The corpus callosum, the other great forebrain commissures, and the septum pellucidum: anatomy, development, and malformation. Neuroradiology. 2010;52:447-477. [PMID: 20422408 DOI: 10.1007/s00234-010-0696-3]

The relationship between cavum septum pellucidum and psychopathic traits in a large forensic sample

Cavum septum pellucidum (CSP) is a neuroanatomical variant of the septum pellucidum that is considered a marker for disrupted brain development. Several small sample studies have reported CSP to be related to disruptive behavior, persistent antisocial traits, and even psychopathy. However, no large-scale samples have comprehensively examined the relationship between CSP, psychopathic traits, and antisocial behavior in forensic samples. Here we test hypotheses about the presence of CSP and its relationship to psychopathic traits in incarcerated males (N = 1432). We also examined the incidence of CSP in two non-incarcerated male control samples for comparison (N = 208 and 125). Ethnic and racial composition was varied with a mean age of 33.1, and an average IQ of 96.96. CSP was evaluated via structural magnetic resonance imaging. CSP was measured by length (number of 1.0 mm slices) in continuous analyses, and classified as absent (0) or present (1+ mm), as well as by size (absent (0), small (1-3), medium (4-5), or large (6+ mm)) for comparison with prior work. The Wechsler Adult Intelligence Scale (WAIS-III), Structured Clinical Interview (SCID-I/P), and Hare Psychopathy Checklist-Revised (PCL-R) were used to assess IQ, substance dependence, and psychopathy, respectively. CSP length was positively associated with PCL-R total, Factor 1 (interpersonal/affective) and Facets 1 (interpersonal) and 2 (affective). CSP was no more prevalent among inmates than among non-incarcerated controls, with similar distributions of size. These results support the hypotheses that abnormal septal/limbic development may contribute to dimensional affective/interpersonal traits of psychopathy, but CSP is not closely associated with antisocial behavior, per se.

Hippocampal Subfields Volume Reduction in High Schoolers with Previous Verbal Abuse Experiences

Objective

Reduced hippocampal volume and alterations in white matter tracts have been frequently reported in adults having the history of emotional maltreatment. We investigated whether these structural change occur in adolescents with previous verbal abuse (VA) experiences.

Methods

Hippocampal subfield volume and white matter structural connectivity measures were assessed in 31 first year male high school students with various degrees of exposure to parental and peer VA.

Results

The high VA group showed significant volume reduction in the left cornu ammonis (CA) 1 and left subiculum compared to the low VA group (p＜0.05). Volumes of left hippocampal subfields CA1 and subiculum were negatively correlated with previous VA experiences (p＜0.05). Increased mean diffusivity (MD) of the splenium of the corpus callosum was related to high VA score across all subjects (p＜0.05). There was an inverse relationship between volume of the CA1 and subiculum and MD of the splenium (p＜0.05).

Conclusion

Exposure to parental and peer VA may affect development of the left hippocampal subfields and the splenium of corpus callosum. These structural alterations can be discernible during adolescence.

Sonographic Development of the Pericallosal Vascularization in the First and Early Second Trimester of Pregnancy

BACKGROUND AND PURPOSE

Anomalies of the corpus callosum are rare. Routine scanning in midtrimester of the pregnancy often fails to identify defective development. The purpose of the study was to identify the pericallosal artery and all its main branching arteries during early gestation from the first trimester onward, to measure the length of the pericallosal artery during its development, and to establish a normal vascular map for each week of development.

MATERIALS AND METHODS

We performed a single-center prospective, longitudinal clinical study in 15 patients between 11 and 22 weeks of gestation. The origin and course of the different blood vessels were identified.

RESULTS

There was a linear association among gestational age, the biparietal diameter, and the length of the pericallosal artery. The curvature of the developing pericallosal artery increases linearly with the gestational age and biparietal diameter, and 4 variations of branching of the callosomarginal artery were observed.

CONCLUSIONS

The pericallosal artery and its branches can be identified and measured from 11 weeks on, and the pericallosal artery takes its characteristic course. A defective course or an abnormal biometry of the pericallosal artery could be an early sonographic marker of abnormal development of the corpus callosum.

Prenatal diagnosis of pericallosal curvilinear lipoma: specific imaging pattern and diagnostic pitfalls

We report the first series of cases of pericallosal curvilinear lipoma (CL) diagnosed prenatally and highlight the limitations in identifying a specific prenatal imaging pattern using ultrasound and magnetic resonance imaging (MRI). In all five of our cases, on ultrasound, the main feature leading to referral was a short corpus callosum. This subtle callosal dysgenesis was associated with a band of hyperechogenicity surrounding the corpus callosum, mimicking the pericallosal sulcus, which increased in size during the third trimester in three of the four cases in which sonographic follow-up was performed. On T2-weighted MRI, this band showed typical hypointensity in all cases; in contrast, on T1-weighted imaging, in only one case was there hyperintensity, suggestive of fat, as seen typically in the postnatal period. For appropriate prenatal counseling regarding outcome, it is important to identify or rule out CL when mild corpus callosal dysgenesis is observed. One should be aware of subtle diagnostic findings, such as a thin band of echogenicity surrounding the corpus callosum that is seen as a band of hypointensity on T2-weighted fetal MRI, and which may increase in size during gestation. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Apert syndrome: magnetic resonance imaging (MRI) of associated intracranial anomalies

INTRODUCTION

Apert syndrome is one of the most common craniosynostosis syndrome caused by mutations in genes encoding fibroblast growth factor receptor 2 (FGFR2). It is characterized by multisuture craniosynostosis, midfacial hypoplasia, abnormal skull base development and syndactyly of all extremities. Apert syndrome is associated with a wide array of central nervous system (CNS) anomalies, possibly the cause of the common occurrence of mental deficiency in patients with Apert syndrome. These CNS anomalies can be broadly classified into two groups; (1) those that are primary malformations and (2) those that occur secondary to osseous deformity/malformation.

CONCLUSION

Familiarity with CNS anomalies associated with Apert syndrome is important to both clinicians and radiologist as it impacts on management and prognostication. Cognitive development of patients has been linked to associated CNS anomalies, timing of surgery and social aspects. These associated anomalies can be broadly classified into (1) those that are primary malformations and (2) those that occur secondary to osseous deformity/malformation, as illustrated in our review paper.

