[Lipoma of calm body revealed by a convulsive crisis: about a case]

Le lipome du corps calleux est une lésion congénitale bénigne très rare, qui peut être isolée ou associée à des degrés divers de dysgénésie du corps calleux. Il peut être asymptomatique ou se révélé par des signes non spécifiques tels que des crises épileptiques, des céphalées, de déficit neurologique ou de démences. L'imagerie en coupe fait le diagnostic aisément. Nous rapportons le cas d'un adolescent de 18 ans qui a présenté une crise convulsive chez qui l'imagerie a révélé un lipome du corps calleux.

A novel mutation in the GBA2 gene in a Japanese patient with SPG46: A case report

Hereditary spastic paraplegia (HSP) is a neurodegenerative disorder characterized by pyramidal weakness and spasticity of the lower limbs. SPG46, one of autosomal recessive HSP, is clinically characterized by spasticity and pyramidal weakness of the lower limbs, mental retardation, congenital bilateral cataract, thin corpus callosum, and hypogonadism in males. Mutations in the nonlysosomal glucosylceramidase β2 (GBA2) gene have been identified in patients with SPG46. A Japanese woman was identified with bilateral cataracts when she was in an elementary school. She felt falling easily, speaking unclearness, and difficulty in walking and raising her left leg in her 30s. Her neurological examination at the age of 44 revealed dysarthria, spasticity in the upper and lower extremities, increased jaw jerk and tendon reflexes in the extremities, bilateral extensor plantar reflexes, ataxia, and pollakiuria. Magnetic resonance imaging showed thinning of the corpus callosum body as well as atrophy in the pons and cerebellum. A novel homozygous c.1838A > G (p.D613G) missense mutation was detected at exon 12 in GBA2. We diagnosed her illness as an autosomal-recessive form of hereditary SPG46. The clinical features matched previously reported phenotype of SPG46. This is the first report of a Japanese patient with SPG46 with a novel mutation in GBA2. We presume that the novel GBA2 missense mutation found in our patient would cause loss of GBA2 activity, resulting in the neurological manifestations of SPG46.

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SPG46 is a rare autosomal recessive hereditary spastic paraplegia.

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In Japan, clinical cases of SPG46 have never been reported.

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We report a case of a Japanese patient with SPG46 with a novel mutation in GBA2.

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She showed cataracts, mild cognitive impairment, spasticity, and cerebellar ataxia.

White matter microstructural alterations in posttraumatic stress disorder: An ROI and whole-brain based meta-analysis

BACKGROUND

Posttraumatic stress disorder (PTSD) is a debilitating mental illness that is thought to be associated with brain white matter (WM) alterations. Individual diffusion tensor imaging (DTI) studies to date have reported inconsistent alterations in FA across different brain regions in patients with PTSD. Here, we aimed to investigate FA in PTSD using both region-of-interest (ROI)-based and whole-brain-based meta-analytic approaches.

OBJECTIVES

Individual ROI-based meta-analysis was carried out in each eligible white matter tract and seed-based D mapping (SDM) meta-analysis was conducted in the whole brain to identify the convergence of FA alterations in PTSD relative to controls.

RESULTS

Seventeen studies were included in ROI-based meta-analysis (≥ 3 studies were included for each ROI, N_PTSD ≥ 80 and N_control ≥ 103 per ROI). Fourteen studies with a total of 322 PTSD and 335 controls were included in whole-brain based meta-analysis. Both ROI and whole-brain meta-analyses showed that patients with PTSD have significantly higher FA in the inferior fronto-occipital fasciculus and lower FA in the genu of corpus callosum. Whole-brain meta-analyses also identified higher FA in the left inferior temporal gyrus and lower FA in the anterior cingulum and left corticospinal tract.

LIMITATIONS

A small number of studies were included in some ROI tracts. Thus the results should be interpreted with caution.

CONCLUSIONS

Our results suggest that PTSD patients have increased FA in areas related to visual processing, but decreased FA in anterior brain regions critical to cognition association and fear regulation.

Morphological changes of the dorsal contour of the corpus callosum during the first two years of life

BACKGROUND

In the medicolegal literature, focal concavities or notching of the corpus callosum has been thought to be associated with fetal alcohol spectrum disorders. Recent work suggests corpus callosum notching is a dynamic and normal anatomical feature, although it has not yet been defined in early life or infancy.

OBJECTIVE

Our purpose was to characterize the dorsal contour of the corpus callosum during the first 2 years of life by defining the prevalence, onset and trajectory of notching on midsagittal T1-weighted images.

MATERIALS AND METHODS

We reviewed retrospectively 1,157 consecutive patients between birth and 2 years of age. Corpus callosum morphology was evaluated and described. A notch was defined as a dorsal concavity of at least 1 mm in depth along the dorsal surface of the corpus callosum. Patient age as well as notch depth, location, number and presence of the pericallosal artery in the notch were noted.

RESULTS

Two hundred thirty-three notches were identified in 549 patients: 36 anterior, 194 posterior and 3 patients with undulations. A statistically significant (R²=0.53, Beta=0.021, P=0.002) positive correlation between posterior notch prevalence and age in months was noted. A positive correlation between age and depth of the posterior notch was also statistically significant (r=0.32, n=179, P≤0.001). A trend for increased anterior notch prevalence with age was identified with significant correlation between visualized pericallosal artery indentation and anterior notching (r=0.20, n=138, P=0.016). Sub-analysis of the first month of life showed corpus callosum notching was not present.

CONCLUSION

The presence of posterior notching increased significantly with age and was more frequent than that of anterior notching. Corpus callosum notching was absent in the first week of life, building on prior studies suggesting corpus callosum notching is acquired. This study provides baseline data on normative corpus callosum notching trajectories by age group during early life, a helpful correlate when associating corpus callosum morphology with disease.

FoxP3 deficiency causes no inflammation or neurodegeneration in the murine brain

Regulatory T cells (Treg) maintain immunological self-tolerance and their functional or numerical deficits are associated with progression of several neurological diseases. We examined the effects of Treg absence on the structure and integrity of the unchallenged murine brain. When compared to control, Treg-deficient FoxP3sf mutant mice showed no differences in brain size, myelin amount and oligodendrocyte numbers. FoxP3sf strain displayed no variations in quantity of neurons and astrocytes, whereas microglia numbers were slightly reduced. We demonstrate lack of neuroinflammation and parenchymal responses in the brains of Treg-deficient mice, suggesting a minor Treg role in absence of blood-brain barrier breakdown.

Deciphering the neural underpinnings of alexithymia in multiple sclerosis

OBJECTIVES

Alexithymia is a personality construct that could occur in up to 53 % of patients with multiple sclerosis (MS). It entails difficulties in identifying and describing one's feelings and an externally oriented thinking. The current work aims to assess the neural underpinnings of alexithymia in this population.

METHODS

Forty-five patients with MS filled in the Toronto Alexithymia Scale (n = 17 with high alexithymia and n = 28 with low alexithymia). Brain magnetic resonance imaging was obtained for each patient and a morphometry algorithm (MorphoBox) was applied to calculate regional brain volumes. All patients underwent a clinical and neuropsychological evaluation which included measures for anxiety, depression, fatigue, daytime sleepiness, and basic and social cognition.

RESULTS

Compared to patients with low alexithymia, patients with high alexithymia had significantly higher fatigue and depression ratings, and lower empathy scores. In addition, they had lower volumes of corpus callosum, deep white matter, pallidum bilaterally, and left thalamus. In the whole cohort, alexithymia scores were inversely correlated with gray matter (thalamus and pallidum bilaterally) and white matter volumes (corpus callosum and bilateral deep white matter) after controlling for covariates (ps<0.05).

CONCLUSION

This study offers insights on the neuropsychological and neural substrates of alexithymia in MS. The current findings are consistent with alexithymia reports in other clinical populations, and suggest an association between alexithymia and atrophy of thalami, pallidum, corpus callosum and deep white matter in MS. Further research is needed to enhance the understanding of alexithymia mechanisms in this clinical context.

Early Progressive Changes in White Matter Integrity Are Associated with Stroke Recovery

Information on microstructural white matter integrity has been shown to explain post-stroke recovery beyond clinical measures and focal brain damage. Especially, knowledge about early white matter changes might improve prediction of outcome. We investigated 42 acute reperfused ischemic stroke patients (mean age 66.5 years, 40% female, median admission NIHSS 9.5) with a symptomatic MRI-confirmed unilateral middle cerebral artery territory infarction 24-72 h post-stroke and after 3 months. All patients underwent neurological examination and brain MRI. Fifteen older healthy controls (mean age 57.3 years) were also scanned twice. We assessed fractional anisotropy (FA), mean diffusivity (MD), axial (AD), and radial diffusivity (RD). Patients showed significantly decreased white matter integrity in the hemisphere affected by the acute infarction 24-72 h post-stroke, which further decreased over 3 months compared with controls. Less decrease in FA of remote white matter tracts was associated with better stroke recovery even after correcting for infarct location and extent. A regression model including baseline information showed that the modified Rankin Scale and mean FA of the genu of the corpus callosum explained 53.5% of the variance of stroke recovery, without contribution of infarct volume. Furthermore, early dynamic FA changes of the corpus callosum within the first 3 months post-stroke independently predicted stroke recovery. Information from advanced MRI measures on white matter integrity at the acute stage, as well as early dynamic white matter degeneration beyond infarct location and extent, improve our understanding of post-stroke reorganization in the affected hemisphere and contribute to an improved prediction of recovery.

