Infantile hydrocephalus: a review of epidemiology, classification and causes

The Genetic Basis of Hydrocephalus

Studies of syndromic hydrocephalus have led to the identification of >100 causative genes. Even though this work has illuminated numerous pathways associated with hydrocephalus, it has also highlighted the fact that the genetics underlying this phenotype are more complex than anticipated originally. Mendelian forms of hydrocephalus account for a small fraction of the genetic burden, with clear evidence of background-dependent effects of alleles on penetrance and expressivity of driver mutations in key developmental and homeostatic pathways. Here, we synthesize the currently implicated genes and inheritance paradigms underlying hydrocephalus, grouping causal loci into functional modules that affect discrete, albeit partially overlapping, cellular processes. These in turn have the potential to both inform pathomechanism and assist in the rational molecular classification of a clinically heterogeneous phenotype. Finally, we discuss conceptual methods that can lead to enhanced gene identification and dissection of disease basis, knowledge that will potentially form a foundation for the design of future therapeutics.

Array-based molecular karyotyping in fetuses with isolated brain malformations identifies disease-causing CNVs

Background

The overall birth prevalence for congenital malformations of the central nervous system (CNS) among Europeans may be as high as 1 in 100 live births. The etiological factors remain largely unknown. The aim of this study was to detect causative copy number variations (CNVs) in fetuses of terminated pregnancies with prenatally detected isolated brain malformations.

Methods

Array-based molecular karyotyping was performed in a cohort of 35 terminated fetuses with isolated CNS malformations. Identified putative disease-causing CNVs were confirmed using quantitative polymerase chain reaction or multiplex ligation-dependent probe amplification.

Results

Based on their de novo occurrence and/or their established association with congenital brain malformations, we detected five disease-causing CNVs in four fetuses involving chromosomal regions 6p25.1-6p25.3 (FOXC1), 6q27, 16p12.3, Xp22.2-Xp22.32 (MID1), and Xp22.32-Xp22.33. Furthermore, we detected a probably disease-causing CNV involving chromosomal region 3p26.3 in one fetus, and in addition, we detected 12 CNVs in nine fetuses of unknown clinical significance. All CNVs except for two were absent in 1307 healthy in-house controls (frequency <0.0008). Each of the two CNVs present in in-house controls was present only once (frequency = 0.0008). Furthermore, our data suggests the involvement of CNTN6 and KLHL15 in the etiology of agenesis of the corpus callosum, the involvement of RASD1 and PTPRD in Dandy-Walker malformation, and the involvement of ERMARD in ventriculomegaly.

Conclusions

Our study suggests that CNVs play an important role in the etiology of isolated brain malformations.

Hydrocephalus in children

Hydrocephalus is a common disorder of cerebral spinal fluid (CSF) physiology resulting in abnormal expansion of the cerebral ventricles. Infants commonly present with progressive macrocephaly whereas children older than 2 years generally present with signs and symptoms of intracranial hypertension. The classic understanding of hydrocephalus as the result of obstruction to bulk flow of CSF is evolving to models that incorporate dysfunctional cerebral pulsations, brain compliance, and newly characterised water-transport mechanisms. Hydrocephalus has many causes. Congenital hydrocephalus, most commonly involving aqueduct stenosis, has been linked to genes that regulate brain growth and development. Hydrocephalus can also be acquired, mostly from pathological processes that affect ventricular outflow, subarachnoid space function, or cerebral venous compliance. Treatment options include shunt and endoscopic approaches, which should be individualised to the child. The long-term outcome for children that have received treatment for hydrocephalus varies. Advances in brain imaging, technology, and understanding of the pathophysiology should ultimately lead to improved treatment of the disorder.

Repeated autologous umbilical cord blood infusions are feasible and had no acute safety issues in young babies with congenital hydrocephalus

BACKGROUND

Babies with congenital hydrocephalus often experience developmental disabilities due to brain injury associated with prolonged increased pressure on the developing brain parenchyma. Umbilical cord blood (CB) infusion has favorable effects in animal models of brain hypoxia and stroke and is being investigated in clinical trials of brain injury in both children and adults. We sought to establish the safety and feasibility of repeated intravenous infusions of autologous CB in young babies with congenital hydrocephalus.