Twenty-Five Diagnoses on Midline Images of the Brain: From Fetus to Child to Adult

Midsagittal images of the brain provide a wealth of anatomic information and may show abnormalities that are pathognomonic for particular diagnoses. Using an anatomy-based approach, the authors identify pertinent anatomic structures to serve as a checklist when evaluating these structures. Subregions evaluated include the corpus callosum, pituitary gland and sellar region, pineal gland and pineal region, brainstem, and cerebellum. The authors present 25 conditions with characteristic identifiable abnormalities at midsagittal imaging. Midsagittal views from multiple imaging modalities are shown, including computed tomography, ultrasonography, and magnetic resonance (MR) imaging. Standard MR imaging sequences are shown, as well as fetal MR and sagittal diffusion-weighted images. To demonstrate these conditions, fetal, neonatal, childhood, adolescent, and young adulthood images are reviewed. The differentiation of normal variants is guided by the understanding of anatomy and pathology. When a specific diagnosis is not possible, the authors present information to evaluate differential considerations and discuss when follow-up imaging may be indicated. The authors hope each case will clarify a pertinent differential diagnosis, appropriately guide patient management, and improve understanding of normal anatomy and identification of pathologic entities. It is in these hopes that the authors have presented a checklist of pertinent anatomy and pathologic entities that can build on existing search patterns. Improved confidence and accuracy in the evaluation of midsagittal images will benefit physicians and patients. ^©RSNA, 2018.

The effect of age and microstructural white matter integrity on lap time variation and fast-paced walking speed

Macrostructural white matter damage (WMD) is associated with less uniform and slower walking in older adults. The effect of age and subclinical microstructural WM degeneration (a potentially earlier phase of WM ischemic damage) on walking patterns and speed is less clear. This study examines the effect of age on the associations of regional microstructural WM integrity with walking variability and speed, independent of macrostructural WMD. This study involved 493 participants (n = 51 young; n = 209 young-old; n = 233 old-old) from the Baltimore Longitudinal Study of Aging. All completed a 400-meter walk test and underwent a concurrent brain MRI with diffusion tensor imaging. Microstructural WM integrity was measured as fractional anisotropy (FA). Walking variability was measured as trend-adjusted variation in time over ten 40-meter laps (lap time variation, LTV). Fast-paced walking speed was assessed as mean lap time (MLT). Multiple linear regression models of FA predicting LTV and MLT were adjusted for age, sex, height, weight, and WM hyperintensities. Independent of WM hyperintensities, lower FA in the body of the corpus callosum was associated with higher LTV and longer MLT only in the young-old. Lower FA in superior longitudinal, inferior fronto-occipital, and uncinate fasciculi, the anterior limb of the internal capsule, and the anterior corona radiate was associated with longer MLT only in the young-old. While macrostructural WMD is known to predict more variable and slower walking in older adults, microstructural WM disruption is independently associated with more variable and slower fast-paced walking only in the young-old. Disrupted regional WM integrity may be a subclinical contributor to abnormal walking at an earlier phase of aging.

Microstructural White Matter Alterations in the Corpus Callosum of Girls With Conduct Disorder

OBJECTIVE

Diffusion tensor imaging (DTI) studies in adolescent conduct disorder (CD) have demonstrated white matter alterations of tracts connecting functionally distinct fronto-limbic regions, but only in boys or mixed-gender samples. So far, no study has investigated white matter integrity in girls with CD on a whole-brain level. Therefore, our aim was to investigate white matter alterations in adolescent girls with CD.

METHOD

We collected high-resolution DTI data from 24 girls with CD and 20 typically developing control girls using a 3T magnetic resonance imaging system. Fractional anisotropy (FA) and mean diffusivity (MD) were analyzed for whole-brain as well as a priori-defined regions of interest, while controlling for age and intelligence, using a voxel-based analysis and an age-appropriate customized template.

RESULTS

Whole-brain findings revealed white matter alterations (i.e., increased FA) in girls with CD bilaterally within the body of the corpus callosum, expanding toward the right cingulum and left corona radiata. The FA and MD results in a priori-defined regions of interest were more widespread and included changes in the cingulum, corona radiata, fornix, and uncinate fasciculus. These results were not driven by age, intelligence, or attention-deficit/hyperactivity disorder comorbidity.

CONCLUSION

This report provides the first evidence of white matter alterations in female adolescents with CD as indicated through white matter reductions in callosal tracts. This finding enhances current knowledge about the neuropathological basis of female CD. An increased understanding of gender-specific neuronal characteristics in CD may influence diagnosis, early detection, and successful intervention strategies.

Role of fetal MRI in the evaluation of isolated and non-isolated corpus callosum dysgenesis: results of a cross-sectional study

PURPOSE

The aims of this study were to characterize isolated and non-isolated forms of corpus callosum dysgenesis (CCD) at fetal magnetic resonance imaging (MRI) and to identify early predictors of associated anomalies.

METHODS

We retrospectively analyzed 104 fetuses with CCD undergoing MRI between 2006 and 2016. Corpus callosum, cavum septi pellucidi, biometry, presence of ventriculomegaly, gyration anomalies, cranio-encephalic abnormalities and body malformations were evaluated. Results of genetic tests were also recorded.

RESULTS

At MRI, isolated CCD was 26.9%, the rest being associated to other abnormalities. In the isolated group, median gestational age at MRI was lower in complete agenesis than in hypoplasia (22 vs 28 weeks). In the group with additional findings, cortical dysplasia was the most frequently associated feature (P = 0.008), with a more frequent occurrence in complete agenesis (70%) versus other forms; mesial frontal lobes were more often involved than other cortical regions (P = 0.006), with polymicrogyria as the most frequent cortical malformation (40%). Multivariate analysis confirmed the association between complete agenesis and cortical dysplasia (odds ratio = 7.29, 95% confidence interval 1.51-35.21).

CONCLUSIONS

CCD is often complicated by other intra-cranial and extra-cranial findings (cortical dysplasias as the most prevalent) that significantly affect the postnatal prognosis. The present study showed CCD with associated anomalies as more frequent than isolated (73.1%). In isolated forms, severe ventriculomegaly was a reliable herald of future appearance of associated features. © 2016 John Wiley & Sons, Ltd.

