Precommissural fornix in the human brain: a diffusion tensor tractography study

MR imaging findings of stage I intravenous leiomyomatosis: a retrospective single-center study in 19 cases

OBJECTIVES

The aim was to explore the magnetic resonance imaging (MRI) features of stage-I intravenous leiomyomatosis (IVL).

MATERIALS AND METHODS

From January 2019 to January 2023, clinical, pathological, and MRI data were collected from 19 cases confirmed by surgical pathology. Two radiologists retrospectively measured the tumor sizes, T1WIs, T2WIs, and ADC values and evaluated contrast-enhanced T1WIs, DWIs, complications and parauterine infiltrations. The number of tumor cells and the total nuclear area were measured. The percentage of tumor cell area out of the total area was used as the tumor cell density.

RESULTS

Nineteen patients with stage-I IVL aged 33 to 66 years (mean age: 46 ± 7.6 years) were included in this study. All 19 cases were located in the myometrium or parametrium, with a mean diameter of 11.2 ± 4.8 cm. Among these cases, 14 (73.6%) were associated with leiomyoma, and six (31.6%) involved the broad ligament. Isointensity was observed in the T1WIs of 12 cases (63.2%), while slight hypointensity was seen in five patients (26.3%). Isointensity was observed in the on T2WIs of four cases (21.1%), and iso- or slight hyperintensity was observed in 15 cases (78.9%). A significant difference was detected between the normalized T2WIs of IVL and myometrium (p < 0.001). A Pearson correlation test showed demonstrated a negative correlation between the ADC and tumor cell density values (r = - 0.946, p < 0.001). Tortuous vessels were present in 17 cases (89.5%) within or next to the lesions, and multiple winding cord-like filling defects were seen in 11 cases (57.9%) within the tortuous vessels on the T2WIs.

CONCLUSION

Identifying the characteristic MRI features of stage-I IVL helped improve the diagnostic accuracy achieves for this rare tumor. Stage-I IVL often presents as a large mass accompanied by leiomyoma, and it easily invades the broad ligament. TIWI signals exhibited isointensity, and T2WI signals contained iso- or slight hyperintensity. Tortuous vessels were present within or next to the lesions, and multiple winding cord-like filling defects were observed within the tortuous vessels on the T2WIs.

Multimodal anatomy of the human forniceal commissure

Ambiguity surrounds the existence and morphology of the human forniceal commissure. We combine advanced in-vivo tractography, multidirectional ex-vivo fiber dissection, and multiplanar histological analysis to characterize this structure’s anatomy. Across all 178 subjects, in-vivo fiber dissection based on the Human Connectome Project 7 T MRI data identifies no interhemispheric connections between the crura fornicis. Multidirectional ex-vivo fiber dissection under the operating microscope demonstrates the psalterium as a thin soft-tissue membrane spanning between the right and left crus fornicis, but exposes no commissural fibers. Multiplanar histological analysis with myelin and Bielchowsky silver staining, however, visualizes delicate cruciform fibers extending between the crura fornicis, enclosed by connective tissue, the psalterium. The human forniceal commissure is therefore much more delicate than previously described and presented in anatomical textbooks. This finding is consistent with the observed phylogenetic trend of a reduction of the forniceal commissure in non-human primates compared to non-primate eutherian mammals.

Anatomical dissection and tractography elucidate the delicate nature of the human forniceal commissure, an interhemispheric white matter circuit.

Contrasting Metabolic Insufficiency in Aging and Dementia

Metabolic insufficiency and neuronal dysfunction occur in normal aging but is exaggerated in dementia and Alzheimer's disease (AD). Metabolic insufficiency includes factors important for both substrate supply and utilization in the brain. Metabolic insufficiency occurs through a number of serial mechanisms, particularly changes in cerebrovascular supply through blood vessel abnormalities (ie, small and large vessel vasculopathy, stroke), alterations in neurovascular coupling providing dynamic blood flow supply in relation to neuronal demand, abnormalities in blood brain barrier including decreased glucose and amino acid transport, altered glymphatic flow in terms of substrate supply across the extracellular space to cells and drainage into CSF of metabolites, impaired transport into cells, and abnormal intracellular metabolism with more reliance on glycolysis and less on mitochondrial function. Recent studies have confirmed abnormal neurovascular coupling in a mouse model of AD in response to metabolic challenges, but the supply chain from the vascular system into neurons is disrupted much earlier in dementia than in equivalently aged individuals, contributing to the progressive neuronal degeneration and cognitive dysfunction associated with dementia. We discuss several metabolic treatment approaches, but these depend on characterizing patients as to who would benefit the most. Surrogate biomarkers of metabolism are being developed to include dynamic estimates of neuronal demand, sufficiency of neurovascular coupling, and glymphatic flow to supplement traditional static measurements. These surrogate biomarkers could be used to gauge efficacy of metabolic treatments in slowing down or modifying dementia time course.

