lobe structures was smaller ipsilaterally to the seizure onset side in most cases. There was a significant amygdala enlargement contralateral to the side of hippocampal sclerosis in both patients with right and left TLE-HS as compared with controls. Selected vermian structures in patients with left but not right TLE-HS had significantly larger GMV than the identical substructures in controls. The structural covariance differed significantly between patients with left and right TLE-HS as compared with HC. The analysis revealed significant negative covariance between anterior vermis and mesial temporal structures in the group with left TLE-HS. No significance was observed for the group with right TLE-HS.

CONCLUSION

There is significant asymmetry in the GMV of cerebral and cerebellar structures in patients with TLE-HS. Morphological changes are distinctly more pronounced in patients with left TLE-HS. The observed structural covariance between the cerebellum and supratentorial structures in TLE-HS suggests associations beyond the mesial temporal lobe structures and thalamus.

Long term sequelae of amygdala enlargement in temporal lobe epilepsy

PURPOSE

Amygdala enlargement (AE) has been reported in drug resistant lesional and non-lesional temporal lobe epilepsy (TLE). Its contribution to development of intractability of epilepsy is at best uncertain. Our aim was to study the natural course of AE in a heterogenous group of TLE patients with follow-up imaging and clinical outcomes.

METHODS

A prospective observational study in patients with TLE with imaging features of AE recruited from epilepsy clinics between 1994 and 2018. Demographic data, details of epilepsy syndrome, outcomes and follow up neuroimaging were extracted.

RESULTS

Forty-two patients were recruited including 19 males (45 %). Mean age at onset of epilepsy was 30.6 years and mean duration of epilepsy was 19.9 years. On MRI, 33 patients had isolated unilateral AE and eleven had AE with hippocampal enlargement (HE). Twenty (48 %) underwent temporal resections with most common histopathology being amygdalar gliosis (40 %). Engel Class IA outcome at last follow up (mean, 10 years) was 60 %. Thirty-four patients had neuroimaging follow up of at least 1 year (mean, 5 years). AE resolved in 6, persisted in 25, evolved into bilateral HS in 1, bilateral mesial temporal atrophy in 1 and ipsilateral mesial temporal atrophy in 1. Resolution of AE was associated with better seizure free outcomes (p = 0.013).

CONCLUSIONS

TLE with AE is associated with favourable prognosis yet not benign. Over 50 % were drug resistant and surgical outcomes were similar to mTLE. Resolution of AE on follow up neuroimaging was associated with better seizure free outcomes.

Anatomo-electro-clinical correlations of hypermotor seizures with amygdala enlargement: Hippocampal seizure origin identified using stereoelectroencephalography

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A drug-resistant epilepsy case showed hypermotor seizures and amygdala enlargement.

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Seizure onset zone was the hippocampus, not amygdala, as revealed by SEEG.

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The enlarged amygdala pathology was classified as FCD type I.

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Selective amygdalohippocampectomy led to good outcomes.

Amygdala enlargement in mesial temporal lobe epilepsy: an alternative imaging presentation of limbic epilepsy

PURPOSE

To assess imaging, clinical, and pathological features of mesial temporal lobe epilepsy (mTLE) patients with amygdala enlargement (AE) in comparison with those with mesial temporal sclerosis (MTS).

METHODS

Clinical, imaging, and pathologic features were retrospectively reviewed in 40 mTLE patients with postoperative follow-up (10 with AE and 30 with MTS). The volumes and signal intensity of the amygdala and hippocampus were assessed in 10 AE, 10 age- and sex-matched MTS patients, and 12 controls (HC).

RESULTS

AE patients had a lower rate of concordant FDG PET (p < 0.05) and required more frequently intracerebral electrodes compared to MTS patients (p < 0.05). AE had larger ipsilateral amygdala (p < 0.0001) and hippocampus volumes (p < 0.0001) compared to MTS and to HC, with no significant differences for other brain structures. Normalized FLAIR signal was higher in the ipsilateral than contralateral amygdala in both AE and MTS (p < 0.001 and p < 0.05, respectively) and higher in the ipsilateral amygdala compared to HC (p < 0.05). In MTS, ADC in the ipsilateral amygdala (867 mm²/s) was higher compared to the contralateral one (804.8 × 10^-6 mm²/s, p < 0.01), compared to HC (773 × 10^-6 mm²/s, p < 0.01) and compared to the ipsilateral amygdala in AE (813.7 × 10^-6 mm²/s, p < 0.05). AE patients had dysplasia (50%) or astrocytic gliosis (50%) of the amygdala extending to the hippocampus and temporal isocortex, and only 2/10 cases had pathologic findings of MTS.