Corpus Callosum and Neglect Syndrome: Clinical Findings After Meningioma Removal and Anatomical Review

Two types of neglect are described: hemispatial and motivational neglect syndromes. Neglect syndrome is a neurophysiologic condition characterized by a malfunction in one hemisphere of the brain, resulting in contralateral hemispatial neglect in the absence of sensory loss and the right parietal lobe lesion being the most common anatomical site leading to it. In motivational neglect, the less emotional input is considered from the neglected side where anterior cingulate cortex harbors the most frequent lesions. Nevertheless, there are reports of injuries in the corpus callosum (CC) causing hemispatial neglect syndrome, particularly located in the splenium. It is essential for a neurosurgeon to recognize this clinical syndrome as it can be either a primary manifestation of neurosurgical pathology (tumor, vascular lesion) or as a postoperative iatrogenic clinical finding. The authors report a postoperative hemispatial neglect syndrome after a falcotentorial meningioma removal that recovered 10 months after surgery and performs a clinical, anatomical, and histological review centered in CC as key agent in neglect syndrome.

THE FEATURES OF BLOOD SUPPLY OF CORPUS CALLOSUM AND THE STRUCTURE OF ITS HEMOMICROCIRCULATORY CHANNEL

Today we know the location of the sources of arterial blood delivery to the corpus callosum and we can approximately say, where are situated the venous vessels that the blood outflows from it to, but it is absolutely unknown, what is the intermediate link – the blood microcirculatory channel. Aim of research. The aim of our research is in identification of the ways of venous outflow from corpus callosum and in clarification of the principle of structural organization of its hemomicrocirculatory channel. Materials and methods. In the work are used the median total preparations of the corpus callosum (together with septum pellucidum and cerebral fornix formations) of 10 men 36–60 years old. Histological paraffin sections, colored by hematoxylin and eosin and according to Van-gieson were made of these preparations, and the methods of plastination of the corpus callosum tissues in epoxy resin with further creation of polished sections of different width and serial fine sections of blocs, for which coloration served the 1 % solution of blue methene for 1% borax solution, were also used. Results. It was established, that the arterial microvessels, starting from vascular plexus that covers the upper surface of corpus callosum, penetrate it as arterioles along interfunicular connective tissue septs that divide its commissural funicles between them. The arterioles are prolonged directly in venous microvessels that can be related to gathering venules. These direct microvascular communications, coming through the thickness of corpus callosum, can be named perforating arteriolovenular anastomoses. The aforesaid collector venules, localized in the lowest sections of interfunicular interlayers, are the direct inflows of venous channel of septum pellucidum. In general system of blood supply of corpus callosum the main arteries on the one side and the veins of septum pellucidum – on the other, are not accompanied by the vessels of opposite type. Conclusions. The blood microcirculatory channel of corpus callosum is the complexly branched in its thickness net of resistive, metabolic and capacitive microvessels, placed on the running way between arterial channel of soft cerebral tunic that covers the upper surface of corpus callosum and collector veins of septum pellucidum, situated below it. The direct shunting tracts between them are perforating arteriolovenular anastomoses.

Structural Connectivity Analysis in Children with Segmental Callosal Agenesis

BACKGROUND AND PURPOSE

Segmental callosal agenesis is characterized by the absence of the intermediate callosal portion. We aimed to evaluate the structural connectivity of segmental callosal agenesis by using constrained spherical deconvolution tractography and connectome analysis.

MATERIALS AND METHODS

We reviewed the clinical-radiologic features of 8 patients (5 males; mean age, 3.9 years). Spherical deconvolution and probabilistic tractography were performed on diffusion data. Structural connectivity analysis, including summary network metrics, modularity analysis, and network consistency measures, was applied in 5 patients and 10 age-/sex-matched controls.

RESULTS

We identified 3 subtypes based on the position of the hippocampal commissure: beneath the anterior callosal remnant in 3 patients (type I), beneath the posterior callosal remnant in 3 patients (type II), and between the anterior and posterior callosal remnants in 2 patients (type III). In all patients, the agenetic segment corresponded to fibers projecting to the parietal lobe, and segmental Probst bundles were found at that level. Ectopic callosal bundles were identified in 3 patients. Topology analysis revealed reduced global connectivity in patients compared with controls. The network topology of segmental callosal agenesis was more variable across patients than that of the control connectomes. Modularity analysis revealed disruption of the structural core organization in the patients.

CONCLUSIONS

Three malformative subtypes of segmental callosal agenesis were identified. Even the absence of a small callosal segment may impact global brain connectivity and modularity organization. The presence of ectopic callosal bundles may explain the greater interindividual variation in the connectomes of patients with segmental callosal agenesis.

An entire universe of the Roman world's architecture found in the human skull

Today's neuroanatomical terminology has its origins in the Romans' way of life, in their civil and military house architecture, as well as in the fields of engineering and technology. Despite the fact that they did not know how the nervous system worked and what the role of each neuroanatomic structure was, over time, especially in Renaissance and early modern times, the anatomists sought descriptive names for the nervous structures they have identified by way of similarity with some ancient items. This study aims to briefly review the influence of Roman architecture, engineering, and technology on neuroanatomic nomenclature, the precursor of modern neuroanatomical terminology.

Interhemispheric Connections between the Primary Visual Cortical Areas via the Anterior Commissure in Human Callosal Agenesis

Aim: In humans, images in the median plane of the head either fall on both nasal hemi-retinas or on both temporal hemi-retinas. Interhemispheric connections allow cortical cells to have receptive fields on opposite sides. The major interhemispheric connection, the corpus callosum, is implicated in central stereopsis and disparity detection in front of the fixation plane. Yet individuals with agenesis of the corpus callosum may show normal stereopsis and disparity vergence. We set out to study a possible interhemispheric connection between primary visual cortical areas via the anterior commissure to explain this inconsistency because of the major role of these cortical areas in elaborating 3D visual perception.

