The hippocampus: normal anatomy and pathology

HIPPOCAMPUS CELL DISORDERS AND NEUROSENSORY TESTS IN MICE (Mus musculus) DUE TO INDUCTION OF EXCESS SODIUM CHLORIDE

Salt or sodium chloride (NaCl) is an additive to give food a salty taste. The use of salt in everyday life is difficult to avoid. Salt has both good and bad effects on the body. The electrolyte content of salt can help launch metabolism in the body, whereas if the body contains too much salt it will cause heart attacks and hypertension. The dose of salt consumption that has been set by the government is 5g/day. This study was conducted to examine the effect of consuming excessive sodium chloride (NaCl) on the ability to smell and to what extent it damages cells in the hippocampus of mice (Mus musculus). The method of this study was CRD (completely randomized design) with 6 replications, 1 group control and 3 repetitions induced by sodium chloride (NaCl) is 260mg/gBB (P1), 520mg/gBB (P2), and 780mg/gBB (P3). The parameters of this study are neurosensory coordination in the form of olfactory response of mice (Mus musculus) to ammonia and cell disruption in the hippocampus (DG & CA) which were observed by histological preparations of Hematoxylin eosin (HE) staining. The results of this study indicate the presence of olfactory disorders in mice (Mus musculus) and cell death in the hippocampus also increased due to excessive sodium chloride (NaCl) induction. The more salt is consumed in daily life, it will disrupt the cells in the hippocampus.

Hippocampal sulcal cavities: prevalence, risk factors and association with cognitive performance. The SMART-Medea study and PREDICT-MR study

Hippocampal sulcal cavities (HSCs) are frequently observed on MRI, but their etiology and relevance is unclear. HSCs may be anatomical variations, or result from pathology. We assessed the presence of HSCs, and their cross-sectional association with demographics, vascular risk factors and cognitive functioning in two study samples. Within a random sample of 92 patients with vascular disease from the SMART-Medea study (mean age = 62, SD = 9 years) and 83 primary care patients from the PREDICT-MR study (mean age = 62, SD = 12 years) one rater manually scored HSCs at 1.5 T 3D T1-weighted coronal images blind to patient information. We estimated relative risks of age, sex and vascular risk factors with presence of HSCs using Poisson regression with log-link function and robust standard errors adjusted for age and sex. Using ANCOVA adjusted for age, sex, and education we estimated the association of the number of HSCs with memory, executive functioning, speed, and working memory. In the SMART-Medea study HSCs were present in 65% and in 52% in the PREDICT-MR study (χ2 = 2.99, df = 1, p = 0.08). In both samples, no significant associations were observed between presence of HSCs and age (SMART-Medea: RR = 1.00; 95%CI 0.98-1.01; PREDICT-MR: RR = 1.01; 95%CI 0.99-1.03), sex, or vascular risk factors. Also, no associations between HSCs and cognitive functioning were found in either sample. HSCs are frequently observed on 1.5 T MRI. Our findings suggest that, in patients with a history of vascular disease and primary care attendees, HSCs are part of normal anatomic variation of the human hippocampus rather than markers of pathology.

Development of a contouring guide in three different head set-ups for hippocampal sparing radiotherapy: a practical approach

BACKGROUNDS

Irradiation of the hippocampus plays a role in neurocognitive toxicity. Its delineation is complex and in practice different head position can vary hippocampus morphology on axial images; so atlas in a single standard position can result ineffective to describe different hippocampal morphologies in different head set-up. The purpose of our study was to develop a guide based on magnetic resonance imaging for hippocampus delineation in three different head set-ups.

MATERIALS AND METHODS

Three patients were selected to elaborate our guide. Patients were submitted to a planning computed tomography of the brain district in different head positions: 1° patient in neutral, 2° patient in over-extended and 3° patient in head hypo-extended position; axial images of 2-mm thickness were obtained. Computed tomography images were fused with diagnostic brain magnetic resonance images; then hippocampus was delineated according to RTOG atlas. Contours were revised by two neuro-radiologists with >5-year expertise in neuroimaging.

RESULTS

A guide was developed for each of three head positions considered. RTOG atlas provided an easy and reliable guide for hippocampus delineation in neutral position of the head. Discrepancies were observed in cranial and caudal limit in case of head over/hypo-extension, as well as in hippocampal morphology near the encephalic trunk where hippocampus takes an oblong shape in over-extended set-up, and short and stocky in hypo-extension.

CONCLUSION

Our guide can represent a useful tool for hippocampal delineation in clinical practice and for different anatomic variations due to different head positions. Certainly, it should be validated in practice.