Fornix Integrity Is Differently Associated With Cognition in Healthy Aging and Non-amnestic Mild Cognitive Impairment: A Pilot Diffusion Tensor Imaging Study in Thai Older Adults

Damage to the fornix leads to significant memory impairment and executive dysfunction and is associated with dementia risk. We sought to identify if fornix integrity and fiber length are disrupted in mild cognitive impairment (MCI) and how they associate with cognition. Data from 14 healthy older adult controls (HCs) and 17 subjects with non-amnestic MCI (n-aMCI) were analyzed. Diffusion tensor imaging (DTI) at 1.5 Tesla MRI was performed to enable manual tracing of the fornix and calculation of DTI parameters. Higher fractional anisotropy of body and column of the fornix was associated with better executive functioning and memory, more strongly in the HC than in the n-aMCI group. Fornix fiber tract length (FTL) was associated with better executive function, more strongly in the n-aMCI than in the HC group, and with better memory, more strongly in the HC than in the n-aMCI group. These results highlight a decline in the contributions of the fornix to cognition in n-aMCI and suggest that maintenance of fornix FTL is essential for sustaining executive functioning in people with n-aMCI.

Endoscopic Interhemispheric Disconnection for Intractable Multifocal Epilepsy: Surgical Technique and Functional Neuroanatomy

BACKGROUND

Callosotomy represents a palliative procedure for intractable multifocal epilepsy. The extent of callosotomy and the benefits of adding anterior and posterior commissurotomy are debated.

OBJECTIVE

To describe a new technique of a purely endoscopic procedure to disconnect the corpus callosum, the anterior, posterior, and habenular commissures through the use of a single burr hole via a transfrontal transventricular route.

METHODS

Our surgical series was retrospectively reviewed in terms of seizure control (Engel's class) and complication rate. Five cadaveric specimens were used to demonstrate the surgical anatomy of commissural fibers and third ventricle.

RESULTS

The procedure may be divided into 3 steps: (1) endoscopic transventricular transforaminal anterior commissure disconnection; (2) disconnection of posterior and habenular commissures; and (3) total callosotomy. Fifty-seven patients were included in the analysis. A favorable outcome in terms of epilepsy control (Engel class 1 to 3) was found in 71.4% of patients undergoing callosotomy coupled with anterior, posterior, and habenular commissure disconnection against 53% of patients with isolated callosotomy (P = .26). Patients with drop attacks had better epilepsy outcome independently from the surgical procedure used.

CONCLUSION

The full endoscopic callosotomy coupled with disconnection of anterior, posterior and habenular commissures is a safe alternative to treat multifocal refractory epilepsy. A gain in seizure outcome might be present in this cohort of patients treated with total interhemispheric disconnection when compared with isolated callosotomy. Larger studies are required to confirm these findings.

Precommissural and postcommissural fornix microstructure in healthy aging and cognition

The fornix is a key tract of the hippocampal formation, whose status is presumed to contribute to age-related cognitive decline. The precommissural and postcommissural fornix subdivisions form respective basal forebrain/frontal and diencephalic networks that may differentially affect aging and cognition. We employed multi-parametric magnetic resonance imaging (MRI) including neurite orientation density and dispersion imaging, quantitative magnetization transfer (qMT), and T1-relaxometry MRI to investigate the microstructural properties of these fornix subdivisions and their relationship with aging and cognition in 149 asymptomatic participants (38-71 years). Aging was associated with increased free water signal and reductions in myelin-sensitive R1 and qMT indices but no apparent axon density differences in both precommissural and postcommissural fibers. Precommissural relative to postcommissural fibers showed a distinct microstructural pattern characterised by larger free water signal and axon orientation dispersion, with lower apparent myelin and axon density. Furthermore, differences in postcommissural microstructure were related to performance differences in object-location paired-associate learning. These results provide novel in vivo neuroimaging evidence for distinct microstructural properties of precommissural and postcommissural fibers that are consistent with their anatomy as found in axonal tracer studies, as well as for a contribution of postcommissural fibers to the learning of spatial configurations.

