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Spectrum of corpus callosum agenesis.

Magnetic resonance imaging and clinical features of 16 children with agenesis of the corpus callosum are reviewed. The patients were classified in three groups. Eight children had agenesis of the corpus callosum without substantial involvement of other brain areas. This group included patients with interhemispheric cyst, lipoma, or partial agenesis (hypogenesis) of the corpus callosum. Four patients in the second group manifested severe telencephalic dysgenesis in addition to agenesis of the corpus callosum. In the third group, agenesis of the corpus callosum was a component of a syndrome in four children. The outcome was not favorable for the majority of patients, even in the first group without significant involvement of other systems. Severe handicaps with developmental delay, intellectual disability, and neurologic deficit were observed in patients with additional telencephalic dysgenesis or syndromic form of corpus callosum agenesis.

Abnormalities, Multiple↗

Dysgenesis of the corpus callosum.

The embryology of the corpus callosum is briefly reviewed in relation to dysgenesis and associated malformations. The morphology, etiology, clinical and radiological features of such malformations are discussed and illustrated.

Abnormalities, Multiple↗

[Corpus callosum agenesis and epileptic seizures].

INTRODUCTION: The corpus callosum is the major neopallial connection between the two cerebral hemispheres. The corpus callosum agenesis (CCA) is found in 14% of CNS malformations. The diagnosis is based on neuroimaging procedures (ultrasonography, CT, MRI). The CCA is usually associated with facial dysmorphia, developmental delay and epileptic seizures. Two casuistic are studied, one with necropsies material and another with CCA patients alive, on which CCA was frequently associated with other CNS malformations, in order to establish the circumstances in which the epileptic seizures have been observed. DEVELOPMENT: It is commonly admitted that the presenting signs or symptoms in individuals with CCA are due to concurrent brain abnormalities and that isolated CCA is essentially asymptomatic. The CCA is a common component in some malformative syndromes, frequent in another, and occasional in many of them. The CCA has been reported in many chromosomal aberrations and less frequently in inborn errors of metabolism and neurocutaneous diseases. In the casuistic studies of 73 patients alive, 25 (39%) have presented epileptic fits: in 24 of them the CCA was associated to another brain abnormalities; in 17 cases, the first seizures was recorded during the first year, in 6 cases between 1 and 3 years and in cases after 2 years: the type of epileptic seizures is variable: neonatal convulsions in 4 cases, infantile spasms in 5, unilateral fits in 3, and partial seizures in 1 case. In the necropsies casuistic with 26 CCA cases, 6 (23%) suffered epileptic fits, all with another malformations of the CNS; in 3 the onset of the seizures was during the newborn period, 2 had infantile spasms during the first years and 1 case generalized seizures during the second year. CONCLUSIONS: 1. Epileptic seizures were observed in 23%-39% of the CCA cases studied. 2. All cases with CCA, except for one, have also another brain abnormality. 3. In 70% of the cases, the onset of the fits takes place during the first year. 4. The type of seizures is variable with predominance of infantile spasms and unilateral seizures.

Agenesis of Corpus Callosum↗

Thrombocytopenia absent corpus callosum syndrome: third case of a distinct clinical entity.

Thrombocytopenia absent corpus callosum, characterized by refractory thrombocytopenia, agenesis of the corpus callosum, hypoplastic cerebellum, abnormal facies, and developmental delay, represents a relatively newly described clinical entity. An 18-month-old girl with agenesis of the corpus callosum, hypoplasia of the cerebellar vermis, hypotonia, and severe developmental delay presented with thrombocytopenia. She had a distinctive facies with microcephaly, broad nasal root with upturned nose, small upper lip, and micrognathia. A bone marrow aspirate and biopsy showed normal cellularity with dysplastic megakaryocytes. Thrombocytopenia absent corpus callosum is compared with other conditions characterized by congenital non-immune thrombocytopenia.

Abnormalities, Multiple↗

Topography of the human corpus callosum.

