Hippocampal malformation as a cause of familial febrile convulsions and subsequent hippocampal sclerosis

Volumetric magnetic resonance imaging differences between complex febrile seizure and recurrent simple febrile seizure

PURPOSE

We investigated the volumetric differences in cortical and subcortical structures between patients with complex febrile seizure (FS) and recurrent simple FS. We aimed to identify the brain morphological patterns of children with complex FS.

METHODS

Twenty-five patients with complex FS and age- and sex-matched 25 patients with recurrent simple FS with structural magnetic resonance imaging (MRI) scans were studied. Cortical volumetric analysis was performed using a voxel-based morphometry method with the CAT12 toolbox within SPM12. FSL-FIRST was used to obtain volume measures of subcortical deep grey matter structures (amygdala, caudate nucleus, thalamus, nucleus accumbens, putamen, globus pallidus, and hippocampus). The volumetric asymmetry index (AI) and laterality index (LI) were calculated for each subcortical structure.

RESULTS

Compared with recurrent simple FS, complex FS demonstrated lower volume in the left putamen (p = .003) and right nucleus accumbens (p = .001). Additionally, patients with complex FS presented a higher magnitude of AI of the nucleus accumbens (p < .001) compared with recurrent simple FS.

CONCLUSIONS

The findings indicate that volumetric analysis may be a useful marker for the detection of FS-induced changes that reflect microstructural alterations. This study is the first to report on alterations in the putamen and nucleus accumbens in FS.

Are brief febrile seizures benign? A systematic review and narrative synthesis

Febrile seizures affect 2%-5% of U.S. children and are considered benign although associated with an increased risk of epilepsy and, rarely, with sudden unexplained death. We compared rates of mortality, neurodevelopmental disorders, and neuropathology in young children with simple and complex febrile seizures to healthy controls. We systematically reviewed studies of 3- to 72-month-old children with simple or complex febrile seizures ≤30 min. We searched studies with outcome measures on mortality, neurodevelopment, or neuropathology through July 18, 2022. Bias risk was assessed per study design. Each outcome measure was stratified by study design. PROSPERO registration is CRD42022361645. Twenty-six studies met criteria reporting mortality (11), neurodevelopment (11), and neuropathology (13), including 2665 children with febrile seizures and 1206 seizure-free controls. Study designs varied: 15 cohort, 2 cross-sectional, 3 case-control, 5 series, and 1 case report. Mortality outcomes showed stark contrasts. Six cohort studies following children after febrile seizure (n = 1348) reported no deaths, whereas four child death series and 1 case report identified 24.1% (108/449) deaths associated with simple (n = 104) and complex (n = 3) febrile seizures ≤30 min. Minor hippocampal histopathological anomalies were common in sudden deaths with or without febrile seizure history. Most electroencephalography (EEG) studies were normal. Neuroimaging studies suggested increased right hippocampal volumes. When present, neurodevelopmental problems usually preexisted febrile-seizure onset. Risk bias was medium or high in 95% (18/19) of cohort and case-control studies vs medium to low across remaining study designs. Research on outcomes after simple or brief complex febrile seizures is limited. Cohort studies suffered from inadequate sample size, bias risk, and limited follow-up durations to make valid conclusions on mortality, neurodevelopment, and neuropathology. Sudden death registries, focused on a very small percentage of all cases, strongly suggest that simple febrile seizures are associated with increased mortality. Although most children with febrile seizures have favorable outcomes, longer-term prospective studies are needed.

Hippocampal Malrotation: A Genetic Developmental Anomaly Related to Epilepsy?

Hippocampal malrotation (HIMAL) is an increasingly recognized neuroimaging feature but the clinical correlation and significance in epilepsies remain under debate. It is characterized by rounded hippocampal shape, deep collateral, or occipitotemporal sulcus, and medial localization of the hippocampus. In this review, we describe the embryonic development of the hippocampus and HIMAL, the qualitative and quantitative diagnosis issues, and the pathological findings of HIMAL. HIMAL can be bilateral or unilateral and more on the left side. Furthermore, the relevance of HIMAL diagnosis in clinical practice, including its role in epileptogenesis and the impact on the pre-surgical decision are reviewed. Finally, the relationship between HIMAL and hippocampal sclerosis (HS) and the possible role of genetics in the etiology of HIMAL are discussed. The evidence so far suggested that HIMAL does not have a significant role in epileptogenesis or surgical decision. HIMAL could be a genetic developmental imaging feature that represents a more diffuse but subtle structural error during brain development. Many questions remain to be explored, such as possible cognitive alteration associated with HIMAL and whether HIMAL predisposes to the development of HS. Further studies using high-quality MRI, unified consensus qualitative and quantitative diagnostic criteria, and comprehensive cognitive assessment are recommended.

A Review of Febrile Seizures: Recent Advances in Understanding of Febrile Seizure Pathophysiology and Commonly Implicated Viral Triggers

Febrile seizures are one of the commonest presentations in young children, with a 2-5% incidence in Western countries. Though they are generally benign, with rare long-term sequelae, there is much to be learned about their pathophysiology and risk factors. Febrile seizures are propagated by a variety of genetic and environmental factors, including viruses and vaccines. These factors must be taken into consideration by a clinician aiming to assess, diagnose and treat a child presenting with fevers and seizures, as well as to explain the sequelae of the febrile seizures to the concerned parents of the child. Our article provides an overview of this common childhood condition, outlining both the underlying mechanisms and the appropriate clinical approach to a child presenting with febrile seizures.

Looking for indicative magnetic resonance imaging signs of hippocampal developmental abnormalities in patients with mesial temporal lobe epilepsy and healthy controls

OBJECTIVE

To evaluate the frequency of qualitative features for hippocampal developmental abnormalities (HiDeA) definition on magnetic resonance imaging (MRI) in mesial temporal lobe epilepsy (MTLE) patients and healthy controls, highlighting which were more sensitive and specific to the epileptic syndrome.

METHODS

We enrolled 93 healthy controls and 187 MTLE patients. Among patients, 133 were MRI-negative and 54 had hippocampal sclerosis (HS). Two blinded, trained investigators defined HiDeA if three signs were present, including at least one of the following: (1) globular hippocampal shape (HCS), (2) verticalized collateral sulcus, and (3) medial positioning of hippocampus (HCP). After evaluating the prevalence of HiDeA in MTLE and controls, we assessed the frequency of each sign. Then, we classified differences in type or number of HiDeA diagnostic features, calculating their sensitivity and specificity. Fisher exact test was used to assess statistical significance.

RESULTS

HiDeA was detected in 36 of 187 MTLE cases (19.25%) and in eight of 93 (8.6%) controls. In particular, HiDeA was present in 25 of 133 (18.8%) patients with MRI-negative MTLE. Among all visual criteria here considered, HCS showed higher sensitivity both in the MRI-negative MTLE group (88%) and in the HS-MTLE group (91%). HCP, thickened subiculum, and reduction of the upper horizontal portion of the parahippocampal gyrus (HCTH) signs demonstrated a 100% specificity in both groups. In healthy controls, HCS was confirmed to have the highest sensitivity (100%), whereas HCP showed the highest specificity (98.8%). All these criteria were statistically associated with HiDeA. Electroencephalographic focus was concordant with the HiDeA side in 52.2% of MTLE patients. An association was not found among signs of HiDeA and treatment responsiveness.

SIGNIFICANCE

We identified characteristic signs of HiDeA, such as HCTH or HCP, differentiating HiDeA features between MTLE and healthy controls. The identification of sensitive and, more importantly, specific criteria of HiDeA could be helpful to make a more confident visual diagnosis.