Trajectory of hippocampal fibres to the contralateral anterior thalamus and mammillary bodies in rats, mice, and macaque monkeys

The routes by which the hippocampal formation projects bilaterally to the anterior thalamic nuclei and mammillary bodies were examined in the mouse, rat, and macaque monkey. Despite using different methods and different species, the principal pattern remained the same. For both target areas, the contralateral hippocampal (subiculum) projections arose via efferents in the postcommissural fornix ipsilateral to the tracer injection, which then crossed hemispheres both in or just prior to reaching the target site within the thalamus or hypothalamus. Precommissural fornix fibres could not be followed to the target areas. There was scant evidence that the ventral hippocampal commissure or decussating fornix fibres contribute to these crossed subiculum projections. Meanwhile, a small minority of postsubiculum projections in the mouse were seen to cross in the descending fornix at the level of the caudal septum to join the contralateral postcommissural fornix before reaching the anterior thalamus and lateral mammillary nucleus on that side. Although the rodent anterior thalamic nuclei also receive nonfornical inputs from the subiculum and postsubiculum via the ipsilateral internal capsule, few, if any, of these projections cross the midline. It was also apparent that nuclei within the head direction system (anterodorsal thalamic nucleus, laterodorsal thalamic nucleus, and lateral mammillary nucleus) receive far fewer crossed hippocampal inputs than the other anterior thalamic or mammillary nuclei. The present findings increase our understanding of the fornix and its component pathways while also informing disconnection analyses involving the hippocampal formation and diencephalon.

Schwalbe's Triangular Fossa: Normal and Pathologic Anatomy on Frozen Cadavers. Anatomo-Magnetic Resonance Imaging Comparison and Surgical Implications in Colloid Cyst Surgery

BACKGROUND

The fornix is a region of greatest neurosurgical interest in regards to its complex anatomy and surgical approaches to this area. The objective of this study was to evaluate the morphology of the triangular recess (TR) and its role in the growth pattern of the colloid cysts (CC) within the third ventricle and in the choice of the surgical approach for their removal. Furthermore, to compare the results of the dissections with measurements performed on a magnetic resonance imaging scan.

METHODS

In the anatomic study, 20 cadaveric specimens were dissected and analyzed. In the radiologic study, a magnetic resonance imaging scan was performed in 20 healthy volunteers. In the clinical study, a retrospective analysis of all the patients affected with CCs microsurgically removed at our institute between 2010 and 2018 was conducted.

RESULTS

In the anatomic study, the width, height, and the area of the TR were respectively 0.31 cm, 0.33cm, and 0.051 cm². In the radiologic study, 3 different typologies of TR were identified: open recess in ventriculomegaly (7 patients); open recess in physiologic ventricular system (3 patients); closed or blind recess (10 patients). Three different growth patterns of CCs were identified: type 1) CCs localized at the foramen of Monro growing behind the fornix and below the third ventricular roof; type 2) CCs growing rostrally between the column of fornix; and type 3) CCs growing above the plane of the third ventricular roof.

CONCLUSIONS

The anatomy of the TR influences the growth pattern of CC within the ventricular cavity and determines the surgical strategy for their removal.

Awakening Neuropsychiatric Research Into the Stria Medullaris: Development of a Diffusion-Weighted Imaging Tractography Protocol of This Key Limbic Structure

