Neuropathologic research strategies in holoprosencephaly

Transitory and Vestigial Structures of the Developing Human Nervous System

As with many body organs, the human central nervous system contains many structures and cavities that may have had functions in embryonic and fetal life but are vestigial or atrophic at maturity. Examples are the septum pellucidum, remnants of the lamina terminalis, Cajal-Retzius neurons, induseum griseum, habenula, and accessory olfactory bulb. Other structures are transitory in fetal or early postnatal life, disappearing from the mature brain. Examples are the neural crest, subpial granular glial layer of Brun over cerebral cortex, radial glial cells, and subplate zone of cerebral cortex. At times persistent fetal structures that do not regress may cause neurological problems or indicate a pathologic condition, such as Blake pouch cyst. Transitory structures thus can become vestigial. Examples are an excessively wide cavum septi pellucidi, suprapineal recess of the third ventricle, trigeminal artery of the posterior fossa circulation, and hyaloid ocular artery. Arrested maturation might be considered another aspect of vestigial structure. An example is the persistent microcolumnar cortical architecture in focal cortical dysplasia type Ia, in cortical zones of chronic fetal ischemia, and in some metabolic/genetic congenital encephalopathies. Some transitory structures in human brain are normal adult structures in lower vertebrates. Recognition of transitory and vestigial structures by fetal or postnatal neuroimaging and neuropathologically enables better understanding of cerebral ontogenesis and avoids misinterpretations.

Excitatory/Inhibitory Synaptic Ratios in Polymicrogyria and Down Syndrome Help Explain Epileptogenesis in Malformations

BACKGROUND

The ratio between excitatory (glutamatergic) and inhibitory (GABAergic) inputs into maturing individual cortical neurons influences their epileptic potential. Structural factors during development that alter synaptic inputs can be demonstrated neuropathologically. Increased mitochondrial activity identifies neurons with excessive discharge rates.

METHODS

This study focuses on the neuropathological examinaion of surgical resections for epilepsy and at autopsy, in fetuses, infants, and children, using immunocytochemical markers, and electron microscopy in selected cases. Polymicrogyria and Down syndrome are highlighted.

RESULTS

Factors influencing afferent synaptic ratios include the following: (1) synaptic short-circuitry in fused molecular zones of adjacent gyri (polymicrogyria); (2) impaired development of dendritic spines decreasing excitation (Down syndrome); (3) extracellular keratan sulfate proteoglycan binding to somatic membranes but not dendritic spines may be focally diminished (cerebral atrophy, schizencephaly, lissencephaly, polymicrogyria) or augmented, ensheathing individual axons (holoprosencephaly), or acting as a barrier to axonal passage in the U-fiber layer. If keratan is diminished, glutamate receptors on the neuronal soma enable ectopic axosomatic excitatory synapses to form; (4) dysplastic, megalocytic neurons and balloon cells in mammalian target of rapamycin disorders; (5) satellitosis of glial cells displacing axosomatic synapses; (6) peri-neuronal inflammation (tuberous sclerosis) and heat-shock proteins.

CONCLUSIONS

Synaptic ratio of excitatory/inhibitory afferents is a major fundamental basis of epileptogenesis at the neuronal level. Neuropathology can demonstrate subcellular changes that help explain either epilepsy or lack of seizures in immature brains. Synaptic ratios in malformations influence postnatal epileptogenesis. Single neurons can be hypermetabolic and potentially epileptogenic.

Fetal neurology: Principles and practice with a life-course perspective

Clinical service, educational, and research components of a fetal/neonatal neurology program are anchored by the disciplines of developmental origins of health and disease and life-course science as programmatic principles. Prenatal participation provides perspectives on maternal, fetal, and placental contributions to health or disease for fetal and subsequent neonatal neurology consultations. This program also provides an early-life diagnostic perspective for neurologic specialties concerned with brain health and disease throughout childhood and adulthood. Animal models and birth cohort studies have demonstrated how the science of epigenetics helps to understand gene-environment interactions to better predict brain health or disease. Fetal neurology consultations provide important diagnostic contributions during critical or sensitive periods of brain development when future neurotherapeutic interventions will maximize adaptive neuroplasticity. Age-specific normative neuroinformatics databases that employ computer-based strategies to integrate clinical/demographic, neuroimaging, neurophysiologic, and genetic datasets will more accurately identify either symptomatic patients or those at risk for brain disorders who would benefit from preventive, rescue, or reparative treatment choices throughout the life span.

Nosip functions during vertebrate eye and cranial cartilage development

BACKGROUND

The nitric oxide synthase interacting protein (Nosip) has been associated with diverse human diseases including psychological disorders. In line, early neurogenesis of mouse and Xenopus is impaired upon Nosip deficiency. Nosip knockout mice show craniofacial defects and the down-regulation of Nosip in the mouse and Xenopus leads to microcephaly. Until now, the exact underlying molecular mechanisms of these malformations were still unknown.

