Dysgenesis of the corpus callosum and associated telencephalic anomalies: MRI

Anomalies of the Corpus Callosum in Prenatal Ultrasound: A Narrative Review for Diagnosis and Further Counseling

The corpus callosum is the major interhemispheric tract that plays an important role in neurological function. Understanding the etiology and embryology development helps the ultrasound diagnosis for disorders of the corpus callosum and further counseling. The nonvisualization of cavum septum pellucidum or dysmorphic cavum septum pellucidum in axial view are indirect signs for beginners to diagnose complete agenesis of corpus callosum (cACC) and partial agenesis of the corpus callosum (pACC). Further coronal view, sagittal view, and fetal magnetic resonance imaging are also important for evaluation. Genetic testing plays an essential tool in anomalies of corpus callosum by revealing the underlying genetic pathophysiology, such as chromosomal anomalies and numerous monogenetic disorders in 30%-45% of ACC. Diagnosis and prediction of prognosis for hypoplasia or hyperplasia of the corpus callosum are more difficult compared to cACC and pACC because of the limited reports in the literature. However, the complex types often had poorer prognostic outcomes compared to the isolated types. Hence, it is important to evaluate and follow fetal conditions thoroughly to rule out intracranial or extracranial anomalies in other systems.

Clinical and Biochemical Features of Hypopituitarism Among Brazilian Children With Zika Virus-Induced Microcephaly

IMPORTANCE

The Zika virus infects progenitor neuron cells, disrupts cerebral development, and, in mice, drives hypothalamic defects. Patients with microcephaly caused by congenital Zika infection present with midline cerebral defects, which may result in hypopituitarism.

OBJECTIVE

To analyze postnatal growth and the presence of clinical and biochemical features associated with hypopituitarism in children with congenital Zika infections.

DESIGN, SETTING, AND PARTICIPANTS

In this prospective cohort study at 2 public referral hospitals in Bahia, Brazil, specializing in the treatment of congenital Zika infection, clinical data and growth parameters of 65 patients with the infection were evaluated. Data were analyzed from April 2017 through July 2018.

EXPOSURE

Congenital Zika infection.

MAIN OUTCOMES AND MEASURES

Length, weight, and head circumference were measured at birth and during follow up (ie, at 27 months of life) for each patient. Basal levels of free thyroxine, thyrotropin, cortisol, corticotropin, prolactin, insulin-like growth factor 1, insulin-like growth factor binding protein 3, urine and plasma osmolality, electrolytes, glucose, and insulin were evaluated at the age of 26 months to 28 months. All patients underwent central nervous system computed tomography scans and ophthalmic and otoacoustic evaluations at the time of this investigation or had done so previously.

RESULTS

Among 65 patients (38 [58.4%] male; median [interquartile range] age at enrollment, 27 [26-28] months), 61 patients presented with severe brain defects (93.8%), including corpus callosum agenesis or hypoplasia (ie, midline brain defects; 25 patients [38.5%]) and optic nerve atrophy (38 patients [58.5%]). Most patients presented with severe neurodevelopmental delay (62 of 64 patients [96.9%]). Past or present clinical signs of hypopituitarism were rare, occurring in 3 patients (4.6%). Severe microcephaly, compared with mild or moderate microcephaly, was associated with a shorter length by median (interquartile range) z score at birth (-1.9 [-2.5 to -1.0] vs -0.3 [-1.0 to 0]; P < .001), but this difference did not persist at 27 months (-1.6 [-2.3 to -0.3] vs -2.9 [-4.0 to -1.2]; P = .06). Growth hormone deficiency or hypothyroidism were not observed in any patients, and glucose and insulin levels were within reference ranges for all patients. Low cortisol levels (ie, below 3.9 µg/dL) were observed in 4 patients (6.2%). These 4 patients presented with low (ie, below 7.2 pg/mL) or inappropriately low (ie, below 30 pg/mL) corticotropin levels. Low corticotropin levels (ie, below 7.2 pg/mL) were observed in 6 patients (9.2%). Diabetes insipidus was evaluated in 21 patients; it was confirmed in 1 patient (4.8%) and suggested in 3 patients (14.3%).