The Stria medullaris (SM) Thalami is a discrete white matter tract that directly connects frontolimbic areas to the habenula, allowing the forebrain to influence midbrain monoaminergic output. Habenular dysfunction has been shown in various neuropsychiatric conditions. However, there exists a paucity of research into the habenula’s principal afferent tract, the SM. Diffusion-weighted tractography may provide insights into the properties of the SM in vivo, opening up investigation of this tract in conditions of monoamine dysregulation such as depression, schizophrenia, addiction and pain. We present a reliable method for reconstructing the SM using diffusion-weighted imaging, and examine the effects of age and gender on tract diffusion metrics. We also investigate reproducibility of the method through inter-rater comparisons. In consultation with neuroanatomists, a Boolean logic gate protocol was developed for use in ExploreDTI to extract the SM from constrained spherical deconvolution based whole brain tractography. Particular emphasis was placed on the reproducibility of the tract, attention to crossing white matter tract proximity and anatomical consistency of anterior and posterior boundaries. The anterior commissure, pineal gland and mid point of the thalamus were defined as anatomical fixed points used for reconstruction. Fifty subjects were scanned using High Angular Resolution Diffusion Imaging (HARDI; 61 directions, b-value 1500 mm³). Following constrained spherical deconvolution whole brain tractography, two independent raters isolated the SM. Each output was checked, examined and cleaned for extraneous streamlines inconsistent with known anatomy of the tract by the rater and a neuroanatomist. A second neuroanatomist assessed tracts for face validity. The SM was reconstructed with excellent inter-rater reliability for dimensions and diffusion metrics. Gender had no effect on the dimensions or diffusion metrics, however radial diffusivity (RD) showed a positive correlation with age. Reliable identification and quantification of diffusion metrics of the SM invites further exploration of this key habenula linked structure in neuropsychiatric disorders such as depression, anxiety, chronic pain and addiction. The accurate anatomical localization of the SM may also aid preoperative stereotactic localization of the tract for deep brain stimulation (DBS) treatment.

Injury of the Precommissural Fornix in a Patient with Subarachnoid Hemorrhage: A Case Report

OBJECTIVES

We investigated injury of the pre- or postcommissural fornix in a patient with subarachnoid hemorrhage (SAH) using diffusion tensor imaging.

CASE DESCRIPTION

A 48-year-old male patient was diagnosed as SAH due to rupture of the right middle cerebral artery bifurcation aneurysm. After 9 weeks from onset, he was transferred to the rehabilitation department and he showed memory impairment. The whole fornix was reconstructed using single-tract fornix model based on a fiber assignment by continuous tracking, and separated fornices (pre- and postcommissural fornices) were reconstructed using 2-tract fornix model based on a probabilistic tractography method. The fractional anisotropy (FA), mean diffusivity, and fiber volume were measured in the patient and 6 normal control subjects. The integrities of both reconstructed whole fornices that were reconstructed using probabilistic tractography method were preserved. By contrast, in the results of 2-tract fornix model, the precommissural fornices showed discontinuations in both fornical cruses. In addition, the FA and fiber volume of both precommissural fornices in the patient were decreased by more than 2 standard deviations of those of normal control subjects.

CONCLUSIONS

Separate evaluations of the pre- and postcommissural fornices using 2-tract fornix model would be useful for diagnosis in patients with memory impairment following SAH.

Resection of tumors of the third ventricle involving the hypothalamus: effects on body mass index using a dedicated surgical approach

Resection of large lesions growing into the third ventricle is considered nowadays still a demanding surgery, due to the high risk of severe endocrine and neurological complications. Some neurosurgical approaches were considered in the past the procedures of choice to access the third ventricle, however they were burden by endocrine and neurological consequences, like memory loss and epilepsy. We report here the endocrine and functional results in a series of patients operated with a recently developed approach specifically tailored for the resection of large lesions growing into the third ventricle. Authors conducted a retrospective analysis on 10 patients, operated between 2011 and 2012, for the resection of large tumors growing into the third ventricle. Total resection was achieved in all patients. No perioperative deaths were recorded and all patients were alive after the follow-up. One year after surgery 8/10 patients had an excellent outcome with a Karnofsky Performance Status of 100 and a Glasgow Outcome score of 5, with 8 patients experiencing an improvement of the Body Mass Index. Modern neurosurgery allows a safe and effective treatment of large lesions growing into the third ventricle with a postoperative good functional status.

The differences of the precommissural and postcommissural fornix in the hippocampal location: a diffusion tensor tractography study

PURPOSE

The precommissural fornix and postcommissural fornix have different connections to the basal forebrain and septal region, and mammillary body, respectively. However, little is known about the differences of the precommissural fornix and postcommissural fornix in the hippocampal location. In this study, using diffusion tensor tractography, we investigated the differences of the precommissural fornix and postcommissural fornix in the hippocampal location.

METHODS

We recruited 25 healthy volunteers for this study. For reconstruction of the precommissural fornix and postcommissural fornix, we placed the seed region of interest on the septal nucleus, and the mammillary body, respectively. The target regions of interest (ROI) was given on the crus of the fornix on the coronal image. Evaluations of the anatomical location of the precommissural fornix and postcommissural fornix were performed using the highest probabilistic location in the hippocampal formation.