This study was undertaken to determine the topographical organization of fibers coursing through the human corpus callosum. We correlated the distribution of Wallerian degeneration in the corpus callosum with the anatomical sites of focal cortical lesions due to ischemic infarctions or circumscribed contusions. Fibers from the inferior frontal and anterior inferior parietal regions course through the rostrum and genu of the corpus callosum. Callosal connections from the temporo-parieto-occipital junctional region course through the splenium and caudal portion of the body of the corpus callosum. Both the superior parietal lobule and the occipital cortex give rise to interhemispheric fibers that course exclusively through the splenium of the corpus callosum. No callosal degeneration was associated with a cortical lesion in the anterior superior frontal region. The topographical organization of fibers in the human corpus callosum appears to be fairly similar to that found in the rhesus monkey (Macaca mulatta).

Animals↗

Fiber composition of the human corpus callosum.

The densities of fibers of different sizes were calculated in ten regions of the corpus callosum of twenty human brains (ten females, ten males). Light microscopic examination revealed a consistent pattern of regional differentiation of fiber types in the corpus callosum. Thin fibers are most dense in the anterior corpus callosum (genu), and decrease in density posteriorly towards the posterior midbody, where they reach a minimum. Towards the posterior corpus callosum (splenium), the density of thin fibers increases again, but in the posterior pole of the callosum the density decreases locally. Large-diameter fibers show a pattern complementary to that of thin fibers, having a peak of density in the posterior midbody and a local increase of density in the posterior pole of the corpus callosum. Across subjects, the overall density of callosal fibers had no significant correlation with callosal area and an increased callosal area indicated an increased total number of fibers crossing through. Considering different fiber sizes, this was only true for small diameter fibers, whose large majority is believed to interconnect association cortex. No sex differences in fiber composition of the corpus callosum were found.

Adult↗

Prenatal diagnosis of agenesis of corpus callosum: what is the neurodevelopmental outcome?

BACKGROUND: Corpus callosum is the largest cerebral commissure that connects neocortical areas. Agenesis of corpus callosum (ACC) can be partial or complete, isolated or associated with other malformations. Its prenatal diagnosis creates problems within parental counselling due to its uncertain prognosis. The aim of this study was to correlate the neurodevelopmental outcome with both the clinical picture and the neuroradiological features, in order to improve prenatal parental counselling in a group of nine children with ACC, prenatally diagnosed by ultrasound and then confirmed by postnatal magnetic resonance imaging (MRI). METHODS: In all patients, cerebral ultrasound scans, electroencephalogram (EEG) examinations, cerebral MRI, cytogenetic analysis, general physical evaluation, neurological examination and neuropsychological assessment (Griffiths Scale, Wechsler Primary and Preschool Scale of Intelligence, Wechsler Intelligence Scale for Children) were carried out. RESULTS: In six patients the callosal agenesis was isolated, while in 3/9 it was associated with other cerebral malformations. Children with isolated callosal agenesis were asymptomatic or presented a mild hypotonia and the EEG was normal in five of them. All children with other associated brain malformations presented epilepsy, poor psychomotor development and cerebral palsy. CONCLUSION: The prenatal suspicion of ACC needs an accurate diagnostic approach, in order to well determine its isolated or associated nature, linked to different neurodevelopmental outcome.

Adolescent↗

Shape differences in the corpus callosum in first-episode schizophrenia and first-episode psychotic affective disorder.

OBJECTIVE: The corpus callosum, the largest white matter tract in the brain, is a midline structure associated with the formation of the hippocampus, septum pellucidum, and cingulate cortex, which have been implicated in the pathogenesis of schizophrenia. Corpus callosum shape deformation, therefore, may reflect a midline neurodevelopmental abnormality. METHOD: Corpus callosum area and shape were analyzed in 14 first-episode psychotic patients with schizophrenia, 19 first-episode psychotic patients with affective disorder, and 18 normal comparison subjects. RESULTS: No statistically significant corpus callosum area differences between groups were found, but there were differences in the structure's shape between the patients with schizophrenia and the comparison subjects. A correlation between width and angle of the corpus callosum was found in patients with affective disorder. CONCLUSIONS: Corpus callosum shape abnormalities in first-episode psychotic patients with schizophrenia may reflect a midline neurodevelopmental abnormality.

Adult↗

Agenesis of the corpus callosum.