Bilateral internuclear and internal ophthalmoplegia due to artery of Percheron infarction

The artery of Percheron (AOP) infarction always manifests as paramedian bilateral thalamic infarcts and might present as paramedian midbrain infarcts. Despite the limited MRA evaluation, due to small size of the artery, careful evaluation of the patient's history, the clinical presentation with imaging findings can facilitate the proper diagnosis.

An unwritten anatomy lesson: The influence of Roman clothing on neuroanatomical terminology: In memoriam Albert L. Rhoton, Jr. (1932-2016)

Throughout the centuries, anatomists attempting to denominate the new structures they discovered have found inspiration in the civilization of ancient Rome and the clothing worn by its citizens. This aricle presents the origins of seven neuroanatomical terms, fimbria, velum, funiculus, lemniscus, corona, splenium, and cingulum, inspired by the clothing and jewellery of Roman women and the military attire of Roman soldiers. Thus, through their apparel, the Romans influenced the Terminologia Anatomica and "clothed" the structures of the brain and spinal cord, making them immortal. Clin. Anat. 29:685-690, 2016. © 2016 Wiley Periodicals, Inc.

Sex differences and laterality of insulin receptor distribution in developing rat hippocampus: an immunohistochemical study

This study aimed to compare the regional distribution of insulin receptor in various portions of newborn rat hippocampus on postnatal days 0 (P0), 7 (P7), and 14 (P14) between male/female and right/left hippocampi. We found that the number of insulin receptor (InsR)-immunoreactive-positive (InsR+) cells in CA1 continued to increase until P7 and remained unchanged thereafter. A marked increase in distribution of InsR+ cells in CA3 from P0 to P14 was observed, although there was a significant decline in the number of InsR+ cells in dentate gyrus (DG) at the same time. No differences between the right/left and male/female hippocampi were detected at P0 (P > 0.05). Seven-day-old female rats showed a higher number of labeled cells in the left than in the right hippocampus. Moreover, the differences between the number of InsR+ cells in area CA1 and CA3 were statistically significant between males and females (P < 0.05). At P14, the number of InsR+ cells was significantly higher in CA1 and DG of males, especially in the right one (P < 0.05). These results indicate the existence of a differential distribution pattern of InsR between the left/right and male/female hippocampi. Together with other mechanisms, these differences may underlie sexual dimorphism and left/right asymmetry in the hippocampus.

Gender differences and lateralization in the distribution pattern of insulin-like growth factor-1 receptor in developing rat hippocampus: an immunohistochemical study

Numerous investigators have provided data supporting essential roles for insulin-like growth factor-I (IGF-I) in development of the brain. The aim of this study was to immunohistochemically determine the distinct regional distribution pattern of IGF-1 receptor (IGF-IR) expression in various portions of newborn rat hippocampus on postnatal days 0 (P0), 7 (P7), and 14 (P14), with comparison between male/female and right/left hippocampi. We found an overall significant increase in distribution of IGF-IR-positive (IGF-IR+) cells in CA1 from P0 until P14. Although, no marked changes in distribution of IGF-IR+ cells in areas CA2 and CA3 were observed; IGF-IR+ cells in DG decreased until P14. The smallest number of immunoreactive cells was present in CA2 and the highest number in DG at P0. Moreover, in CA1, CA3, and DG, the number of IGF-IR+ cells was markedly higher in both sides of the hippocampus in females. Our data also showed a higher mean number of IGF-IR+ cells in the left hippocampus of female at P7. By contrast, male pups showed a significantly higher number of IGF-IR+ cells in the DG of the right hippocampus. At P14, the mean number of immunoreactive cells in CA1, CA3, and DG areas found to be significantly increased in left side of hippocampus of males, compared to females. These results indicate the existence of a differential distribution pattern of IGF-IR between left-right and male-female hippocampi. Together with other mechanisms, these differences may underlie sexual dimorphism and left-right asymmetry in the hippocampus.

Synergistic effects of sodium butyrate, a histone deacetylase inhibitor, on increase of neurogenesis induced by pyridoxine and increase of neural proliferation in the mouse dentate gyrus

We previously observed that pyridoxine (vitamin B(6)) significantly increased cell proliferation and neuroblast differentiation without any neuronal damage in the hippocampus. In this study, we investigated the effects of sodium butyrate, a histone deacetylase (HDAC) inhibitor which serves as an epigenetic regulator of gene expression, on pyridoxine-induced neural proliferation and neurogenesis induced by the increase of neural proliferation in the mouse dentate gyrus. Sodium butyrate (300 mg/kg, subcutaneously), pyridoxine (350 mg/kg, intraperitoneally), or combination with sodium butyrate were administered to 8-week-old mice twice a day and once a day, respectively, for 14 days. The administration of sodium butyrate significantly increased acetyl-histone H3 levels in the dentate gyrus. Sodium butyrate alone did not show the significant increase of cell proliferation in the dentate gyrus. But, pyridoxine alone significantly increased cell proliferation. Sodium butyrate in combination with pyridoxine robustly enhanced cell proliferation and neurogenesis induced by the increase of neural proliferation in the dentate gyrus, showing that sodium butyrate treatment distinctively enhanced development of neuroblast dendrites. These results indicate that an inhibition of HDAC synergistically promotes neurogenesis induced by a pyridoxine and increase of neural proliferation.