METHODS

Infants with severe congenital hydrocephalus and an available qualified autologous CB unit traveled to Duke for evaluation and CB infusion. When possible, the CB unit was utilized for multiple infusions. Patient and CB data were obtained at the time of infusion and analyzed retrospectively.

RESULTS

From October 2006 to August 2014, 76 patients with congenital hydrocephalus received 143 autologous CB infusions. Most babies received repeated doses, for a total of two (n = 45), three (n = 18), or four (n = 4) infusions. There were no infusion-related adverse events. As expected, all babies experienced developmental delays.

CONCLUSION

Cryopreserved CB products may be effectively manipulated to provide multiple CB doses. Repeated intravenous infusion of autologous CB is safe and feasible in young babies with congenital hydrocephalus.

Camk2a-Cre-mediated conditional deletion of chromatin remodeler Brg1 causes perinatal hydrocephalus

Mammalian SWI/SNF-like BAF chromatin remodeling complexes are essential for many aspects of neural development. Mutations in the genes encoding the core subunit Brg1/SmarcA4 or other complex components cause neurodevelopmental diseases and are associated with autism. Congenital hydrocephalus is a serious brain disorder often experienced by these patients. We report a role of Brg1 in the pathogenesis of hydrocephalus disorder. We discovered an unexpected early activity of mouse Camk2a-Cre transgene, which mediates Brg1 deletion in a subset of forebrain neurons beginning in the late embryonic stage. Brg1 deletion in these neurons led to severe congenital hydrocephalus with enlargement of the lateral ventricles and attenuation of the cerebral cortex. The Brg1-deficient mice had significantly smaller subcommissural organs and narrower Sylvian aqueducts than mice that express normal levels of Brg1. Effects were non-cell autonomous and may be responsible for the development of the congenital hydrocephalus phenotype. Our study provides evidence indicating that abnormalities in Brg1 function result in defects associated with neurodevelopmental disorders and autism.

Changes of fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the model of experimental acute hydrocephalus in rabbits

BACKGROUND

To study the integrity of white matter, we investigated the correlation between the changes in neuroradiological and morphological parameters in an animal model of acute obstructive hydrocephalus.

METHODS

Hydrocephalus was induced in New Zealand rabbits (n = 10) by stereotactic injection of kaolin into the lateral ventricles. Control animals received saline in place of kaolin (n = 10). The progression of hydrocephalus was assessed using magnetic resonance imaging. Regional fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) were measured in several white matter regions before and after the infusion of kaolin. Morphology of myelinated nerve fibers as well as of the blood-brain barrier were studied with the help of transmission electron microscopy (TEM) and light microscopy.

RESULTS

Compared with control animals, kaolin injection into the ventricles resulted in a dramatic increase in ventricular volume with compression of basal cisterns, brain shift and periventricular edema (as observed on magnetic resonance imaging [MRI]). The values of ADC in the periventricular and periaqueductal areas significantly increased in the experimental group (P < 0.05). FA decreased by a factor of 2 in the zones of periventricular, periaqueductal white matter and corpus collosum. Histological analysis demonstrated the impairment of the white matter and necrobiotic changes in the cortex. Microsctructural alterations of the myelin fibers were further proved with the help of TEM. Blood-brain barrier ultrastructure assessment showed the loss of its integrity.

CONCLUSIONS

The study demonstrated the correlation of the neuroradiological parameters with morphological changes. The abnormality of the FA and ADC parameters in the obstructive hydrocephalus represents a significant implication for the diagnostics and management of hydrocephalus in patients.

Maternal and infant factors associated with infancy-onset hydrocephalus in Washington State

OBJECTIVE

Hydrocephalus, a complex condition characterized by progressive accumulation of cerebrospinal fluid within the ventricular system of the brain, affects ∼ 6 in 10,000 infants and is heterogeneous in nature. Previous investigations of risk factors have not considered etiologic heterogeneity.

