Imaging the corpus callosum, septum pellucidum and fornix in children: normal anatomy and variations of normality

Intrinsic organization of the corpus callosum

The corpus callosum-the largest commissural fiber system connecting the two cerebral hemispheres-is considered essential for bilateral sensory integration and higher cognitive functions. Most studies exploring the corpus callosum have examined either the anatomical, physiological, and neurochemical organization of callosal projections or the functional and/or behavioral aspects of the callosal connections after complete/partial callosotomy or callosal lesion. There are no works that address the intrinsic organization of the corpus callosum. We review the existing information on the activities that take place in the commissure in three sections: I) the topographical and neurochemical organization of the intracallosal fibers, II) the role of glia in the corpus callosum, and III) the role of the intracallosal neurons.

Interhemispheric coherence of EEG rhythms in children: Maturation and differentiation in corpus callosum dysgenesis

OBJECTIVES

To evaluate the evolution of interhemispheric coherences (ICo) in background and spindle frequency bands during childhood and use it to identify individuals with corpus callosum dysgenesis (CCd).

METHODS

A monocentric cohort of children aged from 0.25 to 15 years old, consisting of 13 children with CCd and 164 without, was analyzed. The ICo of background activity (ICOBckgrdA), sleep spindles (ICOspindles), and their sum (sICO) were calculated. The impact of age, gender, and CC status on the ICo was evaluated, and the sICO was used to discriminate children with or without CCd.

RESULTS

ICOBckgrdA, ICOspindles and sICO increased significantly with age without any effect of gender (p < 10-4), in both groups. The regression equations of the different ICo were stronger, with adjusted R2 values of 0.54, 0.35, and 0.57, respectively. The ICo was lower in children with CCd compared to those without CCd (p < 10-4 for all comparisons). The area under the precision recall curves for predicting CCd using sICO was 0.992 with 98.9 % sensitivity and 87.5 % specificity.

DISCUSSION

ICo of spindles and background activity evolve in parallel to brain maturation and depends on the integrity of the corpus callosum. sICO could be an effective diagnostic biomarker for screening children with interhemispheric dysfunction.

Endoscopic trans-septal interforniceal approach for excision of colloid cysts of the third ventricle using the rotational technique

Colloid cysts of the third ventricle are benign intracranial lesions that account for 0.5 to 2% of all brain tumors and are even rarer in pediatric population. Dandy was the first to successfully excise a colloid cyst of the third ventricle via a transcortical transventricular approach in 1921. For several decades to follow, the transcortical transventricular and transcallosal microsurgical approaches remained the cornerstone of surgical management of these lesions. With time and refinements in endoscopic equipment and techniques, endoscopic resection of colloid cysts evolved into a currently well-established and appealing minimally invasive alternative to microsurgery. Endoscopic endochannel techniques for colloid cysts of the third ventricle may either be transforaminal or trans-septal interforniceal, depending on the pathoanatomical features of the colloid cyst and its relation to the juxtaposed anatomical structures. The endoscopic trans-septal interforniceal approach is required to access the rare subset of colloid cysts that extend superior to the roof of the third ventricle between the two fornices insinuating themselves between the leaflets of the septum pellucidum. In this article, the surgical technique of the endochannel endoscopic trans-septal interforniceal approach is elaborated upon. A representative case is presented along with an operative video.

Imaging of the septum pellucidum: normal, variants and pathology

The septum pellucidum is a largely neglected anatomical midline structure during post-natal neuroimaging interpretation. Conversely, it is one of the anatomical landmarks used on pre-natal ultrasound to access normal midline formation. Because of its importance during the pre-natal period, the awareness of its primary malformative abnormalities is much higher than its disruptive acquired pathologies, often leading the misinterpretation. In this article, we will review the normal septum pellucidum formation, anatomy, and anatomical variants and will describe the imaging findings in primary malformative and secondary disruptive abnormalities affecting the septum pellucidum.

Algorithmic approach to neuroradiological diagnosis with pre-natal MRI: non-visualization of the fetal cavum septi pellucidi on mid-trimester screening ultrasound

ADVANCES IN KNOWLEDGE

A systematic approach by the radiologist to analysis of imaging and other clinical data in the fetus with absent septal leaflets suspected on ultrasound will improve diagnostic efficiency, accuracy, and pre-natal counselling.

Association between Cognitive Impairment and Hippocampal Subfield Volumes in Multiple System Atrophy

This study aimed to explore morphological changes of hippocampal subfields in patients with multiple system atrophy (MSA) with and without cognitive impairment using FreeSurfer-automated segmentation of hippocampal subfield techniques and their relationship with cognitive function. We enrolled 75 patients with MSA classified as cognitively impaired MSA (MSA-CI, n = 40) and cognitively preserved MSA (MSA-CP, n = 35), as well as 68 healthy controls. All participants underwent three-dimensional volume T1-weighted magnetic resonance imaging. The hippocampal subfield volume was measured using FreeSurfer version 7.2 and compared among groups. Regression analyses were performed between the hippocampal subfield volumes and cognitive variables. Compared with healthy controls, the volume of the right cornu ammonis (CA) 2/3 was significantly lower in the MSA-CI group (P=0.029) and that of the left fimbria was significantly higher in the MSA-CP group (P=0.046). Results of linear regression analysis showed that the right CA2/3 volume was significantly correlated with the Frontal Assessment Battery score in patients with MSA (adjusted R ² = 0.282, β = 0.227, and P=0.041). The hippocampal subfield volume decreased in patients with MSA-CI, even at the early disease stages. Specific structural changes in the hippocampus might be associated with cognitive deficits in MSA.

