Embryonic holoprosencephaly: pathology and phenotypic variability

Alobar holoprosencephaly with cebocephaly in a neonate: A rare case report from Northern Tanzania

Introduction and importance

Holoprosencephaly is a rare brain malformation consisting of impaired midline cleavage of the embryonic forebrain presenting with variable features of craniofacial dysmorphism. It affects 1 in 10,000 live births occurring more in females than males. We present a case of alobar HPE and aim to raise awareness on the importance of early prenatal detection and counselling.

Case presentation

We present a case of 3200-gram female baby, born by spontaneous vaginal delivery with APGAR scores of 5 and 6 in the first and fifth minute of life respectively. On admission, the baby was lethargic, had central and peripheral cyanosis, hypothermic with temperature of 32.1 °C, respiratory rate of 65 breaths/min, heart rate of 135 beats/min and oxygen saturation of 94% with an oropharyngeal airway and on oxygen support via a face mask. She had microcephaly, hypotelorism, and a small nose with a single imperforate nostril. She was diagnosed to have alobar holoprosencephaly with cebocephaly. A computed tomography scan of the brain revealed a cephalohematoma in the vertex and an intranasal soft tissue density lesion blocking the entrance measuring approximately 10 × 8.5 mm. Absence of the corpus callosum and septum pellucidum with a resulting monoventricle formed from the lateral ventricles, the fusion of the thalami and a sizeable arachnoid cyst involving the left cerebellar hemisphere were evident. She was started on IV antibiotics and IV fluids. Non-invasive airway management was opted for by the ENT team based on the condition of the baby. She succumbed to death 6 days post admission due to severe respiratory failure.

Clinical discussion

The types of HPE are alobar, semi lobar, lobar and interhemispheric variants. Alobar HPE is the most severe form and is incompatible with life. Clinical presentation entails facial dysmorphism with features of hypotelorism, microcephaly and a blind ended nostril. Alobar and semilobar HPE can reliably be diagnosed with ultrasound during the first and second trimesters of pregnancy. Absence of choroid plexus and fused cortex are pathognomonic characteristic on ultrasound and CT scan respectively.

Conclusion

Alobar holoprosencephaly is a rare brain malformation which is incompatible with life.

Prenatal ultrasound screening of the foetus brain is essential and reliable in making a diagnosis. Absence of the “butterfly” sign in the foetal brain ultrasonography should raise a high index of suspicion for brain malformation with unfavourable outcome. Legal medical termination of pregnancy may serve as an early intervention.

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Holoprosencephaly is a rare midline forebrain malformation.

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The alobar holoprosencephaly type is incompatible with life.

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Ultrasonography is reliable in making the diagnosis.

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Early pregnancy decisions favour compatible outcomes.

Cellular identities in an unusual presentation of cyclopia in a chick embryo

Cyclopia is a congenital anomaly characterized by the presence of a single or partially divided eye in a single orbit at the body midline. This condition is usually associated with other severe facial malformations, such as the absence of the nose and, on rare occasions, the presence of a proboscis located above the ocular structures. The developmental origin of cyclopia in vertebrates is the failure of the embryonic prosencephalon to divide properly during the formation of the two bilateral eyes. Although the developmental origin of the cyclopia-associated proboscis is not clear, it has been suggested that this unique structure results from the disrupted morphogenesis of the olfactory placodes, the main organizers of the developing nose. In this study, we report a spontaneous congenital case of cyclopia with a proboscis-like appendage in a chick embryo. By means of both conventional histology and immunohistochemical methods, we have analyzed this anomaly in detail to suggest an alternative identity for the anatomical embryonic features of cyclopic vertebrate embryos displaying a proboscis. Our findings are discussed in the context of previously reported cases of cyclopia, and provide additional insight into this complex congenital malformation.

Congenital eye anomalies: More mosaic than thought?

The eye is a sensory organ that primarily captures light and provides the sense of sight, as well as delivering non-visual light information involving biological rhythms and neurophysiological activities to the brain. Since the early 1990s, rapid advances in molecular biology have enabled the identification of developmental genes, genes responsible for human congenital diseases, and relevant genes of mutant animals with various anomalies. In this review, we first look at the development of the eye, and we highlight seminal reports regarding archetypal gene defects underlying three developmental ocular disorders in humans: (1) holoprosencephaly (HPE), with cyclopia being exhibited in the most severe cases; (2) microphthalmia, anophthalmia, and coloboma (MAC) phenotypes; and (3) anterior segment dysgenesis (ASDG), known as Peters anomaly and its related disorders. The recently developed methods, such as next-generation sequencing and genome editing techniques, have aided the discovery of gene mutations in congenital eye diseases and gene functions in normal eye development. Finally, we discuss Pax6-genome edited mosaic eyes and propose that somatic mosaicism in developmental gene mutations should be considered a causal factor for variable phenotypes, sporadic cases, and de novo mutations in human developmental disorders.