METHODS

We conducted a case-control study of 1748 children with hydrocephalus identified through birth certificate check boxes and ICD-9 codes of linked hospital discharge records through the first year of life. Control infants were identified from birth records (N = 19,700), frequency matched to cases by year of birth. Three mutually exclusive, nonexhaustive subgroups were identified: hydrocephalus associated with a neural tube defect (n = 332); prenatal-onset hydrocephalus (n = 402); and hydrocephalus associated with intracranial hemorrhage (n = 446). Within each group, we examined associations with maternal age, race/ethnicity, parity, diabetes and hypertension, and infant sex and gestation. We used logistic regression to calculate odds ratios and 95% confidence intervals.

RESULTS

Asian ethnicity was independently associated with an inverse risk of all subtypes of hydrocephalus (hydrocephalus associated with a neural tube defect: odds ratio, 0.44; 95% confidence interval, 0.23 to 0.84; prenatal-onset hydrocephalus: odds ratio, 0.47; 95% confidence interval, 0.27 to 0.83; hydrocephalus associated with intracranial hemorrhage: odds ratio, 0.59; 95% confidence interval, 0.33 to 1.07) compared with whites. Pre-existing diabetes was associated to varying degrees with all three subtypes (hydrocephalus associated with a neural tube defect: odds ratio, 1.94; 95% confidence interval, 0.61 to 6.17; prenatal-onset hydrocephalus: odds ratio, 5.20; 95% confidence interval, 2.60 to 10.40; hydrocephalus associated with intracranial hemorrhage: odds ratio, 5.26; 95% confidence intervals, 2.85 to 9.69). Hypertension had a positive association with hydrocephalus associated with intracranial hemorrhage (odds ratio, 1.91; 95% confidence interval, 1.46 to 2.52) but an inverse association with hydrocephalus associated with a neural tube defect (odds ratio, 0.59; 95% confidence interval, 0.36 to 0.98). Gestation ≤ 30 weeks was associated with all three subgroups, most notably hydrocephalus associated with intracranial hemorrhage (odds ratio, 443.56; 95% confidence intervals, 326.34 to 602.87); nearly two-thirds (64%) of hydrocephalus associated with intracranial hemorrhage infants were born ≤ 30 weeks. Male gender was independently associated only with hydrocephalus associated with intracranial hemorrhage (odds ratio, 1.82; 95% confidence interval, 1.40 to 2.39). No associations were observed with advanced or young maternal age or with parity.

CONCLUSIONS

The different risk profiles seen among these three subgroups support the biologically heterogeneous nature of infantile hydrocephalus. Future research should take specific etiologic subtypes into account.

The efficacy analysis of endoscopic third ventriculostomy in infantile hydrocephalus

Objective

To investigate the efficacy of endoscopic third ventriculostomy (ETV) for infantile hydrocephalus.

Methods

Retrospectively reviewed the 17 infantile hydrocephalus cases who were treated with ETV between July 2009 and June 2013. The study includes 17 patients (4 Han and 13 Hui) between the ages of 51 and 337 days. Five cases with encephalitis history and 2 cases with cerebral hemorrhage, with the remaining 10 cases congenital hydrocephalus. ETVs were performed for all patients with 1 case failing because the severe ventricle inflammatory adhesion, excessive exudation, and vague basilar artery.

Results

Among the 16 successful cases 7 cases improved remarkably : heads and ventricles reduced and cerebral cortexes thickening morphologically. The ventricles of the remaining cases were unchanged.

Conclusion

The ethnic minority account for the majority of the patients in this study. ETV is effective for infantile obstructive hydrocephalus.

Genetics of common malformations

Advanced technology has recently allowed us to study rare Mendelian disorders in an unprecedented manner. The same technology should allow us also to study more common malformations. Many of these are not caused by a variant in a single Mendelian gene but by interplay between series of genetic variants and exogenous influences. Likely the site from which the DNA is derived is of great importance in studying malformations as mosaicism may be much more common than earlier anticipated. Factors other than simple variants in our genomic DNA should be considered in the studies as well. Not only is recognition of someone's liability to disease important, but also determining exogenous factors involved in malformations should receive more attention as it may allow us decrease the burden of malformations in humans.