Occipital‐Callosal Pathways in Children: Validation and Atlas Development
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Diffusion tensor imaging and fiber tracking were used to measure fiber bundles connecting the two occipital lobes in 53 children of 7‐12 years of age. Independent fiber bundle estimates originating from the two hemispheres converge onto the lower half of the splenium. This observation validates the basic methodology and suggests that most occipital‐callosal fibers connect the two occipital lobes. Within the splenium, fiber bundles are organized in a regular pattern with respect to their cortical projection zones. Visual cortex dorsal to calcarine projects through a large band that fills much of the inferior half of the splenium, while cortex ventral to calcarine sends projections through a band at the anterior inferior edge of the splenium. Pathways projecting to the occipital pole and lateral‐occipital regions overlap the dorsal and ventral groups slightly anterior to the center of the splenium. To visualize these pathways in a typical brain, we combined the data into an atlas. The estimated occipital‐callosal fiber paths from the atlas form the walls of the occipital horn of the lateral ventricle, with dorsal paths forming the medial wall and the ventral paths bifurcating into a medial tract to form the inferior‐medial wall and a superior tract that joins the lateral‐occipital paths to form the superior wall of the ventricle. The properties of these fiber bundles match those of the hypothetical pathways described in the neurological literature on alexia.Keywords:
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Objectives The aim of this study was to investigate patients with ischemic infarctions in the territory of the corpus callosum to advance our understanding of this rare stroke subtype by providing comprehensive descriptive and epidemiological data. Methods From January 1, 2010 to June 30, 2014, all cases of acute ischemic stroke diagnosed by clinical manifestation and diffusion weighted imaging in Dalian Municipal Central Hospital were investigated. The patients presenting with corpus callosum infarctions were selected and further allocated into genu and/or body and splenium infarction groups. Proportion, lesion patterns, clinical features, risk factors and etiology of corpus callosum infarction were analyzed. Results Out of 1,629 cases, 59 patients (3.6%) with corpus callosum infarctions were identified by diffusion weighted imaging, including 7 patients who had ischemic lesions restricted to the corpus callosum territory. Thirty six patients had lesions in the splenium (61.0%). Corpus callosum infarction patients suffered from a broad spectrum of symptoms including weakness and/or numbness of the limbs, clumsy speech, and vertigo, which could not be explained by lesions in corpus callosum. A classical callosal disconnection syndrome was found in 2 out of all patients with corpus callosum infarctions. Statistical differences in the risk factor and infarct pattern between the genu and/or body group and splenium group were revealed. Conclusion Corpus callosum infarction and the callosal disconnection syndrome were generally rare. The most susceptible location of ischemic corpus callosum lesion was the splenium. Splenium infarctions were often associated with bilateral cerebral hemisphere involvement (46.2%). The genu and/or body infarctions were associated with atherosclerosis. The most common cause of corpus callosum infarction probably was embolism.
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The location of corpus callosum injury was investigated using magnetic resonance imaging in 92 patients. The anatomical relationships in the region around the corpus callosum were also evaluated to clarify involvement in the mechanism of corpus callosum injury in 20 normal volunteers. Lesions in the posterior half of the corpus callosum accounted for 80% of corpus callosum injuries. The falx was increasingly elongated toward the posterior portion of the corpus callosum and the corpus callosum was thinnest at the body-splenium junction in the normal volunteers. The mechanism of corpus callosum injury apparently involves the following factors. The posterior half of the falx is closer to the corpus callosum than the anterior half. Therefore, the anterior part of the corpus callosum easily moves with lateral movement of the cerebral hemispheres, and the strain is likely to be concentrated in the posterior half of the corpus callosum, because the falx greatly limits lateral movement of the hemisphere in the posterior region. The corpus callosum is easily distorted at the thinnest part of the body-splenium junction. Therefore, corpus callosum injury predominantly occurs in the posterior half of the corpus callosum.
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Very preterm birth (before 33 weeks gestation) is associated with the white matter damage, and a common sequel is reduced size and altered shape of the corpus callosum. We used diffusion tensor MRI to assess the corpus callosum in 63 very preterm and 45 term-born young adults. Indices of white matter microstructure [fractional anisotropy (FA) and mean diffusivity (MD)] were obtained for the genu, body and splenium. Very preterm females had higher MD in the genu than term-born females, indicating altered white matter microstructure. This was associated with lower performance IQ. The groups demonstrated different patterns of correlations between verbal learning and tract-specific FA and MD, consistent with the reorganization of white matter structure in adults born very preterm.
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An area within the corpus callosum, a white matter structure within the cleft that separates the left and right cerebral hemispheres in the mammalian brain, between the genu (anterior region) and the splenium (posterior region).
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No observations of sex differences in the splenium of the human corpus callosum are made. In the data there is no support for the concept that sex related functional hemispherical discrepancies are due to differences in area and width of the splenium of corpus callosum. However variability within a sex is often larger than the variability between the two sexes. The results are discussed with regard to a neurobiological theory of schizophrenia.
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Hypoxic ischemic damage of the corpus callosum after cardiac arrest is a rare condition. Lesions of the splenium of the corpus callosum after hypoxia are bilateral and lead to poor prognosis. Herein, we present a case with good prognosis after cardiac arrest with bilateral lesions of the splenium of corpus callosum.
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Objective:To explore the values of DTI in demonstrating the microstrcture of corpus callosum in normal adults. Methods: 61 healthy adults (20-30 yea older, male 30, female 31 )underwent conventional MRI and DTI. DTI was performed using single shot SE-EPI sequence. b value was 1 000s·mm-2. The diffusion was measured along 13 directions. FA (fractional anisotropy) in genu and splenium of corpus callosum was measured respectively. Statistical analysis was performed. Results: Increased anisotropy was presented in male group in both genu and splenium of corpus callosum. The mean FA of males was 0.724±0.04 and females 0.698±0.05 in genu of corpus callosum. The difference of mean FA between male and female groups was statistically significant (P0.05). The difference of FA in splenium of corpus callosum was significant too, which was 0.716±0.05 for males and 0.695±0.05 for females. Conclusions: Our findings provide evidence for sex difference in the genu and splenium of corpus callosum in normal adults via DTI. DTI permits the quantitative analysis for the direction and arrangement of white matter in vivo non- invasively.
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