Congenital CMV with callosal lipoma and agenesis

Brain plasticity following corpus callosum agenesis or loss: a review of the Probst bundles

The corpus callosum is the largest axonal tract in the human brain, connecting the left and right cortical hemipheres. This structure is affected in myriad human neurodevelopmental disorders, and can be entirely absent as a result of congenital or surgical causes. The age when callosal loss occurs, for example via surgical section in cases of refractory epilepsy, correlates with resulting brain morphology and neuropsychological outcomes, whereby an earlier loss generally produces relatively improved interhemispheric connectivity compared to a loss in adulthood (known as the "Sperry's paradox"). However, the mechanisms behind these age-dependent differences remain unclear. Perhaps the best documented and most striking of the plastic changes that occur due to developmental, but not adult, callosal loss is the formation of large, bilateral, longitudinal ectopic tracts termed Probst bundles. Despite over 100 years of research into these ectopic tracts, which are the largest and best described stereotypical ectopic brain tracts in humans, much remains unclear about them. Here, we review the anatomy of the Probst bundles, along with evidence for their faciliatory or detrimental function, the required conditions for their formation, patterns of etiology, and mechanisms of development. We provide hypotheses for many of the remaining mysteries of the Probst bundles, including their possible relationship to preserved interhemispheric communication following corpus callosum absence. Future research into naturally occurring plastic tracts such as Probst bundles will help to inform the general rules governing axon plasticity and disorders of brain miswiring.

Pai syndrome: report of seven South American patients

Frontonasal dysplasia is etiologically heterogeneous and various subsets are known. Pai syndrome is one subset, which is characterized by mild hypertelorism, midline cleft lip, nasal and facial polyps, pericallosal lipoma, ocular anomalies, and normal neuropsychological development. Here, we report seven South American patients and review earlier reported cases. The phenotype is clinically variable and five reported patients were severely affected. The cause of Pai syndrome is unknown to date. Several literature findings have been noted: nondiagnostic and discordant minor signs in a parent of two separate families with an affected child; discordant phenotype in monozygotic twins in one instance; and a de novo reciprocal translocation, 46,X,t(X;16)(q28;q11.2) in one instance.

Agenesis of the corpus callosum: genetic, developmental and functional aspects of connectivity

Agenesis of the corpus callosum (AgCC), a failure to develop the large bundle of fibres that connect the cerebral hemispheres, occurs in 1:4000 individuals. Genetics, animal models and detailed structural neuroimaging are now providing insights into the developmental and molecular bases of AgCC. Studies using neuropsychological, electroencephalogram and functional MRI approaches are examining the resulting impairments in emotional and social functioning, and have begun to explore the functional neuroanatomy underlying impaired higher-order cognition. The study of AgCC could provide insight into the integrated cerebral functioning of healthy brains, and may offer a model for understanding certain psychiatric illnesses, such as schizophrenia and autism.

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 epidemiology of neonatal tumours. Report of an international working group

Neonatal tumours occur every 12,500-27,500 live births and comprise 2% of childhood malignancies, but there is little clarity as to their real prevalence, sites of origin and pathological nature as reported series vary. As an entity, neonatal tumours provide a unique window of opportunity to study tumours in which minimal environmental interference has occurred. The majority of tumours present with a mass at birth (e.g., teratomas, neuroblastomas, mesoblastic nephroma, fibromatosis), which are not infrequently identified on antenatal ultrasound. Histologically, teratoma and neuroblastoma remain the two main tumour types encountered with soft tissue sarcoma, renal tumours, CNS tumours and leukaemia being the next most common tumour types identified. Malignant tumours are uncommon in the neonatal period per se and benign tumours may have malignant potential. A particular problem exists in clinical classification, as histological features of malignancy do not always correlate with clinical behaviour. Benign tumours may also be life threatening because of their size and location. Other tumours may demonstrate local invasiveness, but no metastatic potential, and tumours that are clearly malignant may demonstrate unpredictable or uncertain behaviour. Screening programmes have brought more tumours to light, but do not appear to affect the overall prognosis. They may provide clues to the stage at which tumours develop in foetu. The aetiology of cancer in children is multifactorial and includes both genetic and environmental factors. The association between congenital abnormalities and tumours is well established (15% of neonatal tumours). Genetic defects are highly likely in neonatal tumours and include those with a high risk of malignancy (e.g., retinoblastoma), but also genetically determined syndromes with an increased risk of malignancy and complex genetic rearrangements. Tumours are mostly genetically related at a cellular level and factors influencing cellular maturation or apoptosis within the developing foetus may continue to operate in the neonatal period. Cytogenetics of neonatal neoplasms appear to differ from neoplasms in older children, thus possibly explaining some of the observed differences in clinical behaviour. Certain constitutional chromosome anomalies, however, specifically favour tumours occurring in the foetal and neonatal period. In support of this hypothesis, certain cytogenetic anomalies appear to be specific to neonates, and a number of examples are explored. Other environmental associations include ionizing radiation, drugs taken during pregnancy, infections, tumours in the mother and environmental exposure.

Cytomegalovirus infection: perinatal implications

Cytomegalovirus (CMV), a member of the herpes virus family, is the most common cause of congenital infection in humans, affecting 0.5-3% of all newborns worldwide. Congenital cytomegalovirus infection is the leading infectious cause of deafness, learning disabilities, and mental retardation in children. The high prevalence of cytomegalovirus in the general population, unpredictability of transmission, and asymptomatic nature of the disease in otherwise healthy women challenge prevention and treatment efforts.