Evaluation of hippocampal infolding angle and incomplete hippocampal inversion in pediatric patients with epilepsy and febrile seizures

Clinicoradiological Profile of Incomplete Hippocampal Inversion Diagnosed on MR Neuroimaging

Background and Purpose

Incomplete hippocampal inversion (IHI) is a developmental failure of normal hippocampal inversion. Previous studies have described IHI in epilepsy and non-epilepsy subjects. IHI has also been reported with malformations of cortical development (MCDs) and corpus callosal agenesis that have association with neuropsychiatric disorders such as autism spectrum disorder (ASD). This study aims to describe the clinical profile of magnetic resonance imaging (MRI)-diagnosed IHI.

Materials and Methods

We studied patients with IHI who were identified after a retrospective review of the MRI archives of the past 3 years. The MRI findings of partial and total IHI were included. The clinical profiles associated with IHI were classified into epilepsy and non-epilepsy categories.

Results

A retrospective review of MRI done over 3 years revealed 54 cases of IHI (32 left-sided, 20 bilateral, and 2 isolated right-sided), and out of 74 IHI, 59 were of total type and 15 partial. Thirty-six subjects (61.1%) had epilepsy (9 with neurodevelopmental problems), 17 subjects (31.5%) had ASD, and 4 subjects (7.4%) had only neurodevelopmental disorders. MCDs were seen in 7 (12.9%): polymicrogyria (4), periventricular heterotopia (2), and pachygyria (1). Hippocampal volume loss was seen in 10, and contralateral mesial temporal sclerosis was seen in 2 patients.

Conclusion

Hippocampal inversion has been reported in MRI scans of patients with epilepsy, ASD, MCDs, and many other related disorders. Further studies are required to know its occurrence among patients who get MRI scans due to many other disorders such as headaches, psychiatric disorders, minor hear trauma, and perinatal insults. If possible, studies among normal populations also need to be done.

Hippocampal rotation is associated with ventricular atrial size

BACKGROUND

Fetal ventriculomegaly is a source of apprehension for expectant parents and may present prognostic uncertainty for physicians. Accurate prenatal counseling requires knowledge of its cause and associated findings as the differential diagnosis is broad. We have observed an association between ventriculomegaly and incomplete hippocampal inversion.

OBJECTIVE

To determine whether ventricular size is related to incomplete hippocampal inversion.

MATERIALS AND METHODS

We retrospectively evaluated pre- and postnatal brain MRIs in normal subjects (mean GA, 31 weeks; mean postnatal age, 27 days) and patients with isolated ventriculomegaly (mean GA, 31 weeks; mean postnatal age, 68 days) at a single academic medical center. Lateral ventricular diameter, multiple qualitative and quantitative markers of hippocampal inversion, and evidence of intraventricular hemorrhage were documented.

RESULTS

Incomplete hippocampal inversion and ventricular size were associated in both normal subjects (n=51) and patients with ventriculomegaly (n=32) (P<0.05). Severe ventriculomegaly was significantly associated with adverse clinical outcome in postnatal (P=0.02) but not prenatal (P=0.43) groups. In all additional cases of isolated ventriculomegaly, clinical outcome was normal over the time of assessment (mean 1±1.9 years; range 0.01 to 10 years).

CONCLUSION

Lateral ventricular atrial diameter and incomplete hippocampal inversion are associated. Less hippocampal inversion correlates with larger atria. For every 1-mm increase in fetal ventricular size, the odds of incomplete hippocampal inversion occurring increases by a factor of 1.6 in normal controls and 1.4 in patients with ventriculomegaly.