A father and son with agenesis of the corpus callosum are described. An 11-year-old boy underwent clinical examination because of poor school performance. On physical and mental examinations he was normal, except for an enlarged head. Computerized tomographic (CT) scan showed agenesis of the corpus callosum. The patient's father also had an enlarged head. Although he had never had any symptoms, he underwent CT scanning, which revealed agenesis of the corpus callosum. Psychological tests showed good communication between the two cerebral hemispheres. All-night sleep EEGs showed asynchronous sleep spindles.

Adult↗

Agenesis and dysgenesis of the corpus callosum.

Agenesis and dysgenesis of the corpus callosum is a frequent anomaly that presents with a spectrum of clinical features and exhibits variable findings in neurological studies. Clinical signs and symptoms are the result of cerebral and extracerebral malformations associated with callosal dysgenesis. Callosal agenesis may be an isolated anomaly or may be syndromic as part of more extensive malformations, metabolic and genetic disorders. The advent of modern techniques and equipment for neuroimaging have allowed us to define with more precision the type and severity of the callosal dysgenesis and accompanying other cerebral malformations. Molecular genetic studies allow the recognition and confirmation of new syndromes that until now were incompletely defined. In the context of these new pathologic entities, a new classification is proposed that may prove to be more useful than the traditional single category, "agenesis of the corpus callosum" and can serve as a basis for a later, more detailed, etiologic classification that integrates morphology and molecular genetics.

Agenesis of Corpus Callosum↗

Image-guided, frameless stereotactic sectioning of the corpus callosum in children with intractable epilepsy.

Corpus callosotomy is an effective neurosurgical procedure for children with intractable atonic or drop attack seizures. While this procedure has not changed significantly over the past three decades, some technical issues remain to be resolved. These include the intraoperative determination of the extent of the callosotomy, the need to stage the procedure, as well as side of approach of craniotomy. We report our 8-year experience with corpus callosotomy using a frameless stereotactic image-guided system (ISG Viewing Wand). Seventeen children with atonic seizures underwent sectioning of the corpus callosum. The mean patient age was 10.5 years. Six children underwent complete callosotomy while 11 underwent resection of the anterior two-thirds. MRI 3D reconstruction of the sagittal sinus and draining cerebral veins was undertaken in all cases. The side of the craniotomy was determined on the basis of favorability of the draining veins with respect to the extent of the callosotomy. The extent of the callosotomy was determined by intraoperative feedback using the ISG Viewing Wand((R)). Nine of 11 patients in the partial callosotomy group and 4 of 6 patients in the complete callosotomy group showed significant improvement in atonic seizures. We conclude that the use of frameless stereotaxy can function as an important adjunct in the planning and conduction of successful sectioning of the corpus callosum in children with intractable seizures.

Adolescent↗

Use of carbon labeling to demonstrate the role of blood monocytes as precursors of the 'ameboid cells' present in the corpus callosum of postnatal rats.

Cells with features suggestive of ameboid motion and phagocytic properties are observed in the rat corpus callosum during the first few days of life. These cells, hereafter referred to as 'ameboid cells', have been investigated in several ways. An electron microscopic study of the corpus callosum in 5- to 7-day-old rats indicated that most 'ameboid cells' were typical macrophages, but some displayed features of monocytes, while others appeared to be transitional between the two types. These observations raised the possibility that blood monocytes were the precursors of 'ameboid cells'. This possibility was tested by injecting a suspension of carbon particles into the circulation of rats of various ages to label and trace monocytes. Within 15 minutes after injection, carbon particles were seen between cells in blood smears as well as in the lumen of capillaries, but not between cells and axons in corpus callosum. By a half hour, a few of the circulationg monocytes, and with time, up to half of them, contained carbon particles. Five days after injection, carbon particles were observed in cells of the corpus callosum identified as 'ameboid cells' of the monocytic and macrophagic type. Such carbon-containing cells were seen in many of the animals injected at the age of 0-1 day, in few of those injected at 3-5 days, and in none of the older animals. Since free carbon had not been observed in corpus callosum spaces, it was concluded that 'ameboid cells' did not pick up carbon locally. The alternative was that blood monocytes, after ingesting carbon particles in the circulation, migrated to the corpus callosum and settled as 'ameboid cells'. In the hope of obtaining a direct confirmation of this conclusion, blood cells obtained from carbon-injected Lewis rats were centrifuged in a Percoll gradient to obtain a fraction which contained 70-80% monocytes, less than 2% granulocytes, and 20-30% lymphocytes. Carbon was present in up to half of the monocytes and 1% of the granulocytes, but not in the lymphocytes; and it was calculated that over 99% of the carbon-labeled cells were monocytes. The cell fraction was then introduced into the blood circulation of 2- to 3-day-old syngeneic Lewis rats, and the animals were sacrificed 5 days later. Occasional carbon-labeled cells appeared not only in liver, spleen and connective tissue, but also in the corpus callosum, where they were identified as 'ameboid cells' of the monocytic and macrophagic type. Even though such cells were infrequent, their presence conclusively demonstrated that at least some 'ameboid cells' of the corpus callosum were derived from circulating blood monocytes.