Delineating septo-optic dysplasia

BACKGROUND

Septo-optic dysplasia (SOD), once a variable triad of septum pellucidum defects (SPDs), optic nerve hypoplasia (ONH), and hypopituitarism, has had multiple findings added, with uncertain causes, definitions, and limits.

METHOD

Literature review.

RESULTS

SOD is a complex vascular sequence with confounders.

CONCLUSIONS

Proximal anterior cerebral artery trunk disruptions cause overlapping primary effects, giving ONH alone most often, and isolated SPD less. ONH disruptions can spread to pituitary, SPD disruptions to the cerebral cortex, causing schizencephaly and related anomalies. Pituitary defects are rare without ONH, and cortical findings are rare without SPD. Extensions are unidirectional, so isolated pituitary or cortical defects are separate from SOD. Micro- an- ophthalmia, a suggested ONH variant, is not part of SOD. Disruption by-products can affect development, causing cognitive and endocrine issues, and structural anomalies such as corpus callosum thinning, ventriculomegaly, and hippocampal and olfactory findings. Limbic extensions may also contribute to the same structural defects as by-products. Midline CNS developmental anomalies can act as disruptive foci, most likely through vascular variants, but have separate pathogenesis. Relative frequencies of specific pituitary hormone defects change as SOD rates increase. Increasing relative rates of midline CNS developmental defects and cortical anomalies are consistent with rising levels of exogenous exposures sensitizing to midline predispositions.

What Are the Double Lines of the Fetal Cavum Septi Pellucidi on Ultrasound?

OBJECTIVE

To demonstrate the significance of the double line appearance of the septi pellucidi laminae (SPL) on fetal ultrasound.

METHOD

A total of 522 uncomplicated singleton pregnancies (15 to 39 weeks' gestational age) with fetal ultrasounds were enrolled. The presence of a single versus double line SP as well as measurement of the cavum septi pellucidi (CSP) was determined retrospectively. Ultrasound settings from the CSP images were recorded. Thickness of the SPL was measured in 20 ultrasound and 14 MRI cases; histology was reviewed from one neonate. Maternal BMI and gestational age were also recorded.

RESULTS

The presence of double line SPL is a normal sonographic finding, seen in 47% (188/403) of normal fetuses. Thickness of the SPL in 10 cases with double line averaged 1.4 mm and in 10 cases with single line averaged 0.8 mm; MRI measurements were within 0.1 mm of the corresponding ultrasound measurements. Double line cavum was more often seen with mid-dynamic contrast range settings (5, 6) rather than high range settings (7-10) (P value <.05). The double line was only visualized on ultrasound when the angle of insonation was at or near perpendicular to the laminae; it was never visualized on coronal ultrasound imaging or MRI imaging.

CONCLUSION

A double line septum pellucidum lamina is a normal finding seen in almost 50% of uncomplicated singleton pregnancies. It may be attributed to borders of cell layers within each lamina that form separate specular reflections on both sides; this can be accentuated by ultrasound settings and beam angulation.

DWI Hyperintensity in the Fornix Fimbria on MRI in Children

BACKGROUND AND PURPOSE

The fornix-fimbria complex is mainly involved in emotions and memory. In brain MR imaging studies of young children, we have occasionally noted DWI hyperintensity in this region. The significance of this finding remains unclear. This study evaluated the DWI signal in the fornix-fimbria complex of children 0-2 years of age, including the frequency of signal hyperintensity and clinical context.

MATERIALS AND METHODS

Brain MR imaging of 714 children 0-2 years of age (mean, 11 months), performed between September 2018 and May 2021, was reviewed and evaluated for DWI signal changes in the fornix-fimbria. All children with available MR imaging studies including DWI were included. Children with poor image quality, poor visualization of the fornix-fimbria region, and missing medical data were excluded. Additional imaging findings were also evaluated. Demographic data were retrieved from the medical files. We compared the ADC values of the fimbria and fornix between children with and without signal changes. The unpaired 2-tailed Student t test and χ² test were used for statistical analysis.

RESULTS

DWI signal hyperintensity of the Fornix-fimbria complex was noted in 53 (7.4%) children (mean age, 10 months). Their mean ADC values were significantly lower than those of the children with normal DWI findings (P < .05). About half of the children had otherwise normal MR imaging findings. When detected, the most common abnormality was parenchymal volume loss (15%). The most common indication for imaging was seizures (26.5%).

CONCLUSIONS

DWI hyperintensity in the fornix-fimbria complex was detected in 7.4% of children 0-2 years of age. The etiology is not entirely clear, possibly reflecting a transient phenomenon.