Incomplete hippocampal inversion in patients with mutations in genes involved in sonic hedgehog signaling

Sonic hedgehog (Shh) signaling pathways are known to play an important role in the morphological development of the hippocampus in vivo, but their actual roles in humans have not been clarified. Hypothalamic hamartoma (HH) is known to be associated with germline or somatic gene mutations of Shh signaling. We hypothesized that patients with HH and mutations of Shh-related genes also show hippocampal maldevelopment and an abnormal hippocampal infolding angle (HIA). We analyzed 45 patients (age: 1-37 years) with HH who underwent stereotactic radiofrequency thermocoagulation and found Shh-related gene mutations in 20 patients. In addition, 44 pediatric patients without HH (age: 2-25 years) who underwent magnetic resonance imaging (MRI) examinations under the same conditions during the same period were included in this study as a control group. HIA evaluated on MRI was compared between patients with gene mutations and the control group. The median HIA at the cerebral peduncle slice in patients with the gene mutation was 74.36° on the left and 76.11° on the right, and these values were significantly smaller than the corresponding values in the control group (80.46° and 80.56°, respectively, p < 0.01). Thus, mutations of Shh-related genes were correlated to incomplete hippocampal inversion. The HIA, particularly at the cerebral peduncle slice, is a potential indicator of abnormalities of the Shh-signaling pathway.

The changing landscape in epilepsy imaging: Unmasking subtle and unique entities

Dramatic changes have occurred recently in the field of epilepsy, including a fundamental shift in the etiology of epileptogenic substrates found at surgery. Hippocampal sclerosis is no longer the most common etiology found at epilepsy surgery and this decrease has been associated with an increase in the incidence of focal cortical dysplasia and encephaloceles. Significant advances have been made in molecular biology and genetics underlying the basis of malformations of cortical development, and our ability to detect epileptogenic abnormalities with MR imaging has markedly improved. This article begins with a discussion of these trends and reviews imaging techniques essential for detecting of subtle epilepsy findings. Representative examples of subtle imaging findings are presented, which are often overlooked but should not be missed. These include temporal lobe encephaloceles, malformations of cortical development (and especially focal cortical dysplasia), hippocampal sclerosis, hippocampal malformation (also known as HIMAL), ulegyria, autoimmune encephalitis, and Rasmussen's encephalitis. Recent findings on the pathophysiology and genetic underpinnings of several causes of localization-related epilepsy are incorporated. For instance, it has been recently found that focal cortical dysplasia IIb, tuberous sclerosis, hemimegalencephaly, and gangliogliomas are all the result of mutations of the mTOR pathway for cell growth.

Incomplete hippocampal inversion: diagnostic criteria and effect on epilepsy, seizure localization and therapeutic outcome in children

PURPOSE

Elaborate a simple Magnetic Resonance Imaging (MRI)-based score to define Incomplete Hippocampal Inversion (IHI) in children (Phase 1), and evaluate the relation of IHI with (A) epilepsy, (B) seizure localization and (C) therapeutic response in a paediatric population (Phase 2).

METHODS

In Phase 1, incompletely inverted hippocampi were matched to completely inverted hippocampi. Multiple qualitative and quantitative hippocampal and extra-hippocampal features were evaluated in coronal-oblique T1-weighted (T1W) and coronal T2-weighted (T2W) images. Multivariate analysis was performed to elaborate the MRI-based score to define IHI. In Phase 2, epilepsy patients were matched to controls, and the T1W and T2W scores were applied. Multivariate analysis was performed to assess the relation of IHI and epilepsy, seizure localization and therapeutic response.

RESULTS

The hippocampal diameter ratio and parahippocampal angle in the coronal-oblique T1-weighted images, and the hippocampal diameter ratio and collateral sulcus depth in the coronal T2-weighted images predicted IHI in Phase 1. Simple and practical imaging-based scores were developed and are available on the website: https://ihiscore.netlify.app/. The Area Under the Receiver Operating Characteristic Curve of the T1W and T2W scores were, respectively, 0.965 and 0.983. In Phase 2, IHI independently predicted epilepsy (OR = 3.144, 95% CI = 1.981-4.991, p < 0.001), temporal lobe epilepsy (OR = 4.237, 95% CI = 1.586-11.318, p = 0.004), and drug resistant epilepsy (OR = 7.000, 95% CI = 2.800-17.500, p < 0.001).