Shared hippocampal abnormalities in sporadic temporal lobe epilepsy patients and their siblings

OBJECTIVE

To examine the shared familial contribution to hippocampal and extrahippocampal morphological abnormalities in patients with sporadic temporal lobe epilepsy (TLE) and their unaffected siblings.

METHODS

We collected clinical, electrophysiological, and T1-weighted magnetic resonance imaging (MRI) data of 18 sporadic patients with TLE without lesions other than hippocampal sclerosis (12 right, 6 left), their 18 unaffected full siblings, and 18 matched healthy volunteers. We compared between-group differences in cortical thickness and volumes of five subcortical areas (hippocampus, amygdala, thalamus, putamen, and pallidum). We determined the subregional extent of hippocampal abnormalities using surface shape analysis. All our imaging results were corrected for multiple comparisons using random field theory.

RESULTS

We detected smaller hippocampal volumes in patients (right TLE: median right hippocampus 1.92 mL, interquartile range [IQR] 1.39-2.62, P < .001; left TLE: left hippocampus 2.05 mL, IQR 1.99-2.33, P = .01) and their unaffected siblings (right hippocampus 2.65 mL, IQR 2.32-2.80, P < .001; left hippocampus 2.39 mL, IQR 2.18-2.53, P < .001) compared to healthy controls (right hippocampus 2.94 mL, IQR 2.77-3.24; left hippocampus 2.71 mL, IQR 2.37-2.89). Surface shape analysis showed that patients with TLE had bilateral subregional atrophy in both hippocampi (right > left). Similar but less-pronounced subregional atrophy was detected in the right hippocampus of unaffected siblings. Patients with TLE had reduced cortical thickness in bilateral premotor/prefrontal cortices and the right precentral gyrus. Siblings did not show abnormalities in cortical or subcortical areas other than the hippocampus.

SIGNIFICANCE

Our results demonstrate a shared vulnerability of the hippocampus in both patients with TLE and their unaffected siblings, pointing to a contribution of familial factors to hippocampal atrophy. This neuroimaging trait could represent an endophenotype of TLE, which might precede the onset of epilepsy in some individuals.

Size of Subcortical Band Heterotopia Influences the Susceptibility to Hyperthermia-Induced Seizures in a Rat Model

Studies conducted in human and rodent models have suggested that preexisting neurodevelopmental defects could predispose immature brains to febrile seizures (FS). However, the impact of the anatomical extent of preexisting cortical malformations on FS susceptibility was never assessed. Here, we induced hyperthermic seizures (HS) in rats with bilateral subcortical band heterotopia (SBH) and found variable degrees of HS susceptibility depending on inter-individual anatomical differences in size and extent of SBH. This indicates that an association exists between the overall extent or location of a cortical malformation, and the predisposition to FS. This also suggests that various predisposing factors and underlying causes may contribute to the etiology of complex FS.

Detection of partial loss of hippocampal striation at 1.5 Tesla magnetic resonance imaging

OBJECTIVES

Partial loss of hippocampal striation (PLHS) is recently described in 3 T and 7 T MR imaging as a sensitive indicator of hippocampal sclerosis.

PRIMARY OBJECTIVE

We described the demographic characteristics of the population with seizure disorder having PLHS at 1.5 T MR imaging and tried to see the relation of PLHS to the classic signs of hippocampal sclerosis.

SECONDARY OBJECTIVE

PLHS was also looked for in a small control population that had no seizure history.

METHODS

This retrospective study had the approval of the institutional review board. In patients demonstrating PLHS on oblique coronal T2-weighted images, the following were recorded: age, sex, EEG findings, side of PLHS, hippocampal atrophy and high signal intensity of the hippocampus. In control population, the following were recorded: age, sex, presence/absence of PLHS and indication for imaging.

RESULTS

The 116 PLHS subjects (age range 2-73 years) included 62 males and 54 females. Sixty-six (56.9%) of our PLHS subjects were less than 18 years of age: 44 (37.9%) under the age of 12 years and 22 (19%) of 12-18 years of age. Classic signs of hippocampal sclerosis were found in only 7 (6%) of the 116 subjects showing PLHS. All patients with classic signs showed PLHS on the same side. Of the control population (25 subjects, age range 3-76 years, 17 males and 8 females), one showed PLHS-he was a treated case of CNS lymphoma with gliotic changes, though there was no history of seizure.

CONCLUSION

PLHS is demonstrated at 1.5 T in both adult and paediatric population in this article and is much more common than the classic signs of hippocampal sclerosis (increased signal intensity and volume loss).

Drug-responsive versus drug-refractory mesial temporal lobe epilepsy: a single-center prospective outcome study

Objectives: To evaluate clinical, electrophysiological, and neuroradiological factors which correlate with the prognosis in patients with mesial temporal lobe epilepsy (MTLE). Methods: This was a single-center prospective outcome study in patients with MTLE. The patients' family history, clinical characteristics, neurophysiological data (electroencephalography - EEG), neuroimaging, antiepileptic therapy, and outcome were collected and analyzed. The population was divided into four groups depending on the frequency of the seizures when they attended their last follow up. All variables and outcome measures were compared between the four groups. Results: In total 83 consecutive patients were included within the four groups. Group 1 (seizure-free) consisted of 7 patients, (9%), Group 2 (rare seizures) consisted of 15 patients (18%), Group 3 (often seizures) consisted of 30 patients (36%), and Group 4 (very often seizures) consisted of 31 patients (37%). The groups did not differ significantly in demographic characteristics. There was a strong positive correlation between resistance to therapy and sleep activation on EEG (p = 0.005), occurrence of focal to bilateral seizures (p = 0.007), automatisms (p = 0.004), and the number of previously used antiepileptic drugs (AEDs) (p = 0.002). There was no association between febrile convulsions (FC), hippocampal sclerosis (HS), and the outcome that was found. Conclusion: MTLE is a heterogeneous syndrome. Establishing the factors responsible for, and associated with, drug resistance is important for optimal management and treatment, as early identification of drug resistance should then ensure a timely referral for surgical treatment is made. This prospective study shows that sleep activation on EEG, ictal automatisms, occurrence of focal to bilateral tonic-clonic seizures, and increased number of tried AEDs are negative prognostic factors.

Neuropathologic features of the hippocampus and amygdala in cats with familial spontaneous epilepsy

OBJECTIVE To investigate epilepsy-related neuropathologic changes in cats of a familial spontaneous epileptic strain (ie, familial spontaneous epileptic cats [FSECs]). ANIMALS 6 FSECs, 9 age-matched unrelated healthy control cats, and 2 nonaffected (without clinical seizures)dams and 1 nonaffected sire of FSECs. PROCEDURES Immunohistochemical analyses were used to evaluate hippocampal sclerosis, amygdaloid sclerosis, mossy fiber sprouting, and granule cell pathological changes. Values were compared between FSECs and control cats. RESULTS Significantly fewer neurons without gliosis were detected in the third subregion of the cornu ammonis (CA) of the dorsal and ventral aspects of the hippocampus as well as the central nucleus of the amygdala in FSECs versus control cats. Gliosis without neuronal loss was also observed in the CA4 subregion of the ventral aspect of the hippocampus. No changes in mossy fiber sprouting and granule cell pathological changes were detected. Moreover, similar changes were observed in the dams and sire without clinical seizures, although to a lesser extent. CONCLUSIONS AND CLINICAL RELEVANCE Findings suggested that the lower numbers of neurons in the CA3 subregion of the hippocampus and the central nucleus of the amygdala were endophenotypes of familial spontaneous epilepsy in cats. In contrast to results of other veterinary medicine reports, severe epilepsy-related neuropathologic changes (eg, hippocampal sclerosis, amygdaloid sclerosis, mossy fiber sprouting, and granule cell pathological changes) were not detected in FSECs. Despite the use of a small number of cats with infrequent seizures, these findings contributed new insights on the pathophysiologic mechanisms of genetic-related epilepsy in cats.

