Corpus Callosum Regions Research Articles

An anisotropic hyperelastic constitutive model of brain white matter in biaxial tension and structural–mechanical relationships

Computational models of the brain require accurate and robust constitutive models to characterize the mechanical behavior of brain tissue. The anisotropy of white matter has been previously demonstrated; however, there is a lack of data describing the effects of multi-axial loading, even though brain tissue experiences multi-axial stress states. Therefore, a biaxial tensile experiment was designed to more fully characterize the anisotropic behavior of white matter in a quasi-static loading state, and the mechanical data were modeled with an anisotropic hyperelastic continuum model. A probabilistic analysis was used to quantify the uncertainty in model predictions because the mechanical data of brain tissue can show a high degree of variability, and computational studies can benefit from reporting the probability distribution of model responses. The axonal structure in white matter can be heterogeneous and regionally dependent, which can affect computational model predictions. Therefore, corona radiata and corpus callosum regions were tested, and histology and transmission electron microscopy were performed on tested specimens to relate the distribution of axon orientations and the axon volume fraction to the mechanical behavior. These measured properties were implemented into a structural constitutive model. Results demonstrated a significant, but relatively low anisotropic behavior, yet there were no conclusive mechanical differences between the two regions tested. The inclusion of both biaxial and uniaxial tests in model fits improved the accuracy of model predictions. The mechanical anisotropy of individual specimens positively correlated with the measured axon volume fraction, and, accordingly, the structural model exhibited slightly decreased uncertainty in model predictions compared to the model without structural properties.

Right hemisphere structures predict poststroke speech fluency.

We sought to determine via a cross-sectional study the contribution of (1) the right hemisphere's speech-relevant white matter regions and (2) interhemispheric connectivity to speech fluency in the chronic phase of left hemisphere stroke with aphasia. Fractional anisotropy (FA) of white matter regions underlying the right middle temporal gyrus (MTG), precentral gyrus (PreCG), pars opercularis (IFGop) and triangularis (IFGtri) of the inferior frontal gyrus, and the corpus callosum (CC) was correlated with speech fluency measures. A region within the superior parietal lobule (SPL) was examined as a control. FA values of regions that significantly predicted speech measures were compared with FA values from healthy age- and sex-matched controls. FA values for the right MTG, PreCG, and IFGop significantly predicted speech fluency, but FA values of the IFGtri and SPL did not. A multiple regression showed that combining FA of the significant right hemisphere regions with the lesion load of the left arcuate fasciculus-a previously identified biomarker of poststroke speech fluency-provided the best model for predicting speech fluency. FA of CC fibers connecting left and right supplementary motor areas (SMA) was also correlated with speech fluency. FA of the right IFGop and PreCG was significantly higher in patients than controls, while FA of a whole CC region of interest (ROI) and the CC-SMA ROI was significantly lower in patients. Right hemisphere white matter integrity is related to speech fluency measures in patients with chronic aphasia. This may indicate premorbid anatomical variability beneficial for recovery or be the result of poststroke remodeling.

Intracranial bleeding from collaterals following carotid artery occlusion

A 53-year-old right-handed woman developed left pulsatile tinnitus. One year later she presented with a severe occipital headache with neck stiffness while defecating. On admission to hospital she was normotensive...

Advanced magnetic resonance neuroimaging in bulbar and limb onset early amyotrophic lateral sclerosis