RESULTS

Here, we show that nosip is expressed in the developing ocular system as well as the anterior neural crest cells of Xenopus laevis. Furthermore, Nosip inhibition causes severe defects in eye formation in the mouse and Xenopus. Retinal lamination as well as dorso-ventral patterning of the retina were affected in Nosip-depleted Xenopus embryos. Marker gene analysis using rax, pax6 and otx2 reveals an interference with the eye field induction and differentiation. A closer look on Nosip-deficient Xenopus embryos furthermore reveals disrupted cranial cartilage structures and an inhibition of anterior neural crest cell induction and migration shown by twist, snai2, and egr2. Moreover, foxc1 as downstream factor of retinoic acid signalling is affected upon Nosip deficiency.

CONCLUSIONS

Nosip is a crucial factor for the development of anterior neural tissue such the eyes and neural crest cells. Developmental Dynamics 247:1070-1082, 2018. © 2018 Wiley Periodicals, Inc.

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.

Neurocristopathies: New insights 150 years after the neural crest discovery

The neural crest (NC) is a transient, multipotent and migratory cell population that generates an astonishingly diverse array of cell types during vertebrate development. These cells, which originate from the ectoderm in a region lateral to the neural plate in the neural fold, give rise to neurons, glia, melanocytes, chondrocytes, smooth muscle cells, odontoblasts and neuroendocrine cells, among others. Neurocristopathies (NCP) are a class of pathologies occurring in vertebrates, especially in humans that result from the abnormal specification, migration, differentiation or death of neural crest cells during embryonic development. Various pigment, skin, thyroid and hearing disorders, craniofacial and heart abnormalities, malfunctions of the digestive tract and tumors can also be considered as neurocristopathies. In this review we revisit the current classification and propose a new way to classify NCP based on the embryonic origin of the affected tissues, on recent findings regarding the molecular mechanisms that drive NC formation, and on the increased complexity of current molecular embryology techniques.

Telencephalic Flexure and Malformations of the Lateral Cerebral (Sylvian) Fissure

After sagittal division of the prosencephalon at 4.5 weeks of gestation, the early fetal cerebral hemisphere bends or rotates posteroventrally from seven weeks of gestation. The posterior pole of the telencephalon thus becomes not the occipital but the temporal lobe as the telencephalic flexure forms the operculum and finally the lateral cerebral or Sylvian fissure. The ventral part is infolded to become the insula. The frontal and temporal lips of the Sylvian fissure, as well as the insula, all derive from the ventral margin of the primitive telencephalon, hence may be influenced by genetic mutations with a ventrodorsal gradient of expression. The telencephalic flexure also contributes to a shift of the hippocampus from a dorsal to a ventral position, the early rostral pole of the hippocampus becoming caudal and dorsal becoming ventral. The occipital horn is the most recent recess of the lateral ventricle, hence most vulnerable to anatomic variations that affect the calcarine fissure. Many major malformations include lack of telencephalic flexure (holoprosencephaly, extreme micrencephaly) or dysplastic Sylvian fissure (lissencephalies, hemimegalencephaly, schizencephaly). Although fissures and sulci are genetically programmed, mechanical forces of growth and volume expansion are proposed to be mainly extrinsic (including ventricles) for fissures and intrinsic for sulci. In fetal hydrocephalus, the telencephalic flexure is less affected because ventricular dilatation occurs later in gestation. Flexures can be detected prenatally by ultrasound and fetal magnetic resonance imaging and should be described neuropathologically in cerebral malformations.

Precocious synapses in 13.5-week fetal holoprosencephalic cortex and cyclopean retina

BACKGROUND

Genetic programming of cerebral development involves tissue morphogenesis and also timing of developmental processes. Precocious synaptogenesis in the neocortical plate was previously demonstrated in 5 of 6 fetuses of 20-31 weeks gestation.

MATERIALS AND METHODS

Neuropathological examination was performed of a 13-week-5-day fetus with trisomy-13, a lobar holoprosencephaly, hydrocephalus, cyclopia and absence of ears. Immunocytochemical demonstration of the synaptic vesicle protein synaptophysin was performed in the brain and retina, along with other neuronal markers.

RESULTS

Synaptophysin reactivity in the cortical plate was patchy and precocious. Radial glial fibres, demonstrated by vimentin, were oriented parallel to the cortical plate rather than perpendicular, probably because of hydrocephalus. A corpus striatum was not identified, but the poorly formed thalamus exhibited synaptophysin reactivity around many neurones. The cyclopean eye had ocular features of maturational delay including persistent hyaloid artery; ganglion cells were reduced in number, but retinal synaptophysin reactivity was paradoxically precocious.

CONCLUSIONS

Holoprosencephaly exhibits abnormal patchy synapse distribution in the neocortex and retina; synaptogenesis was precocious, as we previously described in older fetuses. Too soon an onset of synapse formation may promote early epileptic circuitry, leading to severe infantile epilepsies postnatally. The visual system is the last of the special sensory systems to mature, yet in this case showed too early synapse formation. In HPE, cyclopia and in trisomy 13, total absence of external ears has not been reported; it results from faulty craniofacial induction by neural crest.

Clinical characteristics of central diabetes insipidus in Taiwanese children

BACKGROUND/PURPOSE

Data on the clinical features of children with central diabetes insipidus (CDI) are lacking in Taiwan. This study investigated the clinical manifestations and etiology of CDI in Taiwanese children.