Brain expression of inflammatory mediators in Mesial Temporal Lobe Epilepsy patients

Neuroinflammation may be central in epileptogenesis. In this study we analysed inflammatory reaction markers in brain tissue of Mesial Temporal Lobe Epilepsy with Hippocampal Sclerosis (MTLE-HS) patients. TLR4, IL-1β and IL-10 gene expression as well as the presence of activated HLA-DR+ microglia was evaluated in 23 patients and 10 cadaveric controls. Inflammation characterized by the presence of HLA-DR⁺ microglia and TLR4, IL-1β overexpression was evident in hippocampus and anterior temporal cortex of MTLE-HS patients. Anti-inflammatory IL-10 was also overexpressed in MTLE-HS patients. Our results show that hippocampal neuroinflammation extends beyond lesional limits, as far as the anterior temporal cortex.

Mesial temporal lobe epilepsy with childhood febrile seizure

OBJECTIVES

To evaluate the demographic and clinical manifestations of patients with mesial temporal sclerosis and temporal lobe epilepsy (MTS-TLE) with childhood febrile seizure (FS) and establishing the potential differences as compared to those without FS. We also investigated the surgery outcome in these two groups of patients.

MATERIALS AND METHODS

In this retrospective study, all patients with a clinical diagnosis of drug-resistant TLE due to mesial temporal sclerosis, who underwent epilepsy surgery at Jefferson Comprehensive Epilepsy Center, were recruited. Patients were prospectively registered in a database from 1986 through 2014. Postsurgical outcome was classified into two groups; seizure-free or relapsed. Clinical manifestations and outcome were compared between patients with MTS-TLE with FS and those without FS.

RESULTS

Two hundred and sixty-two patients were eligible for this study. One hundred and seventy patients (64.9%) did not have FS in their childhood, while 92 patients (35.1%) reported experiencing FS in their childhood. Demographic and clinical characteristics of these two groups of patients were not different. Postoperative seizure outcome was not statistically different between these two groups of patients (P = 0.19).

CONCLUSIONS

When MTS is the pathological substrate of TLE, clinical manifestations and response to surgical treatment of patients are very similar in patients with history of febrile seizure in their childhood compared to those without such an experience. In other words, when the subgroup of patients with MTS-TLE and drug-resistant seizures is examined history of childhood febrile seizure loses its value as a distinguishing factor in characteristics or predictive factor for surgery outcome.

Quantitative magnetic resonance imaging traits as endophenotypes for genetic mapping in epilepsy

Over the last decade, the field of imaging genomics has combined high-throughput genotype data with quantitative magnetic resonance imaging (QMRI) measures to identify genes associated with brain structure, cognition, and several brain-related disorders. Despite its successful application in different psychiatric and neurological disorders, the field has yet to be advanced in epilepsy. In this article we examine the relevance of imaging genomics for future genetic studies in epilepsy from three perspectives. First, we discuss prior genome-wide genetic mapping efforts in epilepsy, considering the possibility that some studies may have been constrained by inherent theoretical and methodological limitations of the genome-wide association study (GWAS) method. Second, we offer a brief overview of the imaging genomics paradigm, from its original inception, to its role in the discovery of important risk genes in a number of brain-related disorders, and its successful application in large-scale multinational research networks. Third, we provide a comprehensive review of past studies that have explored the eligibility of brain QMRI traits as endophenotypes for epilepsy. While the breadth of studies exploring QMRI-derived endophenotypes in epilepsy remains narrow, robust syndrome-specific neuroanatomical QMRI traits have the potential to serve as accessible and relevant intermediate phenotypes for future genetic mapping efforts in epilepsy.

•

QMRI traits have the potential to serve as robust intermediate phenotypes for brain-related disorders.

•

Hippocampal volume is the most promising neuroimaging endophenotype for MTLE + HS.

•

Imaging genomics holds great promise in advancing epilepsy genetic research.

•

Studies are encouraged to explore the validity of QMRI traits as endophenotypes for epilepsy.

Hippocampal Malrotation Is Associated With Prolonged Febrile Seizures: Results of the FEBSTAT Study

OBJECTIVE

Hippocampal malrotation is characterized by incomplete hippocampal inversion with a rounded shape and blurred internal architecture. There is still debate about whether hippocampal malrotation has pathologic significance. We present findings from the Consequences of Prolonged Febrile Seizures in Childhood (FEBSTAT) study on the frequency of and risk factors for hippocampal malrotation.

SUBJECTS AND METHODS

FEBSTAT is a prospective multicenter study investigating the consequences of febrile status epilepticus in childhood. MRI studies of 226 patients with febrile status epilepticus were analyzed visually by two board-certified neuroradiologists blinded to clinical details and were compared with MRI studies of 96 subjects with first simple febrile seizure. Quantitative analysis of hippocampal volume was performed by two independent observers.

RESULTS

Hippocampal malrotation was present in 20 of 226 (8.8%) patients with febrile status epilepticus compared with two of 96 (2.1%) control subjects (odds ratio [OR], 4.56; 95% CI, 1.05-19.92). Hippocampal malrotation was exclusively left-sided in 18 of 22 (81.8%) patients and bilateral in the remaining four patients (18.2%). There was no case of exclusively right-sided hippocampal malrotation. Hippocampal malrotation was more common in boys than in girls (OR, 6.1; 95% CI, 1.7-21.5). On quantitative volumetric MRI analysis, the left hippocampal volume was smaller in patients with hippocampal malrotation than in control subjects with simple febrile seizure (p = 0.004), and the right-to-left hippocampal volume ratio was higher in the hippocampal malrotation group than in the simple febrile seizure group (p < 0.001).

CONCLUSION

Hippocampal malrotation is a developmental malformation that predominantly affects the left hippocampus in male patients and is more frequently found in children with prolonged febrile status epilepticus than in control subjects. These data provide further evidence that hippocampal malrotation represents a pathologic error in brain development rather than a normal variant.

Hippocampal abnormalities in magnetic resonance imaging (MRI) of 15q duplication syndromes

Patients with 15q duplication syndromes, including isodicentric chromosome 15 and interstitial duplications, usually present with autism spectrum disorder, intellectual disability, and frequently epilepsy. Neuroimaging studies in these patients are typically reported as normal, but nonspecific findings such as thinning of the corpus callosum and increased pericerebral spaces have been reported. A review of brain magnetic resonance imaging (MRI) studies of 11 individuals seen at the Massachusetts General Hospital Dup15q Center was performed. Hippocampus morphology was specifically reviewed, as a recent neuropathologic study has found frequent hippocampal heterotopias and dysplasias in these disorders. Two subjects had unilateral hippocampal sclerosis and 6 had bilateral hippocampal malformations. Hypoplasia of the corpus callosum was present in 2 subjects.

