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[Isolated familial corpus callosum agenesis prognosis].

Agenesia of corpus callosum belongs to a group of cerebral malformations whose prognosis is uncertain. In such cases, assessment of prognosis may benefit from eventual associated fetal, obstetrical or familial features. We report a patient with an isolated corpus callosum agenesia that led to the discovery of a similar malformation in her father. This observation demonstrates that some forms of isolated and familial corpus callosum agenesia could have a favorable outcome. However, the difficulty of the assessment of prognosis in isolated corpus callosum agenesia is emphasized and the question of parental RMI exploration in such a peculiar context is raised.

Adult↗

Antenatal sonographic findings of agenesis of corpus callosum.

Agenesis of the corpus callosum is a central nervous system anomaly that may be associated with other intracranial abnormalities. It is easily diagnosed in the postnatal period by computed tomographic scan and ultrasound. However, its prenatal sonographic diagnosis remains a challenge. This report will evaluate three cases of fetal agenesis of the corpus callosum, review the antenatal sonographic findings and postnatal outcomes, and provide criteria for the antenatal diagnosis.

Adult↗

[Arterial and venous vascularization of the corpus callosum].

Blood supply of the corpus callosum is assured by two arterial systems, the carotid system mainly and the vertebrobasilar system accessorily. The carotid system intervenes via the pericallosal artery, portion of the anterior cerebral artery distal to the anterior communicating artery. This pericallosal artery can be bihemispheric in 4 to 12% of the cases or azygos in 0.26% of cases. In 20 to 80% of cases, the median callosal artery arises from the communicating artery. The vertebrobasilar system intervenes in splenium vascularization by its terminal branches. These two carotid and vertebrobasilar systems give rise to perforating arteries that assure intrinsic vascularization of the corpus callosum creating a system of regular vascular stitches around the fibers of the corpus callosum. The venous drainage of the corpus callosum is essentially via callosal veins and callosocingulate veins towards the deep venous system of the brain.

Animals↗

[Genetics of agenesis of the corpus callosum].

Agenesis of corpus callosum (ACC) is one of the most common brain malformations observed in humans. It is a heterogeneous malformation, with many etiologies. Isolated ACC is usually sporadic but familial cases have been reported. ACC can complicate numerous polymalformative, either monogenic or chromosomal syndromes. In some of them, for example Aicardi syndrome, Anderman syndrome or acrocallosal syndrome, ACC is a mandatory manifestation. Further identification of the molecular bases of these syndromes will be helpful in understanding the causal heterogeneity of this malformation.

Agenesis of Corpus Callosum↗

Some new trends in the study of the corpus callosum.

In recent years the corpus callosum has provided a model for the study of cortical connections in the adult and developing brain. In particular, aspects of development originally described in the corpus callosum could be generalized to other cortical connections. New frontiers include the analysis of the human corpus callosum, studies of callosal connections at the cellular level and the analysis of dynamic interactions between the hemispheres. Gross morphological parameters of the human corpus callosum have been measured and related to gender, handedness etc. The detailed dendritic and axonal morphology of individual callosal neurons and their development is being defined. Electrophysiological investigations and computer stimulations are stressing temporal aspects of the interactions between the hemispheres.

Animals↗

Ovarian estrogen acts to feminize the female rat's corpus callosum.

The rat corpus callosum (CC) is sexually dimorphic, with the male CC being larger. Ovariectomy (Ovx) on day 12 has been shown to eliminate this sex difference, with callosal values of Ovx females approaching those of male controls. This suggested that postnatal ovarian estrogen affects the size of the female CC. In the present experiment, one group of female rats received Ovx on day 12, and a second group received Ovx followed by chronic implantation of a silastic tube containing beta-estradiol on day 25. Unmanipulated males and sham females served as controls. Examination of the CC at 110 days confirmed our prior findings that males have larger callosa than females and that the Ovx group had increased CC's compared to sham controls. Our new finding was that estrogen treatment was capable of reversing the effects of Ovx. Ovx+estrogen-treated females had decreased CC size as compared to Ovx alone. Indeed, they also had smaller CC values than control females. These findings indicate that ovarian estrogen plays a role in determining CC morphology and that estrogen in the female acts to inhibit overall callosal growth as measured by changes in gross callosal size.

