Regional ependymal upregulation of vimentin in Chiari II malformation, aqueductal stenosis, and hydromyelia

Myelomeningocele-Chiari II malformation-Neurological predictability based on fetal and postnatal magnetic resonance imaging

Objective

This systematic comparison between pre‐ and postnatal imaging findings and postnatal motor outcome assesses the reliability of MRI accuracy in the prognostication of the future long‐term (mean, 11.4 years) ambulatory status in a historic group of postnatally repaired myelomeningocele (MMC) cases.

Methods

A retrospective, single‐center study of 34 postnatally repaired MMC patients was performed. We used fetal and postnatal magnetic resonance imaging (MRI) to compare the fetal and postnatal radiological lesion level to each other and to the postnatal ambulatory level as a standard of reference and analyzed Chiari II malformation characteristics.

Results

In 13/15 (87%) and 29/31 (94%) cases, the functional level was equal to or better than the prenatal and postnatal radiological lesion level. A radiological lesion level agreement within two segments could be achieved in 13/15 (87%) patients. A worse than expected functional level occurred in cases with Myelocele (2/3 patients), coexistent crowding of the posterior fossa (2/3 patients) and/or abnormal white matter architecture, represented by callosal dysgenesis (1/3 patients). In all patients (2/2) with a radiological disagreement of more than two segments, segmentation disorders and scoliosis were observed.

Conclusion

Fetal and postnatal MRI are predictive of the long‐term ambulatory status in postnatally repaired MMC patients.

What's already known about this topic?

Fetal and postnatal magnetic resonance imaging (MRI) show a good correlation in identifying the level of the myelomeningocele (MMC) lesion.

Prenatal ultrasound (US) and fetal MRI show a comparable agreement, within two segments, in predicting the short‐term ambulatory status.

What does this study add?

Fetal and postnatal MRI have a good predictive value for the long‐term ambulatory status in patients with postnatal MMC closure.

MMC patients with worse than expected ambulatory status showed signs of vermian displacement and corpus callosum dysgenesis.

In MMC patients with spinal segmentation disorders and scoliosis, there was a major disagreement between fetal and postnatal MRI, specifically with regard to the MMC lesion level.

Clinical Notes on Chiari Malformation

Chiari malformations (CMs) are variant structural setup of cerebellum and brain stem at the craniovertebral junction. Normally the cerebellum and parts of the brain stem lie above the foramen magnum. When the part of the cerebellum and/or brainstem protrudes into the upper spinal canal through foramen magnum, it is defined as CM. Chiari malformations may develop when part of the skull is smaller than normal or misshapen, due to which the cerebellum herniates into spinal canal through foramen magnum. This compresses the cerebellum and brainstem affecting functions controlled by these parts and blocks the flow of cerebrospinal fluid that surrounds and cushions the brain and spinal cord. Chiari malformation may cause sensory loss, ataxia, weakness, nystagmus, spastic limbs to name a few. Thus, various morbid and mortal neurologic disorders result from CM. Therefore, sound and thorough knowledge of CM and its variant anatomy are essential for diagnosis and management of neurologic disorders. Therefore, review study has been carried out for updating and consolidating the knowledge of all the variations of CMs. Literature search was carried out using databases, SciELO, ScopeMed, MEDLINE, PubMed, and Wiley Online Library. Papers containing original data were selected and secondary references retrieved from bibliographies. Various terms related to CMs were used for net surfing. The knowledge will be of immense importance to neurologists and neurosurgeons to diagnose and treat the CMs and decrease the mortality associated with CM and to radiologists for correctly interpreting the magnetic resonance imaging.

Choosing an anesthetic technique in pregnant women with Arnold – Chiari malformation

We want to present the clinical case of a female patient with the asymptomatic Chiari I type malformation, without surgical correction and with concomitant epilepsy who underwent planned C-section under epidural anesthesia. A 29-year old pregnant women on the 39 week of pregnancy entered the maternity hospital for the delivery. It was decided to conduct a planned caesarean section. The epidural anesthesia with 0.75 % solution of the ropivacaine was chosen as the method of anesthesia. The patient did not receive antiepileptic treatment due to her implacable refusal. She underwent surgery and anesthesia well. On the third day after surgery, the patient suffered of a convulsive as sault, which was stopped by intravenous administration of diazepam. This article briefly describes the genetic background, classification, clinical manifestations and treatment tactics for patients with Chiari malformation and the features of C-section anesthesia in pregnant women with this pathology.