METHODS

From 1983 to 2012, 62 children with permanent diabetes insipidus were enrolled in the study. They were diagnosed at the Department of Pediatrics of National Taiwan University Hospital. Their medical records were thoroughly reviewed and their clinical symptoms and signs, laboratory data, and etiologies were analyzed.

RESULTS

The patients' median age at diagnosis was 10 years and the median interval between initial manifestations and diagnosis was 0.5 years. The most common symptoms and signs were polyuria, polydipsia, nocturia, and growth retardation. Most patients had low urine osmolality and elevated plasma osmolality on diagnosis. Absence of a posterior pituitary hyperintense signal and thickening of the pituitary stalk were common findings on magnetic resonance imaging. Approximately 80% of the patients had anterior pituitary hormone deficiency and all patients had growth hormone deficiency. Approximately 60% of patients had intracranial lesions, the most common causes of which were germ cell tumor and Langerhans cell histiocytosis. Two patients were initially believed to have idiopathic CDI but intracranial lesions were detected during the follow-up period.

CONCLUSION

Because a delayed diagnosis of CDI is common in Taiwanese children, a high index of suspicion is important. The underlying etiology of CDI in children may not initially be obvious. Long-term surveillance is therefore necessary, especially for the early detection of evolving treatable intracranial lesions.

Radial microcolumnar cortical architecture: maturational arrest or cortical dysplasia?

The fetal neocortical plate, from initiation of radial migration at 5 weeks' gestation until midgestation, exhibits radial microcolumnar architecture. Horizontal histologic layering or lamination becomes superimposed in the second half of gestation, although residua of the columnar pattern persist postnatally, particularly where the cortex bends: at the crowns of gyri and in the depths of sulci. Columnar architecture of the cortical plate in the first half of gestation mostly results from radial migration of neuroblasts, but the Cajal-Retzius neurons and GABAergic neuroblasts from tangential migration regulate a transition to horizontal lamination of the mature cortex. In children and adults, prominent columnar architecture is a feature of many focal cortical dysplasias and is now recognized as a distinctive pattern of focal cortical dysplasias in the new International League Against Epilepsy classification. It also occurs, however, in many genetic syndromes and chromosomopathic conditions, including 22q12 deletions (DiGeorge syndrome), in several primary cerebral malformations, in the contralateral cingulate gyrus in hemimegalencephaly, in cortical tubers of tuberous sclerosis, in the margins of porencephalic cysts resulting from prenatal infarcts, and in some inborn metabolic defects such as methylmalonic acidemia. Synaptophysin demonstrates both radial and horizontal lamination of synaptic layers. Persistent fetal cortical architecture is potentially epileptogenic. We conclude that columnar architecture is a maturational arrest in histogenesis of the neocortical plate and becomes a component of cortical dysplasia in the perinatal period. An initially physiological process thus becomes pathologic by virtue of advancing age, but traces of it persist in normal mature brains. It also occurs in many genetic and inborn metabolic diseases and after acquired ischemic insults of the fetal brain.

Neuroembryology and brain malformations: an overview

Modern neuroembryology integrates descriptive morphogenesis with more recent insight into molecular genetic programing and data enabled by cell-specific tissue markers that further define histogenesis. Maturation of individual neurons involves the development of energy pumps to maintain membrane excitability, ion channels, and membrane receptors. Most malformations of the nervous system are best understood in the context of aberrations of normal developmental processes that result in abnormal structure and function. Early malformations usually are disorders of genetic expression along gradients of the three axes of the neural tube, defective segmentation, or mixed lineages of individual cells. Later disorders mainly involve cellular migrations, axonal pathfinding, synaptogenesis, and myelination. Advances in neuroimaging now enable the diagnosis of many malformations in utero, at birth, or in early infancy in the living patient by abnormal macroscopic form of the brain. These images are complimented by modern neuropathological methods that disclose microscopic, immunocytochemical, and subcellular details beyond the resolution of MRI. Correlations may be made of both normal and abnormal ontogenesis with clinical neurological and EEG maturation in the preterm or term neonate for a better understanding of perinatal neurological disease. Precision in terminology is a key to scientific communication.

Seckel syndrome accompanied by semilobar holoprosencephaly and arthrogryposis

Seckel syndrome is a rare autosomal recessive disorder, and its characteristic features include prenatal and postnatal growth retardation, microcephaly, and "bird-like" face with prominent, beak-like nose and micrognathia. Additional abnormalities were described in the cardiovascular, hematopoietic, endocrine, and central nervous systems. We present the magnetic resonance imaging findings of a neonate with Seckel syndrome accompanied by semilobar holoprosencephaly and arthrogryposis. Major brain malformations may be associated with Seckel syndrome. Imaging studies should be performed to determine any central nervous system abnormalities. Considering the basic defect of neuroblast proliferation in Seckel syndrome, neuronal migration disorders should be sought in these patients.