CONCLUSION

AE patients have distinct imaging and pathologic features compared to MTS, and require more extensive preoperative workup. Recognition of AE may improve preoperative assessment in TLE surgical candidates.

Gray Matter and White Matter Abnormalities in Temporal Lobe Epilepsy Patients with and without Hippocampal Sclerosis

The presentation and distribution of gray matter (GM) and white matter (WM) abnormalities in temporal lobe epilepsy (TLE) have been widely studied. Here, we investigated the GM and WM abnormalities in TLE patients with and without hippocampal sclerosis (HS) in five groups of participants: healthy controls (HCs) (n = 28), right TLE patients with HS (n = 26), right TLE patients without HS (n = 30), left TLE patients with HS (n = 25), and left TLE patients without HS (n = 27). We performed a flexible factorial statistical test in a whole-brain voxel-based morphometry analysis to identify significant GM and WM abnormalities and analysis of variance of hippocampal and amygdala regions among the five groups using the FreeSurfer procedure. Furthermore, we conducted multiple regression analysis to assess regional GM and WM changes with disease duration. We observed significant ipsilateral mesiotemporal GM and WM volume reductions in TLE patients with HS compared with HCs. We also observed a slight GM amygdala swelling in right TLE patients without HS. The regression analysis revealed significant negative GM and WM changes with disease duration specifically in left TLE patients with HS. The observed GM and WM abnormalities may contribute to our understanding of the root of epilepsy mechanisms.

Marked accumulation of oligodendroglia-like cells in temporal lobe epilepsy with amygdala enlargement and hippocampal sclerosis

Although an increasing number of cases of temporal lobe epilepsy (TLE) with ipsilateral amygdala enlargement (AE) have been reported, there are few pathological reports, and no clear consensus has been established. Oligodendroglia or oligodendroglia-like cells (OLCs) have recently attracted attention in epilepsy studies. Here, we report the clinical and pathological findings of a 40-year-old male TLE patient with AE and hippocampal sclerosis, in whom histopathological study demonstrated remarkable clustering of OLCs around the uncus. The patient began to have refractory seizures at the age of 14, and preoperative MRI revealed left amygdala enlargement and left hippocampal atrophy. Other examinations were consistent with left mesial temporal epileptogenicity. He underwent surgical resection and achieved seizure freedom. Histopathological study of the amygdala showed swollen neurons with relatively large bodies and thick neurites, accompanied by vacuolar degeneration in the background. Additionally, there were marked clusters of OLCs with round nuclei and densely stained chromatin around the uncus. The OLCs were Olig2-positive. In the hippocampus, severe cell loss in CA1 and granule cell dispersion in the dentate gyrus were found. These findings may provide some insights for further pathological investigations of TLE with non-neoplastic AE.

Amygdala enlargement: Temporal lobe epilepsy subtype or nonspecific finding?

OBJECTIVE

Amygdala enlargement (AE) is observed in patients with temporal lobe epilepsy (TLE), which has led to the suggestion that it represents a distinct TLE subtype; however, it is unclear whether AE is found at similar rates in other epilepsy syndromes or in healthy controls, which would limit its value as a marker for focal epileptogenicity.

METHODS

We compared rates of AE, defined quantitatively from high-resolution T1-weighted MRI, in a large multi-site sample of 136 patients with nonlesional localization related epilepsy (LRE), including TLE and extratemporal (exTLE) focal epilepsy, 34 patients with idiopathic generalized epilepsy (IGE), and 233 healthy controls (HCs).

RESULTS

AE was found in all groups including HCs; however, the rate of AE was higher in LRE (18.4%) than in IGE (5.9%) and HCs (6.4%). Patients with unilateral LRE were further evaluated to compare rates of concordant ipsilateral AE in TLE and exTLE, with the hypothesis that rates of ipsilateral AE would be higher in TLE. Although ipsilateral AE was higher in TLE (19.4%) than exTLE (10.5%), this difference was not significant. Furthermore, among the 25 patients with unilateral LRE and AE, 13 (52%) had either bilateral AE or AE contralateral to seizure onset.