A Fiber Dissection Study of the Anterior Commissure: Correlations with Diffusion Spectrum Imaging Tractography and Clinical Relevance in Gliomas

The anterior commissure, which connects bilateral temporal lobes and olfactive areas, remains elusive in many aspects of its structure and functional role. To comparatively describe anatomical details of the anterior commissure using cadaveric fiber dissection (FD) and diffusion spectrum imaging (DSI) thus refining our knowledge of the tract and exploring its clinical relevance in glioma migration. Twelve normal postmortem hemispheres were treated with Klingler's method and subjected to FD with medial, inferior, and lateral approaches. The FD findings were correlated with DSI tractography results. To illustrate the clinical relevance, two patients with recurrent temporal high-grade glioma are described. Our FD and DSI tractography of the anterior commissure disclosed a new anatomical paradigm. The FD confirmed that the anterior limb (absent sometimes and variable) and the lateral/temporal extension include the rostral portion and caudal portion, respectively, of the anterior commissure fibers. The shape of the lateral/temporal extension predominantly resembles an 'H'. The DSI tractography findings corresponded to these FD results. According to the FD, the Virchow-Robin space is continuous with the subarachnoid space and very close to the anterior commissure. The two clinical cases presented severe disturbances of consciousness and behavior despite good local tumor control. Subsequent magnetic resonance images showed new lesions infiltrating the contralateral temporal lobes. FD combined with DSI provided anatomical details facilitating a better understanding of the anterior commissure. Glioma migration routes to the contralateral temporal lobe included the anterior commissure, Virchow-Robin space, and subarachnoid space and were clinically relevant.

The normal fetal Cavum Septum Pellucidum in MR imaging - New biometric data

BACKGROUND AND PURPOSE

The cavum septum pellucidum (CSP) is an important landmark in the evaluation of the fetal neural axis. A deviation from the ultrasonic normal values may be associated with unfavorable outcomes, and a normal CSP provides reassurance of normal central forebrain development. Today, there is biometric data regarding the normal values for the width of the CSP in fetal ultrasound, but there is no such data for fetal MRI. The aim of this study was to determine the normal values for the measurements of the fetal CSP on MRI.

MATERIALS AND METHODS

We retrospectively examined 307 MRI scans of fetuses between 25 and 41 weeks gestation. Data was collected from the electronic charts of patients who underwent fetal MR imaging at a single tertiary Medical Center. The width and length of the CSP were measured in the axial plane, and the width and height were measured in the coronal plane.

RESULTS

The width and height of the CSP in fetuses tend to decrease starting from the 27th week of gestation onwards. High levels of intraobserver and interobserver agreements were calculated. The sex of the fetus does not appear to influence the biometry of the CSP.

CONCLUSION

This study provides MRI reference values for the dimensions of the CSP starting from the 25th week of gestation. Knowing the normal values for MRI could provide valuable information for researchers and in the decision-making process in patient's consultations.

Normal appearances and dimensions of the foetal cavum septi pellucidi and vergae on in utero MR imaging

Purpose

The aim of this study is to provide normative data about the appearances and dimensions of the cavum septi pellucidi and vergae (CSPV) on in utero MR (iuMR) imaging in second and third trimester foetuses.

Methods

Two hundred normal foetuses (from a low-risk pregnancy, with normal ante-natal USS findings and no intracranial abnormality of iuMR) had iuMR imaging between 18 and 37 gestational weeks (gw). The anatomical features on those studies were compared with published atlases of post-mortem foetal brains. The length, width and volume of the CSPV were measured in all foetuses.

Results

The anatomy of the CSPV and its relationship with the corpus callosum and the fornices on iuMR imaging was comparable with post-mortem data at all gestational ages studied. The length of the CSPV increased throughout pregnancy, whereas the width and volume of CSPV reached a maximum between 29 and 31 gw and then showed a reduction later in pregnancy.

Conclusion

The iuMR imaging features of the CSPV and its close anatomical relations closely correspond to post-mortem data. The CSPV was patent in all cases but we have shown that closure commences in the midpart of the third trimester and advances in a posterior to anterior direction.

Electronic supplementary material

The online version of this article (10.1007/s00234-020-02364-5) contains supplementary material, which is available to authorized users.

Schizencephaly revisited

Purpose

In this paper, I will report the range of appearances of schizencephaly in children and fetuses by reviewing a 10-year experience from a single centre and detail classification systems for the different forms of schizencephaly. This will lead to re-assessment of possible aetiological and mechanistic causes of schizencephaly.

Methods

All cases of pediatric and fetal schizencephaly were located on the local database between 2007 and 2016 inclusive. The studies were reviewed for the presence, location and type of schizencephaly, as well as the state of the (cavum) septum pellucidum, the location of the fornices and the presence of other brain abnormalities.

Results

The review included 21 children and 11 fetuses with schizencephaly. Schizencephaly (type 1) was found in 9% of children but no fetuses, schizencephaly (type 2) was present in 67% of the pediatric cases and in 45% of fetuses, whilst schizencephaly (type 3) was present in approximately 24% of children and 55% of fetuses. Other brain abnormalities were found in 67% of children and 55% of fetuses.

Conclusion

I have proposed a new system for classifying schizencephaly that takes into account all definitions of the abnormality in the literature. Using that approach, I have described the appearances and associations of pediatric and fetal cases of schizencephaly from a single centre. Review of the current literature appears to favour an acquired destructive aetiology for most cases of schizencephaly, and I have proposed a mechanism to explain the cortical formation abnormalities found consistently in and around areas of schizencephaly.