White matter fiber density abnormalities in cognitively normal adults at risk for late-onset Alzheimer's disease

Tau accumulation affecting white matter tracts is an early neuropathological feature of late-onset Alzheimer's disease (LOAD). There is a need to ascertain methods for the detection of early LOAD features to help with disease prevention efforts. The microstructure of these tracts and anatomical brain connectivity can be assessed by analyzing diffusion MRI (dMRI) data. Considering that family history increases the risk of developing LOAD, we explored the microstructure of white matter through dMRI in 23 cognitively normal adults who are offspring of patients with Late-Onset Alzheimer's Disease (O-LOAD) and 22 control subjects (CS) without family history of AD. We also evaluated the relation of white matter microstructure metrics with cortical thickness, volumetry, in vivo amyloid deposition (with the help of PiB positron emission tomography -PiB-PET) and regional brain metabolism (as FDG-PET) measures. Finally we studied the association between cognitive performance and white matter microstructure metrics. O-LOAD exhibited lower fiber density and fractional anisotropy in the posterior portion of the corpus callosum and right fornix when compared to CS. Among O-LOAD, reduced fiber density was associated with lower amyloid deposition in the right hippocampus, and greater cortical thickness in the left precuneus, while higher mean diffusivity was related with greater cortical thickness of the right superior temporal gyrus. Additionally, compromised white matter microstructure was associated with poorer semantic fluency. In conclusion, white matter microstructure metrics may reveal early differences in O-LOAD by virtue of parental history of the disorder, when compared to CS without a family history of LOAD. We demonstrate that these differences are associated with lower fiber density in the posterior portion of the corpus callosum and the right fornix.

Diffusion tensor imaging of the corpus callosum in healthy aging: Investigating higher order polynomial regression modelling

Previous diffusion tensor imaging (DTI) studies confirmed the vulnerability of corpus callosum (CC) fibers to aging. However, most studies employed lower order regressions to study the relationship between age and white matter microstructure. The present study investigated whether higher order polynomial regression modelling can better describe the relationship between age and CC DTI metrics compared to lower order models in 140 healthy participants (ages 18-85). The CC was found to be non-uniformly affected by aging, with accelerated and earlier degradation occurring in anterior portion; callosal volume, fiber count, fiber length, mean fibers per voxel, and FA decreased with age while mean, axial, and radial diffusivities increased. Half of the parameters studied also displayed significant age-sex interaction or intracranial volume effects. Higher order models were chosen as the best fit, based on Bayesian Information Criterion minimization, in 16 out of 23 significant cases when describing the relationship between DTI measurements and age. Higher order model fits provided different estimations of aging trajectory peaks and decline onsets than lower order models; however, a likelihood ratio test found that higher order regressions generally did not fit the data significantly better than lower order polynomial or linear models. The results contrast the modelling approaches and highlight the importance of using higher order polynomial regression modelling when investigating associations between age and CC white matter microstructure.

Focal alterations of the callosal area III in primary lateral sclerosis: An MRI planimetry and texture analysis

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The regional pattern of cerebral alterations in PLS includes the area III of the CC.

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Callosal alterations of the texture parameters entropy and homogeneity were shown in PLS.

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Texture and macrostructure of the callosal area III is targeted as a neuroimaging marker in PLS.

Background

The regional distribution of cerebral morphological alterations in primary lateral sclerosis (PLS) is considered to include the area III of the corpus callosum (CC).

Objective

The study was designed to investigate regional white matter (WM) alterations in the callosal area III by T1 weighted magnetic resonance imaging (T1w-MRI) data in PLS patients compared with healthy controls, in order to identify atrophy and texture changes in vivo.

Methods

T1w-MRI-based white matter mapping was used to perform an operator-independent CC-segmentation for the different areas of the CC in 67 PLS patients vs 82 matched healthy controls and vs 85 ALS patients. The segmentation was followed by texture analysis of the separated CC areas for the PLS patients vs controls and vs ALS patients.

Results

PLS was associated with significant atrophy in the area III of the CC (but not in the other callosal segments), while the alterations in the ALS patients were much more variable and were not significant at the group level. Furthermore, significant regional alterations of the texture parameters entropy and homogeneity in this area were shown in PLS patients and in ALS patients.

Conclusions

This T1w-MRI study demonstrated focused regional CC atrophy and texture alterations limited to the callosal area III (which comprises fibers projecting into the primary motor cortices) in PLS, in comparison to a higher variability in CC size in ALS.

The splenium of the corpus callosum: embryology, anatomy, function and imaging with pathophysiological hypothesis

BACKGROUND AND PURPOSE

The splenium of the corpus callosum is the most posterior part of the corpus callosum. Its embryological development, anatomy, vascularization, function, imaging of pathology, possible pathophysiological mechanisms by which pathology may develop and the clinical consequences are discussed.

METHODS

A literature-based description is provided on development, anatomy and function. MR and CT images are used to demonstrate pathology. The majority of pathology, known to affect the splenium, and the clinical effects are described in three subsections: (A) limited to the splenium, with elaboration on pathophysiology of reversible splenial lesions, (B) pathology in the cerebral white matter extending into or deriving from the splenium, with special emphasis on tumors, and (C) splenial involvement in generalized conditions affecting the entire brain, with a hypothesis for pathophysiological mechanisms for the different diseases.

RESULTS

The development of the splenium is preceded by the formation of the hippocampal commissure. It is bordered by the falx and the tentorium and is perfused by the anterior and posterior circulation. It contains different caliber axonal fibers and the most compact area of callosal glial cells. These findings may explain the affinity of specific forms of pathology for this region. The fibers interconnect the temporal and occipital regions of both hemispheres reciprocally and are important in language, visuospatial information transfer and behavior. Acquired pathology may lead to changes in consciousness.

CONCLUSION

The development, location, fiber composition and vascularization of the splenium make it vulnerable to specific pathological processes. It appears to play an important role in consciousness.

The effect of the MR pulse sequence on the regional corpus callosum morphometry

Background and purposes

Brain morphometry is an important assessment technique to assess certain morphological brain features of various brain regions, which can be quantified in vivo by using high-resolution structural magnetic resonance (MR) imaging. This study aims to investigate the effect of different types of pulse sequence on regional corpus callosum (CC) morphometry analysis.

Materials and methods

Twenty-one healthy volunteers were scanned twice on the same 3T MRI scanner (Magnetom Trio, Siemens, Erlangen, Germany) equipped with an 8-channel head coil. Two different MR pulse sequences were applied to acquire high-resolution 3D T1-weighted images: magnetization-prepared rapid gradient-echo (MP-RAGE) and modified driven equilibrium Fourier transform (MDEFT) pulse sequence. Image quality measurements such as SNR, contrast-to-noise ratio, and relative contrast were calculated for each pulse sequence images independently. The values of corpus callosum volume were calculated based on the vertex of reconstructed surfaces. The paired dependent t test was applied to compare the means of two matched groups.

Results

Three sub-regional CC, namely anterior, mid-anterior, and posterior, resulted in an estimated volume difference between MDEFT and MP-RAGE pulse sequences. Central and mid-posterior sub-regional CC volume resulted in not significant difference between the two named pulse sequences.

Conclusion

The findings of this study demonstrate that combining data from different pulse sequences in a multisite study could make some variations in the results.

[Electroacupuncture promotes regeneration and repair of myelin sheath of corpus callosum in demyelination mice]

OBJECTIVE

To explore the mechanism of electroacupuncture (EA) in accelerating the aggregation of microglia and promoting the remyelination at the location of demyelination.

METHODS

C57BL/6 mice were randomly divided into 4 groups: normal, control, model (LPC) and LPC＋EA. The demyelination model was established by microinjection of Lysolecithin (LPC, 1 µL) into the left corpus callosum. EA (2 Hz/15 Hz, 2－4 mA) was applied to "Baihui"(GV20)and "Zhiyang"(GV9)for 30 min，once daily for 3 days, then, once every other day for 18 days. Immuno-fluorescence staining was used to observe the expression of myelin basic protein (MBP) and Axl tyrosine kinase receptor (Axl), Iba1 and numbers of Olig2-positive oligodendrocytes in the corpus callosum. Western blot was employed to detect the expression of MBP in the corpus callosum, and Oil Red O staining was used to observe changes of number of myelin pieces.