Perfil de habilidades do desenvolvimento em crianças com holoprosencefalia e holoprosencefalia like

OBJETIVO: investigar e comparar o desempenho nas habilidades relacionadas ao desenvolvimento motor, cognitivo, linguístico, de socialização e autocuidados de indivíduos com holoprosencefalia e com holoprosencefalia-like. MÉTODO: participaram deste estudo 20 indivíduos com diagnóstico de holoprosencefalia, na faixa etária de 18 a 72 meses, de ambos os sexos, divididos em 2 grupos. O grupo 1 (G1) composto por 12 indivíduos com sinais clínicos do espectro da holoprosencefalia, e o grupo 2 (G2) com holoprosencefalia-like composto por 8 indivíduos com sinais clínicos do espectro da holoprosencefalia-like. A coleta de dados foi realizada por meio da aplicação do Inventário Portage Operacionalizado que avalia as áreas alvos deste estudo. Para a análise estatística utilizou-se análise descritiva da mediana e dos valores mínimos e máximos e foi aplicado o teste estatístico de Mann Whitney (< 0,05% para significância). RESULTADOS: os grupos 1 e 2 apresentaram alterações em todas as áreas do desenvolvimento avaliadas. Entretanto, os indivíduos do G1, com holoprosencefalia apresentaram maiores comprometimentos nas habilidades: motora, cognitiva, de linguagem, de socialização e autocuidados, quanto comparados aos indivíduos do G2, com holoprosencefalia-like. CONCLUSÃO: o desempenho nas áreas motoras, cognitivas, de linguagem, de socialização e autocuidados de indivíduos com holoprosencefalia e holoprosencefalia-like foi aquém do esperado, principalmente naqueles indivíduos com holoprosencefalia, que se justifica pelo maior comprometimento no sistema nervoso central. A natureza destas alterações pode estar associada ao universo de alterações neurológicas e craniofaciais descritas nestes quadros clínicos e também à influência do ambiente social.

Holoprosencephaly in hungary: birth prevalence and clinical spectrum

A retrospective population based survey of patients born with holoprosencephaly in South-Eastern Hungary between July 1, 1992 and June 30, 2006 was performed. All live birth cases with craniofacial and non-craniofacial abnormalities were included in the study. A total of 9 patients (5 boys and 4 girls) were found with holoprosencephaly among 185 486 live births, which correspond to a birth prevalence of 0.49 per 10,000 live births (95% confidence interval [CI]: 0.17-0.80). These figures were similar to those ones found in New York State and several European regions. In our series one newborn had trisomy 13. Eight patients did not have chromosomal abnormalities on routine testing, 4 of them had craniofacial abnormalities only and another 4 showed non-craniofacial anomalies as well. Three patients died in the neonatal period and another one in childhood. Patients surviving the neonatal period had intellectual and motor handicap, and epilepsy.

Clinical features and outcomes of holoprosencephaly in Korea

The clinical spectrum of holoprosencephaly is broad, and its etiology is heterogeneous. To investigate the clinical spectrum of holoprosencephaly in Korea, we performed a database analysis of 55 cases of holoprosencephaly, including 12 diagnosed postnatally, all from a single institution. The 55 patients were categorized into several types: 37 alobar, eight semilobar, eight lobar, and two middle interhemispheric variant. Associated brain (41.8%) and craniofacial (74.5%) features varied substantially. Of 40 patients studied according to karyotype, chromosomal aberrations were detected in 18 (45.0%). Twenty-seven (49.1%) patients, diagnosed postnatally, exhibited milder types of holoprosencephaly and less profound craniofacial malformations than in prenatal diagnoses. Moreover, in postnatally diagnosed patients, the subgroup surviving longer than 1 month also exhibited a milder holoprosencephaly type and lower incidence of associated craniofacial malformations. The most frequent clinical signs in living children with holoprosencephaly included microcephaly, global developmental delay, and seizures. Holoprosencephaly represents a heterogeneous entity with different clinical manifestations and etiologies. A high index of suspicion, coupled with appropriate imaging studies, can enable accurate diagnoses and prognoses of holoprosencephaly.

Wiring Olfaction: The Cellular and Molecular Mechanisms that Guide the Development of Synaptic Connections from the Nose to the Cortex

Within the central nervous system, the olfactory system fascinates by its developmental and physiological particularities, and is one of the most studied models to understand the mechanisms underlying the guidance of growing axons to their appropriate targets. A constellation of contact-mediated (laminins, CAMs, ephrins, etc.) and secreted mechanisms (semaphorins, slits, growth factors, etc.) are known to play different roles in the establishment of synaptic interactions between the olfactory epithelium, olfactory bulb (OB) and olfactory cortex. Specific mechanisms of this system (including the amazing family of about 1000 different olfactory receptors) have been also proposed. In the last years, different reviews have focused in partial sights, specially in the mechanisms involved in the formation of the olfactory nerve, but a detailed review of the mechanisms implicated in the development of the connections among the different olfactory structures (olfactory epithelium, OB, olfactory cortex) remains to be written. In the present work, we afford this systematic review: the different cellular and molecular mechanisms which rule the formation of the olfactory nerve, the lateral olfactory tract and the intracortical connections, as well as the few data available regarding the accessory olfactory system. These mechanisms are compared, and the implications of the differences and similarities discussed in this fundamental scenario of ontogeny.