CONCLUSIONS AND RELEVANCE

This study found that congenital Zika infection with microcephaly was associated with midline brain defects and optic nerve atrophy. Children with congenital Zika infections presented with prenatal growth impairments with a lack of postnatal catch-up, as shown by persistent short length from birth until 27 months; these impairments were not associated with growth hormone deficiency. Patients also presented with severe developmental delay that was not associated with hypothyroidism, while central adrenal insufficiency and diabetes insipidus occurred in some patients.

The Prenatal Morphomechanic Impact of Agenesis of the Corpus Callosum on Human Brain Structure and Asymmetry

Genetic, molecular, and physical forces together impact brain morphogenesis. The early impact of deficient midline crossing in agenesis of the Corpus Callosum (ACC) on prenatal human brain development and architecture is widely unknown. Here we analyze the changes of brain structure in 46 fetuses with ACC in vivo to identify their deviations from normal development. Cases of complete ACC show an increase in the thickness of the cerebral wall in the frontomedial regions and a reduction in the temporal, insular, medial occipital and lateral parietal regions, already present at midgestation. ACC is associated with a more symmetric configuration of the temporal lobes and increased frequency of atypical asymmetry patterns, indicating an early morphomechanic effect of callosal growth on human brain development affecting the thickness of the pallium along a ventro-dorsal gradient. Altered prenatal brain architecture in ACC emphasizes the importance of conformational forces introduced by emerging interhemispheric connectivity on the establishment of polygenically determined brain asymmetries.

Neuropsychological functioning in dysgenesis of the corpus callosum with colpocephaly

Dysgenesis of the corpus callosum is a rare developmental abnormality in brain structure that is associated with changes in physical appearance, as well as behavioral and cognitive consequences. A relatively commonly co-occurring structural abnormality with callosal dysgenesis is colpocephaly, characterized by enlargement of the posterior lateral ventricles and reductions in posterior brain volume. Although some case studies of individuals with this combination of structural malformations exist, they do not often report results of neuropsychological evaluation. Furthermore, those that do contain neuropsychological data may be of limited generalizability due to unique patient characteristics. The current manuscript overcomes these limitations by presenting the case of a 55-year-old male with callosal dysgenesis and colpocephaly identified in adulthood. The paper includes a full profile of his performance on a comprehensive neuropsychological test battery with discussion of differential diagnosis and treatment planning. Findings indicated low average intellectual abilities with deficits in processing speed, executive functions, and social cognition, consistent with expectations based on callosal dysgenesis. One surprising finding was that despite the significant posterior involvement of colpocephaly, visuospatial skills were a relative strength. The manuscript provides a clear characterization of callosal dysgenesis with colpocephaly to facilitate future clinical comparisons and set the stage for future research on this rare neuromorphological presentation.

Cilia, ciliopathies and hedgehog-related forebrain developmental disorders

Development of the forebrain critically depends on the Sonic Hedgehog (Shh) signaling pathway, as illustrated in humans by the frequent perturbation of this pathway in holoprosencephaly, a condition defined as a defect in the formation of midline structures of the forebrain and face. The Shh pathway requires functional primary cilia, microtubule-based organelles present on virtually every cell and acting as cellular antennae to receive and transduce diverse chemical, mechanical or light signals. The dysfunction of cilia in humans leads to inherited diseases called ciliopathies, which often affect many organs and show diverse manifestations including forebrain malformations for the most severe forms. The purpose of this review is to provide the reader with a framework to understand the developmental origin of the forebrain defects observed in severe ciliopathies with respect to perturbations of the Shh pathway. We propose that many of these defects can be interpreted as an imbalance in the ratio of activator to repressor forms of the Gli transcription factors, which are effectors of the Shh pathway. We also discuss the complexity of ciliopathies and their relationships with forebrain disorders such as holoprosencephaly or malformations of cortical development, and emphasize the need for a closer examination of forebrain defects in ciliopathies, not only through the lens of animal models but also taking advantage of the increasing potential of the research on human tissues and organoids.