Methods: MRI, DTI and tractography of the brain of a 53-year old man with complete callosal agenesis and normal binocular single vision was undertaken. Tractography seed points were placed in both the right and the left V1 and V2. Nine individuals with both an intact corpus callosum and normal binocularity served as controls.

Results: Interhemispheric tracts through the anterior commissure linking both V1 and V2 visual cortical areas bilaterally were indeed shown in the subject with callosal agenesis. All other individuals showed interhemispheric visual connections through the corpus callosum only.

Conclusion: Callosal agenesis may result in anomalous interhemispheric connections of the primary visual areas via the anterior commissure. It is proposed here that these connections form as alternative to the normal callosal pathway and may participate in binocularity.

Age-Specific Dynamics of Corpus Callosum Development in Children and its Peculiarities in Infantile Cerebral Palsy

The age dynamics of corpus callosum development was studied on magnetic resonance images of the brain in children aged 2-11 years without neurological abnormalities and with infantile cerebral palsy. The areas of the total corpus callosum and its segments are compared in the midsagittal images. Analysis is carried out with the use of an original formula: proportion of areas of the anterior (genu, CC2; and anterior part, CC3) and posterior (isthmus, CC6 and splenium, CC7) segments: kCC=(CC2+CC3)×CC6/CC7. The results characterize age-specific dynamics of the corpus callosum development and can be used for differentiation, with high confidence, of the brain of children without neurological abnormalities from the brain patients with infantile cerebral palsy.

Outcomes Associated With Isolated Agenesis of the Corpus Callosum: A Meta-analysis

CONTEXT

Antenatal counseling in cases of agenesis of the corpus callosum (ACC) is challenging.

OBJECTIVES

To ascertain the outcome in fetuses with isolated complete ACC and partial ACC.

DATA SOURCES

Medline, Embase, CINAHL, and Cochrane databases.

STUDY SELECTION

Studies reporting a prenatal diagnosis of ACC. The outcomes observed were: chromosomal abnormalities at standard karyotype and chromosomal microarray (CMA) analysis, additional anomalies detected only at prenatal MRI and at postnatal imaging or clinical evaluation, concordance between prenatal and postnatal diagnosis and neurodevelopmental outcome.

DATA EXTRACTION

Meta-analyses of proportions were used to combine data.

RESULTS

Twenty-seven studies were included. In cACC, chromosomal anomalies occurred in 4.81% (95% confidence interval [CI], 2.2-8.4) of the cases. Gross and fine motor control were abnormal in 4.40% (95% CI, 0.6-11.3) and 10.98% (95% CI, 4.1-20.6) of the cases, respectively, whereas 6.80% (95% CI, 1.7-14.9) presented with epilepsy. Abnormal cognitive status occurred in 15.16% (95% CI, 6.9-25.9) of cases. In partial ACC, the rate of chromosomal anomalies was 7.45% (95% CI, 2.0-15.9). Fine motor control was affected in 11.74% (95% CI, 0.9-32.1) of the cases, and 16.11% (95% CI, 2.5-38.2) presented with epilepsy. Cognitive status was affected in 17.25% (95% CI, 3.0-39.7) of cases.

LIMITATIONS

Different neurodevelopmental tools and time of follow-up of the included studies.

CONCLUSIONS

Children wih a prenatal diagnosis of isolated ACC show several degrees of impairment in motor control, coordination, language, and cognitive status. However, in view of the large heterogeneity in outcomes measures, time at follow-up, and neurodevelopmental tools used, large prospective studies are needed to ascertain the actual occurrence of neuropsychological morbidity of children with isolated ACC.

Fetal development of the corpus callosum: Insights from a 3T DTI and tractography study in a patient with segmental callosal agenesis

Commissural embryology mechanisms are not yet completely understood. The study and comprehension of callosal dysgenesis can provide remarkable insights into embryonic or fetal commissural development. The diffusion tensor imaging (DTI) technique allows the in vivo analyses of the white-matter microstructure and is a valid tool to clarify the disturbances of brain connections in patients with dysgenesis of the corpus callosum (CC). The segmental callosal agenesis (SCAG) is a rare partial agenesis of the corpus callosum (ACC). In a newborn with SCAG the DTI and tractography analyses proved that the CC was made of two separate segments consisting respectively of the ventral part in the genu and body of the CC, connecting the frontal lobes, and the dorsal part in the CC splenium and the attached hippocampal commissure (HC), connecting the parietal lobes and the fornix. These findings support the embryological thesis of a separated origin of the ventral and the dorsal parts of the CC.

Thalamocortical-auditory network alterations following cuprizone-induced demyelination

Background

Demyelination and remyelination are common pathological processes in many neurological disorders, including multiple sclerosis (MS). Clinical evidence suggests extensive involvement of the thalamocortical (TC) system in patients suffering from MS.

Methods

Using murine brain slices of the primary auditory cortex, we investigated the functional consequences of cuprizone-induced de- and remyelination on neuronal activity and auditory TC synaptic transmission in vitro.

Results

Our results revealed an impact of myelin loss and restoration on intrinsic cellular firing patterns, synaptic transmission, and neuronal plasticity in layer 3 and 4 neurons of the auditory TC network. While there was a complex hyper- and depolarizing shift of the resting membrane potential, spontaneous and induced action potential firing was reduced during demyelination and early remyelination. In addition, excitatory postsynaptic potential amplitudes were decreased and induction of LTP was reduced during demyelination.

Conclusions

These data indicate that demyelination-induced impairment of neurons and network activity within the TC system may underlie clinical symptoms observed in demyelinating diseases, corroborating human findings that disease progression is significantly correlated with microstructural tissue damage of the TC system. Further investigation into focal inflammation-induced demyelination models ex vivo and in vivo are needed to understand the functional implication of local and remote lesion formation on TC network activity in MS.

Chiari type 1 malformation, corpus callosum agenesis and patent craniopharyngeal canal in an 11-year-old boy

We describe the neuroimaging findings of an 11-year-old boy who presented with mild occipital headache and precocious puberty. This child was found to have a combination of various midline anomalies including a Chiari type 1 malformation, corpus callosum agenesis and patent craniopharyngeal canal with adjacent intracranial dermoid cyst.