A novel role for zebrafish zic2a during forebrain development

Patterns of transcription factor expression establish a blueprint for the vertebrate forebrain early in embryogenesis. In the future diencephalon, several genes with patterned expression have been identified, yet their specific functions and interactions between them are not well understood. We have uncovered a crucial role for one such gene, zic2a, during formation of the anterior diencephalon in zebrafish. We show that zic2a is required for transcription of the prethalamic markers arx and dlx2a. This function is required during early steps of prethalamic development, soon after its specification. zic genes are evolutionarily related to glis, transcription factors that mediate hedgehog signaling. Intriguingly, the hedgehog signaling pathway also acts to promote development of the prethalamus. We asked if zic2a interacts with hedgehog signaling in the context of forebrain development in zebrafish. Our data show that hedgehog signaling and zic2a function at different times, and therefore act in parallel pathways during forebrain development. Taken together, our results identify Zic2a as a novel regulator of prethalamic development, and show that it functions independently of hedgehog signaling.

Holoprosencephaly with neurogenic hypernatremia: a new case

BACKGROUND

Holoprosencephaly (HPE) is the most common developmental defect of the forebrain and mid-face in humans. It is a disorder of neural induction in which a genetic programming defect results in noncleavage of the forebrain in the sagittal plane and variable hypoplasia of paramedian structures. It occurs in 5-12/10,000 live births. Clinically, there is a nearly continuous spectrum of malformations consistent with HPE. Endocrinopathies, such as diabetes insipidus, hypothyroidism, hypocorticism, and growth hormone deficiency, are frequently associated with HPE. Seizures may occur.

CASE REPORT

We report a new case of semilobar-HPE complicated by neurogenic hypernatremia and no signs of dehydration in a child with microcephaly, spasticity, mental and psychomotor retardation, frontal bones hypoplasia, and mild facial dysmorphism.

A case of partial 14q- with facial features of holoprosencephaly and hydranencephaly

We report a rare case of facial features of holoprosencephaly associated with hydranencephaly, with a de novo proximal interstitial deletion of the long arm of chromosome 14, specifically, del(14)(q13q21). She was born at 37 weeks of gestation and transferred to our institution at 3 years of age. The patient had midline facial anomalies consisting of cleft palate, defective nasal septum, and hypotelorism, together with endocrine abnormalities such as diabetes insipidus and hypothyroidism. Cranial computed tomography revealed the near-total loss of all cerebral tissue, with a frontal part of the cerebral falx lacking. None of the few reports of holoprosencephaly with 14q- chromosomal abnormality describe holoprosencephaly in association with hydranencephaly. The partial deletion of chromosome 14, del(14)(q13q21), may underlie the association of facial features of holoprosencephaly and hydranencephaly.

Acutely and retrospectively diagnosed perinatal stroke: a population-based study

BACKGROUND AND PURPOSE

There are not very many epidemiological studies on perinatal stroke, and many authors suggest that this may be an underdiagnosed condition. The aim of the study was to estimate the incidence of perinatal arterial ischemic and hemorrhagic stroke in Estonia, to study the first clinical signs and to identify possible differences in predisposing factors and outcome between acutely and retrospectively diagnosed cases of perinatal stroke.

METHODS

A retro- and prospective study of acutely (within the first month) and retrospectively diagnosed ischemic and hemorrhagic cases of perinatal stroke was conducted in a children population born in the eastern and southern regions of Estonia during the years 1994 to 2003. Patients were identified from a pilot study, hospital records, and an inquiry of child neurologists and general practitioners. The diagnosis was confirmed in 38 (12 were diagnosed acutely and 26 retrospectively) cases by neuroradiology (MRI or CT).

RESULTS

The incidence rate of perinatal stroke in Estonia is 63 per 100,000 live births. Main clinical findings in the neonatal period were seizures, abnormalities of muscular tone, and disturbed level of alertness. Previously identified risk factors occurred in 32% of cases. Children with early diagnosis had more often adverse events during pregnancy and delivery (P<0.05) and developed more severe stage of hemiparesis compared with children with late diagnosis (P<0.05).

CONCLUSIONS

The incidence rate of 63 per 100,000 live birth is higher than previously reported. Detailed analysis of the first signs of perinatal stroke may improve the early diagnostics of perinatal stroke.

Links between abnormal brain structure and cognition in holoprosencephaly

Converging information on medical issues, motor ability, and cognitive outcomes is essential when addressing long-term clinical management in children with holoprosencephaly. This study considered whether adding more informative structural indices to classic holoprosencephaly categories would increase prediction of cognitive outcomes. Forty-two children with holoprosencephaly were examined to determine the association of deep gray nuclei abnormalities with cognitive abilities and the effect of motor skill deficits on cognitive performance. Additionally, a cognitive profile was described using the Carter Neurocognitive Assessment, an experimental diagnostic instrument designed specifically for young children with severe neurodevelopmental dysfunction. Findings indicated that nonseparation of the deep gray nuclei was significantly associated with the cognitive construct of vocal communication, but not with the cognitive constructs of social awareness, visual attention, or auditory comprehension. Importantly, motor skill deficits did not significantly affect performance on the Carter Neurocognitive Assessment. This study is the first investigation to provide a descriptive overview of specific cognitive skills in this group of children. The results also strongly suggest that this feature of the brain's structure does not predict all aspects of neurodevelopmental function. These findings contribute a critical component to the growing body of knowledge regarding the medical and clinical outcomes of children with holoprosencephaly.