RESULTS

Following modeling, the expression levels of MBP on day 5 and 10 after modeling were significantly decreased (P<0.05, P<0.01), Iba1 expression and Olig2-positive oligodendrocyte numbers on day 10 apparently increased (P<0.001, P<0.01). On day 21 after modeling, the levels of the above mentioned indexes returned to normal. After EA intervention, the levels of MBP expression on day 5 and 10, Axl, Iba1 protein expression and Olig2-positive oligodendrocyte numbers on day 5 were markedly increased (P<0.001，P<0.01，P<0.05), while Iba1 expression on day 10 was considerably decreased in comparison with the model group (P<0.01)．Oil Red O staining showed that on day 5 after modeling, the number of red lipid droplets were obviously increased in the corpus callosum tissue on the injection side, and apparently reduced in the EA group, suggesting a clearance of the accumulated myelin fragments by EA.

CONCLUSION

EA intervention may reduce myelin debris and promote the aggregation of microglial cells and oligodendrocytes to the injured site, accelerate the myelin regeneration and up-regulate the expression of MBP and Axl of corpus callosum in demyelination mice.

A framework for quality control of corpus callosum segmentation in large-scale studies

BACKGROUND

The corpus callosum (CC) is the largest white matter structure in the brain, responsible for the interconnection of the brain hemispheres. Its segmentation is a required preliminary step for any posterior analysis, such as parcellation, registration, and feature extraction. In this context, the quality control (QC) of CC segmentation allows studies on large datasets with no human interaction, and the proper usage of available automated and semi-automated algorithms.

NEW METHOD

We propose a framework for QC of CC segmentation based on the shape signature, computed at 49 distinct resolutions. At each resolution, a support vector machine (SVM) classifier was trained, generating 49 individual classifiers. Then, a disagreement metric was used to cluster these individual classifiers. The final ensemble was constructed by selecting one representation from each cluster.

RESULTS

The proposed framework achieved an area under the curve (AUC) metric of 98.25% on the test set (207 subjects) employing an ensemble composed of 12 components. This ensemble outperformed all individual classifiers.

COMPARISON WITH EXISTING METHODS

To the best of our knowledge, this is the first approach to assess quality of CC segmentations on large datasets without the need for a ground-truth.

CONCLUSIONS

The shape descriptor is robust and versatile, describing the segmentation at different resolutions. The selection of classifiers and the disagreement measure lead to an ensemble composed of high-quality and heterogeneous classifiers, ensuring an optimal trade-off between the ensemble size and high AUC.

Aberrant inter-hemispheric coordination characterizes the progression of minimal hepatic encephalopathy in patients with HBV-related cirrhosis

Patients with hepatitis B virus (HBV)-related cirrhosis (HBV-RC) and minimal hepatic encephalopathy (MHE) exhibit alterations in homotopic inter-hemispheric functional connectivity (FC) and corpus callosum (CC) degeneration. However, the progression of inter-hemispheric dysconnectivity in cirrhotic patients from no MHE (NMHE) to MHE and its association with the progression of diseased-related cognitive impairment remain uncharacterized. We hypothesized that inter-hemispheric dysconnectivity exists in NMHE patients and further deteriorates at the MHE stage, which is associated with performance measured by psychometric hepatic encephalopathy scores (PHES) that can characterize cirrhotic patients with NMHE and MHE. Using inter-hemispheric homotopic FC and CC (and its subfields) volumetric measurements in 31 patients with HBV-RC (17 with NMHE and 14 with MHE) and 37 healthy controls, we verified that MHE patients had significant attenuated inter-hemispheric homotopic FC in the bilateral cuneus, post-central gyrus, inferior parietal lobule, and superior temporal gyms, as well as CC degeneration in total CC, CC2, CC3, and CC4 (each comparison had a corrected P < 0.05). In contrast, NMHE patients had relatively less severe inter-hemispheric homotopic FC and no CC degeneration. In addition, the degeneration of the CC and inter-hemispheric homotopic functional disconnections correlated with poor PHES performances in all cirrhotic patients (NMHE and MHE). Furthermore, impairment of inter-hemispheric homotopic FC partially mediated the association between CC degeneration and worse PHES performance. Notably, a combination of inter-hemispheric homotopic FC and CC volumes had higher discriminative values according to the area under the curve (AUC) score (AUC = 0.908, P < 0.001) to classify patients into MHE or NMHE groups when compared with either alone. Our findings shed light on the progression of inter-hemispheric dysconnectivity in relation to the progression of disease-related cognitive impairment in patients with HBV-RC.

Diffusion time dependency along the human corpus callosum and exploration of age and sex differences as assessed by oscillating gradient spin-echo diffusion tensor imaging

Conventional diffusion imaging uses pulsed gradient spin echo (PGSE) waveforms with diffusion times of tens of milliseconds (ms) to infer differences of white matter microstructure. The combined use of these long diffusion times with short diffusion times (<10 ​ms) enabled by oscillating gradient spin echo (OGSE) waveforms can enable more sensitivity to changes of restrictive boundaries on the scale of white matter microstructure (e.g. membranes reflecting the axon diameters). Here, PGSE and OGSE images were acquired at 4.7 ​T from 20 healthy volunteers aged 20-73 years (10 males). Mean, radial, and axial diffusivity, as well as fractional anisotropy were calculated in the genu, body and splenium of the corpus callosum (CC). Monte Carlo simulations were also conducted to examine the relationship of intra- and extra-axonal radial diffusivity with diffusion time over a range of axon diameters and distributions. The results showed elevated diffusivities with OGSE relative to PGSE in the genu and splenium (but not the body) in both males and females, but the OGSE-PGSE difference was greater in the genu for males. Females showed positive correlations of OGSE-PGSE diffusivity difference with age across the CC, whereas there were no such age correlations in males. Simulations of radial diffusion demonstrated that for axon sizes in human brain both OGSE and PGSE diffusivities were dominated by extra-axonal water, but the OGSE-PGSE difference nonetheless increased with area-weighted outer-axon diameter. Therefore, the lack of OGSE-PGSE difference in the body is not entirely consistent with literature that suggests it is composed predominantly of axons with large diameter. The greater OGSE-PGSE difference in the genu of males could reflect larger axon diameters than females. The OGSE-PGSE difference correlation with age in females could reflect loss of smaller axons at older ages. The use of OGSE with short diffusion times to sample the microstructural scale of restriction implies regional differences of axon diameters along the corpus callosum with preliminary results suggesting a dependence on age and sex.

Cytotoxic Lesion in the Splenium of Corpus Callosum Associated with Intracranial Infection After Deep Brain Stimulation

Cytotoxic lesions of the corpus callosum will be present in a wide range of clinical conditions. The term "cytotoxic lesions of the corpus callosum" reflects our current understanding of the underlying pathophysiology of these lesions and does not necessarily imply confinement to the splenium. Because the symptoms vary and are not specific, the clinical diagnosis can be difficult. Brain magnetic resonance imaging will be of pivotal value in the investigation. We report the case of a patient with obsessive-compulsive disorder who underwent bilateral deep brain stimulation of the nucleus accumbens and developed infection along the surgical path of both electrodes associated with a cytotoxic lesion in the splenium of corpus callosum.

Anatomo-functional correlates of auditory development in infancy

Infant brain development incorporates several intermingled mechanisms leading to intense and asynchronous maturation across cerebral networks and functional modalities. Combining electroencephalography (EEG) and diffusion magnetic resonance imaging (MRI), previous studies in the visual modality showed that the functional maturation of the event-related potentials (ERP) during the first postnatal semester relates to structural changes in the corresponding white matter pathways. Here investigated similar issues in the auditory modality. We measured ERPs to syllables in 1- to 6-month-old infants and related them to the maturational properties of underlying neural substrates measured with diffusion tensor imaging (DTI). We first observed a decrease in the latency of the auditory P2, and in the diffusivities in the auditory tracts and perisylvian regions with age. Secondly, we highlighted some of the early functional and structural substrates of lateralization. Contralateral responses to monoaural syllables were stronger and faster than ipsilateral responses, particularly in the left hemisphere. Besides, the acoustic radiations, arcuate fasciculus, middle temporal and angular gyri showed DTI asymmetries with a more complex and advanced microstructure in the left hemisphere, whereas the reverse was observed for the inferior frontal and superior temporal gyri. Finally, after accounting for the age-related variance, we correlated the inter-individual variability in P2 responses and in the microstructural properties of callosal fibers and inferior frontal regions. This study combining dedicated EEG and MRI approaches in infants highlights the complex relation between the functional responses to auditory stimuli and the maturational properties of the corresponding neural network.

Ultrasound Measurements of Intracranial Structures in Growth-Restricted Neonates with Fetal Blood Flow Redistribution: A Pilot Observational Study

BACKGROUND

Fetal growth restriction (FGR) is associated with neonatal and long-term neuro-morbidity. Preferential redistribution of blood flow to the brain is a common antenatal adaptation in FGR. The impact of this "brain sparing," which may signify severity of FGR, on the growth of brain structures has not been studied.

AIM

To compare corpus callosum (CC), cerebellar, and ventricular measurements of FGR neonates with evidence of fetal blood flow redistribution with those of gestation-matched appropriately grown (AGA) neonates.

METHODS

This was a pilot, prospective observational study conducted at a tertiary level neonatal unit in Melbourne, Australia. Cranial ultrasound was done between days 1 and 3 of life in FGR and AGA neonates.