The 2016 Bernard Sachs Lecture: Timing in Morphogenesis and Genetic Gradients During Normal Development and in Malformations of the Nervous System

Nervous system development is quadradimensional. Both normal ontogenesis and developmental malformations are explained in the context of the fourth dimension, timing. Timing of the onset of either the genetic expression of a mutation or an epigenetic event that may be teratogenic is primordial in determining morphogenesis and the forms of malformations with their functional consequences. Multiple genotypes may cause similar phenotypes or a single genotype with different degrees of retained normal genetic expression may result in variable phenotypes. In this treatise, examples are presented of these principles, including both delayed and precocious maturation of processes such as synaptogenesis that may be out of synchrony with other simultaneous processes of neuronal maturation. In postzygotic somatic mosaicism, timing of onset determines not only the character but also the extent of a lesion; focal cortical dysplasia IIb and hemimegalencephaly are the same disease, both sharing activation of the mTOR pathway as the primary mechanism; the difference is timing of onset within the 33 mitotic cycles of the periventricular neuroepithelium. Genetic expression often follows gradients along the 3 axes of the neural tube. Defective gradients often can be identified by their morphological result without knowing the precise mutation. Upregulation in the vertical axis produces hyperplasia or duplication of either dorsal or ventral structures, whereas downregulation yields hypoplasia or fusion in the midline of bilateral structures. Disorders of segmentation or neuromere formation in the neural tube are increasingly recognized as another pathogenesis of cerebral dysgenesis. Our recent investigations show the participation of the U-fibre layer beneath FCD in epileptic networks because of neuronal dispersion with elaborate synaptic plexi and a barrier to deep heterotopia.

Cerebellar networks and neuropathology of cerebellar developmental disorders

The cerebellar system is a series of axonal projections and synaptic circuits as networks, similar to those of the limbic system and those subserving the propagation and spread of seizures. Three principal cerebellar networks are identified and cerebellar disease often affects components of the networks other than just the cerebellar cortex. Contemporary developmental neuropathology of the cerebellum is best considered in the context of alterations of developmental processes: embryonic segmentation and genetic gradients along the three axes of the neural tube, individual neuronal and glial cell differentiation, migration, synaptogenesis, and myelination. Precisely timed developmental processes may be delayed or precocious rhombencephalosynapsis and pontocerebellar hypoplasia exemplify opposite gradients in the horizontal axis. Chiari II malformation may be reconsidered as a disorder of segmentation rather than simply due to mechanical forces upon normally developing hindbrain structures. Cellular nodules in the roof of the fourth ventricle are heterotopia of histologically differentiated but architecturally disoriented and disorganized neurons and glial cells; they often are less mature immunocytochemically than similar cells in adjacent normal folia. Cell rests are nodules of undifferentiated neuroepithelial cells. Both are frequent in human fetuses and neonates. Axonal projections from heterotopia to adjacent cerebellar folia or nuclei are few or absent, hence these nodules are clinically silent despite neuronal differentiation.

Comparison of posterior fossa decompression with and without duraplasty for the surgical treatment of Chiari malformation type I in adult patients: A retrospective analysis of 103 patients

Chiari malformation type I (CM-I) is a congenital neurosurgical disease about the herniation of cerebellar tonsil through the foramen magnum. A variety of surgical techniques for CM-I have been used, and there is a controversy whether to use posterior fossa decompression with duraplasty (PFDD) or posterior fossa decompression without duraplasty (PFD) in CM-I patients. Here, we compared the clinical results and effectiveness of PFDD and PFD in adult patients with CM-I. The cases of 103 adult CM-I patients who underwent posterior fossa decompression with or without duraplasty from 2008 to 2014 were reviewed retrospectively. Patients were divided into 2 groups according to the surgical techniques: PFDD group (n = 70) and PFD group (n = 33). We compared the demographics, preoperative symptoms, radiographic characteristics, postoperative complications, and clinical outcomes between the PFD and PFDD patients. No statistically significant differences were found between the PFDD and PFD groups with regard to demographics, preoperative symptoms, radiographic characteristics, and clinical outcomes(P > 0.05); however, the postoperative complication aseptic meningitis occurred more frequently in the PFDD group than in the PFD group (P = 0.027). We also performed a literature review about the PFDD and PFD and made a summary of these preview studies. Our study suggests that both PFDD and PFD could achieve similar clinical outcomes for adult CM-I patients. The choice of surgical procedure should be based on the patient's condition. PFDD may lead to a higher complication rate and autologous grafts seemed to perform better than nonautologous grafts for duraplasty.