Differential regulation of the zebrafish orthopedia 1 gene during fate determination of diencephalic neurons

BACKGROUND

The homeodomain transcription factor Orthopedia (Otp) is essential in restricting the fate of multiple classes of secreting neurons in the neuroendocrine hypothalamus of vertebrates. However, there is little information on the intercellular factors that regulate Otp expression during development.

RESULTS

Here, we identified two otp orthologues in zebrafish (otp1 and otp2) and explored otp1 in the context of the morphogenetic pathways that specify neuroectodermal regions. During forebrain development, otp1 is expressed in anterior groups of diencephalic cells, positioned in the preoptic area (PO) (anterior alar plate) and the posterior tuberculum (PT) (posterior basal plate). The latter structure is characterized by Tyrosine Hydroxylase (TH)-positive cells, suggesting a role for otp1 in the lineage restriction of catecholaminergic (CA) neurons. Disruptions of Hedgehog (HH) and Fibroblast Growth Factor (FGF) pathways point to the ability of SHH protein to trigger otp1 expression in PO presumptive neuroblasts, with the attenuating effect of Dzip1 and FGF8. In addition, our data disclose otp1 as a determinant of CA neurons in the PT, where otp1 activity is strictly dependent on Nodal signaling and it is not responsive to SHH and FGF.

CONCLUSION

In this study, we pinpoint the evolutionary importance of otp1 transcription factor in cell states of the diencephalon anlage and early neuronal progenitors. Furthermore, our data indicate that morphogenetic mechanisms differentially regulate otp1 expression in alar and basal plates.

Neuroimaging in cerebral palsy: Patterns of brain dysgenesis and injury

Despite advances in obstetric and neonatal care, the overall prevalence of cerebral palsy has remained stable, supporting the belief that pathogenesis is primarily due to prenatal brain dysgenesis and injury. Neuroimaging studies have consistently shown abnormalities in 70% to 90% of affected children, facilitating clinical classification into groups with early brain malformations, white-matter injury, neonatal encephalopathies, and a heterogeneous group of postnatally acquired disorders. White-matter injury, well seen on conventional magnetic resonance imaging (MRI), is the leading cause of cerebral palsy in children born preterm. As many as 20% of very low birthweight infants have cystic and/or diffuse white-matter injury, termed periventricular leukomalacia, with evidence of associated pathology in other cortical and subcortical structures. In the group with acute, term perinatal pathology, a variety of imaging modalities, in addition to MRI, have diagnostic utility. In general, when added to conventional MRI, advanced techniques, such as diffusion tensor imaging, diffusion-weighted imaging, and magnetic resonance spectroscopy, provide a more complete picture of structural and functional brain abnormalities. The results have led to improved understanding of pathogenesis, especially in regard to periventricular leukomalacia and hypoxic-ischemic encephalopathy. This information might lead to interventions preventing brain injury in preterm infants and asphyxiated term newborns.

Endocrine disorders associated with holoprosencephaly

OBJECTIVE

To investigate the incidence of endocrinopathies in holoprosencephaly (HPE) and correlate the severity of the endocrinopathies with the neuroanatomic abnormalities.

STUDY DESIGN

We reviewed the histories and medical records of 117 children with HPE for endocrinopathies and related treatments. Neuroimaging studies were graded for severity of HPE, hypothalamus non-separation, and pituitary abnormalities.

RESULTS

Diabetes insipidus (DI) occurred in 70% of patients with classic HPE. The severity of the DI correlated with the grade of HPE and hypothalamic non-separation (p < 0.0001). Anterior pituitary dysfunctions were much less common. Hypothyroidism was identified in 11% of patients, hypocorticism in 7%, and growth hormone deficiency in 5%. Only one patient with middle interhemispheric variant of holoprosencephaly (MIH) had any of these disorders.

CONCLUSIONS

Patients with HPE have a high incidence of DI that may be related to the failure of cleavage of hypothalamic nuclei. Anterior pituitary dysfunctions are much less common than DI.