Analysis of Variance↗

Sexual dimorphism and handedness in the human corpus callosum based on magnetic resonance imaging.

The corpus callosum (CC) is a major anatomical and functional commissure linking the two cerebral hemispheres. With MR imaging in the sagittal plane, the corpus callosum can be depicted in great detail. Mid-sagittal magnetic resonance images of 80 normal individuals were analyzed to assess whether or not the morphology of the corpus callosum and its parts are related to sex and handedness. The subjects were 40 males (20 right-handers and 20 left-handers) and 40 females (20 right-handers and 20 left-handers). The midsagittal area of the corpus callosum was divided into seven sub-areas using Witelson's method. The most striking morphological changes concerned left-handers, who had larger areas of the anterior body, posterior body and isthmus than right-handers. In addition, right-handed males had larger rostrums and isthmuses than right-handed females. These significantly increased areas were related to handedness in right-handed males. However, left-handed males had larger anterior and posterior bodies than right-handed males. In contrast, there was no significant difference between left-handers and right-handers in females. The areas of the rostrum and posterior body of the corpus callosum increased significantly with sex in males. Moreover, there were no significant age-related changes in the total corpus callosum and sub-areas of the corpus callosum. In conclusion, these anatomical changes in corpus callosum morphology require taking the sexual definition and dominant handedness into consideration.

Adult↗

Sonographic recognition of agenesis of the corpus callosum.

Agenesis of the corpus callosum may be diagnosed successfully in vivo when sonograms demonstrate absence of corpus callosum; absence of pericallosal and cingulate sulci; "sunburst" pattern of sulci along the medial surface of the hemisphere; wide interhemispheric fissure; elevation of the third ventricle; small, laterally positioned frontal horns with concave medial borders; large, laterally positioned and inverted cingulate gyri; and Probst lateral callosal bundles. Comparison of necropsy specimens with sonograms from eight patients with callosal agenesis illustrates the anatomic basis for these diagnostic features.

Abnormalities, Multiple↗

Dichotic listening in patients with partial section of the corpus callosum.

Patients with a complete section of the corpus callosum have been observed to exhibit strong left-ear suppression when different speech stimuli are presented to both ears simultaneously (so-called dichotic listening). Data concerning the locus of corpus callosum damage that causes strong left-ear suppression remains scanty. In the present investigation, a consonant-vowel syllable dichotic listening test was given to five right-handed patients with partial sections of the corpus callosum, which were located using MRI and accurately defined measurement procedures. The following two measurement methods were used: (i) the genu-splenium (G-S) method, in which a lesion was localized in the anteroposterior dimension relative to the total length of the corpus callosum, defined as the distance between the most anterior point of the genu to the most posterior point of the splenium; and (ii) the rostrum-splenium (R-S) method, which takes into account the curvature of the corpus callosum, and in which a lesion was localized relative to the total length of the corpus callosum, defined as the length of the curved line from the tip of the rostrum to the end of the splenium. Results were compared with scores from 50 normal control subjects. Strong left-ear suppression was observed in two patients, who had surgical sections of the posterior 15.5-18.5% of the corpus callosum as measured with the G-S method, or the posterior 20-24% of the corpus callosum as measured with the R-S method. The suppression phenomenon persisted for more than 10 years post-surgery. On the other hand, the remaining three patients, who had lesions anterior to the posterior 17-28% of the corpus callosum as measured with the G-S method or 20-33% as measured with the R-S method exhibited no left-ear extinction. Despite the common assumption that damage to the posterior part of the trunk of the corpus callosum causes strong left-ear suppression, the results from the G-S method indicated that damage to the splenium defined as the posterior one-fifth of the segment between the anterior-most and posterior-most points of the corpus callosum, cause strong left-ear suppression. By the R-S method, results showed that damage to the splenium (the posterior one-fifth of the curvature of the corpus callosum) and possibly the part extending to the most posterior part of the trunk (the posterior one-quarter of the curvature) causes strong left-ear suppression.

Adult↗

The arteries of the corpus callosum: a microsurgical anatomic study.