Review: Hippocampal sclerosis in epilepsy: a neuropathology review

Hippocampal sclerosis (HS) is a common pathology encountered in mesial temporal lobe epilepsy (MTLE) as well as other epilepsy syndromes and in both surgical and post-mortem practice. The 2013 International League Against Epilepsy (ILAE) classification segregates HS into typical (type 1) and atypical (type 2 and 3) groups, based on the histological patterns of subfield neuronal loss and gliosis. In addition, granule cell reorganization and alterations of interneuronal populations, neuropeptide fibre networks and mossy fibre sprouting are distinctive features of HS associated with epilepsies; they can be useful diagnostic aids to discriminate from other causes of HS, as well as highlighting potential mechanisms of hippocampal epileptogenesis. The cause of HS remains elusive and may be multifactorial; the contribution of febrile seizures, genetic susceptibility, inflammatory and neurodevelopmental factors are discussed. Post-mortem based research in HS, as an addition to studies on surgical samples, has the added advantage of enabling the study of the wider network changes associated with HS, the long-term effects of epilepsy on the pathology and associated comorbidities. It is likely that HS is heterogeneous in aspects of its cause, epileptogenetic mechanisms, network alterations and response to medical and surgical treatments. Future neuropathological studies will contribute to better recognition and understanding of these clinical and patho-aetiological subtypes of HS.

Temporal Cortex Morphology in Mesial Temporal Lobe Epilepsy Patients and Their Asymptomatic Siblings

Temporal cortex abnormalities are common in patients with mesial temporal lobe epilepsy due to hippocampal sclerosis (MTLE+HS) and believed to be relevant to the underlying mechanisms. In the present study, we set out to determine the familiarity of temporal cortex morphologic alterations in a cohort of MTLE+HS patients and their asymptomatic siblings. A surface-based morphometry (SBM) method was applied to process MRI data acquired from 140 individuals (50 patients with unilateral MTLE+HS, 50 asymptomatic siblings of patients, and 40 healthy controls). Using a region-of-interest approach, alterations in temporal cortex morphology were determined in patients and their asymptomatic siblings by comparing with the controls. Alterations in temporal cortex morphology were identified in MTLE+HS patients ipsilaterally within the anterio-medial regions, including the entorhinal cortex, parahippocampal gyrus, and temporal pole. Subtle but similar pattern of morphology changes with a medium effect size were also noted in the asymptomatic siblings. These localized alterations were related to volume loss that appeared driven by shared contractions in cerebral cortex surface area. These findings indicate that temporal cortex morphologic alterations are common to patients and their asymptomatic siblings and suggest that such localized traits are possibly heritable.

Co-occurring malformations of cortical development and SCN1A gene mutations

OBJECTIVE

To report on six patients with SCN1A mutations and malformations of cortical development (MCDs) and describe their clinical course, genetic findings, and electrographic, imaging, and neuropathologic features.

METHODS

Through our database of epileptic encephalopathies, we identified 120 patients with SCN1A mutations, of which 4 had magnetic resonance imaging (MRI) evidence of MCDs. We collected two further similar observations through the European Task-force for Epilepsy Surgery in Children.

RESULTS

The study group consisted of five males and one female (mean age 7.4 ± 5.3 years). All patients exhibited electroclinical features consistent with the Dravet syndrome spectrum, cognitive impairment, and autistic features. Sequencing analysis of the SCN1A gene detected two missense, two truncating, and two splice-site mutations. Brain MRI revealed bilateral periventricular nodular heterotopia (PNH) in two patients and focal cortical dysplasia (FCD) in three, and disclosed no macroscopic abnormality in one. In the MRI-negative patient, neuropathologic study of the whole brain performed after sudden unexpected death in epilepsy (SUDEP), revealed multifocal micronodular dysplasia in the left temporal lobe. Two patients with FCD underwent epilepsy surgery. Neuropathology revealed FCD type IA and type IIA. Their seizure outcome was unfavorable. All four patients with FCD exhibited multiple seizure types, which always included complex partial seizures, the area of onset of which co-localized with the region of structural abnormality.

SIGNIFICANCE

MCDs and SCN1A gene mutations can co-occur. Although epidemiology does not support a causative role for SCN1A mutations, loss or impaired protein function combined with the effect of susceptibility factors and genetic modifiers of the phenotypic expression of SCN1A mutations might play a role. MCDs, particularly FCD, can influence the electroclinical phenotype in patients with SCN1A-related epilepsy. In patients with MCDs and a history of polymorphic seizures precipitated by fever, SCN1A gene testing should be performed before discussing any epilepsy surgery option, due to the possible implications for outcome.

Origins of temporal lobe epilepsy: febrile seizures and febrile status epilepticus

Temporal lobe epilepsy (TLE) and hippocampal sclerosis (HS) commonly arise following early-life long seizures, and especially febrile status epilepticus (FSE). However, there are major gaps in our knowledge regarding the causal relationships of FSE, TLE, HS and cognitive disturbances that hamper diagnosis, biomarker development and prevention. The critical questions include: What is the true probability of developing TLE after FSE? Are there predictive markers for those at risk? A fundamental question is whether FSE is simply a marker of individuals who are destined to develop TLE, or if FSE contributes to the risk of developing TLE. If FSE does contribute to epileptogenesis, then does this happen only in the setting of a predisposed brain? These questions are addressed within this review, using information gleaned over the past two decades from clinical studies as well as animal models.

Surgical and postmortem pathology studies: contribution for the investigation of temporal lobe epilepsy

Pathology studies in epilepsy patients bring useful information for comprehending the physiopathology of various forms of epilepsy, as well as aspects related to response to treatment and long-term prognosis. These studies are usually restricted to surgical specimens obtained from patients with refractory focal epilepsies. Therefore, most of them pertain to temporal lobe epilepsy (TLE) with mesial temporal sclerosis (MTS) and malformations of cortical development (MCD), thus providing information of a selected group of patients and restricted regions of the brain. Postmortem whole brain studies are rarely performed in epilepsy patients, however they may provide extensive information on brain pathology, allowing the analysis of areas beyond the putative epileptogenic zone. In this article, we reviewed pathology studies performed in epilepsy patients with emphasis on neuropathological findings in TLE with MTS and MCD. Furthermore, we reviewed data from postmortem studies and discussed the importance of performing these studies in epilepsy populations.

Etiology of hippocampal sclerosis: evidence for a predisposing familial morphologic anomaly

OBJECTIVE

We sought evidence of a hereditary component for hippocampal sclerosis (HS) by determining whether close relatives of probands with temporal lobe epilepsy (TLE) with HS also had asymptomatic HS or subtle variation in hippocampal morphology.

METHODS

First-degree relatives from 15 families in which probands had TLE with HS and 32 age- and sex-matched controls were included in the study. Left and right hippocampal volumes and T2 relaxometry were measured using 3-tesla MRI.

RESULTS

Thirty-two asymptomatic first-degree relatives and 3 relatives with a history of seizures or epilepsy were studied. None of the first-degree relatives had HS on visual analysis and T2 relaxation times were normal, excluding the presence of HS. Mean hippocampal volume was smaller (6.4%) in asymptomatic relatives (2.94 ± 0.27 cm(3), 95% confidence interval = 2.87-3.01) than in controls (3.14 ± 0.22 cm(3), 95% confidence interval = 3.09-3.19, p < 0.005); the effect was greater in relatives of probands with a positive family history of epilepsy. The relatives also had more asymmetric hippocampi (asymmetric index 0.92 ± 0.05) than controls (0.96 ± 0.03, p = 0.001).

CONCLUSIONS

Small asymmetric hippocampi in healthy relatives are likely to represent a familial developmental variant that may predispose to the formation of TLE with HS. The underlying histopathology of these small hippocampi is unknown. This observation may provide an imaging marker for future studies seeking susceptibility genes for HS.