Introduction:Amyotrophic lateral sclerosis (ALS) is a fatal and most common motor neuron disease, caused by progressive loss of motor neurons. Diffusion tensor imaging (DTI) and magnetic resonance spectroscopic (MRS) studies detect pathological changes in neuronal fibers in vivo. We evaluated the role of DTI and MRS in early course of the disease, which may prove beneficial in the early diagnosis and better management.Materials and Methods:Twenty-one patients with ALS and 13 age-matched controls received 1.5T DTI and three-dimensional multi-voxel MRS. Fractional anisotropy (FA), apparent diffusion coefficient, N-acetyl aspartate (NAA)/Creatine (Cr), and NAA/Choline (Ch) ratios were analyzed in various regions of the brain and compared with healthy controls. ALS patients were classified as definite, possible, and probable category, and patients were also studied in limb versus bulbar onset.Results:Decreased FA and increase mean diffusivity values in regions of corticospinal tract (CST) and corpus callosum (CC) was consistent finding in definite and probable disease category (P < 0.05). In possible disease, CC involvement was not significant. NAA/Cr and NAA/Ch ratios were lower in CC and regions of CST. However, in possible disease, CC involvement was not significant, while regions of CST were showing significant reduction in NAA/Cr and NAA/Ch ratios (P < 0.05).Conclusion:DTI and MRS detect changes associated with ALS even in the early phase of the disease. Bulbar onset and limb onset ALS patients show different pattern of involvement. Extramotor involvement suggested by CC involvement is a feature seen in bulbar onset patient and can suggest poor outcome in such patients. The present findings may be helpful for designing further studies in the direction of more early diagnosis of disease and its management.

Predicting progression from mild cognitive impairment to Alzheimer's disease using longitudinal callosal atrophy

IntroductionWe investigate whether longitudinal callosal atrophy could predict conversion from mild cognitive impairment (MCI) to Alzheimer's disease (AD). MethodsLongitudinal (baseline + 1-year follow-up) MRI scans of 132 MCI subjects from the Alzheimer's Disease Neuroimaging Initiative were used. A total of 54 subjects did not convert to AD over an average (±SD) follow-up of 5.46 (±1.63) years, whereas 78 converted to AD with an average conversion time of 2.56 (±1.65) years. Annual change in the corpus callosum thickness profile was calculated from the baseline and 1-year follow-up MRI. A logistic regression model with fused lasso regularization for prediction was applied to the annual changes. ResultsWe found a sex difference. The accuracy of prediction was 84% in females and 61% in males. The discriminating regions of corpus callosum differed between sexes. In females, the genu, rostrum, and posterior body had predictive power, whereas the genu and splenium were relevant in males. DiscussionAnnual callosal atrophy predicts MCI-to-AD conversion in females more accurately than in males.

Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players.

Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI through tackle football and later-life corpus callosum (CC) microstructure using magnetic resonance diffusion tensor imaging (DTI). Forty retired National Football League (NFL) players, ages 40-65, were matched by age and divided into two groups based on their AFE to tackle football: before age 12 or at age 12 or older. Participants underwent DTI on a 3 Tesla Siemens (TIM-Verio) magnet. The whole CC and five subregions were defined and seeded using deterministic tractography. Dependent measures were fractional anisotropy (FA), trace, axial diffusivity, and radial diffusivity. Results showed that former NFL players in the AFE <12 group had significantly lower FA in anterior three CC regions and higher radial diffusivity in the most anterior CC region than those in the AFE ≥12 group. This is the first study to find a relationship between AFE to RHI and later-life CC microstructure. These results suggest that incurring RHI during critical periods of CC development may disrupt neurodevelopmental processes, including myelination, resulting in altered CC microstructure.

Low-grade medullary astrocytoma presenting with supratentorial malignant glioma. Is it dissemination and malignant transformation?

Astrocytomas are the most common pediatric brain tumors and account for 40.9% of cerebral and 7.7% of all childhood cancers. Here we present a 16 yr male child who was diagnosed and operated for astrocytoma (grade II) of medulla oblongata; he received radiotherapy for residual tumor postoperatively. The patient developed large anaplastic astrocytoma (grade III) in splenium of corpus callosum and bilateral parieto-occipital region after 3 yr of first operation. It seems this tumor disseminated from brainstem, though primary site remained silent because of the effect of postoperative radiation therapy. It might have disseminated through ventricular cerebrospinal fluid pathways. Little is known about low-grade astrocytoma with dissemination and their malignant transformation to high-grade glioma. The optimum therapy or combinations of therapies for such tumors remains unclear. Few aspects of dissemination and malignant transformation of low-grade astrocytoma to high-grade or appearance of fresh tumor etc are discussed in this report.