OBJECTIVE: The corpus callosum is the major commissural pathway connecting the hemispheres of the human brain. It is particularly important, because various tumors and vascular lesions can be located in and around the corpus callosum, and it is a route through which pass several surgical approaches. Performing accurate surgery in this region and avoiding damage to normal structures require that the neurosurgeon have adequate knowledge of the anatomy of the intricate blood supply to this area. METHODS: In 20 cadaver brains, the arteries of the corpus callosum were examined under the operating microscope, with particular attention to the origin, course, anastomoses, number, and caliber of the arteries. RESULTS: In all specimens, the pericallosal and posterior pericallosal arteries were found to be the main sources of blood supply to the corpus callosum. In 80% of the specimens, the anterior communicating artery gave rise to either a subcallosal artery or a median callosal artery, each of which made a substantial contribution to the blood supply of the corpus callosum. A detailed examination of the anatomic features of all the main arteries of supply revealed anastomoses within the callosal sulcus that formed the pericallosal pial plexus. This network supplied the corpus callosum, the radiation of the corpus callosum, and the cingulate gyrus. CONCLUSION: Familiarity with the details of the vascularity of the corpus callosum is crucial when performing surgery in this region. The additional, significant data described expands the knowledge of this anatomy, which can enhance the surgeon's ability to accomplish a more accurate and successful exploration.

Cadaver↗

Fractional anisotropy-based divisions of midsagittal corpus callosum.

The authors first divided the midsagittal corpus callosum of 22 healthy volunteers using three different subdivision methods: Witelson's geometric subdivision, boundary model-based subdivision, and medial model-based subdivision. Next, subdivisions of the corpus callosum were clustered on the basis of homogeneity of the fractional anisotropy values as produced from diffusion tensor images. Nine subregions of corpus callosum, similar in location and size, were successfully clustered when medial model-based or boundary model-based subdivisions were applied. These nine subregions of the corpus callosum were different from the seven subregions defined by Witelson's geometric subdivision, especially at the anterior and posterior tips of the corpus callosum. Our method of corpus callosum division can be potentially utilized to assess structural changes in the midsagittal corpus callosum.

Adult↗

Lipoma of the corpus callosum.

A case of corpus callosum lipoma with presumptive diagnosis is presented. Review of the literature disclosed 84 cases with such diagnoses. Lipoma of the corpus callosum is a rare intracranial lesion, perhaps congenital and often asymptomatic, but can present with seizure disorder, headache, mental changes, paresis or paralysis. Twenty-one patients had been operated upon. Surgical treatment seems to be of no value in this disease.

Adolescent↗

Gender- and age-related differences in the morphology of the corpus callosum.

The size and shape of the adult corpus callosum may vary with gender and age. There is, however, little data on the morphology of the corpus callosum in the Indian population. The purpose of this study was to measure the size of the corpus callosum in normal adult Indian males and females, and to identify gender- and age-related differences. The size of the corpus callosum on midsagittal section was measured in 100 (50 males, 50 females) normal adult Indians using magnetic resonance imaging. The length of the corpus callosum, the width of the genu, trunk, and splenium, the area of the splenium, and the total area of the corpus callosum were measured. The length of the brain also was measured. Means were compared for significant difference by gender using the Student's unpaired t-test and by age using ANOVA followed by Duncan's multiple range test. Gender was estimated by discriminant function analysis and age was estimated by regression analysis from significant parameters. The corpus callosum was longer in males and the discriminant score to differentiate gender was determined with an accuracy of 66%. The length of the corpus callosum increased with age and regression equations for predicting age was derived from the length of the corpus callosum. The width of the trunk and genu decreased with age in males but not in females.

Adolescent↗

Gender differences in the corpus callosum of neonates.

The gender difference of corpus callosum is a long standing controversy. Some investigators have reported that adult females have a more bulbous splenium and larger area relative to brain size, but others failed to replicate this. Few studies have reported on sexual dimorphism during development. Midsagittal ultrasonographs were obtained through the anterior fontanelle of healthy Korean neonates (100 males, 100 females) and were analyzed with NIH Image. The total area of corpus callosum and sub-regions of corpus callosum showed no gender differences. However, the male corpus callosum had significantly more height than that of the female whereas there was no difference in width of the corpus callosum. The estimated average thickness of corpus callosum was greater in the female splenium.

Corpus Callosum↗

Hump-shaped corpus callosum.