RESULTS

The precommissural fornix and postcommissural fornix were located at an average of 83.9 and 87.5% between the lateral margin of the red nucleus and collateral sulcus on the axial plane, and 77.2 and 81.4% between the lateral margin of the midbrain and the inferior longitudinal fasciculus on the coronal plane. Significant differences of location in the medio-lateral direction were observed in the axial and coronal plane (p < 0.05). However, no significant differences of location in the antero-posterior direction were observed between precommissrual and postcommissural fornix (p > 0.05).

CONCLUSIONS

The reconstructed precommissural fornix and postcommissural fornix were connected to the cornu ammonis 1(CA1) of the hippocampus, and the precommissural fornix was located more laterally to the postcommissural fornix in the CA1.

The status of the precommissural and postcommissural fornix in normal ageing and mild cognitive impairment: An MRI tractography study

The fornix connects the hippocampal formation with structures beyond the temporal lobe. Previous tractography studies have typically reconstructed the fornix as one unified bundle. However, the fornix contains two rostral divisions: the precommissural fornix and the postcommissural fornix. Each division has distinct anatomical connections and, hence, potentially distinct functions. Diffusion weighted MRI and spherical deconvolution based tractography were employed to reconstruct these separate fornix divisions and to examine their microstructural properties in both healthy ageing and Mild Cognitive Impairment (MCI). Reliable reconstructions of precommissural and postcommissural fibres were achieved in both groups, with their fibres retaining largely separate locations within the anterior body of the fornix. Ageing and MCI had comparable effects on the two segments. Ageing was associated with changes in mean, axial and radial diffusivity but not with alterations of fibre population-specific diffusion properties, estimated with the hindrance modulated orientational anisotropy (HMOA). Individual HMOA variation in postcommissural, but not precommissural, fibres correlated positively (and unrelated to age) with visual recall performance. This provides novel evidence for a role of postcommissural fibres, which connect structures of the extended hippocampal network, in episodic memory function. Separating the fornix into its two principal divisions brings new opportunities for distinguishing different hippocampal networks.

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Fornix has two rostral divisions with distinct anatomical connections

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New tractography protocol for separating precommissural and postcommissural fornix

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Positive correlation between postcommissural HMOA and episodic memory

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Age-related increases in diffusivity but not in HMOA of fornix

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Mild Cognitive Impairment affects microstructure in both divisions

Endoscopic-Assisted (Through a Mini Craniotomy) Corpus Callosotomy Combined With Anterior, Hippocampal, and Posterior Commissurotomy in Lennox-Gastaut Syndrome

BACKGROUND:

Corpus callosotomy is a palliative procedure especially for Lennox-Gastaut semiology without localization with drop attacks.

OBJECTIVE:

To describe endoscopic-assisted complete corpus callosotomy combined with anterior, hippocampal, and posterior commissurotomy.

METHODS:

Patients with drug refractory epilepsy having drop attacks as the predominant seizure type, bilateral abnormalities on imaging, and moderate to severe mental retardation were included. All underwent a complete workup (including magnetic resonance imaging).

RESULTS:

Patients (n = 16, mean age 11.4 ± 6.4 years, range 6-19 years) had a mean seizure frequency of 24.5 ± 19.8/days (range 1-60) and a mean intelligence quotient of 25.23 ± 10.71. All had syndromic diagnosis of Lennox-Gastaut syndrome, with the following etiologies: hypoxic insult (10), lissencephaly (2), bilateral band heterotropia (2), and microgyria and pachygyria (2). Surgery included complete callosotomy and the section of anterior and posterior commissure by microscopic approach through a mini craniotomy (11) and endoscopic-assisted approach (5). Complications included meningitis (1), hyperammonemic encephalopathy (2), and acute transient disconnection (5). There was no mortality or long-term morbidity. Mean follow-up was 18 ± 4.7 months (range 16-27 months). Drop attacks stopped in all. Seizure frequency/duration decreased &gt;90% in 10 patients and &gt;50% in 5 patients, and increased in 1 patient. All patients attained presurgical functional levels in 3 to 6 months. Child behavior checklist scores showed no deterioration. Parental questionnaires reported 90% satisfaction attributed to the control of drop attacks. The series was compared retrospectively with an age/sex-matched cohort (where a callosotomy only was performed), and showed better outcome for drop attacks (P &lt; .003).

CONCLUSION:

This preliminary study demonstrated the efficacy and safety of complete callosotomy with anterior, hippocampal, and posterior commissurotomy in Lennox-Gastaut syndrome (drop attacks) with moderate to severe mental retardation.