MR-based morphometry of the posterior fossa in fetuses with neural tube defects of the spine

Objectives

In cases of “spina bifida,” a detailed prenatal imaging assessment of the exact morphology of neural tube defects (NTD) is often limited. Due to the diverse clinical prognosis and prenatal treatment options, imaging parameters that support the prenatal differentiation between open and closed neural tube defects (ONTDs and CNTDs) are required. This fetal MR study aims to evaluate the clivus-supraocciput angle (CSA) and the maximum transverse diameter of the posterior fossa (TDPF) as morphometric parameters to aid in the reliable diagnosis of either ONTDs or CNTDs.

Methods

The TDPF and the CSA of 238 fetuses (20–37 GW, mean: 28.36 GW) with a normal central nervous system, 44 with ONTDS, and 13 with CNTDs (18–37 GW, mean: 24.3 GW) were retrospectively measured using T2-weighted 1.5 Tesla MR -sequences.

Results

Normal fetuses showed a significant increase in the TDPF (r = .956; p<.001) and CSA (r = .714; p<.001) with gestational age. In ONTDs the CSA was significantly smaller (p<.001) than in normal controls and CNTDs, whereas in CNTDs the CSA was not significantly smaller than in controls (p = .160). In both ONTDs and in CNTDs the TDPF was significantly different from controls (p<.001).

Conclusions

The skull base morphology in fetuses with ONTDs differs significantly from cases with CNTDs and normal controls. This is the first study to show that the CSA changes during gestation and that it is a reliable imaging biomarker to distinguish between ONTDs and CNTDs, independent of the morphology of the spinal defect.

Coexistence of Chiari 2 malformation and moyamoya syndrome in a 17-year-old girl

A 17-year-old female with Chiari 2 malformation developed cerebral infarction with angiographically typical bilateral moyamoya vessels manifesting as sudden onset of moderate left hemiparesis. Magnetic resonance imaging revealed multiple infarcts in the right frontal lobe, agenesis of the corpus callosum, upward herniation of the dorsal cerebellum, tectal beak of the midbrain, and downward herniation of the cerebellar vermis. Cerebral angiography demonstrated occlusion of the bilateral internal carotid arteries and basal moyamoya vessels. Single photon emission computed tomography showed significantly reduced regional cerebral blood flow in the right frontoparietal cortex. The cerebral vascular reactivity to acetazolamide was diminished in both cerebral hemispheres. She underwent superficial temporal artery-middle cerebral artery anastomosis combined with encephalo-myo-synangiosis on the right, and on the left 6 months later. Cerebral angiography performed 4 months after the second operation showed good patency of the bypasses and substantial collateral vessels in both cerebral hemispheres. This association may have happened by chance, and a common etiology is uncertain, but a currently undetermined genomic component might have contributed to the disease progression.

Pathogenesis of cerebral malformations in human fetuses with meningomyelocele

Background

Fetal spina bifida aperta (SBA) is characterized by a spinal meningomyelocele (MMC) and associated with cerebral pathology, such as hydrocephalus and Chiari II malformation. In various animal models, it has been suggested that a loss of ventricular lining (neuroepithelial/ependymal denudation) may trigger cerebral pathology. In fetuses with MMC, little is known about neuroepithelial/ependymal denudation and the initiating pathological events.

The objective of this study was to investigate whether neuroepithelial/ependymal denudation occurs in human fetuses and neonates with MMC, and if so, whether it is associated with the onset of hydrocephalus.

Methods

Seven fetuses and 1 neonate (16–40 week gestational age, GA) with MMC and 6 fetuses with normal cerebral development (22–41 week GA) were included in the study. Identification of fetal MMC and clinical surveillance of fetal head circumference and ventricular width was performed by ultrasound (US). After birth, MMC was confirmed by histology. We characterized hydrocephalus by increased head circumference in association with ventriculomegaly. The median time interval between fetal cerebral ultrasound and fixing tissue for histology was four days.