Longitudinal changes in the DTI measures, anti-GFAP expression and levels of serum inflammatory cytokines following mild traumatic brain injury

The majority of human mild traumatic brain injuries (mTBI; 70%) lack radiological evidence of injury, yet may present long term cognitive, and behavioral dysfunctions. With the hypothesis of evident damaged neural tissue and immunological consequences during acute phase of mTBI, we used closed skull weight-drop TBI model to address human mTBI condition. Serum cytokines (TNF-α, IL-10) and glial fibrillary acidic protein (GFAP) expression were examined at day 0 (control, pre-injury), 4h, day 1, day 3 and day 5 post injury (PI). Diffusion tensor imaging (DTI) was performed at similar timepoints to identify neuroinflammation translation into imaging abnormalities and monitor injury progression. DTI indices including mean diffusivity (MD), radial diffusivity (RD), fractional anisotropy and axial diffusivity values were quantified from cortex (CTX), hippocampus and corpus callosum regions. One way ANOVA showed significant increase in TNF-α at 4h and IL-10 at day 1 PI as compared to control. GFAP+ cells were significantly increased at day 3 and day 5 as compared to control in CTX. Repeated measures ANOVA revealed significant decreases in MD, RD values in CTX at day 3 and day 5 as compared to day 0. A significant, inverse correlation was observed between cortical MD (r=−0.74, p=0.01), AD (r=−0.60, p=0.03) and RD (r=−0.72, p=0.01) values with mean GFAP+ cells in the cortical region. These findings suggest that mTBI leads to elevated cytokine expression and subsequent hypertrophy of astrocytic processes. The increased numbers of reactive glial cells contribute diffusion restrictions in the CNS leading to reduced MD and RD values. These findings are in line with the deficits and pathologies associated with clinical mTBI, and support the use of mTBI model to address pathology and therapeutic options.

Accelerated corpus callosum development in prematurity predicts improved outcome.

To determine: (1) whether corpus callosum (CC) size and microstructure at 7 years of age or their change from infancy to 7 years differed between very preterm (VP) and full-term (FT) children; (2) perinatal predictors of CC size and microstructure at 7 years; and (3) associations between CC measures at 7 years or trajectories from infancy to 7 years and neurodevelopmental outcomes. One hundred and thirty-six VP (gestational age [GA] <30 weeks and/or birth weight <1,250 g) and 33 FT children had usable magnetic resonance images at 7 years of age, and of these, 76 VP and 16 FT infants had usable data at term equivalent age. The CC was traced and divided into six sub-regions. Fractional anisotropy, mean, axial, radial diffusivity and volume were measured from tractography. Perinatal data were collected, and neurodevelopmental tests administered at 7 years' corrected age. VP children had smaller posterior CC regions, higher diffusivity and lower fractional anisotropy compared with FT 7-year-olds. Reduction in diffusivity over time occurred faster in VP than FT children (P ≤ 0.002). Perinatal brain abnormality and earlier GA were associated with CC abnormalities. Microstructural abnormalities at 7 years or slower development of the CC were associated with motor dysfunction, poorer mathematics and visual perception. This study is the first to demonstrate an accelerated trajectory of CC white matter diffusion following VP birth, associated with improved neurodevelopmental functioning. Findings suggest there is a window of opportunity for neurorestorative intervention to improve outcomes. Hum Brain Mapp 36:3733-3748, 2015. © 2015 Wiley Periodicals, Inc.