Biometry reference range of the corpus callosum in neonates: An observational study

This study aims to present the reference range of corpus callosum by ultrasound imaging in neonates and to develop a clinically feasible screening method for congenital abnormalities of corpus callosum.An observational study was conducted between January 2015 and July 2016; 2D and 3D ultrasound evaluations were conducted and virtural organ computer-aided analysis was applied in the volume calculation of corpus callosum. The following parameters were measured: thickness of the rostum, thickness of the genu, thickness of the body, thickness of the splenium, anterior-posterior distance, true length of the corpus callosum and the volume of the corpus callosum. Inter- and intraobserver agreement was also evaluated. The corrected gestational age was between 38+0 and 47+2 weeks. The least-mean-square method was used to create the growth curve for each parameter.Complete data sets were available in 317 neonates, ranging from 0 to 28 days of age. Reference values from the 1st to 99th percentiles were provided. All parameters showed a nonlinear growth trend with age. Inter- and intraobserver agreement was excellent for 2D and 3D parameters.Our results suggested that computer techniques can assist in the volume assessment of corpus callosum. The 2D and 3D ultrasound data of 7 morphologic parameters may facilitate the identification of corpus callosum anomalies based on a large population.

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.

Endoscopic colloid cyst excision: surgical techniques and nuances

BACKGROUND

Endoscopic excision of colloid cysts is currently well established as a minimally invasive and highly effective technique that is associated with less morbidity in comparison to microsurgical resection.

METHODS

Operative charts and videos of patients undergoing endoscopic colloid cyst excision were retrieved from the senior author's database of endoscopic procedures and reviewed. This revealed nine trans-foraminal and three trans-septal procedures. Description of the surgical techniques was then formulated.

CONCLUSIONS

Variation of the technique is based on the specific patho-anatomical features of the colloid cyst being resected. For the trans-foraminal approach, we think that the rotational technique is associated with a more complete removal of the cyst wall and consequently lower recurrence rate.

In Utero MR Imaging of Fetal Holoprosencephaly: A Structured Approach to Diagnosis and Classification

BACKGROUND AND PURPOSE

Holoprosencephaly is a rare developmental brain abnormality with a range of severity. We describe our experience in diagnosing holoprosencephaly in the fetus with in utero MR imaging. We hypothesized that including in utero MR imaging in the diagnostic pathway will improve the detection of holoprosencephaly compared with ultrasonography and allow better assessment of the severity.

MATERIALS AND METHODS

We report on holoprosencephaly identified from ultrasonography and/or a diagnosis of holoprosencephaly made with in utero MR imaging. We compare the diagnoses made with sonography and in utero MR imaging in each case and compare the 2 methods of assessing the severity of holoprosencephaly.

RESULTS

Thirty-five fetuses are reported, including 9 in which the diagnosis of holoprosencephaly was made on ultrasonography but not confirmed on in utero MR imaging. Of the 26 cases of holoprosencephaly diagnosed on in utero MR imaging, 12 were not recognized on ultrasonography.

CONCLUSIONS

Our results show that in utero MR imaging has a major role in diagnosing or refuting a diagnosis of fetal holoprosencephaly made on ultrasonography. In utero MR imaging also assists in grading the severity of fetal holoprosencephaly.

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.

Congenital brain malformations in the neonatal and early infancy period

Congenital brain malformations are a major cause of morbidity and mortality in pediatric patients who are younger than 2 years. Optimization of patient care requires accurate diagnosis, which can be challenging as congenital brain malformations include an extensive variety of anomalies. Radiologic imaging helps to identify the malformations and to guide management. Understanding radiologic findings necessitates knowledge of central nervous system embryogenesis. This review discusses the imaging of congenital brain malformations encountered in patients who are younger than 2 years in the context of brain development.

Antenatal diagnosis of agenesis of the corpus callosum

AIM

To estimate the diagnostic performance of ultrasound in detecting agenesis of the corpus callosum (ACC).

MATERIALS AND METHODS

A retrospective review was performed of 1722 in utero MRI examinations. All cases were identified in which the fetus had been referred from ultrasonography with a diagnosis of ACC and those in which ACC was given as a diagnosis on the in utero MRI study. The MRI was assumed to provide the correct diagnosis of ACC and descriptive statistics of diagnostic accuracy for ultrasound were calculated.

RESULTS

Of the 1722 ultrasound examinations performed, 121 had a diagnosis of ACC and approximately 50% were confirmed at MRI. Forty-two fetuses with ACC not suspected at ultrasonography were also identified at MRI. Ultrasonography had a positive predictive value of 47% (95% CI: 38-56%) and a negative predictive value of 97% (95% CI: 96-98%) for detecting ACC.

CONCLUSION

Ultrasound is poor in diagnosing ACC and in utero MRI should be performed if there is any suspicion on antenatal ultrasonography.