Early developmental outcomes in children following convulsive status epilepticus: a longitudinal study

PURPOSE

Convulsive status epilepticus (CSE) is the most common pediatric neurologic emergency and is often associated with unfavorable neurodevelopmental outcomes. The early developmental trajectory of children following CSE has not been previously investigated, leaving a gap in our understanding of how these adverse long-term outcomes emerge.

METHODS

We prospectively recruited children aged between 1 and 42 months from a predefined geographic region of North London who had at least one episode of CSE and classified them as prolonged febrile seizures (PFS) or nonfebrile CSE. Neuropsychological and imaging investigations were conducted within 6 weeks of CSE (baseline) and were repeated a year later (follow-up). Neurodevelopment was assessed using the Bayley Scales of Infant Development III and compared to normally developing children. Predictors of neurodevelopmental scores at baseline and follow-up were investigated using regression analyses.

KEY FINDINGS

Of the 54 children that underwent investigations a mean of 38 days following CSE, 27 had PFS (mean age 18.4 months) and 27 had nonfebrile CSE (mean age 15.5 months). In addition, 17 healthy controls were assessed (mean age 20.49 months). Children with nonfebrile CSE had a worse developmental outcome than children with PFS (p < 0.002), despite there being no differences in seizure characteristics. In contrast to expectations, the PFS group had a worse developmental outcome than controls (p = 0.002). There were no significant differences in performance from baseline to 1-year follow-up for the 70.4% of children who provided data. Seizure characteristics were not shown to be significant predictors of performance.

SIGNIFICANCE

CSE is associated with developmental impairments within 6 weeks of the acute event that continue to be present a year onward. This is also true of PFS cases that under-perform relative to controls despite mean scores within the clinically normal range. The absence of a change in performance from baseline to follow-up as well as the lack of a relationship between seizure characteristics and developmental outcomes supports the notion that premorbid abilities may be overshadowing any direct effects of CSE itself on outcome.

Isolated febrile seizures are not associated with structural abnormalities of the limbic system

The nature of the relationship between childhood febrile seizures (CFSs) and temporal lobe epilepsy (TLE) remains unknown. The purpose of this study was to perform a comprehensive analysis of measures of structural changes of the hippocampus and limbic white matter to determine whether structural abnormalities previously demonstrated in TLE were present in adults with isolated CFS. Twenty-three adults with past CFS but no history of nonfebrile seizures and 21 controls underwent research MRI for measurement of volume, T2 and mean diffusivity of the hippocampus and fractional anisotropy of the fornix and cingulum. No significant group differences were found in any of the measured parameters. These findings suggest that structural abnormalities of the hippocampus and limbic white matter that have been demonstrated in TLE are not associated with isolated CFS.

Peritrigonal and temporo-occipital heterotopia with corpus callosum and cerebellar dysgenesis

OBJECTIVE

To describe a homogeneous subtype of periventricular nodular heterotopia (PNH) as part of a newly defined malformation complex.

METHODS

Observational study including review of brain MRI and clinical findings of a cohort of 50 patients with PNH in the temporo-occipital horns and trigones, mutation analysis of the FLNA gene, and anatomopathologic study of a fetal brain.

RESULTS

There were 28 females and 22 males. All were sporadic with the exception of an affected mother and son. Epilepsy occurred in 62%, cerebellar signs in 56%, cognitive impairment in 56%, and autism in 12%. Seventy percent were referred within the 3rd year of life. Imaging revealed a normal cerebral cortex in 76% and abnormal cortical folding in 24%. In all patients the hippocampi were under-rotated and in 10% they merged with the heterotopia. Cerebellar dysgenesis was observed in 84% and a hypoplastic corpus callosum in 60%. There was no gender bias or uneven gender distribution of clinical and anatomic severity. No mutations of FLNA occurred in 33 individuals examined. Heterotopia in the fetal brain revealed cytoarchitectonic characteristics similar to those associated with FLNA mutations; cortical pathology was not typical of polymicrogyria. Cerebellar involvement was more severe and the hippocampi appeared simple and under-rotated.

CONCLUSIONS

This series delineates a malformation complex in which PNH in the trigones and occipito-temporal horns is associated with hippocampal, corpus callosum, and cerebellar dysgenesis. This subtype of PNH is distinct from classic PNH caused by FLNA mutations.

MRI abnormalities following febrile status epilepticus in children: the FEBSTAT study

OBJECTIVE

The FEBSTAT study is a prospective study that seeks to determine the acute and long-term consequences of febrile status epilepticus (FSE) in childhood.

METHODS

From 2003 to 2010, 199 children age 1 month to 5 years presenting with FSE (>30 minutes) were enrolled in FEBSTAT within 72 hours of the FSE episode. Of these, 191 had imaging with emphasis on the hippocampus. All MRIs were reviewed by 2 neuroradiologists blinded to clinical details. A group of 96 children with first simple FS who were imaged using a similar protocol served as controls.

RESULTS

A total of 22 (11.5%) children had definitely abnormal (n = 17) or equivocal (n = 5) increased T2 signal in the hippocampus following FSE compared with none in the control group (p < 0.0001). Developmental abnormalities of the hippocampus were more common in the FSE group (n = 20, 10.5%) than in controls (n = 2, 2.1%) (p = 0.0097) with hippocampal malrotation being the most common (15 cases and 2 controls). Extrahippocampal imaging abnormalities were present in 15.7% of the FSE group and 15.6% of the controls. However, extrahippocampal imaging abnormalities of the temporal lobe were more common in the FSE group (7.9%) than in controls (1.0%) (p = 0.015).

CONCLUSIONS

This prospective study demonstrates that children with FSE are at risk for acute hippocampal injury and that a substantial number also have abnormalities in hippocampal development. Follow-up studies are in progress to determine the long-term outcomes in these children.

IL-1β induction and IL-6 suppression are associated with aggravated neuronal damage in a lipopolysaccharide-pretreated kainic acid-induced rat pup seizure model

OBJECTIVES

Reportedly, hippocampal neuronal degeneration by kainic acid (KA)-induced seizures in rats <14 days old was enhanced by lipopolysaccharide (LPS). This study was to test the hypothesis that cytokines such as interleukin (IL)-1β, IL-6 and tumor necrosis factor-α are associated with aggravated neuronal damage.

MATERIALS AND METHODS

Sixty male Sprague-Dawley, 14-day-old rats were used. Experiments were conducted in saline, LPS + saline, saline + KA and LPS + KA groups. Intraperitoneal LPS injections (0.04 mg/kg) were administered 3 h prior to KA injection (3 mg/kg).

RESULTS

The LPS + KA group showed a tendency toward shorter latency to seizure onset (p = 0.086) and significantly longer seizure duration (p < 0.05) compared with the KA group. Induction of the proconvulsant cytokine IL-1β in rat pup brains was significantly greater in the LPS + KA group compared to the KA group (38.8 ± 5.5 vs. 9.2 ± 1.0 pg/µg; p < 0.05); however, IL-6 levels were higher in the KA group than in the LPS + KA group (108.7 ± 6.8 vs. 60.9 ± 4.7 pg/µg; p < 0.05). The difference in tumor necrosis factor-α between the LPS + KA group and the KA group was insignificant (12.1 ± 0.6 vs. 10.9 ± 2.3 pg/µg; p = 0.64).

CONCLUSIONS

Our results showed an increase in the proconvulsant cytokine IL-1β and a decrease in a potentially neuroprotective cytokine, IL-6, in rat pups treated with LPS + KA. These results warrant further investigation into the possible role of IL-1β induction and IL-6 suppression in LPS-promoted neuronal damage.