Polymorphism within a Neuronal Activity-Dependent Enhancer of NgR1 Is Associated with Corpus Callosum Morphology in Humans

The human Nogo-66 receptor 1 (NgR1) gene, also termed Nogo receptor 1 or reticulon 4 receptor (RTN4R) and located within 22q11.2, inhibits axonal growth and synaptic plasticity. Patients with the 22q11.2 deletion syndrome show multiple changes in brain morphology, with corpus callosum (CC) abnormalities being among the most prominent and frequently reported. Thus, we hypothesized that, in humans, NgR1 may be involved in CC formation. We focused on rs701428, a single nucleotide polymorphism of NgR1, which is associated with schizophrenia. We investigated the effects of the rs701428 genotype on CC structure in 50 healthy participants using magnetic resonance imaging. Polymorphism of rs701428 was associated with CC structural variation in healthy participants; specifically, minor A allele carriers had larger whole CC volumes and lower radial diffusivity in the central CC region compared with major G allele homozygous participants. Furthermore, we showed that the NgR1 3′ region, which contains rs701428, is a neuronal activity-dependent enhancer, and that the minor A allele of rs701428 is susceptible to regulation of enhancer activity by MYBL2. Our results suggest that NgR1 can influence the macro- and microstructure of the white matter of the human brain.

Mild Cognitive Impairment is Associated With White Matter Integrity Changes in Late-Myelinating Regions Within the Corpus Callosum.

Degenerative brain changes in Alzheimer's disease may occur in reverse order of normal brain development based on the retrogenesis model. This study tested whether evidence of reverse myelination was observed in mild cognitive impairment (MCI) using a data-driven analytic approach based on life span developmental data. Whole-brain high-resolution diffusion tensor imaging scans were obtained for 31 patients with MCI and 79 demographically matched healthy older adults. Comparisons across corpus callosum (CC) regions of interest (ROIs) showed decreased fractional anisotropy (FA) in the body but not in the genu or splenium; early-, middle-, and late-myelinating ROIs restricted to the CC revealed decreased FA in late- but not early- or middle-myelinating ROIs. Voxelwise group differences revealed areas of lower FA in MCI, but whole-brain differences were equally distributed across early-, middle-, and late-myelinating regions. Overall, results within the CC support the retrogenesis model, although caution is needed when generalizing these results beyond the CC.

Two distinct populations of doublecortin-positive cells in the perilesional zone of cortical infarcts.

BackgroundRecovery following stroke depends on cellular plasticity in the perilesional zone (PZ). Doublecortin (DCX), a protein mainly labeling immature neurons in neurogenic niches is also highly expressed in the vicinity of focal cortical infarcts. Notably, the number of DCX+ cells positively correlates with the recovery of functional deficits after stroke though the nature and origin of these cells remains unclear.ResultsIn the present study, we aimed to characterize the population of DCX+ cells in the vicinity of ischemic infarcts in a mouse model in detail. Employing a photothrombosis model, distinct immunohistochemical techniques, stereology and confocal microscopy, we show that: i) DCX+ cells in the perilesional zone do not constitute a homogenous population and two cell types, stellate and polar cells can be distinguished according to their morphology. ii) Stellate cells are mainly located in the lateral and medial vicinity of the insult and express astrocytic markers. iii) Polar cells are found almost exclusively in the corpus callosum region including in the preserved deep cortical layers close to the subventricular zone (SVZ). Further, they do not show any colocalisation of glial markers. Polar morphology and distribution suggest a migration towards the lesion.ConclusionsIn summary, our findings provide evidence that in mice DCX+ cells in the perilesional zone of cortical infarcts comprise a distinct cell population and the majority of cells are of glial nature.Electronic supplementary materialThe online version of this article (doi:10.1186/s12868-015-0160-8) contains supplementary material, which is available to authorized users.