Colloid cysts posterior and anterior to the foramen of Monro: Anatomical features and implications for endoscopic excision

Background:

Colloid cysts are usually located at the rostral part of the third ventricle in proximity to the foramina of Monro. Some third ventricular colloid cysts, however, attain large sizes, reach a very high distance above the roof of the third ventricle, and pose some challenges during endoscopic excision. These features led to the speculation that for such a pattern of growth to take place, the points of origin of these cysts should be at areas away from the foramina of Monro at which some anatomical “windows” exist that are devoid of compact, closely apposed forniceal structures.

Methods:

A review of the literature on anatomical variations of the structures in the vicinity of the roof of the third ventricle and on reported cases with similar features was conducted.

Results:

Colloid cysts may grow vertically up past the roof of the third ventricle through anatomical windows devoid of the mechanical restraint of the forniceal structures.

Conclusion:

Some anatomical variations of the forniceal structures may allow unusually large sizes and superior vector of growth of a retro- or post-foraminal colloid cyst. Careful preoperative planning and knowledge of the pertinent pathoanatomy of these cysts before endoscopic excision is very important to avoid complications.

The indusium griseum and the longitudinal striae of the corpus callosum

In the eighteenth century, Lancisi described the indusium griseum (IG) and the longitudinal striae (LS) of the corpus callosum. The IG is a thin neuronal lamina above the corpus callosum, covered on each side of the midline by the medial and lateral LS. The medial LS (nerves of Lancisi) and lateral LS are two pairs of myelinated fiber bands found in the gray matter of the IG on the dorsal aspect of the corpus callosum. Embryologically, the IG and LS are dorsal remnants of the archicortex of the hippocampus and fornix and thus they are considered components of the limbic system. Recent studies using immunohistochemistry reported that acetylcholine, dopamine, noradrenaline, 5-hydroxytryptamine and GABA neurons innervate the IG. Newer imaging techniques, such as high field MRI and diffusion tensor imaging, provide new tools for studying these structures, whose true function remains still unclear. The present paper reviews the history of the discovery of the IG and LS of the corpus callosum, with a holistic overview on these interesting structures from the anatomical, embryological, neurochemical, radiological and clinical perspective.

An anatomic review of thalamolimbic fiber tractography: ultra-high resolution direct visualization of thalamolimbic fibers anterior thalamic radiation, superolateral and inferomedial medial forebrain bundles, and newly identified septum pellucidum tract

BACKGROUND

Images obtained through ultra-high-field 7.0-tesla magnetic resonance imaging with track-density imaging provide clear, high-resolution tractograms that have been hitherto unavailable, especially in deep brain areas such as the limbic and thalamic regions. This study is a largely pictorial description of the deep fiber tracts in the brain using track-density images obtained with 7.0-T diffusion-weighted imaging.

METHODS

To identify the fiber tracts, we selected 3 sets of tractograms and performed interaxis correlation between them. These tractograms offered an opportunity to extract new information in areas that have previously been difficult to examine using either in vivo or in vitro human brain tractography.

RESULTS

With this new technique, we identified 4 fiber tracts that have not previously been directly visualized in vivo: septum pellucidum tract, anterior thalamic radiation, superolateral medial forebrain bundle, and inferomedial forebrain bundle.

CONCLUSIONS

We present the high-resolution images as a tool for researchers and clinicians working with neurodegenerative and psychiatric diseases, such as Parkinson disease, Alzheimer disease, and depression, in which the accurate positioning of deep brain stimulation is essential for precise targeting of nuclei and fiber tracts.

Non-visualisation of cavum septi pellucidi: implication in prenatal diagnosis?

OBJECTIVE

This manuscript reviews congenital anomalies and imaging findings associated with non-visualisation of the cavum septi pellucidi (CSP) found on prenatal sonogram.

BACKGROUND

Observation of a normal cavum septi pellucidi (CSP) is an important landmark in the second and third trimester prenatal ultrasound evaluation of the fetal brain, and its visualisation provides reassurance of normal central forebrain development. Non-visualisation of the CSP is a prenatal sonographic finding, which in most cases is associated with neuroanatomical anomalies that include agenesis of the corpus callosum, schizencephaly, septo-optic dysplasia, holoprosencephaly, chronic hydrocephalus and acquired fetal brain injury. Isolated septal deficiency, a rare but controversial entity, is considered a variant of normal. Common pitfalls in the sonographic evaluation of CSP include columns of the fornix that mimic CSP, and prominent cavum vergae that can simulate non-visualisation of the CSP. When non-visualisation of the CSP is suspected, magnetic resonance imaging (MRI) of the fetal brain can confirm and evaluate associated anomalies.

CONCLUSION

Visualisation of the CSP is an integral component of the prenatal ultrasound and its non-visualisation is associated with other malformations, diagnosis of which is aided by MRI.

TEACHING POINTS

• Cavum septi pellucidi (CSP) is an important landmark in the prenatal ultrasound evaluation of the fetal brain, and is a marker for normal central forebrain development. • Non-visualisation of the CSP is most commonly associated with other neuroanatomical abnormalities. • Examination of the fetal brain by MRI can confirm the sonographic findings and evaluate for associated anomalies.

Optimized surgical approach to third ventricular choroid plexus papillomas of young children based on anatomical variations

BACKGROUND

Choroid plexus papilloma (CPP) in the third ventricle is a rare benign intracranial tumor.

METHODS

We report 3 pediatric cases of CPP in the third ventricle. The lesions were totally removed by a different surgical approach in each case.