RESULTS

Cranial ultrasound on 20 FGR, gestation (mean ± SD) 31.4 ± 3.1 weeks, weight 1,205 ± 463 g, and 20 AGA neonates, 31.1 ± 3.0 weeks, 1,668 ± 490 g, was performed. CC length was significantly decreased in FGR neonates as compared to AGA neonates (35.28 ± 3.47 vs. 38.83 ± 4.05 mm, p = 0.0002). CC was significantly thinner at genu (3.36 ± 0.66 vs. 4.04 ± 0.83 mm, p = 0.007), body (1.97 ± 0.36 vs. 2.27 ± 0.39 mm, p = 0.02), and splenium (4.07 ± 0.76 vs. 4.72 ± 0.75 mm, p = 0.003) in FGR vs. AGA neonates. CC-fastigium length was also significantly decreased (39.65 ± 3.87 vs. 41.96 ± 4.50 mm, p = 0.04). Similarly, FGR neonates showed decreased transverse cerebellar diameter (36.15 ± 5.51 vs. 38.81 ± 7.21 mm, p = 0.02), but ventricular measurements were comparable. In multivariate analysis, these differences were evident independent of the birth weight.

CONCLUSIONS

CC and cerebellar measurements are significantly smaller in FGR neonates with fetal blood flow redistribution, which warrants further study.

Maternal immune activation during pregnancy impacts on brain structure and function in the adult offspring

Gestational infection constitutes a risk factor for the occurrence of psychiatric disorders in the offspring. Activation of the maternal immune system (MIA) with subsequent impact on the development of the fetal brain is considered to form the neurobiological basis for aberrant neural wiring and the psychiatric manifestations later in offspring life. The examination of validated animal models constitutes a premier resource for the investigation of the neural underpinnings. Here we used a mouse model of MIA based upon systemic treatment of pregnant mice with Poly(I:C) (polyriboinosinic-polyribocytidilic acid), for the unbiased and comprehensive analysis of the impact of MIA on adult offspring brain activity, morphometry, connectivity and function by a magnetic resonance imaging (MRI) approach. Overall lower neural activity, smaller brain regions and less effective fiber structure were observed for Poly(I:C) offspring compared to the control group. The corpus callosum was significantly smaller and presented with a disruption in myelin/ fiber structure in the MIA progeny. Subsequent resting-state functional MRI experiments demonstrated a paralleling dysfunctional interhemispheric connectivity. Additionally, while the overall flow of information was intact, cortico-limbic connectivity was hampered and limbic circuits revealed hyperconnectivity in Poly(I:C) offspring. Our study sheds new light on the impact of maternal infection during pregnancy on the offspring brain and identifies aberrant resting-state functional connectivity patterns as possible correlates of the behavioral phenotype with relevance for psychiatric disorders.

Structural differences between male and female brains

Research based on structural magnetic resonance imaging (MRI) has revealed a number of sex differences in the anatomy of the human brain. The first part of this chapter presents an excerpt of these findings discriminating among effects on a global, regional, and local level. While findings are far from consistent and conclusive, there is general consensus with respect to sex-specific brain size, with male brains being bigger on average than female brains. So, the question arises as to whether any of the observed sex differences are merely driven by brain size. The second part of this chapter thus sheds light on a unique scientific attempt to discriminate between brain size effects and sex effects. The overarching goal of this chapter is to exemplify the variety of findings and to demonstrate that the presence, magnitude, and direction of significant sex differences strongly depend on the measurement applied. The assumption that sex differences are simply a by-product of brain size, rather than pure (size independent) sex effects has proven to be true for some but certainly not all findings. Therefore, when examining the possible sexual dimorphism of the brain, it is imperative to avoid oversimplification and generalization.

Post-shunting corpus callosal signal change and review of the literature

MRI signal changes in the corpus callosum can be seen in 8.3% of patients following shunt insertion for obstructive hydrocephalus. Several causes have been hypothesised, including mechanical compression, decompression associated oedema and ischaemia, and overshunting. We present a case of a patient with a pineal tumour of intermediate differentiation (WHO grade III), which had caused long-term obstructive hydrocephalus due to compression of the tectal plate and cerebral aqueduct. Following insertion of a shunt, prominent changes in the corpus callosum became evident on CT and MRI characterised by oedema and swelling, particularly affecting the dorsal surface of the corpus callosum. This pattern of signal change, although dramatic, should not be mistaken for other pathologies.

Organization of the commissural fiber system in congenital and late-onset blindness

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Larger anterior commissure (AC) in congenitally (CB) and late blind (LB) subjects.

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Decreased fractional anisotropy (FA) of the posterior part of AC (pAC) in CB and LB.

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Decreased FA in pAC is paralleled by increased number of pAC streamlines in CB only.

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Selective reduction of the splenium of the corpus callosum (CC) in CB and LB.

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Reduction of splenium correlated with decrease in streamlines and tract volume.

We investigated the effects of blindness on the structural and functional integrity of the corpus callosum and the anterior commissure (AC), which together form the two major components of the commissural pathways. Twelve congenitally blind (CB), 15 late blind (LB; mean onset of blindness of 16.6 ± 8.9 years), and 15 matched normally sighted controls (SC) participated in a multimodal brain imaging study. Magnetic resonance imaging(MRI) data were acquired using a 3T scanner, and included a structural brain scan, resting state functional MRI, and diffusion-weighted imaging. We used tractography to divide the AC into its anterior (aAC) and posterior (pAC) branch. Virtual tract dissection was performed using a deterministic spherical deconvolution tractography algorithm. The corpus callosum was subdivided into five subregions based on the criteria described by Witelson and modified by Bermudez and Zatorre. Our data revealed decreased fractional anisotropy of the pAC in CB and LB compared to SC, together with an increase in the number of streamlines in CB only. In addition, the AC surface area was significantly larger in CB compared to SC and LB, and correlated with the number of streamlines in pAC (rho = 0.55) and tract volume (rho = 0.46). As for the corpus callosum, the splenial part was significantly smaller in CB and LB, and fewer streamlines passed through it. We did not find group differences in functional connectivity of cortical areas connected by fibers crossing any of the five callosal subregions. The present data suggest that the two main components of the commissural system undergo neuroplastic changes, irrespective of the age of onset of blindness, although the alterations observed in the AC are more important in congenital than late-onset blindness.

One-year changes in brain microstructure differentiate preclinical Huntington's disease stages

OBJECTIVE

To determine whether brain imaging markers of tissue microstructure can detect the effect of disease progression across the preclinical stages of Huntington's disease.

METHODS

Longitudinal microstructural changes in diffusion imaging metrics (mean diffusivity and fractional anisotropy) were investigated in participants with presymptomatic Huntington's disease (N = 35) stratified into three preclinical subgroups according to their estimated time until onset of symptoms, compared with age- and gender-matched healthy controls (N = 19) over a 1y period.

RESULTS

Significant differences were found over the four groups in change of mean diffusivity in the posterior basal ganglia and the splenium of the corpus callosum. This overall effect was driven by significant differences between the group far-from-onset (FAR) of symptoms and the groups midway- (MID) and near-the-onset (NEAR) of symptoms. In particular, an initial decrease of mean diffusivity in the FAR group was followed by a subsequent increase in groups closer to onset of symptoms. The seemingly counter-intuitive decrease of mean diffusivity in the group furthest from onset of symptoms might be an early indicator of neuroinflammatory process preceding the neurodegenerative phase. In contrast, the only clinical measure that was able to capture a difference in 1y changes between the preclinical stages was the UHDRS confidence in motor score.

CONCLUSIONS

With sensitivity to longitudinal changes in brain microstructure within and between preclinical stages, and potential differential response to distinct pathophysiological mechanisms, diffusion imaging is a promising state marker for monitoring treatment response and identifying the optimal therapeutic window of opportunity in preclinical Huntington's disease.

Circuits generating secondarily generalized seizures

Mapping the circuits underlying the generation and propagation of seizures is critically important for understanding their pathophysiology. We review evidence to suggest that circuits engaged in secondarily generalized seizures are likely to be more complex than those currently proposed. Focal seizures have been proposed to engage canonical thalamocortical circuits that mediate primarily generalized absence seizures, leading to secondarily generalized tonic-clonic seizures. In addition to traveling through the canonical thalamocortical circuits, secondarily generalized seizures could also travel through the striatum, globus pallidus, substantia nigra reticulata, and corpus callosum to the contralateral hemisphere. Recruitment of principal neurons in superficial layers 2/3 of the cortex can play a critical role in corticocortical seizure spread. Understanding the neuronal structures engaged in generating secondarily generalized seizures could provide novel targets for neuromodulation for the treatment of seizures. Furthermore, these sites may be loci of neuronal plasticity facilitating epileptogenesis. This article is part of the Special Issue "Proceedings of the 7th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures".