A large interhemispheric glioependymal cyst associated with partial defect of the corpus callosum in an elderly man

Interhemispheric cysts are congenital, and usually present symptoms during childhood. However, they are occasionally detected in adults. These cystic lesions are sometimes associated with defects of the corpus callosum. Although defects of the corpus callosum by themselves do not present clinical symptoms, they are often accompanied by other brain malformations. A man in his late 60s was found dead at the scene of a fire. At autopsy, his brain weighed 1223 g and had a large interhemispheric cyst, measuring 5.5 × 4.5 × 4.0 cm in size. The cyst contained clear fluid but was not connected to the ventricular system. On slices of the cerebrum, the corpus callosum did not connect the right and left cerebral hemispheres, and the right lateral ventricle was dilated. By the existence of the cyst, compressed by the cyst, the hemispheres were displaced on either side. Histologically, the cerebral parenchyma around the cyst was slightly edematous but structurally normal. Immunohistochemically, both glial fibrillary acidic protein and podoplanin were expressed in the cystic components. Thus, the cystic lesion was diagnosed as a glioependymal cyst. In this case, because the cyst was located at the interhemispheric space between the right and left frontal lobes, the individual experienced no obvious symptoms, despite its large size. The individual's brain malformations included the partial defect of the corpus callosum and the cyst. The dilation of the right lateral ventricle was considered to result from the location of the cyst. Under the influence of the cyst, the third ventricle was displaced downward, and one or both of the interventricular foramen were obstructed. The decedent had burns over his whole body. Burns to the epiglottis and soot in the airway were also observed. Volatile hydrocarbons, such as benzene and styrene, were detected in the blood. The percentage of carboxyhemoglobin levels in a total of hemoglobin levels were 19-25%. Therefore, the individual's cause of death was established as death by fire.

Congenital pial AVF along the falx cerebri with complete agenesis of the corpus callosum and bilateral parasagittal pachygyria-polymicrogyria secondary to chronic ischemia

OBJECTIVE

Pial arteriovenous fistula (AVF) is an extremely rare entity due to direct arterial connection with the venous plexus without an intervening capillary network. The objective of this article is to describe a unique case of congenital pial AVF along the interhemispheric falx with complete callosal agenesis and malformation of cortical development within the bilateral anterior cerebral artery territories. We also demonstrated the distinctive feature of temporal stability of the extensive intracranial abnormalities without active intervention. Less than 100 cases have been reported thus far, most of which involve the adult rather than pediatric age group. A comprehensive literature review of congenital pial AVF will also be included.

CASE DESCRIPTION

A 5-year-old child presented with headache and complex partial seizures. Imaging of the brain revealed the presence of polymicrogyria-pachygyria in the parasagittal frontoparietal lobes with associated underlying white matter hypodensities. Complete agenesis of the corpus callosum was also seen. In addition, enlarged and tortuous vessels were noted along the interhemispheric falx with no appreciable nidus. Bilateral dilated and tortuous ACAs were seen supplying the network of abnormal vessels along the falx. The radiological findings were stable on a follow-up MRI 12 years later.

CONCLUSION

Our reported case adds to current limited knowledge of this rare entity in the pediatric age group, which is traditionally treated aggressively and urgently. Our case demonstrated temporal stability of this lesion with no detrimental complications observed. This suggests that the outcome of pial AVFs with conservative treatment may not be as grim as previously thought.

Absent circle of Willis with vascular pollarding in an adult with colpocephaly: A developmental perspective

Absent circle of Willis (COW) has been described in cases of severe forms of cerebral developmental anomalies such as alobar prosencephaly. However, there are no reports of absent COW in patients with a milder form of cerebral abnormality such as colpocephaly. We report a unique case of an adult with colpocephaly and absent COW and discuss their association from a developmental perspective.

Cortical dysplasias, and corpus callosum and posterior fossa abnormalities: correlation of clinical findings with magnetic resonance imaging (MRI) characteristics

This study examined clinical findings and magnetic resonance imaging (MRI) characteristics in 114 patients with cortical dysplasia and corpus callosum and posterior fossa abnormalities to determine the clinical findings with the extent of the lesions on MRI. The age of patients was between 1 day and 15 years. Group 1 included 74 patients with corpus callosum abnormalities and/or cortical dysplasias and group 2 included 40 patients with posterior fossa abnormalities, which were isolated and/or associated with cortical dysplasia and/or corpus callosum abnormalities. Although associated congenital abnormality apart from central nervous system abnormalities, syndrome, or systemic disorder were more common in group 2 than group 1 patients (P < .05), we did not find a difference between the groups for psychomotor retardation and epilepsy (P > .05).