Developmental anomalies of the corpus callosum are agenesis, hypogenesis, or hypoplasia. In this case, a hump-shaped anomaly was present in the body of the corpus callosum. The rostrum, genu, and splenium of the corpus callosum were normal. In addition, a split was present within this hump, connecting the lateral ventricles. No additional anomalies were present. This type of anomaly has not been previously reported in the literature.

Agenesis of Corpus Callosum↗

Sonography of fetal agenesis of the corpus callosum: a survey of 35 cases.

Agenesis of the corpus callosum was identified by ultrasound examination in 35 fetuses between 19 and 37 weeks' gestation. The ultrasound findings included absence of the corpus callosum and cavum septum pellucidum (hypoplasia in one case of partial agenesis of the corpus callosum), a typical 'teardrop' configuration of the lateral ventricles, distension of the interhemispheric fissure, upward displacement of the third ventricle, radiate arrangement of the medial cerebral gyri, and abnormal branching of the anterior cerebral artery. Associated anomalies were identified in 20 fetuses, including heterogeneous malformations and chromosomal aberrations (mosaic-trisomy 8 in three, trisomy 18 in two and partial duplication 8p in one). Five cases of agenesis of the corpus callosum were identified in a population of pregnant patients prospectively investigated because of genetic risk for agenesis of the corpus callosum or related syndromes. In this group, no diagnostic errors were made. Long-term neurological follow-up (6 months to 11 years) was available in 11 infants with antenatal diagnosis of isolated agenesis of the corpus callosum. Normal intellectual development was present in nine, and a low intellect (developmental quotient between 70 and 85) was found in two. It is concluded that fetal agencies of the corpus callosum is associated with elusive sonographic findings that can, however, be accurately identified by targeted examinations. In routine sonograms, an increased atrial width and/or failure to visualize the cavum septum pellucidum should arise the suspicion of fetal agencies of the corpus callosum. Given the high frequency of associated anomalies, prenatal diagnosis of agencies of the corpus callosum dictates the need for a careful survey of fetal anatomy and karyotyping. The prognosis is isolated agencies of the corpus callosum remains uncertain, although it is expected that a normal or boarderline intellectual development will occur in many cases.

Journal Article↗

Meta-analysis of corpus callosum size in schizophrenia.

Studies with MRI have shown differences in corpus callosum size between schizophrenic patients and controls. Most have found that the corpus callosum is smaller in schizophrenic patients, but in only a minority was this finding statistically significant, perhaps due to small sample sizes. Therefore a meta-analysis of 11 published studies of corpus callosum morphology in schizophrenia was conducted to ascertain whether there was a significant difference in corpus callosum size between schizophrenic patients and normal controls. These studies combined comprised 313 patients and 281 controls. Measures of corpus callosum midsagittal area, length, and corpus callosum area:brain area ratio were used in the meta-analysis. There was overall a statistically significant reduction in corpus callosum area in schizophrenic patients compared with controls (P < 0.02). Differences between patients and controls in measures of corpus callosum: brain area and corpus callosum length were not statistically significant. Age and corpus callosum area were related in both patients and controls. The influences on the corpus callosum of overall alterations of brain size, sex, handedness, and psychiatric illness in general remains to be determined.

Adult↗

EEG coherence reflects regional corpus callosum area in Alzheimer's disease.

OBJECTIVE: Correlations between corpus callosum size and interhemispheric EEG coherence were investigated as measures of interhemispheric connectivity in patients with Alzheimer's disease. METHODS: 11 patients underwent both magnetic resonance imaging and quantitative electroencephalography to assess corpus callosum size and interhemispheric coherence. For comparison, corpus callosum size was measured in 24 healthy elderly control subjects. RESULTS: Corpus callosum cross sectional area was significantly reduced in Alzheimer patients relative to controls. Posterior interhemispheric coherence (alpha and beta frequencies) correlated significantly with the size of posterior corpus callosum area, and anterior coherence (delta, theta, and alpha frequencies) with the size of anterior corpus callosum area in the Alzheimer patients. CONCLUSION: Region specific correlations between corpus callosum size and EEG coherence suggest that the decline in interhemispheric connectivity in Alzheimer's disease results from a specific loss of cortical association neurones projecting through the corpus callosum.

Aged↗