Dominance wave propagation during binocular rivalry in mild glaucoma

Glaucoma is both a progressive optic neuropathy and a neurodegenerative disease affecting structures in the primary visual pathway. Other vision-associated areas may also be affected, including the corpus callosum which is involved in inter-hemispheric transfer. This study evaluated dominance wave propagation during binocular rivalry to probe the efficacy of the inter-hemispheric transfer in 20 patients with mild open angle glaucoma and 25 age-matched controls. The two groups were matched for functional measures such as stereo-acuity, binocular visual acuity, and visual field mean deviation. Monocular functional and structural measures were equivalent for the left and right eye of each participant. Using Wilson et al.'s travelling wave paradigm [Nature, 412 (2001) 907-910], intra- and inter-hemispheric failure rates of traveling wave transmission and the travelling wave propagation times were recorded for the two groups. For the control group, the wave propagation failure rate was significantly greater for the inter- than for the intra-hemispheric condition, but for the glaucoma group, the failure rates were equally high for the two conditions. The wave propagation time was significantly longer for the inter- than for the intra-hemispheric condition for the control group, while the opposite was true for the glaucoma group. These results reveal changes in the wave dynamics of rivalry dominance in patients with mild glaucoma who otherwise have normal performance on standard functional measures.

Effects of prenatal exposure to particulate matter air pollution on corpus callosum and behavioral problems in children

OBJECTIVE

Air pollution (AP) may affect neurodevelopment, but studies about the effects of AP on the growing human brain are still scarce. We aimed to investigate the effects of prenatal exposure to AP on lateral ventricles (LV) and corpus callosum (CC) volumes in children and to determine whether the induced brain changes are associated with behavioral problems.

METHODS

Among the children recruited through a set of representative schools of the city of Barcelona, (Spain) in the Brain Development and Air Pollution Ultrafine Particles in School Children (BREATHE) study, 186 typically developing participants aged 8-12 years underwent brain MRI on the same 1.5 T MR unit over a 1.5-year period (October 2012-April 2014). Brain volumes were derived from structural MRI scans using automated tissue segmentation. Behavioral problems were assessed using the Strengths and Difficulties Questionnaire (SDQ) and the criteria of the Attention Deficit Hyperactivity Disorder DSM-IV list. Prenatal fine particle (PM_2.5) levels were retrospectively estimated at the mothers' residential addresses during pregnancy with land use regression (LUR) models. To determine whether brain structures might be affected by prenatal PM_2.5 exposure, linear regression models were run and adjusted for age, sex, intracranial volume (ICV), maternal education, home socioeconomic vulnerability index, birthweight and mothers' smoking status during pregnancy. To test for associations between brain changes and behavioral outcomes, negative binomial regressions were performed and adjusted for age, sex, ICV.

RESULTS

Prenatal PM_2.5 levels ranged from 11.8 to 39.5 μg/m³ during the third trimester of pregnancy. An interquartile range increase in PM_2.5 level (7 μg/m³) was significantly linked to a decrease in the body CC volume (mm³) (β = -53.7, 95%CI [-92.0, -15.5] corresponding to a 5% decrease of the mean body CC volume) independently of ICV, age, sex, maternal education, socioeconomic vulnerability index at home, birthweight and mothers' smoking status during the third trimester of pregnancy. A 50 mm³ decrease in the body CC was associated with a significant higher hyperactivity subscore (Rate Ratio (RR) = 1.09, 95%CI [1.01, 1.17) independently of age, sex and ICV. The statistical significance of these results did not survive to False Discovery Rate correction for multiple comparisons.

CONCLUSIONS

Prenatal exposure to PM_2.5 may be associated with CC volume decrease in children. The consequences might be an increase in behavioral problems.

A Callosal Catastrophe: Toxic Leukoencephalopathy Associated with Thermogenic Weight Loss Supplement Use

BACKGROUND

The use of weight loss drugs and dietary supplements is common, but safety profiles for these drugs are largely unknown. Reports of toxicity have been published, and the use of these agents should be considered in clinical differential diagnoses.

METHODS

We report the case of a patient with toxic leukoencephalopathy and hyponatremia associated with oral consumption of a thermogenic dietary supplement and essential oils.

RESULTS

A 30-year-old woman presented after 2 days of headache, blurred vision, photophobia, vomiting, and hand spasms. She was taking a thermogenic dietary supplement daily for 6 months as well as a number of essential oils. Examination revealed mild right sided ataxia and diffuse hyperreflexia. Neuroimaging demonstrated bilaterally symmetric T2 hyperintensities of the corpus callosum and periventricular white matter. Approximately 18 h after admission she became unresponsive with brief extensor posturing and urinary incontinence. She partially recovered, but 1 h later became unresponsive with dilated nonreactive pupils and extensor posturing (central herniation syndrome). She was intubated, hyperventilated, and given hyperosmotic therapy. Emergent imaging showed diffuse cerebral edema. Intracranial pressure was elevated but normalized with treatment; she regained consciousness the following day. She was extubated one day later and discharged on hospital day 5. She was seen 2 months later with no further symptoms and a normal neurologic examination.

CONCLUSIONS

The pathophysiology of this patient's hyponatremia and toxic leukoencephalopathy is unknown. However, physicians must be aware of the association between thermogenic dietary supplements and toxic leukoencephalopathy. Vigilance for life-threatening complications including hyponatremia and cerebral edema is critical.

Progressive sensorineural hearing loss many years preceding completion of Susac's syndrome triad: A case report

Susac's syndrome (SuS) is a rare disorder with a clinical triad of encephalopathy, sensorineural hearing loss, and branch retinal artery occlusions. We report a 7-year-old girl who presented with chronic, progressive sensorineural hearing loss, who, years later, presented with encephalopathy and vision loss. Such prolonged period between symptoms is unusual and to our knowledge, this is the longest interval between onset of hearing loss and completion of the full triad in SuS. In addition, she had a protracted disease course, requiring multiple immune therapies for disease control.

Corpus callosum microstructural and macrostructural abnormalities in schizophrenia according to the stage of disease

Corpus callosum (CC) volume and surface (macrostructural) studies remain controversial and have not considered the illness duration (ID) systematically. Regardless of ID, some CC macrostructural studies have shown no difference between SZ patients and healthy controls (HC), whereas others have reported macrostructural abnormalities in SZ. Conversely, CC microstructural studies are more in agreement with alterations in CC integrity regardless of the patients' ID, but the direction and degree of these abnormalities over time remain unknown. Moreover, no study has explored both the micro- and macrostructure of the CC in SZ by considering the stage of disease. Both CC micro- and macrostructural data were investigated in 43 SZ patients and compared between two patient groups (21 patients with a short ID and 22 with a long ID) and HC (23 participants) using diffusion tensor and structural imaging. CC microstructural alterations were detected in both SZ groups compared to the HC group, without differences between the SZ groups. In contrast, CC macrostructural alterations were only found in the long ID group. CC microstructural alterations might be detected in schizophrenia at an early stage, without an increase of magnitude thereafter, while CC macrostructural alterations might become apparent at later stages of the illness.

The Relationship between Corpus Callosum Morphometric Measurements and Age/Gender Characteristics: A Comprehensive MR Imaging Study

Objective

The objective of the study was to examine a possible relationship between morphometric corpus callosum (CC) measurements, age, and gender characteristics using MR images.

Materials and Methods

The medical data and MR examinations of 436 consecutive subjects were retrospectively reviewed. The CC thickness from five different sites, and additionally splenium length, height, and total length of the CC, and the splenium index (SI) were measured with a mid-sagittal T1-weighted sequence. Those measurements were compared with age and gender characteristics.

Results

A weak but statistically significant negative correlation was found between age and thicknesses of genu and all body portions of CC (P = ≤0.001 for all, r = -0.32 for genu, r = -0.317 for B1, r = -0.328 for B2, r = -0.328 for B2, and r = -0.194 for B3 and B4). There was a weak but statistically significant positive correlation between age and the lengths of CC and splenium (P ≤ 0.022 for both, r = 0.112 for CC length and r = 0.11 for splenium length). The second part of the body (B2) was thicker in females (P = 0.014). On the other hand, the CC and splenium lengths were greater in males compared to females (P = 0.029 for both).

Conclusion

We designed a comprehensive MRI study to investigate a possible relationship between normal morphometric CC measurements in 436 healthy subjects. We preferred splenium length and SI as the main splenium measurements instead of direct splenium thickness, due to discrepancies regarding splenium measurement methods in the medical literature. There was a wide spectrum of results, and we compared those results with existing medical literature.