Atypical meningioma in the posterior fossa associated with colpocephaly and agenesis of the corpus callosum

Colpocephaly is an abnormal enlargement of the occipital horns, i.e., the posterior or rear portions of the lateral ventricles of the brain, and is associated with several other brain abnormalities. Colpocephaly is occasionally misdiagnosed as hydrocephalus, and various etiologies have been postulated, including genetic disorders and errors of morphogenesis. Meanwhile, chromosomal losses including 22q and rarely 21q are observed in malignant and atypical meningiomas. We report an uncommon case of a 67-year-old woman with colpocephaly and an atypical meningioma in the posterior fossa. There were no neurological deficits or family history of hereditary neuropsychiatric disorders. Brain magnetic resonance (MR) images showed bilateral enlarged occipital horns, agenesis of corpus callosum, and a cerebellar mass in the right cerebellar hemisphere. Right suboccipital craniotomy was performed, and the tumor was resected totally. Pathological study of the surgical specimen showed findings of atypical meningioma, and the postoperative course was uneventful until hydrocephalus developed. At 36th day after tumor removal, the patient undertook an external ventricular drainage followed by replacement of the ventriculoperitoneal shunt. We discuss the importance of colpocephaly in terms of the differential diagnosis for hydrocephalus and review the pertinent literature.

Diffusion MRI abnormalities in pediatric neurological disorders

Diffusion-weighted imaging (DWI) makes it possible to measure early changes in cellular function in the central nervous system. The purpose of this article is to discuss the diagnostic value of diffusion-weighted and diffusion tensor imaging (DTI) in different pediatric cerebral disorders. First, the principles of DWI and DTI are briefly reviewed. The clinical usefulness of these imaging techniques is then discussed using cases with pediatric neurological disorders, such as hypoxic-ischemic encephalopathy in neonates, trauma (shaken baby syndrome), encephalopathy or encephalitis in infants, posterior reversible encephalopathy syndrome and congenital brain anomaly (callosal dysgenesis). In addition, using DTI, we evaluate normal brain development, particularly in the corpus callosum and cortico-spinal tract, and discuss the application of DTI to the study of white matter in the developing brain.

MR demonstration of complete cerebellar and corpus callosum agenesis

Complete cerebellar agenesis is a very rare entity, which occurs during the early period of embryogenesis and is usually associated with severe motor dysfunction. We report a case of complete cerebellar agenesis with complete corpus callosum agenesis diagnosed on magnetic resonance imaging (MRI). These anomalies were also associated with rudimentary pons.

[Agenesis of the corpus callosum in a premature infant associated with Langdon-Down syndrome]

INTRODUCTION

Agenesis of the corpus callosum is an abnormality of the part of the brain connecting the two cerebral hemispheres. It can be partial, complete or atypical. The fibers from the cerebral cortex project towards the homotypical region of the contra-lateral cortex passing through the corpus callosum, and crossing the middle line. The absence of corpus callosum causes failure of information transfer from one hemisphere to the other. Children with this anomaly present with learning disabilities and trouble with memorizing facts. Agenesis of corpus callosum may be of syndromic or non-syndromic type. The more common form is the one not associated with any syndrome. The agenesis of corpus callosum is more frequent in male children.

CASE REPORT

This paper presents a child from a twin pregnancy with partial absence of corpus callosum. The pregnancy was not controlled. It ended in premature birth. The afflicted twin is a boy, second in birth order. Apart from agenesis of corpus callosum, he also suffers from Down syndrome. The first twin is healthy, with corpus callosum and with normal karyotype. There was no consanquinity. In the 6th month of pregnancy the mother suffered from infection of the upper respiratory tract that might be the etiological factor of this anomaly. The child was born with hypotrophy, and all anthropometric parameters were below the third percentile. In the neonatal period, the agenesis of corpus callosum was diagnosed by ultrasonic examination and confirmed by CT and MR examinations. The child is now three and a half month old. Active monitoring of the psychical and motor development will show whether there will be any retardation in the psycho-motor development and later deficiency of the higher corticalfunctions and intelligence.

DISCUSSION AND CONCLUSION

The clinical characteristics of this anomaly are numerous. They range from asymptomatic cases, with normal intellectual capacity, to severe mental retardation. Radiological and genetic markers cannot make a difference between the asymptomatic and symptomatic characteristics of the disease. Therefore, it is very difficult to give genetic advice if the diagnosis is made prenatally. This part of the central nervous system is very well visualized by ultrasonic examination, thus in the absence of corpus callosum a special attention must be paid to other parts of the central nervous system, for diagnosing associated anomalies. If the diagnosis of agenesis of corpus callosum is made prenatally by ultrasound, a MR examination is advised for diagnosing other anomalies, especially in the central nervous system like lissencephalia, schizocephalia or heterotopia of the gray matter, where MR examination is superior to others.