Embryology of the neural crest: its inductive role in the neurocutaneous syndromes

Neural crest cells are first recognized at the lateral margin of the neural placode shortly after gastrulation, although they are not committed to their diverse fates until later. After dorsal closure of the neural tube, neural crest cells separate and migrate throughout the embryo to form many structures of ectodermal origin (eg, dorsal root and autonomic ganglia, peripheral nerve sheaths) and mesodermal origin (eg, blood vessels, melanocytes, adipose tissue, membranous bone, connective tissue, most of the ocular globe). Terminal differentiation occurs after migration is complete. Three regions of the neural tube generate neural crest: rhombencephalon, mesencephalon, and prosencephalon, each with a different migratory pattern. The most important genes promoting neural crest differentiation and migration are those with a dorsalizing influence in the vertical axis of the neural tube (eg, PAX3, BMP4, ZIC2), some segmentation genes (eg, WNT1), genes that inhibit neural crest (eg, EGR2), and neural crest-specific differentiating genes (eg, SLUG, SOX10). In the neurocutaneous syndromes, diverse features result from abnormal neural crest differentiation, providing a more encompassing embryologic basis for these disorders than the traditional view that these syndromes are somehow related to skin and brain because both are ectodermal derivatives. Abnormal angiogenesis, areas of abnormal pigmentation that sometimes follow the lines of Blashko, nerve sheath proliferations, disorders of chromaffin tissue, lipomes and benign and malignant tumors are frequent features. Many defective genes in neurocutaneous syndromes have an additional function as tumor suppressors. Interactions between genes associated with these disorders and others essential to neural crest formation, migration, and differentiation, are a likely molecular genetic basis for these diseases. The craniofacial abnormalities associated with many cerebral malformations and cutaneous lesions in some neurocutaneous syndromes emphasize an important inductive role of the neural tube in the development of non-neural tissues, mediated through neural crest.

Does asymptomatic septal agenesis exist? A review of 34 cases

BACKGROUND

Primary septal agenesis (PSA) is a rare brain malformation that can be isolated or part of developmental brain abnormalities (holoprosencephaly, septo-optic dysplasia or cortical malformation). Such associated malformation can be subtle, leading to difficulties in the prenatal management of PSA. Moreover, the neurological prognosis of isolated PSA remains debatable.

OBJECTIVE

The aims of the study were to specify the patterns and frequency of brain malformations associated with septal agenesis (SA), to identify the clinical prognosis, and to discuss the aetiology of PSA with the new insights provided by molecular genetics.

MATERIALS AND METHODS

The study consisted of a 14-year retrospective review of brain MRI in 34 patients having PSA (mean age, 5 years). Chiasm and optic nerves were not evaluated. Post-hydrocephalus SA or incomplete data were excluded. The clinical data were correlated to the MRI patterns.

RESULTS

The study disclosed 82.5% associated lesions with MRI (28/34): 11 neuronal migration disorders, 9 holoprosencephalies (HP), 7 pituitary stalk interruptions, 1 corpus callosum partial agenesis; 17.5% (6/34) of cases were apparently isolated PAS. Clinically, the patients had motor dysfunction in 68% (23/34), mental retardation in 65% (22/34), blindness in 24% (8/34), endocrinological defects in 21% (7/34) and epilepsy in 18% (6/34) of cases. Nine percent of patients (3/34) were neurologically normal (including one with scoliosis and two infants younger than 2 years at the last follow-up). Patients with bilateral cortical anomalies and HP (even if mild) had the worst neurological prognosis. A severe motor impairment was present without evidence of hemispheric anomaly in 12% of patients (4/34). Interestingly, the frontal lobes were involved in 90% of cortical anomalies and HP, supporting the malformative aetiology of PSA.

CONCLUSIONS

PSA rarely appears isolated and severe psychomotor impairment may occur in apparently isolated forms. These unfavourable results should be highlighted and need to be confirmed by a prospective study.

The role of Zic genes in neural development

The Zic family of zinc-finger proteins plays a crucial role in neural development. Zic genes are vertebrate homologs of odd-paired, the Drosophila pair-rule gene. Their gene products have zinc-finger domains similar to those of Gli proteins, which act as transcriptional regulators in hedgehog signaling. Recent studies of human, mouse, frog, fish and ascidian Zic homologs have provided evidence that Zic genes are involved in a variety of developmental processes, including neurogenesis, myogenesis, skeletal patterning, and left-right axis establishment. Zic genes appear to have multiple roles in neural development. They control the initial phase during which ectoderm differentiates into neuroectoderm, and they may act as bridges between secreted neural tissue induction signals and the basic-helix-loop-helix class of neurogenesis-inducing transcriptional regulatory factors. Studies of loss-of-function mutations with differing Zic gene subtypes show that the Zic family of genes controls the process of neurulation. Mutations result in neural tube defects, which are seen at different rostrocaudal levels depending on which Zic gene subtype has been affected. Development of holoprosencephaly, forebrain anomalies, and cerebellar dysgenesis indicate that region-specific morphogenesis of the CNS is also controlled by Zic genes. The underlying molecular actions of Zic gene products, which allow them to control development, remain a mystery. Recent molecular characterization has shown that Zic proteins are able to bind Gli-binding DNA sequences in a sequence-specific manner, but with lower affinity than Gli proteins. Zic proteins also can activate transcription from several promoters. Furthermore, Zic and Gli proteins interact physically via their zinc-finger domains, raising the possibility that Zic proteins can act as transcriptional cofactors and modulate the hedgehog-signaling pathway. Clarification of the specific cooperating factors is therefore required in each case. Other evidence also suggests that Zic proteins can inhibit neuronal differentiation by activating Notch signals. This association might be is a clue toward understanding of the multifunctional property of Zic proteins because Notch signaling also is implicated in the control of several developmental processes.