Estimating axon conduction velocity in vivo from microstructural MRI

The conduction velocity (CV) of action potentials along axons is a key neurophysiological property central to neural communication. The ability to estimate CV in humans in vivo from non-invasive MRI methods would therefore represent a significant advance in neuroscience. However, there are two major challenges that this paper aims to address: (1) Much of the complexity of the neurophysiology of action potentials cannot be captured with currently available MRI techniques. Therefore, we seek to establish the variability in CV that can be captured when predicting CV purely from parameters that have been reported to be estimatable from MRI: inner axon diameter (AD) and g-ratio. (2) errors inherent in existing MRI-based biophysical models of tissue will propagate through to estimates of CV, the extent to which is currently unknown. Issue (1) is investigated by performing a sensitivity analysis on a comprehensive model of axon electrophysiology and determining the relative sensitivity to various morphological and electrical parameters. The investigations suggest that 85% of the variance in CV is accounted for by variation in AD and g-ratio. The observed dependency of CV on AD and g-ratio is well characterised by the previously reported model by Rushton. Issue (2) is investigated through simulation of diffusion and relaxometry MRI data for a range of axon morphologies, applying models of restricted diffusion and relaxation processes to derive estimates of axon volume fraction (AVF), AD and g-ratio and estimating CV from the derived parameters. The results show that errors in the AVF have the biggest detrimental impact on estimates of CV, particularly for sparse fibre populations (AVF<0.3). For our equipment set-up and acquisition protocol, CV estimates are most accurate (below 5% error) where AVF is above 0.3, g-ratio is between 0.6 and 0.85 and AD is high (above 4μm). CV estimates are robust to errors in g-ratio estimation but are highly sensitive to errors in AD estimation, particularly where ADs are small. We additionally show CV estimates in human corpus callosum in a small number of subjects. In conclusion, we demonstrate accurate CV estimates are possible in regions of the brain where AD is sufficiently large. Problems with estimating ADs for smaller axons presents a problem for estimating CV across the whole CNS and should be the focus of further study.

Sarm1 deletion reduces axon damage, demyelination, and white matter atrophy after experimental traumatic brain injury

Traumatic brain injury (TBI) often damages axons in white matter tracts and causes corpus callosum (CC) atrophy in chronic TBI patients. Injured axons encounter irreversible damage if transected, or alternatively may maintain continuity and subsequently either recover or degenerate. Secondary mechanisms can cause further axon damage, myelin pathology, and neuroinflammation. Molecular mechanisms regulating the progression of white matter pathology indicate potential therapeutic targets. SARM1 is essential for execution of the conserved axon death pathway. We examined white matter pathology following mild TBI with CC traumatic axonal injury in mice with Sarm1 gene deletion (Sarm1-/-). High resolution ultrastructural analysis at 3 days post-TBI revealed dramatically reduced axon damage in Sarm1-/- mice, as compared to Sarm1+/+ wild-type controls. Sarm1 deletion produced larger axons with thinner myelin, and attenuated TBI induced demyelination, i.e. myelin loss along apparently intact axons. At 6 weeks post-TBI, Sarm1-/- mice had less demyelination and thinner myelin than Sarm1+/+ mice, but axonal protection was no longer observed. We next used Thy1-YFP crosses to assess Sarm1 involvement in white matter neurodegeneration and neuroinflammation at 8 weeks post-TBI, when significant CC atrophy indicates chronic pathology. Thy1-YFP expression demonstrated continued CC axon damage yet absence of overt cortical pathology. Importantly, significant CC atrophy in Thy1-YFP/Sarm1+/+ mice was associated with reduced neurofilament immunolabeling of axons. Both effects were attenuated in Thy1-YFP/Sarm1-/- mice. Surprisingly, Thy1-YFP/Sarm1-/- mice had increased CC astrogliosis. This study demonstrates that Sarm1 inactivation reduces demyelination, and white matter atrophy after TBI, while the post-injury stage impacts when axon protection is effective.

Interhemispheric functional connectivity in the zebra finch brain, absent the corpus callosum in normal ontogeny

Bilaterally symmetric intrinsic brain activity (homotopic functional connectivity; FC) is a fundamental feature of the mammalian brain's functional architecture. In mammals, homotopic FC is primarily mediated by the corpus callosum (CC), a large interhemispheric white matter tract thought to balance the bilateral coordination and hemispheric specialization critical for many complex brain functions, including human language. The CC first emerged with the Eutherian (placental) mammals ∼160 MYA and is not found among other vertebrates. Despite this, other vertebrates also exhibit complex brain functions requiring hemispheric specialization and coordination. For example, the zebra finch (Taeniopygia guttata) songbird learns to sing from tutors much as humans acquire speech and must balance hemispheric specialization and coordination to successfully learn and produce song. We therefore tested whether the zebra finch also exhibits homotopic FC, despite lacking the CC. Resting-state fMRI analyses demonstrated widespread homotopic FC throughout the zebra finch brain across development, including within a network required for learned song that lacks direct interhemispheric structural connectivity. The presence of homotopic FC in a non-Eutherian suggests that ancestral pathways, potentially including indirect connectivity via the anterior commissure, are sufficient for maintaining a homotopic functional architecture, an insight with broad implications for understanding interhemispheric coordination across phylogeny.

Patterning of corpus callosum integrity in glioma observed by MRI: Effect of 2D bi-axial lamellar brain architecture

PURPOSE

Corpus callosum (CC) is a main channel histologically for glioma spreading, downgrading the prognosis, the infiltration occurring through cellular reaction-diffusion process. Preliminary clinical trial indicates that CC's surgical interruption appreciably enhances clinical outcome. We aim to find how high-grade glioma phenomenology is reflected in CC parameters, including various 3D diffusion eigenvalues differentially, whereby this information may be utilized for planning radiotherapy and surgical intervention.

METHODS

Using 3 Tesla MRI diffusion-tensor imaging of glioma patients and matched controls, we formulated the callosal volume, fibre count, and 3D directional diffusivity eigenvalues (λ₁-λ₂-λ₃), utilizing FDT/FMRIB-based analysis.

RESULTS

In glioma, the callosal volume, fibre count and normalized volume decreases (p < 0.001), while axial diffusivity λ₁ and radial diffusivity component λ₂ significantly increase (p = 0.03, p = 0.04). Though not expected, the other radial diffusivity component λ₃ remains unchanged (p = 0.11). Increase of λ₁ and λ₂ is due to gliomatous migration across the two directions (eigenvectors of λ₁, λ₂), which correlate respectively with medio-lateral commissural fibres and dorso-ventral perforating fibres in CC. These are corroborated by collateral radiological findings and immunohistological staining of those two fibre-systems in cat and human.

CONCLUSION

In glioma, the two diffusivities (λ₁, λ₂), enhance due to fluidic edema permeation through CC's bi-axial lamina-type structural scaffold, formed by mediolateral commissural fibres and dorsoventral perforating cingulo-septal fibres. On other hand, the two radial diffusivities (λ₂, λ₃) are physiologically different and can be distinguished as lamellar diffusivity and focal diffusivity respectively. Lamellar diffusivity λ₂ needs to be considered for MRI-assisted surgical intervention and radiotherapy planning in glioma.

Diffusion abnormalities in the corpus callosum in first episode schizophrenia: Associated with enlarged lateral ventricles and symptomatology

INTRODUCTION

Abnormalities in the corpus callosum (CC) and the lateral ventricles (LV) are hallmark features of schizophrenia. These abnormalities have been reported in chronic and in first episode schizophrenia (FESZ). Here we explore further associations between CC and LV in FESZ using diffusion tensor imaging (DTI).

METHODS

. Sixteen FESZ patients and 16 healthy controls (HC), matched on age, gender, and handedness participated in the study. Diffusion and structural imaging scans were acquired on a 3T GE Signa magnet. Volumetric measures for LV and DTI measures for five CC subdivisions were completed in both groups. In addition, two-tensor tractography, the latter corrected for free-water (FA_t), was completed for CC. Correlations between LV and DTI measures of the CC were examined in both groups, while correlations between DTI and clinical measures were examined in only FESZ.

RESULTS

Results from two-tensor tractography demonstrated decreased FA_t and increased trace and radial diffusivity (RD_t) in the five CC subdivisions in FESZ compared to HC. Central CC diffusion measures in FESZ were significantly correlated with volume of the LV, i.e., decreased FA_t values were associated with larger LV volume, while increased RD_t and trace values were associated with larger LV volume. In controls, correlations were also significant, but they were in the opposite direction from FESZ. In addition, decreased FA_t in FESZ was associated with more positive symptoms.

DISCUSSION

Partial volume corrected FA_t, RD_t, and trace abnormalities in the CC in FESZ suggest possible de- or dys-myelination, or changes in axonal diameters, all compatible with neurodevelopmental theories of schizophrenia. Correlational findings between the volume of LV and diffusion measures in FESZ reinforce the concept of a link between abnormalities in the LV and CC in early stages of schizophrenia and are also compatible with neurodevelopmental abnormalities in this population.

Development of a transcallosal tractography template and its application to dementia

Understanding the architecture of transcallosal connections would allow for more specific assessments of neurodegeneration across many fields of neuroscience, neurology, and psychiatry. To map these connections, we conducted probabilistic tractography in 100 Human Connectome Project subjects in 32 cortical areas using novel post-processing algorithms to create a spatially precise Trancallosal Tract Template (TCATT). We found robust transcallosal tracts in all 32 regions, and a topographical analysis in the corpus callosum largely agreed with well-established subdivisions of the corpus callosum. We then obtained diffusion MRI data from a cohort of patients with Alzheimer's disease (AD) and another with progressive supranuclear palsy (PSP) and used a two-compartment model to calculate free-water corrected fractional anisotropy (FA_T) and free-water (FW) within the TCATT. These metrics were used to determine between-group differences and to determine which subset of tracts was best associated with cognitive function (Montreal Cognitive Assessment (MoCA)). In AD, we found robust between-group differences in FW (31/32 TCATT tracts) in the absence of between-group differences in FA_T. FW in the inferior temporal gyrus TCATT tract was most associated with MoCA scores in AD. In PSP, there were widespread differences in both FA_T and FW, and MoCA was predicted by FA_T in the inferior frontal pars triangularis, preSMA, and medial frontal gyrus TCATT tracts as well as FW in the inferior frontal pars opercularis TCATT tract. The TCATT improves spatial localization of corpus callosum measurements to enhance the evaluation of treatment effects, as well as the monitoring of brain microstructure in relation to cognitive dysfunction and disease progression. Here, we have shown its direct relevance in capturing between-group differences and associating it with the MoCA in AD and PSP.