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

Thyroid hormone (TH) is essential for the developing brain, and because the fetal thyroid develops relatively late in gestation, the maternal TH supply is critical for fetal brain development. However, if the mother has hypothyroidism during pregnancy, fetal brain and neuropsychological development may be compromised. Rodents experiencing maternal TH insufficiency show abnormal corpus callosum (CC) morphology, but it is not known if children born to women treated for hypothyroidism (HYPO) show similar effects. The purpose of the current study was to investigate HYPO for CC morphology and morphometry and to determine whether any specific CC abnormalities were associated aspects of maternal hypothyroidism and were correlated with reduced neuropsychological functioning in the children. ANALYZE software was used to trace CCs in archived magnetic resonance imaging scans from 22 HYPO and 22 matched controls. Areas of two sub-regions and six segments and different shape metrics (angles, lengths, ratios) were determined. CC parameters were correlated with maternal thyrotropin (TSH) values and number of hypothyroid trimesters as well as the child's neuropsychological test performance. HYPO showed a smaller anterior CC and genu and larger posterior CC and splenium areas than controls as well as shape abnormalities in genu and splenium. Results were correlated with the duration of maternal hypothyroidism. Executive function skills were positively associated with genu size in HYPO, while verbal comprehension skills were negatively associated with splenium and overall posterior CC sizes. Maternal hypothyroidism contributes to CC abnormalities in the offspring, and effects differ for anterior versus posterior CC regions.

Resilience and corpus callosum microstructure in adolescence.

Resilience is the capacity of individuals to resist mental disorders despite exposure to stress. Little is known about its neural underpinnings. The putative variation of white-matter microstructure with resilience in adolescence, a critical period for brain maturation and onset of high-prevalence mental disorders, has not been assessed by diffusion tensor imaging (DTI). Lower fractional anisotropy (FA) though, has been reported in the corpus callosum (CC), the brain's largest white-matter structure, in psychiatric and stress-related conditions. We hypothesized that higher FA in the CC would characterize stress-resilient adolescents. Three groups of adolescents recruited from the community were compared: resilient with low risk of mental disorder despite high exposure to lifetime stress (n = 55), at-risk of mental disorder exposed to the same level of stress (n = 68), and controls (n = 123). Personality was assessed by the NEO-Five Factor Inventory (NEO-FFI). Voxelwise statistics of DTI values in CC were obtained using tract-based spatial statistics. Regional projections were identified by probabilistic tractography. Higher FA values were detected in the anterior CC of resilient compared to both non-resilient and control adolescents. FA values varied according to resilience capacity. Seed regional changes in anterior CC projected onto anterior cingulate and frontal cortex. Neuroticism and three other NEO-FFI factor scores differentiated non-resilient participants from the other two groups. High FA was detected in resilient adolescents in an anterior CC region projecting to frontal areas subserving cognitive resources. Psychiatric risk was associated with personality characteristics. Resilience in adolescence may be related to white-matter microstructure.

Abstract 2: Structural Integrity of the Corpus Callosum Correlates with Sensorimotor Impairment after Stroke

Introduction: Responsiveness to motor rehabilitation varies greatly after stroke. Improved knowledge of the brain correlates of motor function are needed to assist in the development of more effective and personalized rehabilitation protocols. Changes in the integrity of the ipsilesional corticospinal tract after stroke have been well documented, but less is known about changes in the corpus callosum (CC). The purpose of this study was to determine if structural integrity of the motor and sensory portions of the CC change after stroke and whether any such changes are related to clinical measures of sensorimotor impairment and function. Methods: Fifty-five individuals with chronic stroke (age 60.5±13.2; days post-stroke 351.9±560; UE Fugl-Meyer (FM) motor score 38.5±14.6, no lesion in the CC) and 16 age-matched controls underwent diffusion tensor imaging (DTI) and behavioral assessments. Mean fractional anisotropy (FA) values for the motor and sensory regions of the CC were extracted and examined in relation to motor system behavioral measures including the UEFM, Box &amp; Blocks (BB), Nottingham sensory score, and Stroke Impact Scale (SIS) hand subsection. Results: Participants with stroke had significantly lower FA values compared to controls in both the motor and sensory CC regions ( p &lt;0.02) despite their strokes sparing the CC. In the CC motor region, FA was related to UEFM, BB, and SIS scores, such that higher structural integrity correlated with better motor status ( ρ &gt;0.30, p &lt;0.03 across comparisons). In the CC sensory region, FA was related to UEFM and SIS scores ( ρ &gt;0.31, p &lt;0.02) as well as Nottingham sensory scores (ρ=0.33, p&lt;0.05). CC motor and sensory FA did not correlate with FA in the ipsilesional peduncle ( ρ &lt;0.12, p &gt;0.40), suggesting that the magnitude of change in each region of the motor system was distinct. Conclusions: Decreased structural connectivity between the sensorimotor regions of the two hemispheres is related to motor impairment in chronic stroke in a manner that is distinct from corticospinal tract injury. Interventions that target the communication between hemispheres during motor rehabilitation may be warranted.