The white matter tracts of the cerebrum in ventricular surgery and hydrocephalus

OBJECTIVE The relationship of the white matter tracts to the lateral ventricles is important when planning surgical approaches to the ventricles and in understanding the symptoms of hydrocephalus. The authors' aim was to explore the relationship of the white matter tracts of the cerebrum to the lateral ventricles using fiber dissection technique and MR tractography and to discuss these findings in relation to approaches to ventricular lesions. METHODS Forty adult human formalin-fixed cadaveric hemispheres (20 brains) and 3 whole heads were examined using fiber dissection technique. The dissections were performed from lateral to medial, medial to lateral, superior to inferior, and inferior to superior. MR tractography showing the lateral ventricles aided in the understanding of the 3D relationships of the white matter tracts with the lateral ventricles. RESULTS The relationship between the lateral ventricles and the superior longitudinal I, II, and III, arcuate, vertical occipital, middle longitudinal, inferior longitudinal, inferior frontooccipital, uncinate, sledge runner, and lingular amygdaloidal fasciculi; and the anterior commissure fibers, optic radiations, internal capsule, corona radiata, thalamic radiations, cingulum, corpus callosum, fornix, caudate nucleus, thalamus, stria terminalis, and stria medullaris thalami were defined anatomically and radiologically. These fibers and structures have a consistent relationship to the lateral ventricles. CONCLUSIONS Knowledge of the relationship of the white matter tracts of the cerebrum to the lateral ventricles should aid in planning more accurate surgery for lesions within the lateral ventricles.

Corpus callosum abnormalities: neuroradiological and clinical correlations

AIM

To study neuroradiological features in pediatric patients with corpus callosum abnormalities, using new functional subtyping for the corpus callosum, and to correlate the features with the clinical presentation.

METHOD

We performed a retrospective review of 125 patients with radiologically identified abnormalities of the corpus callosum seen between 1999 and 2012. The study reviewed clinical features, genetic etiology, and chromosomal microarray (CMA) results. We used a new functional classification for callosal abnormalities based on embryological and anatomical correlations with four classes: complete agenesis, anterior agenesis (rostrum, genu, body), posterior agenesis (isthmus, splenium), and complete hypoplasia (thinning). We also studied the presence of extracallosal abnormalities.

RESULTS

The new functional callosal subtyping did not reveal significant differences between the various subtypes in association with neurological outcome; however, the presence of cardiac disease was found more frequently in the group with complete agenesis. Thirty-seven per cent (46/125) had identifiable causes: of these, 48% (22/46) had a monogenic disorder, 30% (14/46) had a pathogenic chromosomal copy-number variant detected by CMA or karyotype, and 22% (10/46) had a recognizable clinical syndrome for which no confirmatory genetic test was available (namely Aicardi syndrome/septo-optic dysplasia and Goldenhar syndrome). The diagnostic yield for a significant CMA change was 19%. The presence of Probst bundles was found to be associated with a better neurodevelopmental outcome.

INTERPRETATION

The functional classification system alone 'without clinical data' cannot predict the functional outcome. The presence of extracallosal brain abnormalities and an underlying genetic diagnosis predicted a worse neurodevelopmental outcome. This study highlights the importance of CMA testing and cardiac evaluation as part of a routine screen.

The double massa intermedia

Background:

To describe the rare finding of a double massa intermedia (MI). Typically, the MI (interthalamic adhesion) is a single bridge of gray matter connecting the medial surfaces of the thalami.

Methods:

Twelve formalin- and alcohol-fixed human third ventricles were examined from superior to inferior by fiber dissection technique under ×6 to ×40 magnifications and with the endoscope.

Results:

In all hemispheres, the anterior and posterior commissure were defined. The MI, which bridges the medial surfaces of the thalami, was defined in all hemispheres. In one hemisphere, there was a second bridge between the thalami, located posteroinferior to the common MI. Endoscopic view confirmed that there was a second MI in this specimen. The MI usually traverses the third ventricle posterior to the foramen of Monro and connects the paired thalami. The MI is an important landmark during endoscopic and microscopic surgeries of the third ventricle. Although a double MI is very rare, surgeons should be aware of the possibility in their surgical planning.

Conclusion:

The surgeon should be aware of the possibility of a double MI to avoid confusion during third ventricle surgery.

Characterization of an Inherited Neurologic Syndrome in Toyger Cats with Forebrain Commissural Malformations, Ventriculomegaly and Interhemispheric Cysts

BACKGROUND

In children, frequent congenital malformations with concomitant agenesis of the corpus callosum are diagnosed by neuroimaging in association with other cerebral malformations, including interhemispheric cysts and ventriculomegaly. Similar studies providing full characterization of brain defects by in vivo magnetic resonance imaging (MRI), and correlations with the pertinent anatomic pathologic examinations are absent in veterinary medicine.

HYPOTHESIS/OBJECTIVES

Congenital brain defects underlie the neurologic signs observed in Toyger cats selectively bred for a short ear phenotype.

ANIMALS

Using proper pedigree analysis and genetic evaluations, 20 related Oriental-derived crossbred Toyger cats were evaluated. Seven clinically healthy (carrier) cats and 13 clinically affected cats that had neurologic signs, short ear phenotype and concomitant complex brain anomalies were studied.

METHODS

Complete physical and neurologic examinations and MRI were performed in all clinically healthy and affected cats. Postmortem and histopathologic examinations were performed in 8 affected cats and 5 healthy cats.

RESULTS

Neurologic and MRI investigations confirmed 13 clinically affected cats with structural brain abnormalities. Ventriculomegaly with frequent concomitant supratentorial interhemispheric, communicating ventricular type-1b cysts and multiple midline and callosal malformations were detected in all cats displaying neurologic signs. Genetic analysis confirmed autosomal recessive mode of inheritance with no chromosomal abnormalities.

CONCLUSIONS AND CLINICAL IMPORTANCE

Neuroanatomic dissections and histopathology were helpful for evaluation of abnormalities in midline brain structures, and for the full characterization of cysts. However, MRI was more sensitive for detection of small cysts. In this feline model, MRI diagnosis had extremely good correlation with pathologic abnormalities noted in the subset of animals that were examined by both modalities.

Corpus callosotomy

BACKGROUND

Corpus callosotomy is an effective, relatively low-risk, palliative procedure for a selected population of patients with medically intractable epilepsy. Here we describe this technique.