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.

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.

Agénésie partielle du corps calleux de l’enfant

PURPOSE

The diagnosis of corpus callosum agenesis (CCA) with prenatal MRI relies on indirect signs. However, they are known to be inconstant in case of incomplete CCA. The purpose of this study is to specify the frequency of indirect signs in partial CCA to approach the reliability of fetal MRI.

MATERIALS AND METHODS

This retrospective study included 33 children with partial CCA. MRI were reviewed by two observers and a standardized radiological and clinical data collection was performed. Depending on the ratio CC length/anteroposterior brain diameter, two groups were statistically compared: subtotal partial CCA and mild partial CCA.

RESULTS

14% of patients had none indirect sign and 33% had only one sign. We found a significative difference of frequency for most of the indirect signs. 48% of patients had other cerebral anomalies. Clinical correlation showed no statistical difference between the two groups.

CONCLUSION

This series shows that indirect signs are inconstant in partial CCA and related to the CC length. In contrast, mild and subtotal CCA have a similar neurological outcome. These data suggest that greatest care has to be taken in the interpretation of fetal MRI.

The Syndrome of Frontonasal Dysplasia, Callosal Agenesis, Basal Encephalocele, and Eye Anomalies - Phenotypic and Aetiological Considerations

We report ten sporadic cases of Brazilian patients with facial midline defects, callosal agenesis, basal encephalocele, and ocular anomalies. This very rare cluster of anomalies has been well reported before. However, only until recently it is recognized as a syndrome belonging to frontonasal dysplasia spectrum. The ten cases confirm a distinct clinical entity and help to define the phenotype more precisely than previously. Up to now etiology remains unknown, although we conjecture that it is due to a mutation in TGIF gene.

Disgenesia do corpo caloso e más-formações associadas: achados de tomografia computadorizada e ressonância magnética

O termo disgenesia do corpo caloso refere-se a uma má-formação deste com origem na embriogênese do telencéfalo. O relato analisa os achados de tomografia computadorizada e ressonância magnética em 11 pacientes com disgenesia calosa e em um caso de corpo caloso normal com lipoma associado. Esta pode ser distinguida em três grupos: agenesia total (três casos), agenesia parcial (seis casos) e hipoplasia (dois casos). Anomalias associadas foram observadas em nove casos, incluindo má-formação de Chiari tipo II (um caso), esquizencefalia (um caso), cisto inter-hemisférico (dois casos), heterotopia nodular (um caso), cisto de Dandy-Walker (um caso) e lipoma do corpo caloso (quatro casos). Este artigo demonstra um espectro destes distúrbios, auxiliando na sua interpretação diagnóstica.

Fetal neurologic consultations

The pediatric neurologist can fulfill a useful role as a subspecialty consultant concerning the fetus with a suspected brain disorder, given that neurologic disease may occur before the intrapartum period. Brain disorders detected in the neonatal period may also reflect fetal brain damage before dysfunction is first documented. Medical conditions during the antepartum or intrapartum periods can alternatively predispose the fetus or neonate to express brain dysfunction at a later period, with either de novo or compounded brain injury. The pediatric neurologist must, therefore, consider maternal, placental, and fetal diseases on which a neonatal encephalopathy may be superimposed. This review article provides the neurologist with an integrative approach to fetal neurology, emphasizing perspectives from other subspecialties concerning maternal-fetal medicine, pathology, and neonatology, as well as other pediatric subspecialties. Evaluation of future strategies for either fetal or neonatal brain resuscitation will need to consider the developmental context in which a suspected brain injury occurred during the antepartum, intrapartum, and neonatal periods.

Anterior commissure absence without callosal agenesis: a new brain malformation

The authors report a novel human brain malformation characterized by the absence of the anterior commissure without callosal agenesis, but associated with gross unilateral panhemispheric malformation incorporating subependymal heterotopia, subcortical heterotopia, and gyral abnormalities including temporal malformation and polymicrogyria. In contrast, a normal anterior commissure was found in 125 control subjects and in 113 other subjects with a range of brain malformations.