RESULTS

When remarkable hydrocephalus is present, the transcortical approach is easier to perform, but may expose the patient to epilepsy and subdural effusion postoperatively. The transcallosal approach offers direct exposure of the ventricle system with minimal risk of cortical damage. The transcallosal-transforaminal approach with posterior enlargement of the foramen of Monro along the choroidal fissure provides a direct trajectory into the third ventricle through the natural cleft. The transcallosal-interforniceal approach does not depend on the size of the foramen of Monro, but it carries a risk for damage to the both fornices. The midline plane of the septum pellucidum and the forniceal columns in children are sometimes easily identifiable and separable, and in such cases the transcallosal-interforniceal approach appears to be a safe route for tumors extending to the posterior third ventricle. The interforniceal approach should be reserved for lesions that cannot be removed safely via the transforaminal approach.

CONCLUSIONS

Young children have a small total blood volume and fragile cardiovascular status. Therefore, it is critical to preserve the venous system and to ligate the feeding artery before extirpation of the tumor. The surgical approach to the third ventricular CPPs should be tailored to individual children based on tumor size, location, and vascularity.

Different patterns of fornix damage in idiopathic normal pressure hydrocephalus and Alzheimer disease

BACKGROUND AND PURPOSE

The fornix contains efferent fibers of the hippocampus and is in close contact with the corpus callosum. Part of the fornix is directly attached to the corpus callosum, and another part is suspended from the corpus callosum via the septum pellucidum. DTI can be used to evaluate the morphology and microstructural integrity of the fornix. We examined the pattern of fornix damage in patients with iNPH or AD.

MATERIALS AND METHODS

We enrolled 22 patients with iNPH, 20 with AD, and 20 healthy controls. DTI data were obtained. The morphology (volume, length, and mean cross-sectional area) and FA values of the fornix were evaluated by using tract-specific analysis and compared among groups.

RESULTS

The volume, cross-sectional area, and FA value of the fornix were significantly smaller in patients with iNPH than in controls, whereas the length was significantly greater. In patients with AD, the volume, mean cross-sectional area, and FA value of the fornix were significantly smaller than those in controls, whereas the length was not altered. The fornix was significantly longer in patients with iNPH than in patients with AD, whereas the volume and cross-sectional areas were significantly smaller.

CONCLUSIONS

Our results suggest that the different pathogeneses of these diseases lead to fornix damage through different mechanisms: through mechanical stretching due to lateral ventricular enlargement and corpus callosum deformation in patients with iNPH, and through degeneration secondary to hippocampal atrophy in patients with AD.

White matter alteration in idiopathic normal pressure hydrocephalus: tract-based spatial statistics study

BACKGROUND AND PURPOSE

White matter alteration in iNPH has not been well-investigated. TBSS is a voxelwise statistical analysis developed for DTI data. We aimed to elucidate the cerebral white matter alteration in patients with iNPH by using DTI and to test the accuracy of TBSS analysis.

MATERIALS AND METHODS

DTI data were obtained from 20 patients with iNPH and 20 age- and sex-matched controls. The FA values were evaluated by using TBSS, region-of-interest and tract-specific analysis of the CST. The accuracy of TBSS analysis was tested by using "back-projection" of TBSS results and by comparing the TBSS analysis results with those of region-of-interest and tract-specific analysis.

RESULTS

Back-projection of the TBSS results showed accurate registration of the whole brain, with the exception of parts of the thalamus, fornix, and white matter around the posterior body of the lateral ventricle. The TBSS analysis results were consistent with those of the region-of-interest analysis and tract-specific analysis. In patients with iNPH compared with control subjects, the FA values were significantly decreased in parts of the corpus callosum, periventricular white matter, and juxtacortical white matter in the frontal and parietal lobes. In contrast, FA values were significantly increased in the internal capsule, extending to the white matter in the centrum semiovale.

CONCLUSIONS

Our results suggest that patients with iNPH have various patterns of white matter damage and that TBSS analysis is a promising tool for performing accurate voxelwise statistical analysis of the iNPH brain, with the exception of misregistered areas.

The use of in utero MR imaging to delineate developmental brain abnormalities in multifetal pregnancies

BACKGROUND AND PURPOSE

iuMR has been shown to increase the detection rate of developmental abnormalities of the CNS, though most reports are limited to singleton pregnancies. The hypothesis tested in this study was that iuMR performed in multifetal pregnancies will show additional information about fetal CNS abnormalities in a similar proportion of cases when compared with singleton pregnancies.

MATERIALS AND METHODS

Fifty women with multifetal pregnancies were recruited consecutively carrying at least 1 fetus with a suspected developmental fetal CNS abnormality on sonography. All had iuMR at the same center by using the same MR imaging protocol. When the sonography and MR imaging reports were discrepant, 1 fetomaternal expert assessed the reports independently to predict in what percentage a change in prognosis/counseling would have occurred if iuMR was included in the diagnostic pathway.

RESULTS

There was agreement between the sonography and iuMR reports in 66% and disagreement in 34% of cases. The major cause for discrepancy was the presence or absence of the corpus callosum, which accounted for 10/17 of the disagreements. In 12/17 of the discrepant cases, the effect on management was judged to be significant.