METHOD

An interhemispheric microsurgical approach is performed. Neuronavigation facilitates orientation. The callosal body is transected through to the roof of the ipsilateral ventricle using an ultrasonic aspirator; the genu and rostrum are then identified and also split. If a total callosotomy is performed, transection of the splenium is performed with care given to preserve the crus of the fornix.

CONCLUSIONS

Meticulous microsurgical technique and knowledge of the limbic system's anatomy is essential to keeping this procedure safe and effective.

Normal development

Numerous events are involved in brain development, some of which are detected by neuroimaging. Major changes in brain morphology are depicted by brain imaging during the fetal period while changes in brain composition can be demonstrated in both pre- and postnatal periods. Although ultrasonography and computed tomography can show changes in brain morphology, these techniques are insensitive to myelination that is one of the most important events occurring during brain maturation. Magnetic resonance imaging (MRI) is therefore the method of choice to evaluate brain maturation. MRI also gives insight into the microstructure of brain tissue through diffusion-weighted imaging and diffusion tensor imaging. Metabolic changes are also part of brain maturation and are assessed by proton magnetic resonance spectroscopy. Understanding and knowledge of the different steps in brain development are required to be able to detect morphologic and structural changes on neuroimaging. Consequently alterations in normal development can be depicted.

Callosotopy: leg motor connections illustrated by fiber dissection

Precise anatomical knowledge of the structure of the corpus callosum is important in split-brain research and during neurosurgical procedures sectioning the callosum. According to the classic literature, commissural fibers connecting the motor cortex are situated in the anterior part of the corpus callosum. On the other hand, more recent imaging studies using diffusion tensor imaging indicate a more posterior topography of callosal fibers connecting motor areas. Topographical knowledge is especially critical when performing disconnective callosotomies in epilepsy patients who experience sudden loss of leg motor control, so-called epileptic drop attacks. In the current study, we aim to precisely delineate the topography of the leg motor connections of the corpus callosum. Of 20 hemispheres obtained at autopsy, 16 were dissected according to Klingler's fiber dissection technique to study the course and topography of callosal fibers connecting the most medial part of the precentral gyrus. Fibers originating from the anterior bank of the central sulcus were invariably found to be located in the isthmus of the corpus callosum, and no leg motor fibers were found in the anterior part of the callosum. The current results suggest that the disconnection of the pre-splenial fibers, located in the posterior one-third of the corpus callosum, is paramount in obtaining a good outcome after callosotomy.

Absent circle of Willis with vascular pollarding in an adult with colpocephaly: A developmental perspective

Absent circle of Willis (COW) has been described in cases of severe forms of cerebral developmental anomalies such as alobar prosencephaly. However, there are no reports of absent COW in patients with a milder form of cerebral abnormality such as colpocephaly. We report a unique case of an adult with colpocephaly and absent COW and discuss their association from a developmental perspective.

Aberrant supracallosal longitudinal bundle: MR features, pathogenesis and associated clinical phenotype

OBJECTIVE

To describe the MRI and structural features of a peculiar malformation of the corpus callosum (CC) in a group of young patients with intellectual disability.

METHODS

We studied with conventional MRI and DTI a group of subjects showing an aberrant supracallosal bundle, characterized by the presence of a triangle-shaped bulging above the dorsal surface of CC on the midline. Clinical evaluations, CGH-array and instrumental analysis were also collected.

RESULTS

Among 85 patients with malformed CC, we identified 15 subjects that showed the supracallosal bundle. The CC was thickened in five cases, long and thinned in three cases, short and thinned in three cases and it had a "ribbon-like" appearance in four subjects. Additional brain anomalies were present in eight cases. DTI colour maps and tractography showed that the bundle had an antero-posterior longitudinal orientation and that the tract bifurcated posteriorly, ending in the posterior hippocampi. Patients had different combinations of neurological symptoms, but all showed mild or severe intellectual disability.

CONCLUSIONS

Combining radiological and genetic data with embryological knowledge of the development of cerebral commissures, we hypothesize that the supracallosal bundle represents a vestigial structure, the dorsal fornix, present during fetal life. Its persistence is associated with intellectual disability.

KEY POINTS

• An aberrant longitudinal bundle can be detected above corpus callosum. • The presence of the supracallosal bundle is associated with intellectual disability. • The supracallosal bundle may represent a persistent dorsal fornix.

Abnormal shape of the cavum septi pellucidi: an indirect sign of partial agenesis of the corpus callosum

OBJECTIVE

To describe and assess the presence of a new indirect sign of partial agenesis of the corpus callosum (pACC): an abnormally shaped cavum septi pellucidi (CSP).

METHODS

We analyzed retrospectively images from all 71 cases of pACC seen at two referral centers between September 2006 and April 2014. Abnormally shaped CSP was diagnosed when its lateral dimension was greater than its anteroposterior dimension in the axial transthalamic plane, and the incidence of this sign was assessed. We also examined the following variables: gestational age at referral, indication for referral, which (if any) of the four corpus callosal segments were abnormal, presence of other, previously established, indirect signs of callosal agenesis (ACC) and presence of additional cerebral or extracerebral anomalies.

RESULTS

In 56 of the 71 (79%) cases, the CSP was measurable; it was abnormally shaped in 19 (34%) of these cases, 15 (79%) of which had no other indirect signs of pACC. Of 23 cases with isolated pACC and no other indirect signs, 12 (52%) had an abnormally shaped CSP.

CONCLUSIONS

In a significant proportion of cases of pACC detected prenatally, the shape of the CSP is abnormal. This should be considered an additional indirect sign of pACC, and is frequently the only clue to the diagnosis. When observing this sign in a screening context, pACC should be considered, and an attempt to visualize the corpus callosum directly in the midsagittal plane is suggested.

Variability of Forebrain Commissures in Callosal Agenesis: A Prenatal MR Imaging Study

BACKGROUND AND PURPOSE

Agenesis of the corpus callosum, even when isolated, may be characterized by anatomic variability. The aim of this study was to describe the types of other forebrain commissures in a large cohort of randomly enrolled fetuses with apparently isolated agenesis of the corpus callosum at prenatal MR imaging.