Perspectives on the neural connectivity of the fornix in the human brain

The fornix is involved in the transfer of information on episodic memory as a part of the Papez circuit. Diffusion tensor imaging enables to estimate the neural connectivity of the fornix. The anterior fornical body has high connectivity with the anterior commissure, and brain areas relevant to cholinergic nuclei (septal forebrain region and brainstem) and memory function (medial temporal lobe). In the normal subjects, by contrast, the posterior fornical body has connectivity with the cerebral cortex and brainstem through the splenium of the corpus callosum. We believe that knowledge of the neural connectivity of the fornix would be helpful in investigation of the neural network associated with memory and recovery mechanisms following injury of the fornix.

Neural connectivity of the anterior body of the fornix in the human brain: diffusion tensor imaging study

A few studies have reported on the neural connectivity of the fornix in the human brain, however, little is known about the neural connectivity of the anterior body of the fornix. In this study, we used diffusion tensor imaging in investigation of the neural connectivity of the anterior body of the fornix in normal subjects. Forty healthy subjects were recruited for this study. A seed region of interest was placed on the anterior body of the fornix using the FMRIB Software Library. Connectivity was defined as the incidence of connection between the anterior body of the fornix and any neural structure of the brain at the threshold of 5, 25, and 50 streamlines. In all subjects, the anterior body of the fornix showed 100% connectivity to the anterior commissure and hypothalamus at thresholds of 5, 25, and 50. On the other hand, regarding the thresholds of 5, 25, and 50, the anterior body of the fornix showed connectivity to the septal forebrain region (53.8, 23.8, and 15.0%), frontal lobe via anterior commissure (41.3,12.5, and 10.0%), medial temporal lobe (85.0,66.3, and 62.5%), lateral temporal lobe (75.0, 56.3, and 35.0%), occipital lobe (21.3, 5.0, and 1.3%), frontal lobe via septum pellucidum (28.8, 13.8, and 8.8%), tegmentum of midbrain (7.5, 5.0, and 0%), tectum of midbrain (2.5,0, and 0%), and tegmentum of pons (5.0,0, and 0%). The anterior body of the fornix showed high connectivity with the anterior commissure and hypothalamus, and brain areas relevant to cholinergic nuclei (the septal forebrain region and brainstem) and memory function (the medial temporal lobe).

Diffusion tensor tractography for the dorsal spinocerebellar tract in the human brain

Using diffusion tensor tractography, we attempted to investigate and identify the anatomy of the dorsal spinocerebellar tract (SCT) in the human brain. We recruited 26 healthy volunteers. The dorsal SCT was determined by selection of fibers passing through three regions of interest. We found that all dorsal SCTs terminated in the ipsilateral cerebellum; in contrast, in 25 (48%) of 52 hemispheres, the dorsal SCT crossed into the contralateral hemisphere via the vermis of the anterior lobe.

Neural connectivity of the posterior body of the fornix in the human brain: diffusion tensor imaging study

Little is known about the neural connectivity of the fornix in the human brain. In the current study, using diffusion tensor imaging, we attempted to investigate the neural connectivity of the posterior body of the fornix in the normal human brain. A total of 43 healthy subjects were recruited for this study. DTIs were acquired using a sensitivity-encoding head coil at 1.5T. For connectivity of the posterior body of the fornix, a seed region of interest was used on the posterior body of the fornix. Connectivity was defined as the incidence of connection between the posterior body of the fornix and any neural structure of the brain at the threshold of 5, 25, and 50 streamline. At the threshold of 5, 25, and 50, the posterior body of the fornix showed connectivity to the precentral gyrus (37%, 19%, and 15%), the postcentral gyrus (25%, 11.5%, and 7%), the posterior parietal cortex (16.5%, 5%, and 5%), the brainstem (12%, 4.5%, and 3.5%), the crus of the fornix (34%, 10.5%, and 7%), the contralateral splenium of the corpus callosum (12.5%, 5%, and 0%), and the ipsilateral splenium of the CC (69.8%%, 33.7%, and 23.3%), respectively. Findings of this study showed that the posterior body of the fornix had connectivity with the cerebral cortex, the brainstem, the fornical crus, and the contralateral splenium through the splenium of the corpus callosum in normal subjects. We believe that the results of this study would be helpful in investigation of the neural network related to memory and recovery mechanisms following fornical injury in the human brain.