CONCLUSION

Results suggest that AE, as defined with MRI volumetry, may represent an associated feature of nonlesional localization related epilepsy with limited seizure onset localization value.

Disruptions in cortico-subcortical covariance networks associated with anxiety in new-onset childhood epilepsy

Anxiety disorders represent a prevalent psychiatric comorbidity in both adults and children with epilepsy for which the etiology remains controversial. Neurobiological contributions have been suggested, but only limited evidence suggests abnormal brain volumes particularly in children with epilepsy and anxiety. Since the brain develops in an organized fashion, covariance analyses between different brain regions can be investigated as a network and analyzed using graph theory methods. We examined 46 healthy children (HC) and youth with recent onset idiopathic epilepsies with (n = 24) and without (n = 62) anxiety disorders. Graph theory (GT) analyses based on the covariance between the volumes of 85 cortical/subcortical regions were investigated. Both groups with epilepsy demonstrated less inter-modular relationships in the synchronization of cortical/subcortical volumes compared to controls, with the epilepsy and anxiety group presenting the strongest modular organization. Frontal and occipital regions in non-anxious epilepsy, and areas throughout the brain in children with epilepsy and anxiety, showed the highest centrality compared to controls. Furthermore, most of the nodes correlating to amygdala volumes were subcortical structures, with the exception of the left insula and the right frontal pole, which presented high betweenness centrality (BC); therefore, their influence in the network is not necessarily local but potentially influencing other more distant regions. In conclusion, children with recent onset epilepsy and anxiety demonstrate large scale disruptions in cortical and subcortical brain regions. Network science may not only provide insight into the possible neurobiological correlates of important comorbidities of epilepsy, but also the ways that cortical and subcortical disruption occurs.

Suspected new-onset autoimmune temporal lobe epilepsy with amygdala enlargement

OBJECTIVE

Recent reports define temporal lobe epilepsy with amygdala enlargement (TLE-AE) as a distinct electroclinical syndrome comparable to TLE with hippocampal sclerosis. In this retrospective observational study, we present the largest consecutive series of patients with new-onset TLE-AE to date and describe clinical characteristics and seizure outcome, and we aim to explore underlying autoimmune mechanisms within this syndrome.

METHODS

We reviewed all consecutive patients between 2004 and 2014 at our tertiary epilepsy center at the University of Bonn, Germany, with new-onset (<5 years) TLE-AE, negative serum antibody (ab) test results, and with available follow-up data for at least 12 months.

RESULTS

We identified 40 patients (23 male) with TLE-AE with a median age at epilepsy onset of 51 years (range 10-73) and a median disease duration of 11 months (range 0.5-55) at first presentation. At follow-up, 50% of the entire cohort achieved seizure freedom. Of interest, patients with remittent features of AE at follow-up (N = 24) had a superior outcome compared to those with stable magnetic resonance imaging (MRI) features of AE (N = 16): 17 (71%) of 24 were seizure-free for at least 6 months compared to 3 (19%) of 16, respectively (p = 0.003). MRI volumetry confirmed significantly enlarged amygdalae in TLE-AE in relation to healthy controls, and additionally showed significantly greater volume reductions in patients with remittent AE compared to those with stable AE.

SIGNIFICANCE

TLE-AE is a clinical syndrome beginning mostly in middle age, and in addition to its known association with ab-positive limbic encephalitis, it occurs in an ab-negative condition. Remission of AE in the course of the disease could be identified as a predictor for a favorable clinical outcome and is suspicious of an autoimmune etiology, although we could not confirm this hypothesis unequivocally with currently available noninvasive diagnostic tools.

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.

Amygdala Volumetry in Patients with Temporal Lobe Epilepsy and Normal Magnetic Resonance Imaging

BACKGROUND

It has been suggested that the pathophysiology of temporal lobe epilepsy may relate to abnormalities in various brain structures, including the amygdala. Patients with mesial temporal lobe epilepsy (MTLE) without MRI abnormalities (MTLE-NMRI) represent a challenge for diagnosis of the underlying abnormality and for presurgical evaluation. To date, however, only few studies have used quantitative structural Magnetic Resonance Imaging-based techniques to examine amygdalar pathology in these patients.