Analysis for the Association Between Corpus Callosum Thickness and Corpus Callosotomy Outcomes for Patients With Epileptic Spasms or Tonic Spasms

BACKGROUND

This retrospective study is designed to determine whether the thickness of the corpus callosum can predict corpus callosotomy outcome in pediatric patients with epileptic or tonic spasms.

METHODS

We retrospectively studied 25 patients (18 boys) with intractable childhood-onset epileptic or tonic spasms who underwent corpus callosotomy between March 2008 and January 2017. Seizure outcomes were classified as favorable (class I and II of Engel's outcome classification) or unfavorable (class III and IV of Engel's outcome classification) at 12 months postoperatively. We measured the corpus callosum area on the midline and maximum cerebral area on the para-midline in sagittal magnetic resonance images just before surgery. We statistically analyzed the associations between surgical outcomes and corpus callosum area, corpus callosum area/maximum cerebral area (corpus callosum/cerebrum ratio), or age at magnetic resonance imaging just before surgery, using univariate and multivariate logistic regression analyses.

RESULTS

Age at surgery ranged from six to 237 months (mean: 119). Main seizure types were epileptic spasms in 17 patients and tonic spasms in eight. Favorable outcomes occurred in 10 (40%) patients and unfavorable outcomes in 15 (60%). Both corpus callosum area and corpus callosum/cerebrum ratio did not show significant associations with the outcomes in the univariate and multivariate analyses. The 95% confidence intervals of corpus callosum/cerebrum ratio strongly overlapped between the favorable and unfavorable outcome groups.

CONCLUSIONS

Our data failed to support that corpus callosum thickness on the sagittal image is associated with corpus callosotomy outcomes in pediatric patients with epileptic spasms or tonic spasms.

Susac Syndrome: Clinical characteristics, diagnostic findings and treatment in 19 cases

Susac's Syndrome (SS), which was first described in 1979, is a rare and presumably autoimmune disorder characterized by encephalopathy, hearing loss, and visual disturbance resulting from branch retinal artery occlusion (BRAO). This study reports 19 SS patients' clinical characteristics, MRI features, CSF analysis, treatment strategies and outcomes. At initial presentation, only three of 19 patients demonstrated the complete clinical triad. Clinic presentation varied from isolated hemiparesis to the full triad (encephalopathy, hearing loss and visual disturbances). Corpus callosum (CC) involvement was noted in the MRI of 18 patients (97%) and BRAO was detected in 17 (95%) patients. All patients were treated with intravenous methylprednisolone after the initial assessment. This case series is presented to emphasize the differences in clinical presentation of SS and the importance of MRI and FFA in diagnosis.

Disrupted interhemispheric resting-state functional connectivity and structural connectivity in first-episode, treatment-naïve generalized anxiety disorder

BACKGROUND

Aberrant functional and structural connectivity are considered to be involved in the underlying neural mechanism of generalized anxiety disorder (GAD). However, alterations in functional and structural interactions between the bilateral hemispheres are rarely examined. The current study aimed to characterized interhemispheric resting-state functional connectivity and white matter microstructural integrity of the corpus callosum in patients with GAD.

METHODS

Resting-state Blood oxygen level-dependent and diffusion tensor image were acquired for patients with GAD and healthy subjects. The two groups were matched in age, gender, education years. The voxel-mirrored homotopic connectivity (VMHC) of whole brain and white matter integrity of the corpus callosum (CC) were compared between the two groups. Their correlations with clinical measures were further performed.

RESULTS

Compare to controls, decreased resting-state VMHC were found in the precentral gyrus, middle cingulate gyrus and insula/putamen in patients with GAD. No regions of increased VMHC were detected in GAD. Compared to controls, GAD patients showed decreased fractional anisotropy (FA) values in CC2. In GAD group, further Pearson's correlation analyses showed that VMHC of the midcingulate gyrus positively correlated with FA of CC2, FA of CC2 negatively correlated with anxiety severity. Further mediation analyses demonstrated that attenuated VMHC in bilateral midcingulate gyrus partly mediated the association between white matter integrity of CC2 sub-region and anxiety severity.

CONCLUSION

Our findings suggested impairment of interhemispheric coordination in GAD. Moreover, disrupted interhemispheric connectivity correlated with anxiety severity in GAD. Our findings provided a novel clue about the neural mechanism of GAD, and may contribute to further deep exploration and treatment of GAD.

LIMITATIONS

The study was lack of comparison with non-GAD anxiety disorders.

Diffusion weighted imaging evidence of extra-callosal pathways for interhemispheric communication after complete commissurotomy

The integrity of white matter architecture in the human brain is related to cognitive processing abilities. The corpus callosum is the largest white matter bundle interconnecting the two cerebral hemispheres. "Split-brain" patients in whom all cortical commissures have been severed to alleviate intractable epilepsy demonstrate remarkably intact cognitive abilities despite the lack of this important interhemispheric pathway. While it has often been speculated that there are compensatory alterations in the remaining interhemispheric fibers in split-brain patients several years post-commissurotomy, this has never been directly shown. Here we examined extra-callosal pathways for interhemispheric communication in the brain of a patient who underwent complete cerebral commissurotomy using diffusion weighted imaging tractography. We found that compared with a healthy age-matched comparison group, the split-brain patient exhibited increased fractional anisotropy (FA) of the dorsal and ventral pontine decussations of the cortico-cerebellar interhemispheric pathways. Few differences were observed between the patient and the comparison group with respect to FA of other long-range intrahemispheric fibers. These results point to specific cerebellar anatomical substrates that may account for the spared interhemispheric coordination and intact cognitive abilities that have been extensively documented in this unique patient.

Characteristics of neurological Wilson's disease with corpus callosum abnormalities

BACKGROUND

Wilson's disease (WD) is an autosomal recessive disease of impaired copper metabolism. Previous study demonstrated that WD with corpus callosum abnormalities (WD-CCA) was limited to the posterior part (splenium). This study aimed to compare clinical features between WD-CCA and WD without corpus callosum abnormalities (WD-no-CCA).

METHODS

Forty-one WD patients who had markedly neurological dysfunctions were included in this study. We retrospectively reviewed clinical, biochemical characteristics and MRI findings in the 41 WD patients. All patients were assessed using the Unified Wilson's Disease Rating Scale.

RESULTS

Nine patients had corpus callosum abnormalities, 4 of 9 patients had abnormal signal in the genu and splenium, 5 of 9 patients had abnormal signal only in the splenium. WD-CCA had longer course (9.9 ± 4.0 years vs. 3.4 ± 3.6 years, p<0.01), more severe neurological dysfunctions (37.6 vs. 65.9, p<0.01) and higher psychiatric symptoms scores (11.2 vs. 22.5, p<0.01) than WD-no-CCA. The MRI findings indicated that WD-CCA had higher ratio than WD-no-CCA in globus pallidus (88.9% vs. 43.8%, p = 0.024) and thalamus (100% vs. 59.4%, p = 0.038). The index of liver function and copper metabolism had no significant in WD-CCA and WD-no-CCA patients.

CONCLUSION

Our findings indicate Wilson's disease can involve the posterior as well as the anterior part of CC and patients with CC involvement had more extensive brain lesions, more severe neurological dysfunctions and psychiatric symptoms.

Corpus Callosum: Molecular Pathways in Mice and Human Dysgeneses

The corpus callosum is the largest of the 3 telencephalic commissures in eutherian (placental) mammals. Although the anterior commissure, and the hippocampal commissure before being pushed dorsally by the expanding frontal lobes, cross through the lamina reuniens (upper part of the lamina terminalis), the callosal fibers need a transient interhemispheric cellular bridge to cross. This review describes the molecular pathways that initiate the specification of the cells comprising this bridge, the specification of the callosal neurons, and the repulsive and attractive guidance molecules that convey the callosal axons toward, across, and away from the midline to connect with their targets.

White matter microstructure and cognitive outcomes in relation to neonatal inflammation in 6-year-old children born preterm

BACKGROUND

Cognitive outcomes in preterm (PT) children have been associated with microstructural properties of white matter. PT children who experienced neonatal inflammatory conditions have poorer cognitive outcomes than those who did not. The goal of this study was to contrast white matter microstructure and cognitive outcomes after preterm birth in relation to the presence or absence of severe inflammatory conditions in the neonatal period.