Age Factors↗

Morphometry of the corpus callosum in Chinese children: relationship with gender and academic performance.

BACKGROUND: The corpus callosum has been widely studied, but no study has demonstrated whether its size and shape have any relationship with language and calculation performance. OBJECTIVE: To examine the morphometry of the corpus callosum of normal Chinese children and its relationship with gender and academic performance. MATERIALS AND METHODS: One hundred primary school children (63 boys, 37 girls; age 6.5-10 years) were randomly selected and the standardized academic performance for each was ascertained. On the mid-sagittal section of a brain MRI, the length, height and total area of the corpus callosum and its thickness at different sites were measured. These were correlated with sex and academic performance. RESULTS: Apart from the normal average dimension of the different parts of the corpus callosum, thickness at the body-splenium junction in the average-to-good performance group was significantly greater than the below-average performance group in Chinese language (P=0.005), English language (P=0.02) and mathematics (P=0.01). The remainder of the callosal thickness showed no significant relationship with academic performance. There was no significant sex difference in the thickness of any part of the corpus callosum. CONCLUSIONS: These findings raise the suggestion that language and mathematics proficiency may be related to the morphometry of the fibre connections in the posterior parietal lobes.

Child↗

Lipoma of the corpus callosum associated with frontal and facial anomalies.

Seven patients with a corpus callosum lipoma associated with a frontal cranial defect with or without a superficial lipoma or a fronto-nasal dysplasia, were encountered over a period of 12 years. This group of patients is reported as these associated lesions may provide a lead to the cause of lipomas of the corpus callosum as well as of the different lesions in the fronto-facial region. From our experience and that of others, the frontal lesion may be an extracranial lipoma, a frontal bone defect, with or without an external lipoma, a lipomeningocele connecting the extracranial lipoma through a frontal defect with the corpus callosum lipoma, a frontal encephalocele. Fronto-nasal dysplasia associated with a corpus callosum lipoma, seems to form an independent group although some of these patients may have other extracranial lesions as well. It is suggested by the authors that as the primitive mesenchyme gives rise to the meninx primitiva as well as to the fronto-facial skeleton a disturbance of the neural crest may give rise to these combined lesions. Further analysis of similar cases may indicate the timing of these events, and perhaps reveal a common causative factor.

Adult↗

Sex and environmental influences on the size and ultrastructure of the rat corpus callosum.

A contested report of sex differences in the size of the splenium of the corpus callosum in humans prompted the present examination of the corpus callosum in the rat. We have previously found that sex differences can vary with the rearing environment. Consequently, male and female rats were raised from weaning to 55 days of age in either a complex or an isolated environment. There were no sex differences in the size of the corpus callosum in sagittal cross section in these rats; however, rats of both sexes had a larger posterior third of the corpus callosum if they were raised in the complex environment. Because the corpus callosum continues to grow in size past 55 days of age, we examined socially housed rats at 113 days and again found no sex differences. The splenium was examined with electron microscopy in complex and isolation reared rats at 55 days of age. The ultrastructural analysis revealed differences that were not apparent from gross size measures. Females had more unmyelinated axons regardless of environment, and females from the complex environment had more myelinated axons than comparably housed males. In contrast, males in the complex environment had larger myelinated axons than females. Rats of both sexes from the complex environment had larger and more unmyelinated axons than isolated rats. In addition in myelinated axons, plasticity in the females occurred through changes in axon number and in males, through axon size. Thus sex differences exist in axonal number and size and the environment influences these differences.