CONCLUSIONS

We conclude that iuMR has a similar rate of discrepancy to sonography in multifetal pregnancies compared with the published data concerning singleton pregnancies. Our analysis of the effect on management shows that changes in the decision to consider termination of pregnancy would have occurred in 12/17 of the discrepant cases (ie, in 24% of our cases overall).

Biometry of the corpus callosum in children: MR imaging reference data

BACKGROUND AND PURPOSE

The availability of data relating to the biometry of the CC in children that are easy to use in daily practice is limited. We present a reference biometry of the CC in MR imaging in a large cohort of children.

MATERIALS AND METHODS

Cerebral MR imaging studies of children with normal examination findings were selected retrospectively. Children born preterm and those with or at risk of developing cerebral malformations were excluded. The following parameters were measured: FOD, APD, LCC, GT, BT, IT, ST, and the S/T. Inter- and intraobserver agreement and sex effect were evaluated.

RESULTS

Six hundred twenty-two children were included (320 boys, 302 girls), ranging from 1 day to 15 years of age. Normal values (from the 3rd to 97th percentile) are provided for each parameter. All parameters showed rapid growth up to 3 years of age followed by slower (FOD, APD, LCC, GT and ST) or absent (S/T) growth. Growth of BT and IT was completed by 7-8 years. CC modeling (IT/ST) was completed by 3 years. FOD was larger in boys from the age of 1 year (statistically significant). The other parameters did not show any sex effect. Inter- and intraobserver agreement was excellent for all parameters except for IT.

CONCLUSIONS

As measured, our data result in easy and reproducible MR imaging biometry of the CC in children.

Selectively reduced posterior corpus callosum size in a population-based sample of young adults born with low birth weight

BACKGROUND AND PURPOSE

Several studies suggest that VLBW is associated with a reduced CC size later in life. We aimed to clarify this in a prospective, controlled study of 19-year-olds, hypothesizing that those with LBWs had smaller subregions of CC than the age-matched controls, even after correcting for brain volume.

MATERIALS AND METHODS

One hundred thirteen survivors of LBW (BW <2000 grams) without major handicaps and 100 controls underwent a 3T MR examination of the brain. The cross-sectional area of the CC (total callosal area, and the callosal subregions of the genu, truncus, and posterior third) was measured. Callosal areas were adjusted for head size.

RESULTS

The posterior third subregion of the CC was significantly smaller in individuals born with a LBW compared with controls, even after adjusting for size of the forebrain. Individuals who were born with a LBW had a smaller CC (mean area, 553.4 mm(2)) than the controls (mean area, 584.1 mm(2)). Differences in total area, however, did not remain statistically significant after adjusting for FBV.

CONCLUSIONS

The uncorrected callosal size in 19-years-olds born with LBW was smaller than that of normal controls. However, after adjusting for FBV, the group difference was restricted to the posterior third. The clinical impact of a smaller posterior part needs further investigation.

Developmental anomalies of the medial septal area: possible implication for limbic epileptogenesis

INTRODUCTION

The maldevelopment of the midline structures is connected with neurologic disorders. The cavum septum pellucidum (CSP) exists in the fetal period, then it is re-absorbed. The presence of unfused leaflets/fornices may be considered important in the genesis of neurodevelopmental abnormalities inclunding epilepsy. The limbic system includes a group of interconnected gray and white matter structures; in this circuit, the fornix is an important white matter connection with the septum pellucidum.

METHODS

Five children, 3-10 years of age, with epilepsy and an unfused septum pellucidum and fornices on MRI, were evaluated by diffusion tensor imaging-fiber tracking (DTI-FT) in order to explore the integrity of the axonal microenviroment of these structures.

RESULTS

The patients had generalized tonic-clonic seizures (GTCS). The electroencephalogram (EEG) showed focal-temporal abnormalities with secondary generalization. Magnetic resonance imaging (MRI) and DTI-FT demonstrated the CSP, and the presence of the fornix's body split into two bundles with the fornices separated.

CONCLUSION

The fornix appears more involved than CSP alone, as suggested by fornix atrophy observed in MTLE. Even if epilepsy is suggested to be a grey matter disorder, changes in the underlying brain connectivity have an important contribution in seizure generation and diffusion. In addition, the interconnections of medial septal area with hyppocampus, amygdala and entorhinal cortex, have led to the hypothesis of functional limbic epilepsy. In our patients, the role of DTI was not conclusive since the definition of the number of unmyelinated fibers responsible for epilepsy could not be demonstrated probably for a limited number of seizures and for a short period of drug administration.

Evaluation of white matter changes in agyria-pachygyria complex using diffusion tensor imaging

Associated abnormalities of the white matter in patients with agyria-pachygyria complex have rarely been investigated using new imaging modalities like diffusion tensor imaging. The present study evaluated the white matter changes of 9 children with agyria-pachygyria complex using diffusion tensor imaging. Regions of interest were placed in 17 white matter tracts. Compared with normal controls, the axial diffusivity of the genu of the corpus callosum, corticospinal tract, and fornix in patients with agyria-pachygyria complex was decreased. In the subcortical white matter without changes in T2-weighted image, there were significant decreases in fractional anisotropy and axial diffusivity and increases in radial diffusivity, indicating significant alterations of the white matter. Since axial diffusivity and radial diffusivity reflect changes in the axon and myelin, respectively, the findings here indicate disturbance in both axonal and myelin development in agyria-pachygyria complex.