METHODS

PT children (n = 35), born at gestational age 22-32 weeks, were classified as either PT+ (n = 12) based on a neonatal history of inflammatory conditions, including bronchopulmonary dysplasia, necrotizing enterocolitis or culture positive sepsis, or PT- (n = 23) based on the absence of the three inflammatory conditions. Full term (FT) children (n = 43) served as controls. Participants underwent diffusion MRI and cognitive testing (intelligence, reading, and executive function) at age 6 years. The corpus callosum was segmented into 7 regions using deterministic tractography and based on the cortical projection zones of the callosal fibers. Mean fractional anisotropy (FA) and mean diffusivity (MD) were calculated for each segment. General linear models with planned contrasts assessed group differences in FA, MD and cognitive outcomes. Pearson correlations assessed associations of white matter metrics and cognitive outcome measures.

RESULTS

FA was significantly lower and MD was significantly higher in PT+ compared to PT- or FT groups in multiple callosal segments, even after adjusting for gestational age. Executive function scores, but not intelligence or reading scores, were less favorable in PT+ than in PT- groups. Among the entire sample, occipital FA was significantly correlated with IQ (r = 0.25, p < 0.05), reading (r = 0.32, p < 0.01), and executive function (r = -0.28, p < 0.05) measures. Anterior frontal FA and superior parietal FA were significantly correlated with executive function (r = -0.25, r = 0.23, respectively, p < 0.05).

CONCLUSIONS

We observed differences in the white matter microstructure of the corpus callosum and in the cognitive skills of 6-year-old PT children based on their history of neonatal inflammation. Neonatal inflammation is one medical factor that may contribute to variation in long-term neurobiological and neuropsychological outcomes in PT samples.

Familial Hydrocephalus and Dysgenesis of the Corpus Callosum Associated with Xp22.33 Duplication and Stenosis of the Aqueduct of Sylvius with X-Linked Recessive Inheritance Pattern

INTRODUCTION

X-linked recessive mutations predominantly affect male fetuses with milder or no abnormalities in female siblings. Most reports show only one affected member in the family. We are reporting a family affected with hydrocephalus, stenosis of the aqueduct of Sylvius, dysgenesis of the corpus callosum, and Xp22.33 microduplication.

CASE PRESENTATION

Eighteen-year-old patient was evaluated for her 2 pregnancies; the first was a male fetus with severe hydrocephalus and the second a female fetus with mild hydrocephalus. Postnatal MRI evaluation of the male neonate revealed stenosis of the aqueduct of Sylvius, dysgenesis of the corpus callosum, and severe hydrocephalus requiring ventriculoperitoneal shunt. Postnatal MRI evaluation of the female neonate revealed mild hydrocephalus, stenosis of the aqueduct of Sylvius, and mild dysgenesis of the corpus callosum. The female baby did not require surgical intervention. Genetic testing of the mother and the 2 children revealed a 439 Kb duplication of Xp22.33.

DISCUSSION

This family demonstrates typical X-linked recessive heritability. X-inactivation is a compensatory mechanism that explains the mild symptoms of the female child and the severe symptoms of the male child. This familial case shows the importance of prenatal testing and genetic counseling and testing, including karyotype and chromosomal microarray.

Mechanism of Corpus Callosum Infarction Associated with Acute Hydrocephalus: Clinical, Surgical, and Radiological Evaluations for Pathophysiology

BACKGROUND

Corpus callosum (CC) infarction has been reported to be rare because of the rich blood supply in the CC. The pathophysiology of CC infarction associated with acute hydrocephalus is unknown. The aim of the present study was to clarify the characteristics and mechanism of CC infarction associated with acute noncommunicating hydrocephalus (ANCH).

METHODS

We reviewed clinical the data from all patients who had undergone surgical intervention for ANCH at Chiba University Hospital from January 2008 to March 2018. Patients with vascular lesions, a history of hydrocephalus, and lacking magnetic resonance imaging studies were excluded. The clinical, surgical, and radiological parameters were obtained retrospectively for pathophysiological analysis.

RESULTS

A total of 23 patients with ANCH who had undergone surgical intervention and had met the inclusion criteria were included in the present study. Of the 23 patients, 6 (23%) had developed CC infarction. All CC infarctions were located in the splenium. Although no clinical or surgical features were associated with splenial infarction, the radiological parameters of lateral ventricle enlargement and a narrower callosal angle at the posterior commissure and the foramen of Monro were significantly associated with splenial infarction.

CONCLUSION

The present study has presented evidence that increased intraventricular pressure by ANCH applied transversely in the splenium will directly induce compression of the superior branch of the posterior callosal artery and pericallosal pial plexus, resulting in splenium-specific infarction in patients with ANCH.

Child abuse interacts with hippocampal and corpus callosum volume on psychophysiological response to startling auditory stimuli in a sample of veterans

Child abuse (CA), which is linked to posttraumatic stress disorder (PTSD), has been associated with a reduction in both hippocampal and corpus callosum (CC) volume. However, few studies have explored these relationships on psychophysiological variables related to trauma exposure. Therefore, we assessed whether the interaction between CA and hippocampal and CC volume were associated with enhanced fear potentiated psychophysiological response patterns in a sample of Veterans. 147 Veteran participants who were part of a larger study of Gulf War Illness were exposed to startling sounds in no, ambiguous, and high threat conditions and also provided MRI data. The Clinician Administered PTSD Scale and Trauma History Questionnaire were used to measure PTSD and CA respectively. Psychophysiological response was measured by EMG, SCR, and heart rate. Repeated-measures mixed linear models were used to assess the significance of CA by neural structure interactions. CA interacted with both hippocampal and CC volume on psychophysiological response magnitudes, where participants with CA and smaller hippocampal volume had greater EMG (p < 0.01) and SCR (p < 0.05) magnitudes across trials and over threat conditions. Participants with CA and smaller CC volume had greater SCR magnitudes across trials and over threat conditions (p < 0.01). Hippocampal and genu volume mediated CA and psychophysiological response magnitude. CA may impact psychophysiological response via a reduction in hippocampal and CC volume. Volumetric reduction in these structures may indicate a neurofunctional, CA-related increase in threat sensitivity, which could portend increased PTSD susceptibility and adverse interpersonal and social consequences across the lifespan.

Astrocyte ablation induced by La-aminoadipate (L-AAA) potentiates remyelination in a cuprizone demyelinating mouse model

Chronic demyelination in the central nervous system (CNS) is accompanied by an increase in the number of reactive astrocytes and astrogliosis. There are controversial issues regarding astrocytes and their roles in demyelinating diseases in particular for multiple sclerosis (MS). We aimed to evaluate possible roles for pharmacologic astrocyte ablation strategy using La-aminoadipate (L-AAA) on remyelination in a cuprizone model of demyelination. Male C57BL/6 mice were fed with 0.2% cuprizone for 12 weeks followed by 2-week administration of L-AAA through a cannula inserted 1 mm above the corpus callosum. Rotarod test showed a significant decrease in the range of motor coordination deficits after ablation of astrocytes in mice receiving cuprizone. Results of Luxol fast blue (LFB) and transmission electron microscopy (TEM) for evaluation of myelin content within the corpus callosum revealed a noticeable rise in the percentage of myelinated areas and in the number of myelinated fibers after L-AAA administration in the animals. Astrocyte ablation reduced protein expressions for GFAP (an astrocyte marker) and Iba-1 (a microglial marker), but increased expression of Olig2 (an oligodendrocyte marker) assessed by immunofluorescence. Finally, expression of genes related to recruitment of microglia (astrocyte chemokines CXCL10 and CXCL12) and suppression of oligodendrocyte progenitor cell (OPC) differentiation (astrocyte peptides ET-1 and EDNRB) showed a considerable decrease after administration of L-AAA (for all p < 0.05). These results are indicative of improved remyelination after ablation of astrocytes possibly through hampering microgliosis and astrogliosis and a further rise in the number of matured Olig2⁺ cells.

Selective micro-structural integrity impairment of the isthmus subregion of the corpus callosum in alcohol-dependent males

BACKGROUND

Previous studies have provided evidence that alcohol-dependent patients have abnormality in corpus callosum (CC); however, it is unclear whether micro-structural integrity of the CC subregions is differentially affected in this disorder.

METHODS

In this study, a total of 39 male individuals, including 19 alcohol-dependent patients and 20 age-matched healthy controls, underwent diffusion tensor imaging (DTI). CC was reconstructed by DTI tractography and was divided into seven subregions. Multiple diffusion metrics of each subregion were compared between two groups.

RESULTS

Compared to healthy controls, patients exhibited increased axial diffusivity (P = 0.007), radial diffusivity (P = 0.009) and mean diffusivity (P = 0.005) in the isthmus. In addition, we observed that daily alcohol intake was correlated positively with radial diffusivity and mean diffusivity and negatively with fractional anisotropy, while abstinence time of hospitalization was negatively correlated with mean diffusivity in the patients.

CONCLUSION

These findings suggest a selective micro-structural integrity impairment of the corpus callosum subregions in alcohol dependence, characterized by axon and myelin alterations in the isthmus.