Changes in the corpus callosum in women with late-stage bipolar disorder.

This study investigated the differences in corpus callosum (CC) volumes between women with early-stage and late-stage bipolar I (BP I) disorder using the criteria previously described in the literature. We compared women with early- and late-stage BP I using criteria described in the Staging Systems Task Force Report of the International Society for Bipolar Disorders. We included 20 patients with early stage and 21 patients with late-stage BP I and a group of 25 healthy controls. Patients and controls underwent structural magnetic resonance imaging. Information on the clinical features of bipolar disorder was collected using a standardized questionnaire. Anatomical volumes of five regions of CC were compared between the three groups. Women with late-stage BP I disorder had reduced posterior CC volumes compared with early-stage bipolar I patients and controls (F = 6.05; P = 0.004). The difference was significant after controlling for age, comorbidity with post-traumatic stress disorder, psychotic symptoms during mood episodes, and current use of medication. The posterior CC was significantly decreased in volume in women with late-stage bipolar disorder. These findings suggest that CC may be an anatomical target of neuroprogression in the course of bipolar disorder in women.

A longitudinal study investigating sub-threshold symptoms and white matter changes in individuals with an ‘at risk mental state’ (ARMS)

BackgroundEvidence supports disruption in white matter (WM) connectivity in established schizophrenia, however, it is unclear when these abnormalities occur during the course of illness and if they are progressive. Here we investigated whether WM abnormalities predate illness onset by examining a group of individuals with an ‘at risk mental state’ (ARMS) and assess whether there is evidence of progressive change. We hypothesized that WM abnormalities are associated with symptom change. MethodsSixteen healthy controls and 41 ARMS subjects at baseline underwent Diffusion Tensor Imaging (DTI). Sub-threshold positive symptoms were measured using the Scale of Prodromal Symptoms (SOPS). Imaging and symptoms were re-administered in the ARMS group after one year (52weeks). Fractional anisotropy (FA) value differences between ARMS and control groups at baseline were localized using the method of Tract-Based Spatial Statistics (TBSS). ResultsAt baseline, FA was significantly reduced in a sub-region of the corpus callosum (CC) in the ARMS group as a whole compared to controls. This reduction was also found in the 34 individuals who did not transition (ARMS-N) during the one-year follow-up. However, the ARMS-N group showed a significant improvement in sub-threshold positive symptoms at follow-up, which was correlated with an increase in FA in the same CC region (r=−0.664, p<0.001). DiscussionThere was a significant FA reduction in the CC in individuals at high risk for psychosis regardless of transition status at one year. This suggests that WM abnormalities in the CC may represent a biological vulnerability to psychosis. Improvement in sub-threshold positive symptoms was associated with improvement in measures of WM integrity in the CC. This may suggest that neurobiological ‘resilience’ is associated with improved outcomes, although this notion requires future study.

A greater involvement of posterior brain areas in interhemispheric transfer in autism: fMRI, DWI and behavioral evidences.