The corpus callosum: white matter or terra incognita

The corpus callosum is the largest white matter structure in the brain, consisting of 200-250 million contralateral axonal projections and the major commissural pathway connecting the hemispheres of the human brain. The pathology of the corpus callosum includes a wide variety of entities that arise from different causes such as congenital, inflammatory, tumoural, degenerative, infectious, metabolic, traumatic, vascular and toxic agents. The corpus callosum, or a specific part of it, can be affected selectively. Numerous pathologies of the corpus callosum are encountered during CT and MRI. The aim of this study is to facilitate a better understanding and thus treatment of the pathological entities of the corpus callosum by categorising them according to their causes and their manifestations in MR and CT imaging. Familiarity with its anatomy and pathology is important to the radiologist in order to recognise its disease at an early stage and help the clinician establish the optimal therapeutic approach.

Acute white matter differences in the fornix following mild traumatic brain injury using diffusion tensor imaging

The integrity of the fornix using diffusion tensor imaging (DTI) in adolescent participants with acute mild traumatic brain injury (mTBI) compared to a demographically matched control group was examined. Fractional anisotropy (FA) in the fornix was elevated in the mild traumatic brain injured group. Performance on the Automated Neuropsychological Assessment Metrics (ANAM) was lower in the group with mTBI. A relation was found between lower performance on cognitive tasks and higher FA. The potential role of fornix injury as a basis of memory and processing speed deficits in mTBI is discussed.

Corpus callosum agenesis and rehabilitative treatment

Corpus callosum agenesis is a relatively common brain malformation. It can be isolated or included in a complex alteration of brain (or sometimes even whole body) morphology. It has been associated with a number of neuropsychiatric disorders, from subtle neuropsychological deficits to Pervasive Developmental Disorders.

Etiology and pathogenetic mechanisms have been better understood in recent years, due to the availability of more adequate animal models and the relevant progresses in developmental neurosciences. These recent findings are reviewed (through a MedLine search including papers published in the last 5 years and most relevant previously published papers) in view of the potential impact on children's global functioning and on the possible rehabilitative treatment, with an emphasis on the possibility to exploit brain plasticity and on the use of the ICF-CY framework.

Septopreoptic holoprosencephaly: a mild subtype associated with midline craniofacial anomalies

SUMMARY

HPE is a congenital brain malformation characterized by failure of the prosencephalon to divide into 2 hemispheres. We have identified 7 patients who have a mild subtype of HPE in which the midline fusion was restricted to the septal region or preoptic region of the telencephalon. This subtype, which we call septopreoptic HPE, falls in the spectrum of lobar HPE, but lacks significant frontal neocortical fusion seen in lobar HPE. Other imaging characteristics include thickened or dysplastic fornix, absent or hypoplastic anterior CC, and single unpaired ACA. The SP was fully formed in 4, partially formed in 2, and absent in 1. Mild midline craniofacial malformation, such as SMMCI and CNPAS were found in 86% and 71%, respectively. Patients outside of infancy often manifested language delay, learning disabilities, or behavioral disturbances, while motor function was relatively spared.

A prospective study of fetuses with isolated ventriculomegaly investigated by antenatal sonography and in utero MR imaging

BACKGROUND AND PURPOSE

Fetal ventriculomegaly (VM) is important because of its high prevalence and high risk of association with other brain abnormalities. The purpose of this article was to investigate the hypotheses that including in utero MR imaging (iuMR) in the diagnostic pathway for fetuses with isolated VM on antenatal imaging will show other brain abnormalities in a high proportion of cases and that these will have a significant effect on clinical management.

MATERIALS AND METHODS

One hundred forty-seven pregnant women were recruited prospectively from 8 fetomaternal centers in Britain. All of the fetuses had VM diagnosed on sonography but no other abnormality. iuMR was performed, and the results of the examinations were compared with those of sonography. Two fetomaternal experts made independent assessments of the effects of any new diagnoses on clinical management.

RESULTS

Categoric assessments of ventricular size were the same in approximately 90% of fetuses. Other abnormalities were shown in 17% of fetuses. The most frequent additional brain abnormality shown on iuMR was agenesis of the corpus callosum. Severe VM was associated with an approximately 10-fold increase in the risk of another brain abnormality being present when compared with fetuses with mild VM. The most profound effects on clinical management, however, were found in cases of mild VM.

CONCLUSIONS

This work supports our hypotheses by showing a high detection rate of other brain pathology when iuMR was used to supplement antenatal sonography (17%). In a high proportion of cases, the detection of the extra pathology would have led to significant changes in clinical management.

Effects of failed commissuration on the septum pellucidum and fornix: implications for fetal imaging

In the previous article, we considered the normal appearances of the midline stuctures of the brain as they appear on high-resolution magnetic resonance imaging. In this article, we discuss the effects of failed commissuration on the midline structures. We highlight some of the misconceptions of this process that may lead to misdiagnosis of agenesis of the corpus callosum in utero.