MATERIAL/METHODS

Based on clinical examination, 24-hour video EEG recordings and MRI findings, 50 patients with EEG lateralized TLE and normal structural Magnetic Resonance Imaging results were included in this study. Volumetric magnetic resonance imaging (MRI) studies of the amygdalas and hippocampi were conducted in 50 non-epileptic controls (age 7-79 years) and 50 patients with MTLE with normal MRI on a 1.5-Tesla scanner. Visual assessment and amygdalar volumetry were performed on oblique coronal T2W and T1W MP-RAGE images respectively. The T2 relaxation times were measured using the 16-echo Carr-Purcell-Meiboom-Gill sequence (TE, 22-352). Volumetric data were normalized for variation in head size between individuals. Results were assessed by SSPS statistic program.

RESULTS

Individual manual volumetric analysis confirmed statistically significant amygdala enlargement (AE) in eight (16%) patients. Overall, among all patients with AE and a defined epileptic focus, 7 had predominant increased volume ipsilateral to the epileptic focus. The T2 relaxometry demonstrated no hyperintense signal of the amygdala in any patient with significant AE.

CONCLUSIONS

This paper presented AE in a few patients with TLE and normal MRI. These findings support the hypothesis that there might be a subgroup of patients with MTLE-NMRI in which the enlarged amygdala could be related to the epileptogenic process.

Cardiac Asystole Triggered by Temporal Lobe Epilepsy with Amygdala Enlargement

A 25-year-old previously healthy man was hospitalized for syncope. While standing, he suddenly lost consciousness, followed by a generalized tonic clonic seizure. An electrocardiogram demonstrated asystole. No cardiac abnormalities were detected on the echocardiogram, cardiac magnetic resonance imaging (MRI), positron emission tomography, or a coronary angiogram. An electrophysiological study showed normal sinus node and atrioventricular node function. An electroencephalogram revealed small spike waves in the fronto-temporal region. Brain MRI demonstrated a left-sided amygdala enlargement. To the best of our knowledge, this is the first case of temporal lobe epilepsy with an amygdala enlargement that induced cardiac asystole.

Structural imaging biomarkers of sudden unexpected death in epilepsy

The mechanisms underlying sudden unexpected death in epilepsy (SUDEP) remain unclear. Wandschneider et al. reveal increased amygdalo-hippocampal volume in cases of SUDEP and in individuals at high risk, compared to individuals at low risk and people without epilepsy. Findings are consistent with histopathological reports in sudden infant death syndrome.

Sudden unexpected death in epilepsy is a major cause of premature death in people with epilepsy. We aimed to assess whether structural changes potentially attributable to sudden death pathogenesis were present on magnetic resonance imaging in people who subsequently died of sudden unexpected death in epilepsy. In a retrospective, voxel-based analysis of T₁ volume scans, we compared grey matter volumes in 12 cases of sudden unexpected death in epilepsy (two definite, 10 probable; eight males), acquired 2 years [median, interquartile range (IQR) 2.8] before death [median (IQR) age at scanning 33.5 (22) years], with 34 people at high risk [age 30.5 (12); 19 males], 19 at low risk [age 30 (7.5); 12 males] of sudden death, and 15 healthy controls [age 37 (16); seven males]. At-risk subjects were defined based on risk factors of sudden unexpected death in epilepsy identified in a recent combined risk factor analysis. We identified increased grey matter volume in the right anterior hippocampus/amygdala and parahippocampus in sudden death cases and people at high risk, when compared to those at low risk and controls. Compared to controls, posterior thalamic grey matter volume, an area mediating oxygen regulation, was reduced in cases of sudden unexpected death in epilepsy and subjects at high risk. The extent of reduction correlated with disease duration in all subjects with epilepsy. Increased amygdalo-hippocampal grey matter volume with right-sided changes is consistent with histo-pathological findings reported in sudden infant death syndrome. We speculate that the right-sided predominance reflects asymmetric central influences on autonomic outflow, contributing to cardiac arrhythmia. Pulvinar damage may impair hypoxia regulation. The imaging findings in sudden unexpected death in epilepsy and people at high risk may be useful as a biomarker for risk-stratification in future studies.