CONCLUSION

The association between IHI and temporal lobe epilepsy (and the lack of association with extra-temporal epilepsy) favours the possibility of a relation between IHI and the pathophysiology of seizures in epileptic patients. Furthermore, IHI is a potential prognostic marker for therapeutic response in epilepsy.

Hippocampal Malrotation Could Be Less Significant in Epilepsy Caused by Focal Cortical Dysplasia Type I and Type II

Objectives

Debates over the relationship between hippocampal malrotation (HIMAL) and epilepsy continue without consensus. This study explores the role of HIMAL in a cohort of epilepsy caused by focal cortical dysplasia (FCD).

Methods

In this study, 90 patients with epilepsy caused by FCD type I and type II and 48 healthy adults underwent a 3 Tesla MRI following a dedicated epilepsy protocol for the analysis of the prevalence and morphologic features of HIMAL. In addition, numerous clinical characteristics and hippocampal volumes were evaluated.

Results

The cohort included a total of 90 patients (32 were HIMAL, 58 were non-HIMAL). Among these patients, 32 (35.6%) had HIMAL (22 left, four right, and six bilateral), which did not differ from the 48 controls, where 16 (33.3%) had HIMAL (12 left, two right, and two bilateral). Neither the quantitative features of HIMAL (diameter ratio, dominant inferior temporal sulcus height ratio, medial distance ratio, dominant inferior temporal sulcus angle, and parahippocampal angle), nor the accompanying characteristics of HIMAL (vertical dominant inferior temporal sulcus, enlarged temporal horn, and a low position of ipsilateral fornix) showed differences between patients with FCD and controls. No statistical difference in the clinical characteristics between FCD patients with HIMAL and those without was found. Neither the side nor the existence of HIMAL was correlated with the lateralization and location of FCD. As to the hippocampal volume, there was no difference between FCD patients with HIMAL and those without.

Conclusion

Hippocampal malrotation is a common morphologic variant in healthy controls as well as in patients with epilepsy caused by FCD type I and type II. Hippocampal malrotation could be less significant in epilepsy caused by FCD type I and type II.

KCC2 rs2297201 Gene Polymorphism Might be a Predictive Genetic Marker of Febrile Seizures

Introduction: Febrile seizures (FS) are the most common neurological disease in childhood. The etiology of FS is the subject of numerous studies including studies regarding genetic predisposition. Aim: The aim of the study was to analyze the association of TRPV1 rs222747 and KCC2 rs2297201 gene polymorphisms with the occurrence of FS. Materials and Methods: The study included 112 patients diagnosed with FS classified as simple febrile seizures (SFS) or complex febrile seizures (CFS). We analyzed selected polymorphisms of KCC2 and TRPV1 genes using the Real-time PCR method. Results: The CT and TT genotypes of the rs2297201 polymorphism of the KCC2 gene are significantly more common in the group of children with FS than the control group (p = .002) as well as the allele T of this polymorphism (p = .045). Additionally, genotypes CT and TT of the rs2297201 polymorphism of the KCC2 gene were more frequent in the group of children with CFS compared to the control group (p < .001). Different genotypes and alleles of the rs222747 TRPV1 gene polymorphism were not associated with the occurrence of febrile seizures or epilepsy, nor were associated with the occurrence of a particular type of febrile seizure (p = .252). Conclusion: These results indicate that the CT and TT genotypes, as well as the T allele of rs2297201 polymorphism of the KCC2 gene, could be a predisposing factor for the FS, as well as the occurrence of CFS.

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.