A small corpus callosum (CC) is one of the most replicated neurobiological findings in autism spectrum (AS). However, its effect on interhemispheric (IH) communication is unknown. We combined structural (CC area and DWI), functional (task-related fMRI activation and connectivity analyses) as well as behavioral (Poffenberger and Purdue tasks) measures to investigate IH integration in adult AS individuals of typical intelligence. Despite similar behavioral IH transfer time and performances in bimanual tasks, the CC sub-regions connecting frontal and parietal cortical areas were smaller in AS than in non-AS individuals, while those connecting visual regions were similar. The activation of visual areas was lower in AS than in non-AS individuals during the presentation of visual stimuli. Behavioral IH performances were related to the properties of CC subregions connecting motor areas in non-AS individuals, but to the properties of posterior CC regions in AS individuals. Furthermore, there was greater functional connectivity between visual areas in the AS than in the non-AS group. Levels of connectivity were also stronger in visual than in motor regions in the autistic subjects, while the opposite was true for the non-autistic group. Thus, visual IH transfer plays an important role in visuo-motor tasks in AS individuals. These findings extend the well established enhanced role of perception in autistic cognition to visuo-motor IH information transfer.

E10 Correlations Between Iron Content In The Corpus Callosum And Huntington's Disease Clinical Measures

Background Higher iron concentration in subcortical grey matter structures is documented in Huntington’s disease (HD) but the iron content on white matter (WM) is less well documented. We previously investigated the iron level in the WM corpus callosum in HD reporting a lower iron level in posterior callosal subregion. Furthermore we explored the iron content in the callosal fibres, reporting a lower iron content in HD in few tracts, such as occipital (Occ), the superior parietal (PP), the orbital frontal (OF). Aims To examine whether callosal tracts, who were different in iron content correlated with the main clinical scales (the Disease Burden index, the UHDRS I and the UHDRS II). Methods Subjects groups included 25 HD patients, 25 presymptomatic HD (PreHD) subjects, 40 healthy controls. Tractography was performed for each region of the corpus callosum by manually drawing two regions of interest on each individuals fractional anisotropy colour map, then value were extracted from the Iron images coregistrered. To test for correlation among callosal and clinical data a Partial Correlation (covering for gender and age) was performed. Results Results showed significantly correlation among the Occ callosal tract and all the clinical data. The SP correlated with the UHDRSI and UHDRSII. Conclusion We found that the lower is the iron content in the Occ and SP callosal fibres the worse are the symptoms. These results can be explained like a failure of the remyelination processes in the first stage of HD (“demyelination hypothesis”).

Automatic DTI-based parcellation of the corpus callosum through the watershed transform

INTRODUCTION: Parcellation of the corpus callosum (CC) in the midsagittal cross-section of the brain is of utmost importance for the study of diffusion properties within this structure. The complexity of this operation comes from the absence of macroscopic anatomical landmarks to help in dividing the CC into different callosal areas. In this paper we propose a completely automatic method for CC parcellation using diffusion tensor imaging (DTI). METHODS: A dataset of 15 diffusion MRI volumes from normal subjects was used. For each subject, the midsagital slice was automatically detected based on the Fractional Anisotropy (FA) map. Then, segmentation of the CC in the midsgital slice was performed using the hierarchical watershed transform over a weighted FA-map. Finally, parcellation of the CC was obtained through the application of the watershed transform from chosen markers. RESULTS: Parcellation results obtained were consistent for fourteen of the fifteen subjects tested. Results were similar to the ones obtained from tractography-based methods. Tractography confi�rmed that the cortical regions associated with each obtained CC region were consistent with the literature. CONCLUSIONS: A completely automatic DTI-based parcellation method for the CC was designed and presented. It is not based on tractography, which makes it fast and computationally inexpensive. While most of the existing methods for parcellation of the CC determine an average behavior for the subjects based on population studies, the proposed method reflects the diffusion properties specifi�c for each subject. Parcellation boundaries are found based on the diffusion properties within each individual CC, which makes it more reliable and less affected by differences in size and shape among subjects.