Importance of genetic factors in the occurrence of epilepsy syndrome type: a twin study

Although there is strong evidence that genetic factors contribute to risk for epilepsy, their role in the determination of syndrome type is less clear. This study was undertaken to address this question. Information related to epilepsy was obtained from twins included in 455 monozygotic and 868 dizygotic pairs ascertained from population-based twin registries in Denmark, Norway and the United States. Syndrome type was determined based on medical record information and detailed clinical interviews and classified using the International Classification Systems for the Epilepsies and Epileptic Syndromes. Concordance rates were significantly increased in monozygotic versus dizygotic pairs for all major syndrome groups except localization-related cryptogenic epilepsy. Among generalized epilepsies, genetic factors were found to play an important role in the determination of childhood absence, juvenile absence, juvenile myoclonic, and idiopathic generalized epilepsy; and to a lesser degree for epilepsies with grand mal seizures on awakening. Among localization-related epilepsies, genetic factors contributed to risk for localization-related idiopathic and symptomatic syndromes overall, but did not appear to play an important role in determining risk for frontal, occipital or temporal lobe epilepsy. These results suggest that, while genetic factors contribute to risk for major syndrome types, determined when possible, their contribution to risk for localization-related syndrome sub-types, as defined by specific focality, may be modest.

Hippocampal size anomalies in a community-based cohort with childhood-onset epilepsy

OBJECTIVES

Epidemiologic evidence suggests the natural history of refractory mesial temporal lobe epilepsy is complicated, yet little is known about the hippocampus from the nontertiary center perspective.

METHODS

In a community-based cohort, individuals with nonsyndromic focal epilepsy with onset <16 years and controls had research MRI scans. Hippocampal (HC) volumes were manually measured, corrected for total brain volume, and converted to Z scores (Z(HC)) based on the controls' values. Volumes in cases and controls were compared.

RESULTS

Average volumes were not significantly different in cases with unknown cause (n = 117) relative to controls (n = 63). The group with structural and other conditions (n = 23) had significantly smaller volumes. Asymmetry (larger/smaller HC) did not vary among the 3 groups. Hippocampal variances were significantly larger in each epilepsy group relative to controls. In the unknown cause group, 25 (21%) had extreme() values: 15 (13%) with Z(HC) >1.96; 10 (9%) with Z(HC) <-1.96. By contrast, 2/63 (3%) controls had extreme values (p = 0.001). Within the unknown cause group, temporal lobe epilepsy (TLE) cases were more likely to have extreme hippocampal volumes than non-TLE (31% vs 15%, p = 0.03). Extreme volumes were generally interpreted as normal visually. These anomalies were not associated with seizure remission or pharmacoresistance.

CONCLUSIONS

Classic mesial TLE with hippocampal sclerosis is an uncommon finding in the general population. Volume anomalies, both large and small, are often bilateral. The significance of these findings is unclear; however, speculations regarding preexisting hippocampal pathology (e.g., dysplasia) as a factor in TLE and other neocortical epilepsies have been made by others.

Hippocampal damage after prolonged febrile seizure: one case in a consecutive prospective series

The factors that contribute to hippocampal damage as a sequela, and its frequency, in patients experiencing febrile status epilepticus, remain unknown. Of the 472 patients with febrile seizures admitted to our hospital between February 2004 and August 2008, 77 had prolonged seizures. Among them, 59 underwent magnetic resonance imaging (MRI). A 21-month-old girl showed hippocampal changes after her first episode of febrile status epilepticus. The seizure lasted about 35 min, with eye deviation to the right and ictal rhythmic discharges in the left hemisphere. MRI at 72 h after the seizure revealed high-signal intensities in T(2) and fluid-attenuated inversion recovery (FLAIR) images of the left hippocampus. Left hippocampal volume diminished over the next several months suggesting the occurrence of neuronal cell death. In no other cases, not even those with longer seizure durations, did significant hippocampal changes develop. The frequency of hippocampal damage was 1.7% in this case series. The involvement of factors other than seizure duration merits further study.

Increased temporolimbic cortical folding complexity in temporal lobe epilepsy

OBJECTIVE

Converging evidence suggests that abnormalities of brain development may play a role in the pathogenesis of temporal lobe epilepsy (TLE). As sulco-gyral patterns are thought to be a footprint of cortical development, we set out to quantitatively map folding complexity across the neocortex in TLE. Additionally, we tested whether there was a relationship between cortical complexity and features of hippocampal maldevelopment, commonly referred to as malrotation.

METHODS

To quantify folding complexity, we obtained whole-brain surface-based measures of absolute mean cortical curvature from MRI scans acquired in 43 drug-resistant patients with TLE with unilateral hippocampal atrophy, and 40 age- and sex-matched healthy controls. In patients, we correlated changes in cortical curvature with 3-dimensional measures of hippocampal positioning.

RESULTS

We found increased folding complexity in the temporolimbic cortices encompassing parahippocampal, temporopolar, insular, and fronto-opercular regions. Increased complexity was observed ipsilateral to the seizure focus in patients with left TLE (LTLE), whereas these changes were bilateral in patients with right TLE (RTLE). In both TLE groups, increased temporolimbic complexity was associated with increased hippocampal malrotation. We found tendencies for increased complexity in bilateral posterior temporal cortices in LTLE and contralateral parahippocampal cortices in RTLE to be predictive of unfavorable seizure outcome after surgery.

CONCLUSION

The anatomic distribution of increased cortical complexity overlapping with limbic seizure networks in TLE and its association with hippocampal maldevelopment further imply that neurodevelopmental factors may play a role in the epileptogenic process of TLE.

Classic hippocampal sclerosis and hippocampal-onset epilepsy produced by a single "cryptic" episode of focal hippocampal excitation in awake rats

In refractory temporal lobe epilepsy, seizures often arise from a shrunken hippocampus exhibiting a pattern of selective neuron loss called "classic hippocampal sclerosis." No single experimental injury has reproduced this specific pathology, suggesting that hippocampal atrophy might be a progressive "endstage" pathology resulting from years of spontaneous seizures. We posed the alternative hypothesis that classic hippocampal sclerosis results from a single excitatory event that has never been successfully modeled experimentally because convulsive status epilepticus, the insult most commonly used to produce epileptogenic brain injury, is too severe and necessarily terminated before the hippocampus receives the needed duration of excitation. We tested this hypothesis by producing prolonged hippocampal excitation in awake rats without causing convulsive status epilepticus. Two daily 30-minute episodes of perforant pathway stimulation in Sprague-Dawley rats increased granule cell paired-pulse inhibition, decreased epileptiform afterdischarge durations during 8 hours of subsequent stimulation, and prevented convulsive status epilepticus. Similarly, one 8-hour episode of reduced-intensity stimulation in Long-Evans rats, which are relatively resistant to developing status epilepticus, produced hippocampal discharges without causing status epilepticus. Both paradigms immediately produced the extensive neuronal injury that defines classic hippocampal sclerosis, without giving any clinical indication during the insult that an injury was being inflicted. Spontaneous hippocampal-onset seizures began 16-25 days postinjury, before hippocampal atrophy developed, as demonstrated by sequential magnetic resonance imaging. These results indicate that classic hippocampal sclerosis is uniquely produced by a single episode of clinically "cryptic" excitation. Epileptogenic insults may often involve prolonged excitation that goes undetected at the time of injury.

Amygdala and hippocampus enlargement during adolescence in autism

OBJECTIVE

The amygdala and hippocampus are key components of the neural system mediating emotion perception and regulation and are thought to be involved in the pathophysiology of autism. Although some studies in children with autism suggest that there is an enlargement of amygdala and hippocampal volume, findings in adolescence are sparse.