Neuroimaging in cerebral palsy

Parents and clinicians concerned about high-risk infants and children with motor delay or cerebral palsy seek information on cause, treatment, prognosis, and recurrence risk. Used in combination with history and examination, neuroimaging studies can improve diagnosis and management. In premature infants, cranial ultrasound is a reliable, noninvasive diagnostic modality. Nuclear magnetic resonance techniques including magnetic resonance imaging and diffusion weighted imaging can be used effectively in neonatal encephalopathies. In children with motor delay and cerebral palsy syndromes including spastic diplegia, quadriplegia, hemiplegia, and extrapyramidal movement disorders, conventional magnetic resonance imaging has become an important determinant of diagnosis and management. The aim of this article is to help clinicians select and interpret imaging studies of benefit in clinical care.

Neuroimaging in spasticity and movement disorders

Advances in neuroimaging provide unique opportunities to evaluate brain structure, biochemistry, and function. Although a number of imaging techniques have been used in newborns, cranial ultrasonography in premature infants and nuclear magnetic resonance modalities, including magnetic resonance imaging and diffusion-weighted imaging, in high-risk term infants are of foremost benefit. Interpretation is based on knowledge of characteristic imaging findings in specific childhood neurologic disorders and an understanding of differential diagnosis in cerebral palsy syndromes, such as spastic diplegia and various subtypes of extrapyramidal cerebral palsy. This review focuses on imaging studies that can be effectively used in at-risk infants and in children with spasticity and movement disorders to refine diagnosis and guide therapeutic interventions.

Neurocristopathies presenting with neurologic abnormalities associated with Hirschsprung's disease

Neurocristopathies are a group of diverse disorders resulting from defective growth, differentiation, and migration of the neural crest cells. Hirschsprung's disease, namely aganglionic megacolon, is the consequence of defective migration of neural crest cells on to the colonic submucosa and is therefore considered a neurocristopathy. We report on four children in whom was diagnosed a neurocristopathy, associating Hirschsprung's disease with a wide spectrum of neurologic abnormalities. The patients included two children presenting the phenotypic features of the Goldberg-Shprintzen syndrome: distinct dysmorphic facial features, microcephaly, and mental retardation, along with agenesis of the corpus callosum and cortical malformations associated with intractable seizures in one child. The third newborn presented with the Haddad syndrome: short-segment Hirschsprung's disease associated with the congenital central hypoventilation syndrome requiring permanent artificial ventilation. In the fourth child, absence of the corpus callosum was associated with mild dysmorphic features, borderline cognitive abilities, and attention-deficit disorder. Therefore, awareness of a possible neurocristopathy associated with neurologic abnormalities should be taken into account in any patient newly diagnosed with Hirschsprung's disease to detect the abnormalities early and promptly manage them. A thorough neurologic examination and a developmental assessment, including magnetic resonance imaging of the brain and electroencephalography, should be performed for any child presenting with an aganglionic megacolon, especially those presenting with seizures, developmental delay, or even congenital hypoventilation.

Molecular genetic and morphologic integration in malformations of the nervous system for etiologic classification

Molecular genetics has brought new insight into the etiology and pathogenesis of nervous system malformations, and provided a means of precise genetic diagnosis including the prenatal detection of many cerebral dysgeneses. Many cerebral malformations previously thought to be a single disorder are now known to be common end results of many independent genetic mutations. Examples are holoprosencephaly and lissencephaly. Gradients of genetic expression along the axes of the neural tube established at the time of gastrulation may explain many varieties and clinical expressions of cerebral malformations, including the involvement of non-neural tissues, such as midfacial hypoplasia from defective neural crest migration. A new classification of CNS malformations is proposed that integrates, but does not discard traditional morphologic criteria, but integrates them with new molecular genetic criteria.

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.

New insights into craniosynostosis

Craniosynostosis is a congenital developmental disorder involving premature fusion of cranial sutures, often associated with multiple neurological manifestations. The perspective of this group of disorders has changed dramatically in the new era of molecular genetics. In the last decade a large literature with new concepts in craniosynostosis has appeared. More than 100 syndromes associated with craniosynostosis have been described, and in about a dozen, the molecular defect has been identified. Pediatric neurologists are less aware than geneticists, neurosurgeons, and craniofacial surgeons of these changes. General concepts about craniosynostosis are here presented with updates of clinical and genetic aspects of well-defined syndromes such as Apert, Crouzon, Pfeiffer, Saethre-Chotzen. Evidence of their relationship with fibroblast growth factor receptors (FGFRs) 1, 2, and 3, and with causative genes such as TWIST has been documented. New and other less common syndromes also are discussed. The differences between positional and synostotic plagiocephaly are important, as well as the cause of nonsyndromic craniosynostosis. The prognosis and neurological outcome of patients, including "benign" forms of craniosynostosis, are other important aspects. Major advances have occurred in understanding pathogenesis, diagnosis, and treatment of craniosynostosis. The role of local dura mater and apoptosis; modalities of imaging such as prenatal ultrasound and three-dimensional and spiral CT have improved the accuracy in diagnosis, and the new approaches in surgical treatment involving efficient and less invasive methods, are evidence of these advances.