Animals↗

The existence of a separate, brief critical period for the corpus callosum to affect visual development.

The critical period for the role of the corpus callosum in visual development was explored in terms of the length of time during which the callosum has any influence on the development of visual acuity. Cats were given a surgical section of the posterior corpus callosum at 1, 2, 3, 4 and 29 weeks of age. These, as well as normal and operated control cats, were behaviorally tested for visual acuity thresholds from 5 through 29 weeks of age. Only the 1, 2 and 3 week callosum-sectioned cats showed deficits in visual acuity; the 4 and 29 week callosum-sectioned cats had acuity thresholds equivalent to those of the control cats. These results define a relatively brief critical period of time during which the corpus callosum effectively interacts with the developing visual system. This critical period ends during the fourth postnatal week; throughout the first postnatal month the corpus callosum's effectiveness in altering subsequent visual development gradually declines. Using the amount of acuity deficit as the measure of alteration of visual development, the input of the corpus callosum during the first postnatal month is as critical to visual development as is normal visual input during the first 4-6 postnatal months.

Animals↗

Development of the human fetal corpus callosum: a high-resolution, cross-sectional sonographic study.

OBJECTIVE: To establish reference ranges during human pregnancy for normal fetal corpus callosum dimensions. DESIGN: In a prospective, cross-sectional study of 258 fetuses between 16 and 37 weeks of gestation, measurements of the length, width, and thickness at the level of the anterior mid-body of the corpus callosum were performed, using high-resolution, transvaginal and transabdominal transducers. RESULTS: The mean length of the corpus callosum was 27.2 (standard deviation, 1.2; 95% confidence interval, 26.02-28.37) mm. Width and thickness of the corpus callosum were 5.6 (standard deviation, 1.6; 95% confidence interval, 5.41-5.82) mm and 1.9 (standard deviation, 0.7; 95% confidence interval, 1.87-2.06) mm, respectively. The size of the corpus callosum as a function of gestational age was expressed by regression equations: length (mm) = -20.40 + 1.92 x gestational age; width (mm) = -0.052 + 0.225 x gestational age; thickness (mm) = -0.174 + 0.085 x gestational age. The dimension-gestational age correlation coefficients were: r = 0.779 for length, r = 0.676 for width and r = 0.494 for thickness; these were statistically significant (P < 0.01). The maximum increase in thickness and width of the corpus callosum occurred between 19 and 21 weeks' gestation, while its length followed a constant growth rate. The normal mean length, width and thickness of the corpus callosum per week, and the 95% confidence limits, were defined. CONCLUSIONS: The present study offers normative measurements of the fetal corpus callosum and may facilitate a more objective diagnosis of its congenital abnormalities.

Corpus Callosum↗

The management of arteriovenous malformations of the corpus callosum.

A series of 15 arteriovenous malformations (AVMs) of the corpus callosum--9% of 170 intracranial AVMs admitted to the School of Medicine of the University of Rome during a 30-yr period--was studied. In all cases the lesion concerned mainly the corpus callosum, although in some it also involved the surrounding structures, such as septum pellucidum, tela choroidea, and the mesial hemisphere. These malformations are divided into three groups, namely, those involving mainly the genu, the truncus, or the splenium of the corpus callosum. The last predominated in the present series. Each type has a peculiar angiographic appearance. In general these lesions are fed by branches from the anterior cerebral and/or posterior cerebral arteries, although in some cases minor contributions from the middle cerebral artery may also be present. Vascularization is often bilateral. Venous drainage occurs through the inferior and/or superior sagittal sinuses and/or the Galen system. As to clinical presentation, Subarachnoid Hemorrhage (SAH) is the usual presenting symptom and tends to recur frequently. Neurological localizing symptoms are infrequent, as are seizures; psychological symptoms are an exception. Of the 4 cases managed conservatively, only one had no further episodes of bleeding and remained free of complaints. On the other hand, surgical results of the 11 operated patients were satisfactory, in the sense that no mortality and low morbidity were recorded. Accordingly, surgical treatment of AVMs of the corpus callosum is recommended as a rule.

Adolescent↗