METHOD

We measured amygdala and hippocampus volume in a homogeneous group of adolescents with autism (12 through 18 years; n = 23) and compared them with an age-, sex-, and IQ-matched control group (n = 29) using a validated automated segmentation procedure in 1.5-T magnetic resonance images. All analyses were adjusted for total brain volume.

RESULTS

Repeated-measures analysis revealed a significant group x hemisphere x brain structure interaction (p = .038), even when corrected for total brain volume. Post-hoc analysis showed that the right amygdala and left hippocampus were significantly enlarged (p = .010; p = .015) in the autism compared with the control group. There were no significant correlations between age and amygdala or hippocampus volume.

CONCLUSIONS

The abnormal enlargement of the amygdala and hippocampus in adolescents with autism adds to previous findings of enlargement of these structures in children with autism. This may reflect increased activity of these structures and thereby altered emotion perception and regulation. Our results could therefore be interpreted in light of developmental adaptation of the autistic brain to a continuous overflow of emotional learning experiences.

Voxel-based morphometry of sporadic epileptic patients with mesiotemporal sclerosis

PURPOSE

In refractory temporal lobe epilepsy (rTLE), gray matter (GM) abnormalities are not confined to the hippocampus but also are found in extrahippocampal structures. Very recently we observed in mild TLE (mTLE) with or without mesiotemporal sclerosis (MTS), GM reductions in regions outside the presumed epileptogenic focus. To date, there are no studies that directly investigate whether whole-brain GM volume differs between rTLE and mTLE. Herein, we used optimized voxel-based morphometry (VBM) to identify GM abnormalities beyond the hippocampus in both rTLE and mTLE with evidence of MTS.

METHODS

Brain magnetic resonance imaging (MRI) and optimized VBM were performed in 19 unrelated patients with mTLE, 19 patients with rTLE, and 37 healthy controls. MRI diagnosis of MTS was based on the atrophy of the hippocampal formation and/or mesiotemporal hyperintensity on fluid-attenuated inversion recovery (FLAIR) or T(2) images, or both.

RESULTS

No patients (rTLE and mTLE) had generalized tonic-clonic or complex partial seizures for at least 3 weeks before scanning. Both mTLE and rTLE patients showed GM volume reduction of the bilateral thalamus, left hippocampus, and sensorimotor cortex compared with controls. No significant GM difference was found between rTLE and mTLE groups.

DISCUSSION

In both rTLE and mTLE, VBM shows GM reductions not confined to the hippocampus involving mainly the thalamus bilaterally. This finding together with the lack of significant GM differences between the two TLE groups supports the hypothesis that mTLE and rTLE might lie along a biologic continuum, suggesting a pathophysiologic role of the thalamus in partial epilepsy.

FLAIR signal and texture analysis for lateralizing mesial temporal lobe epilepsy

Standard magnetic resonance (MR) imaging analysis in several cases of mesial temporal lobe epilepsy (mTLE) either fail to show an identifiable hippocampal asymmetry or provide only subtle distinguishing features that remain inconclusive. A retrospective analysis of hippocampal fluid-attenuated inversion recovery (FLAIR) MR images was performed in cases of mTLE addressing, particularly, the mean and standard deviation of the signal and its texture. Preoperative T1-weighted and FLAIR MR images of 25 nonepileptic control subjects and 36 mTLE patients with Engel class Ia outcomes were analyzed. Patients requiring extraoperative electrocorticography (ECoG) with intracranial electrodes and thus judged to be more challenging were studied as a separate cohort. Hippocampi were manually segmented on T1-weighted images and their outlines were transposed onto FLAIR studies using an affine registration. Image intensity features including mean and standard deviation and wavelet-based texture features were determined for the hippocampal body. The right/left ratios of these features were used with a linear classifier to establish laterality. Whole hippocampal within-subject volume ratios were assessed for comparison. Mean and standard deviation of FLAIR signal intensities lateralized the site of epileptogenicity in 98% of all cases, whereas analysis of wavelet texture features and hippocampal volumetry each yielded correct lateralization in 94% and 83% of cases, respectively. Of patients requiring more intensive study with extraoperative ECoG, 17/18 were lateralized effectively by the combination of mean and standard deviation ratios despite a ratio of mean signal intensity near one in some. The analysis of mean and standard deviation of FLAIR signal intensities provides a highly sensitive method for lateralizing the epileptic focus in mTLE over that of volumetry or texture analysis of the hippocampal body.

Neuropathology of focal epilepsies: a critical review

A broad spectrum of structural lesions can be histopathologically identified in surgical brain specimens obtained from patients with focal, therapy-refractory epilepsies. In our experience with 4512 tissue samples collected at the German Neuropathological Reference Center for Epilepsy Surgery, three clinicopathological entities are most common: mesial temporal sclerosis (40%), long-term epilepsy-associated tumors (27%), and malformations of cortical development (13%). Notwithstanding, a systematic histopathological and molecular-genetic analysis is mandatory to unravel the underlying pathogenic mechanism of epilepsy-associated lesions and may contribute to our current understanding of pharmacoresistance and epileptogenesis. However, an interdisciplinary approach is necessary to further explore predictive parameters with respect to postsurgical seizure relief and memory impairment, and also to identify new pharmacological targets.

Resective surgery is possible in patients with temporal lobe epilepsy due to bilateral isolated hippocampal malformation

Various hippocampal malformations have been described in the context of widespread cortical malformations in patients with epilepsy. Isolated hippocampal malformations however are very rarely identified on MR imaging studies. Little is known about the epileptogenicity of these malformations and their pathologic appearance. We present a case with severe bilateral hippocampal malformations who underwent right temporal lobectomy due to intractable temporal lobe epilepsy. Postoperative examination of the resected hippocampus revealed abnormal shape of the dentate gyrus and an atypical convolution of the CA1 pyramidal cell-subicular layers. After surgery, the patient has been seizure free.

Sudden death, febrile seizures, and hippocampal and temporal lobe maldevelopment in toddlers: a new entity

Recently, we reported hippocampal and temporal lobe abnormalities in 5 toddlers with sudden unexplained death in childhood (SUDC). The association of these anomalies with a high incidence (40%) of individual/family histories of simple febrile seizures in the cases raised concern that febrile seizures can be associated with death. In a series of 64 toddlers with sudden death, we tested the hypothesis that an SUDC subset is characterized by hippocampal and temporal lobe maldevelopment and an individual and/or family history of simple familial seizures. Cases of sudden and unexplained death in children aged 1.0 to 5.9 years (median 1.7 years) were divided into groups based upon a history of febrile or nonfebrile seizures, familial febrile seizures, and autopsy classification of cause of death. Forty-nine of the 64 cases (77%) were classified as SUDC, of which 40% had an individual/family history of febrile seizures. Of the 26 SUDC cases with available hippocampal sections, 62% (16/26) had hippocampal and temporal lobe anomalies, including 82% (9/11) of cases with an individual/family history of febrile seizures. Cases with these anomalies were all found dead during a sleep period, typically in the prone (87%) position. We conclude that a potential new entity may account for the majority of SUDC in toddlers, defined by sleep-related death in the prone position, individual/family history of febrile seizures, and hippocampal and temporal lobe anomalies. The mechanism of death appears analogous to sudden death in (temporal lobe) epilepsy, with a putative unwitnessed seizure during sleep leading to airway occlusion and death. This study mandates further research into the potential link between simple febrile seizures and death.