Hippocampal sulcal cavities: prevalence, risk factors and relationship to memory impairment

While hippocampal volumes have been extensively examined in neuropsychiatric disorders and ageing, small areas of signal variation within the hippocampus commonly observed on MRI, described as hippocampal sulcal cavities (HSCs), have received less attention. We review the published literature on HSCs to examine their prevalence, putative aetiological factors such as hypertension, and possible cognitive correlates. HSCs were reported in 77% (66% weighted mean) of patients with memory disorders and 48% (47% weighted mean) of controls, and the prevalence increased with age in healthy subjects (r=0.64, p=0.047). A number of studies reported hypertension as a risk factor, and related their presence to poorer memory function. Further work is needed to fully understand the clinical significance of these lesions.

High-resolution 7T MRI of the human hippocampus in vivo

PURPOSE

To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging.

MATERIALS AND METHODS

Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16-channel head coil. Sequences included a full field of view T1-weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA)=08:58), T2*-weighted 2D fast field echo (T2*W 2D FFE: TA=05:20), and susceptibility-weighted imaging (SWI: TA=04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.

RESULTS

T1W 3D TFE images with 700 microm isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in-plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in-plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus.

CONCLUSION

In vivo 7T MR imaging can take advantage of higher signal-to-noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy.

High-resolution 7T MRI of the human hippocampus in vivo

PURPOSE

To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging.

MATERIALS AND METHODS

Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16-channel head coil. Sequences included a full field of view T1-weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA)=08:58), T2*-weighted 2D fast field echo (T2*W 2D FFE: TA=05:20), and susceptibility-weighted imaging (SWI: TA=04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.

RESULTS

T1W 3D TFE images with 700 microm isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in-plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in-plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus.

CONCLUSION

In vivo 7T MR imaging can take advantage of higher signal-to-noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy.

A reliable method for measurement and normalization of pediatric hippocampal volumes

A robust standardized method for segmentation, quantification, and normalization of pediatric hippocampal volumes using magnetic resonance imaging is presented. The method will find application in time course measurements of hippocampal volumes in pediatric patients who suffer from temporal lobe epilepsy and was tested prospectively on six control patients (13-60 mo of age). The un-normalized hippocampal volumes obtained using our segmentation method ranged from 3.85 to 6.38 mL, in agreement with previously published results. Inter- and intraobserver variability of the segmentation method was determined to be 13.3% and 2.8%, respectively. Four different methods of volume normalization were tested. Normalization is required to adjust for age-related increases in hippocampal volume. The normalization approach that seemed to compensate best for growth-related hippocampal volume changes was based on a simple estimation of intracranial volumes. This is the first report of a consistent and reliable method for segmentation and normalization of hippocampi from pediatric patients that can be used to study the progression of neurologic diseases in children.

A new method for the in vivo volumetric measurement of the human hippocampus with high neuroanatomical accuracy

Accurate and reproducible in vivo measurement of hippocampal volumes using magnetic resonance (MR) imaging is complicated by the morphological complexity of the structure. Additionally, separation of certain parts of the hippocampus from the adjacent brain structures on MR images is sometimes very difficult. These difficulties have led most investigators to either use arbitrary landmarks or to exclude certain parts of the structure from their measurements. Based on three-dimensional MR data, we have developed a reliable in vivo volumetric measurement of the human hippocampus. In contrast to most of the previously described volumetric MR-based methods, we aimed to sample the entire hippocampal formation using its true anatomical definition. This was accomplished by relying on the capacity of the BRAINS software to simultaneously visualize in multiple planes, to "telegraph" tracings or cursor position from one plane to another, and to simultaneously rely on multispectral data from three different image sets (T1, T2, and tissue classified). The methods for identifying boundaries and measuring the hippocampal volume are described. The method has excellent reliability, sensitivity, and specificity. The method may be of use in studies of structure-function relationships in neuropsychiatric disorders such as schizophrenia, temporal lobe epilepsy, and Alzheimer's disease. Future work will use these measurements as training data for a neural net-based technique to identify the anatomical boundaries automatically.