Results

At 16 weeks GA, we observed neuroepithelial/ependymal denudation in the aqueduct and telencephalon together with sub-cortical heterotopias in absence of hydrocephalus and/or Chiari II malformation. At 21–34 weeks GA, we observed concurrence of aqueductal neuroepithelial/ependymal denudation and progenitor cell loss with the Chiari II malformation, whereas hydrocephalus was absent. At 37–40 weeks GA, neuroepithelial/ependymal denudation coincided with Chiari II malformation and hydrocephalus. Sub-arachnoidal fibrosis at the convexity was absent in all fetuses but present in the neonate.

Conclusion

In fetal SBA, neuroepithelial/ependymal denudation in the telencephalon and the aqueduct can occur before Chiari II malformation and/or hydrocephalus. Since denuded areas cannot re-establish cell function, neuro-developmental consequences could induce permanent cerebral pathology.

Natriuretic peptides, but not nitric oxide donors, elevate levels of cytosolic guanosine 3',5'-cyclic monophosphate in ependymal cells ex vivo

Atrial natriuretic peptide-(1-28) (ANP), brain natriuretic peptide-(1-32) (BNP) and C-Type natriuretic polypeptide (CNP) occur in the brain, are concentrated in the anteroventral area of the third cerebral ventricle and participate in the regulation of body fluid homeostasis. The ventricles of the mammalian brain are lined by a continuous monolayered epithelium of polyciliated ependymal cells. In the adult rat, the ependymocytes continue to express the intermediate filament vimentin, but do not contain glial fibrillary acidic protein. Ependymal functions are poorly understood, but may extend to osmoregulation and volume sensing. Ependymal cells possess receptors for the natriuretic peptides, and in cell culture respond to them with an increase in their cyclic GMP content. In this study, a cyclic GMP-specific antibody was employed together with an ex vivo brain slice system to assess the ependymal response to ANP, BNP and CNP under close to life-like conditions. While ANP in concentrations of 0.1 nM and 1 nM had no effect, at concentrations of 10nM and 100 nM it increased ependymal cyclic GMP levels in a concentration-dependent manner. The other natriuretic peptides BNP, and CNP, also increased the cyclic GMP content of ependymocytes, while nitric oxide (NO) donors had no effect. However, in contrast to the natriuretic peptides, the NO donors elevated the level of cyclic GMP in the brain parenchyma below the ependymal layer.

Extensive hydromyelia

Hydromyelia is frequently associated with dissociated sensory loss, scoliosis, and upper limb weakness. This report describes the case of a 9-year old male with an extensive hydromyelia associated with a spinal cord tumor and an oligosymptomatic clinical presentation.

Ependymal Denudation and Alterations of the Subventricular Zone Occur in Human Fetuses With a Moderate Communicating Hydrocephalus

In mutant rodents, ependymal denudation occurs early in fetal life, preceding the onset of a communicating hydrocephalus, and is a key event in the etiology of this disease. The present investigation was designed to obtain evidence whether or not ependymal denudation occurs in 16- to 40-week-old human fetuses developing a communicating hydrocephalus (n = 8) as compared to fetuses of similar ages with no neuropathologic alterations (n = 15). Sections through the walls of the cerebral aqueduct and lateral ventricles were processed for lectin binding and immunocytochemistry using antibodies against ependyma, astroglia, neuroblasts, and macrophages markers. Anticaveolin was used as a functional marker of the fetal ependyma. The structural and functional molecular markers are differentially expressed throughout the differentiation of the human fetal ependyma. Denudation of the ependyma of the aqueduct and lateral ventricles occurred in all fetuses developing a communicating hydrocephalus, including the youngest ones studied. The denuded surface area increased in parallel with the fetus age. The possibility is advanced that in many or most cases of human fetal hydrocephalus there is a common defect at the ependymal cell lineage leading to ependymal detachment. Evidence was obtained that in hydrocephalic human fetuses a process to repair the denuded areas takes place during the fetal life. In hydrocephalic fetuses, detachment of the ependyma of the lateral ventricles resulted in the (i) loss of the germinal ependymal zone, (ii) disorganization of the subventricular zone and, (iii) abnormal migration of neuroblasts into the ventricular cavity. Thus, detachment of the ependymal layer in hydrocephalic fetuses would not only be associated with the pathogenesis of hydrocephalus but also to abnormal neurogenesis.