MATERIALS AND METHODS

All fetuses with apparent isolated agenesis of the corpus callosum undergoing prenatal MR imaging from 2004 to 2014, were evaluated for the presence of the anterior or a vestigial hippocampal commissure assessed in consensus by 2 pediatric neuroradiologists.

RESULTS

Overall, 62 cases of agenesis of the corpus callosum were retrieved from our data base. In 3/62 fetuses (4.8%), no forebrain commissure was visible at prenatal MR imaging, 23/62 fetuses (37.1%) presented with only the anterior commissure, and 20/62 fetuses (32.3%) showed both the anterior commissure and a residual vestigial hippocampal commissure, whereas in the remaining 16/62 fetuses (25.8%), a hybrid structure merging a residual vestigial hippocampal commissure and a rudiment of the corpus callosum body was detectable. Postnatal MR imaging, when available, confirmed prenatal forebrain commissure findings.

CONCLUSIONS

Most fetuses with apparent isolated agenesis of the corpus callosum showed at least 1 forebrain commissure at prenatal MR imaging, and approximately half of fetuses also had a second commissure: a vestigial hippocampal commissure or a hybrid made of a hippocampal commissure and a rudimentary corpus callosum body. Whether such variability is the result of different genotypes and whether it may have any impact on the long-term neurodevelopmental outcome remains to be assessed.

Cavum Septum Pellucidum in Retired American Pro-Football Players

Previous studies report that cavum septum pellucidum (CSP) is frequent among athletes with a history of repeated traumatic brain injury (TBI), such as boxers. Few studies of CSP in athletes, however, have assessed detailed features of the septum pellucidum in a case-control fashion. This is important because prevalence of CSP in the general population varies widely (2% to 85%) between studies. Further, rates of CSP among American pro-football players have not been described previously. We sought to characterize MRI features of the septum pellucidum in a series of retired pro-football players with a history of repeated concussive/subconcussive head traumas compared with controls. We retrospectively assessed retired American pro-football players presenting to our memory clinic with cognitive/behavioral symptoms in whom structural MRI was available with slice thickness ≤2 mm (n=17). Each player was matched to a memory clinic control patient with no history of TBI. Scans were interpreted by raters blinded to clinical information and TBI/football history, who measured CSP grade (0-absent, 1-equivocal, 2-mild, 3-moderate, 4-severe) and length according to a standard protocol. Sixteen of 17 (94%) players had a CSP graded ≥2 compared with 3 of 17 (18%) controls. CSP was significantly higher grade (p<0.001) and longer in players than controls (mean length±standard deviation: 10.6 mm±5.4 vs. 1.1 mm±1.3, p<0.001). Among patients presenting to a memory clinic, long high-grade CSP was more frequent in retired pro-football players compared with patients without a history of TBI.

Absent cavum septum pellucidum: a review with emphasis on associated commissural abnormalities

The cavum septum pellucidum (CSP) is an important fetal midline forebrain landmark, and its absence often signifies additional underlying malformations. Frequently detected by prenatal sonography, absence of the CSP requires further imaging with pre- or postnatal MRI to characterize the accompanying abnormalities. This article reviews the developmental anatomy of the CSP and the pivotal role of commissurization in normal development. An understanding of the patterns of commissural abnormalities associated with absence of the CSP can lead to improved characterization of the underlying spectrum of pathology.

MIR137HG risk variant rs1625579 genotype is related to corpus callosum volume in schizophrenia

Genome-wide association studies implicate the MIR137HG risk variant rs1625579 (MIR137HGrv) within the host gene for microRNA-137 as a potential regulator of schizophrenia susceptibility. We examined the influence of MIR137HGrv genotype on 17 subcortical and callosal volumes in a large sample of individuals with schizophrenia and healthy controls (n=841). Although the volumes were overall reduced relative to healthy controls, for individuals with schizophrenia the homozygous MIR137HGrv risk genotype was associated with attenuated reduction of mid-posterior corpus callosum volume (p=0.001), along with trend-level effects in the adjacent central and posterior corpus callosum. These findings are unique in the literature and remain robust after analysis in ethnically homogenous and single-scanner subsets of the larger sample. Thus, our study suggests that the mechanisms whereby MIR137HGrv works to increase schizophrenia risk are not those that generate the corpus callosum volume reductions commonly found in the disorder.

Microstructural changes in thickened corpus callosum in children: contribution of magnetic resonance diffusion tensor imaging

BACKGROUND

Thickened corpus callosum is a rare finding and its pathophysiology is not well known. An anomalous supracallosal bundle has been depicted by fiber tracking in some cases but no diffusion tensor imaging metrics of thickened corpus callosum have been reported.

OBJECTIVE

To use diffusion tensor imaging (DTI) in cases of thickened corpus callosum to help in understanding its clinical significance.

MATERIALS AND METHODS

During a 7-year period five children (ages 6 months to 15 years) with thickened corpus callosum were studied. We determined DTI metrics of fractional anisotropy (FA), mean diffusivity, and axial (λ1) and radial (λ2, λ3) diffusivity and performed 3-D fiber tracking reconstruction of the thickened corpus callosum. We compared our results with data from the literature and 24 age-matched controls.

RESULTS

Brain abnormalities were seen in all cases. All children had at least three measurements of corpus callosum thickness above the 97th percentile according to age. In all children 3-D fiber tracking showed an anomalous supracallosal bundle and statistically significant decrease in FA (P = 0.003) and λ1 (P = 0.001) of the corpus callosum compared with controls, but no significant difference in mean diffusivity and radial diffusivity.

CONCLUSION

Thickened corpus callosum was associated with abnormal bundles, suggesting underlying axonal guidance abnormality. DTI metrics suggested abnormal fiber compactness and density, which may be associated with alterations in cognition.

Structural brain defects

Up to 14% of patients with congenital metabolic disease may show structural brain abnormalities from perturbation of cell proliferation, migration, and/or organization. Most inborn errors of metabolism have a postnatal onset. Abnormalities from genetic disease processes have a prenatal onset. Energy impairment, substrate insufficiency, cell membrane receptor and cell signaling abnormalities, and toxic byproduct accumulation are associations between genetic disorders and structural brain anomalies. Collective imaging patterns of brain abnormalities can provide clues to the underlying etiology. We review selected metabolic diseases associated with brain malformations and highlight characteristic clinical and imaging manifestations that help narrow the differential diagnosis.