History of simple febrile seizures is associated with hippocampal abnormalities in adults

SUMMARY BACKGROUND

It is unclear whether the hippocampal abnormality in temporal lobe epilepsy (TLE) is a consequence or the cause of afebrile or febrile seizures (FSs). We investigated whether hippocampal abnormalities are present in healthy adults>15 years after a simple FS.

METHODS

Eight healthy subjects (5 men) with a history of simple FS (FS+ group) and eight sex- and aged-matched control subjects (FS- group) were investigated by three MR methods: blinded visual inspection of the MRI pictures; automatic voxel-based volumetry; and T2 relaxation time measurements.

RESULTS

The mean total volume of the two hippocampi was 5.36 +/- 1.33 cm(3)in the FS+ group and 6.63 +/- 1.46 cm(3)in the FS- group (p = 0.069). The T2 values in the anterior part of the left hippocampus (p = 0.036) and in the middle part of the right hippocampus (p = 0.025) were elevated in the FS+ subjects. The mean volume of the right hippocampus was 3.05 +/- 0.8 cm(3)in the FS+ men and 4.05 +/- 0.48 cm(3)in the FS- men (p = 0.043). The mean total volume of the two hippocampi was 5.38 +/- 1.4 cm(3)in the FS+ men and 7.48 +/- 1.14 cm(3)in the FS- men (p = 0.043). There were three FS+ men in whom hippocampal abnormalities including hippocampal sclerosis (HS) and dysgenesis were observed on visual inspection.

CONCLUSIONS

A history of simple FS in childhood can be associated with hippocampal abnormalities in adults. These abnormalities are probably more pronounced in men. Simple FS may not be as a benign event as previously thought. Our findings suggest that hippocampal abnormalities associated with FS are not necessarily epileptogenic.

Mesial temporal lobe epilepsy: clinical and neuropathologic findings of familial and sporadic forms

PURPOSE

To evaluate the clinical and hippocampal histological features of patients with mesial temporal lobe epilepsy (MTLE) in both familial (FMTLE) and sporadic (SMTLE) forms.

METHODS

Patients with FMTLE (n = 20) and SMTLE (n = 39) who underwent surgical treatment for refractory seizures were studied at the University of São Paulo School of Medicine at Ribeirão Preto. FMTLE was defined when at least two individuals in a family had clinical diagnosis of MTLE. Hippocampi from all patients were processed for Nissl/HE and Timm's stainings. Both groups were compared for clinical variables, hippocampal cell densities, and intensity of supragranular mossy fiber staining.

RESULTS

There were no significant differences between FMTLE and SMTLE groups in the following: age at the surgery, age of first usual epileptic seizure, history of initial precipitating injury (IPI), age of IPI, latent period, ictal and interictal video-EEG patterns, presence of hippocampal atrophy and signal changes at MRI, and postoperative outcome. In addition, no differences were found in cell densities in hippocampal cornu ammonis subfields (CA1, CA2, CA3, CA4), fascia dentata, polymorphic region, subiculum, prosubiculum, and presubiculum. However, patients with SMTLE had greater intensity of mossy fiber Timm's staining in the fascia dentata-inner molecular layer (p< 0.05).

DISCUSSION

Patients with intractable FMTLE present a clinical profile and most histological findings comparable to patients with SMTLE. Interestingly, mossy fiber sprouting was less pronounced in patients with FMTLE, suggesting that, when compared to SMTLE, patients with FMTLE respond differently to plastic changes plausibly induced by cell loss, neuronal deafferentation, or epileptic seizures.

Major depression in temporal lobe epilepsy with hippocampal sclerosis: clinical and imaging correlates

PURPOSE

Refractory temporal lobe epilepsy (TLE) is often associated with hippocampal sclerosis (HS). Patients with major depression (MD) may also show structural abnormalities in the limbic system. Co-occurrence of TLE with HS and MD is not uncommon. We have investigated the clinical and morphological characteristics of TLE patients in relation to MD.

METHODS

34 TLE patients with HS were assessed at a Comprehensive Epilepsy Programme. All relevant clinical data were obtained, including the history of antecedent events to epilepsy. MD was diagnosed based on detailed psychiatric investigation. MRI was used to measure the volume and tissue signal (T2 relaxometry) of the hippocampus and amygdala. The imaging data were expressed as a percentage of the values obtained in a series of 55 controls.

RESULTS

A history of MD was present in 15 (44%) of 34 patients. Patients with MD had a longer duration of their epilepsy (p<0.05) and a lower frequency of antecedent events (13% with MD, 58% without MD, p<0.05). Both groups had a similar degree of ipsilateral HS (small hippocampal volume, increased hippocampal T2 relaxation time) and demonstrated bilateral amygdaloid atrophy. However, the contralateral amygdala showed lower signal in the presence of MD (97 (9) ms; no MD 103 (8) ms; ANCOVA, p = 0.02).

CONCLUSION

The integrity of the amygdala may influence mood disturbances in TLE patients with HS, as depression was associated with a relative preservation of the contralateral amygdala. In contrast, hippocampal abnormalities were not related to the presence of depression.

Early seizures: causal events or predisposition to adult epilepsy?

Past studies have been unable to confirm whether early seizures predispose to epilepsy in adults. Seizures in infancy were classically thought to cause brain lesions that led to epilepsy in adulthood. However, these infants were not thought to have epilepsy, but acute events that included seizures. Accumulating evidence suggests that early seizures may be associated with, or cause, brain damage; or alternatively, they may be the first expression of a genetic or lesional predisposition to epilepsy. The course of early seizures ranges from transient to life-long, depending on epilepsy syndrome, causes, and treatment. The main factors that determine late or persisting epilepsy after the occurrence of early seizures are protracted seizures, tonic seizures, and involvement of mesial temporal structures. A developmental approach to seizure disorders will aid understanding of epilepsy in adults and improve the design of antiepileptic agents for children and adults.

Interobserver and within-subject variances of T2-relaxation time and 1H-metabolite ratios in the normal hippocampus

PURPOSE

To investigate the magnetic resonance (MR) reproducibility of normal hippocampal volume (HV), temporal lobe volume (TLV), transversal relaxation time (T(2)) and (1)H-MR spectroscopy ((1)H-MRS) metabolite ratios.

MATERIALS AND METHODS

Two sets of HV, TLV, T(2) and MR spectroscopic metabolite signal ratios were determined in 27 healthy volunteers. HV and TLV were measured with a T(1)-weighted MR sequence; whereas T(2) measurements were performed with conventional spin-echo (CSE) and fast spin-echo (FSE) MR imaging sequences. The interobserver and within-subject variances of T(2) measurements were estimated.

RESULTS

Estimated right and left HV coefficients of variation (CV)=0.13. FSE T(2) measurements showed no significant differences in the interobserver (CV=0.02) and within-subject variances (CV=0.02). Measurements showed no differences in the interobserver (CV=0.02) and within-subject (CV=0.04) variances for the CSE T(2) of the right and left hippocampi. Metabolite ratios between N-acetyl aspartate (NAA) and creatine (Cr), choline (Cho) and creatine, and NAA and choline plus creatine (Cho + Cr) for the right hippocampus were 2.29+/-0.19, 1.52+/-0.14 and 0.91+/-0.05, respectively. Metabolite ratios for the left hippocampus were 2.18+/-0.10, 1.48+/-0.10 and 0.88+/-0.06, respectively.

CONCLUSIONS

HV, TLV, T(2) and (1)H MRS metabolite ratio measurements showed fair reproducibility with small CVs, and no differences in the interobserver and within-subject variances, including no differences between right and left TLV, and in the right and left T(2).