Incomplete hippocampal inversion in schizophrenia: prevalence, severity, and impact on hippocampal structure

Incomplete hippocampal inversion (IHI) is an anatomical variant of the human brain resulting from an arrest in brain development, especially prevalent in the left hemisphere. We hypothesized that IHI is more common in schizophrenia and contributes to the well-known hippocampal structural differences. We studied 199 schizophrenia patients and 161 healthy control participants with 3 T MRI to establish IHI prevalence and the relationship of IHI with hippocampal volume and asymmetry. IHI was more prevalent (left hemisphere: 15% of healthy control participants, 27% of schizophrenia patients; right hemisphere: 4% of healthy control participants, 10% of schizophrenia patients) and more severe in schizophrenia patients compared to healthy control participants. Severe IHI cases were associated with a higher rate of automated segmentation failure. IHI contributed to smaller hippocampal volume and increased R > L volume asymmetry in schizophrenia. The increased prevalence and severity of IHI supports the neurodevelopmental model of schizophrenia. The impact of this developmental variant deserves further exploration in studies of the hippocampus in schizophrenia.

Incomplete hippocampal inversion and epilepsy: A systematic review and meta-analysis

OBJECTIVE

Incomplete hippocampal inversion (IHI) is a relatively frequent radiological finding at visual inspection in both epilepsy and healthy controls, but its clinical significance is unclear. Here, we systematically retrieve and assess the association between epilepsy and IHI using a meta-analytic approach. Additionally, we estimate the prevalence of IHI in patients with malformation of cortical development (MCD).

METHODS

We systematically searched two databases (Embase and PubMed) to identify potentially eligible studies from their inception to December 2019. For inclusion, studies were population-based, case-control, observational studies reporting on epilepsy and IHI. The risk of developing epilepsy in IHI (estimated with odds ratio [ORs]) and the frequency of IHI among patients with MCD are provided.

RESULTS

We screened 3601 records and assessed eligibility of 2812 full-text articles. The final material included 13 studies involving 1630 subjects. Seven studies (1329 subjects: 952 epileptic and 377 nonepileptic) were included for the estimation of the risk of developing epilepsy in the presence of IHI. The estimated OR of active epilepsy in IHI was 1.699 (95% confidence interval = 0.880-3.281), with moderate heterogeneity across studies (I²  = 71%). Seven studies (591 patients) provided information about the frequency of IHI in MCD. Up to one third of patients with MCD (27.9%) presented coexistent IHI.

SIGNIFICANCE

The present findings confirm that IHI is commonly observed in patients with MCD especially in periventricular nodular heterotopia or polymicrogyria. However, the estimated OR indicates overall weak increased odds of epilepsy in people with IHI, suggesting that the presence of isolated IHI cannot be considered a strong independent predictor for epilepsy development. Clear-cut neuroradiological criteria for IHI and advanced postprocessing analyses on structural magnetic resonance imaging scans are recommended to highlight differences between epileptogenic and nonepileptogenic IHI.

Febrile seizures: an overview

Background

Febrile seizures are the most common neurologic disorder in childhood. Physicians should be familiar with the proper evaluation and management of this common condition.

Objective

To provide an update on the current understanding, evaluation, and management of febrile seizures.

Methods

A PubMed search was completed in Clinical Queries using the key terms ‘febrile convulsions’ and ‘febrile seizures’. The search strategy included meta-analyses, randomized controlled trials, clinical trials, observational studies, and reviews.

Results

Febrile seizures, with a peak incidence between 12 and 18 months of age, likely result from a vulnerability of the developing central nervous system to the effects of fever, in combination with an underlying genetic predisposition and environmental factors. The majority of febrile seizures occur within 24 hours of the onset of the fever. Febrile seizures can be simple or complex. Clinical judgment based on variable presentations must direct the diagnostic studies which are usually not necessary in the majority of cases. A lumbar puncture should be considered in children younger than 12 months of age or with suspected meningitis. Children with complex febrile seizures are at risk of subsequent epilepsy. Approximately 30–40% of children with a febrile seizure will have a recurrence during early childhood. The prognosis is favorable as the condition is usually benign and self-limiting. Intervention to stop the seizure often is unnecessary.

Conclusion

Continuous preventative antiepileptic therapy for the prevention of recurrent febrile seizures is not recommended. The use of intermittent anticonvulsant therapy is not routinely indicated. Antipyretics have no role in the prevention of febrile seizures.