Children born to women treated for hypothyroidism during pregnancy show abnormal corpus callosum development

BACKGROUND

Thyroid hormone (TH) is essential for the developing brain, and because the fetal thyroid develops relatively late in gestation, the maternal TH supply is critical for fetal brain development. However, if the mother has hypothyroidism during pregnancy, fetal brain and neuropsychological development may be compromised. Rodents experiencing maternal TH insufficiency show abnormal corpus callosum (CC) morphology, but it is not known if children born to women treated for hypothyroidism (HYPO) show similar effects. The purpose of the current study was to investigate HYPO for CC morphology and morphometry and to determine whether any specific CC abnormalities were associated aspects of maternal hypothyroidism and were correlated with reduced neuropsychological functioning in the children.

METHODS

ANALYZE software was used to trace CCs in archived magnetic resonance imaging scans from 22 HYPO and 22 matched controls. Areas of two sub-regions and six segments and different shape metrics (angles, lengths, ratios) were determined. CC parameters were correlated with maternal thyrotropin (TSH) values and number of hypothyroid trimesters as well as the child's neuropsychological test performance.

RESULTS

HYPO showed a smaller anterior CC and genu and larger posterior CC and splenium areas than controls as well as shape abnormalities in genu and splenium. Results were correlated with the duration of maternal hypothyroidism. Executive function skills were positively associated with genu size in HYPO, while verbal comprehension skills were negatively associated with splenium and overall posterior CC sizes.

CONCLUSIONS

Maternal hypothyroidism contributes to CC abnormalities in the offspring, and effects differ for anterior versus posterior CC regions.

Corpus callosum atrophy associated with the degree of cognitive decline in patients with Alzheimer's dementia or mild cognitive impairment: a meta-analysis of the region of interest structural imaging studies

Individual structural neuroimaging studies of the corpus callosum (CC) in Alzheimer's disease (AD) and mild cognitive impairment (MCI) with the region of interest (ROI) analysis have yielded inconsistent findings. The aim of this study was to conduct a meta-analysis of structural imaging studies using ROI technique to measure the CC midsagittal area changes in patients with AD or MCI. Databases of PubMed, the Cochrane Library, the ISI Web of Science, and Science Direct from inception to June 2014 were searched with key words "corpus callosum" or "callosal", plus "Alzheimer's disease" or "mild cognitive impairment". Twenty-three studies with 603 patients with AD, 146 with MCI, and 638 healthy controls were included in this meta-analysis. Effect size was used to measure the difference between patients with AD or MCI and healthy controls. Significant callosal atrophy was found in MCI patients with an effect size of -0.36 (95% CI, -0.57 to -0.14; P = 0.001). The degree of the CC atrophy in mild AD was less severe than that in moderate AD with a mean effect size -0.69 (95% CI, -0.89 to -0.49) versus -0.92 (95% CI, -1.16 to -0.69), respectively. Comparing with healthy controls, patients with MCI had atrophy in the anterior portion of the CC (i.e., rostrum and genu). In contrast, patients with AD had atrophy in both anterior and posterior portions (i.e., splenium). These results suggest that callosal atrophy may be related to the degree of cognitive decline in patients with MCI and AD, and it may be used as a biomarker for patients with cognitive deficit even before meeting the criteria for AD.

Disrupted developmental organization of the structural connectome in fetuses with corpus callosum agenesis

Agenesis of the corpus callosum is a model disease for disrupted connectivity of the human brain, in which the pathological formation of interhemispheric fibers results in subtle to severe cognitive deficits. Postnatal studies suggest that the characteristic abnormal pathways in this pathology are compensatory structures that emerge via neural plasticity. We challenge this hypothesis and assume a globally different network organization of the structural interconnections already in the fetal acallosal brain. Twenty fetuses with isolated corpus callosum agenesis with or without associated malformations were enrolled and fiber connectivity among 90 brain regions was assessed using in utero diffusion tensor imaging and streamline tractography. Macroscopic scale connectomes were compared to 20 gestational age-matched normally developing fetuses with multiple granularity of network analysis. Gradually increasing connectivity strength and tract diffusion anisotropy during gestation were dominant in antero-posteriorly running paramedian and antero-laterally running aberrant pathways, and in short-range connections in the temporoparietal regions. In fetuses with associated abnormalities, more diffuse reduction of cortico-cortical and cortico-subcortical connectivity was observed than in cases with isolated callosal agenesis. The global organization of anatomical networks consisted of less segregated nodes in acallosal brains, and hubs of dense connectivity, such as the thalamus and cingulate cortex, showed reduced network centrality. Acallosal fetal brains show a globally altered connectivity network structure compared to normals. Besides the previously described Probst and sigmoid bundles, we revealed a prenatally differently organized macroconnectome, dominated by increased connectivity. These findings provide evidence that abnormal pathways are already present during at early stages of fetal brain development in the majority of cerebral white matter.

Functional topography of the corpus callosum investigated by DTI and fMRI

This short review examines the most recent functional studies of the topographic organization of the human corpus callosum, the main interhemispheric commissure. After a brief description of its anatomy, development, microstructure, and function, it examines and discusses the latest findings obtained using diffusion tensor imaging (DTI) and tractography (DTT) and functional magnetic resonance imaging (fMRI), three recently developed imaging techniques that have significantly expanded and refined our knowledge of the commissure. While DTI and DTT have been providing insights into its microstructure, integrity and level of myelination, fMRI has been the key technique in documenting the activation of white matter fibers, particularly in the corpus callosum. By combining DTT and fMRI it has been possible to describe the trajectory of the callosal fibers interconnecting the primary olfactory, gustatory, motor, somatic sensory, auditory and visual cortices at sites where the activation elicited by peripheral stimulation was detected by fMRI. These studies have demonstrated the presence of callosal fiber tracts that cross the commissure at the level of the genu, body, and splenium, at sites showing fMRI activation. Altogether such findings lend further support to the notion that the corpus callosum displays a functional topographic organization that can be explored with fMRI.