Holoprosencephaly with Clefts: Data of 85 Patients, Treatment and Outcome: Part 1: History, Subdivisions, and Data on 85 Holoprosencephalic Cleft Patients

CONTEXT

Cleft patients with Holoprosencephaly (HPE) constitute a controversy due to a variable facial appearance. HPE appearance varies from only a columella to a prolabium-premaxilla complex agenesis up to a common unilateral or bilateral cleft lip and palate with a single central incisor, various brain deformities, and/or even normal brain development. It is challenging to designate such various appearances, to understand their etiopathogenesis, and to choose the most appropriate management. Literature was reviewed for diagnostic criteria, pregnancy history, clinical findings, brain development, survival rate, initial perioperative management, and postsurgical midfacial growth in cleft patients with HPE. The findings were compared with a clinical database of 85 cleft patients with HPE at the Department of Maxillofacial and Oral Surgery, University of Pretoria.

AIMS OF PART 1

The aim of the study is to overcome disparities widely existing among clinicians regarding definitive diagnostic criteria, especially in cases with a common appearance of a uni- or bilateral cleft lip alveolus or cleft lip, alveolus and palate deformity, and cases presenting facial structural agenesis.

MATERIALS AND METHODS

A literature search related to diagnostic criteria was compared to results of a cleft HPE database from a single tertiary institution.

RESULTS

HPE cleft cases can be allocated to one of the following subdivisions: (1) columella complex agenesis (Ag-Colum), (2) prolabium-premaxilla-columella complex agenesis in cleft lip-alveolus deformities (Ag-CLA), (3) prolabium-premaxilla-columella agenesis in cases with complete cleft lip alveolus palate (Ag-CLAP), and (4) standard type (holoprosencephaly in patients with a standard cleft) with uni- or bilateral CLA or CLAP, hard and soft palate cleft (hPsP), and atrophic premaxillae, with or without single central incisor. Further, incidence, variation in brain development, and appearances in HPE cleft patients of different races and gender, epilepsy, and early death are discussed. Conclusion: This paper adds new data and facts to the existing literature related to cleft lip and palate patients suffering from HPE.

Morphometric analysis of the brain vesicles during the human embryonic period by magnetic resonance microscopic imaging

The development of the brain vesicles between Carnegie stages (CS) 17 and 23 was analyzed morphometrically using 177 magnetic resonance image data derived from the Kyoto Collection of Human Embryos. Whole embryonic volume was 106.55 ± 21.08 mm(3) at CS17, exponentially increasing to CS23 when it reached 1357.28 ± 392.20 mm(3). Length of brain vesicles was 29.83 ± 2.52 mm at CS17, increased almost linearly and reached 49.31 ± 6.66 mm at CS23. The rate of increase was approximately 4.2 times higher on the dorsal side than on the ventral side. The increase in the length of the brain vesicles resulted mainly from that of the prosencephalon, and the rate of increase was three times higher on the dorsal side than on the ventral side of the prosencephalon.

Holoprosencephaly and holoprosencephaly-like phenotypes: Review of facial and molecular findings in patients from a craniofacial hospital in Brazil

Here we report on the clinical and genetic data for a large sample of Brazilian patients studied at the Hospital de Reabilitação de Anomalas Craniofaciais-Universidade de São Paulo (HRAC-USP) who presented with either the classic holoprosencephaly or the holoprosencephaly-like (HPE-L) phenotype. The sample included patients without detected mutations in some HPE determinant genes such as SHH, GLI2, SIX3, TGIF, and PTCH, as well as the photographic documentation of the previously reported patients in our Center. The HPE-L phenotype has been also called of HPE "minor forms" or "microforms." The variable phenotype, the challenge of genetic counseling, and the similarities to patients with isolated cleft lip/palate are discussed.

3-D reconstruction of a human fetus with combined holoprosencephaly and cyclopia

Background

The purpose of this study was to examine a human fetus with combined holoprosencephaly and cyclopia by means of histology and 3-D reconstruction to determine the internal structure and extent of the malformation.

Methods

The head from a human fetus at 20 weeks gestation and a diagnosis of holoprosencephaly and cyclopia was investigated histologically and three-dimensionally reconstructed with CAD techniques. The cranial bones, blood vessels, nerves, eye and brain anlagen were reconstructed.

Results

The 3-D reconstruction revealed both severe malformation and absence of the facial midline bones above the maxilla, and a malformation of the maxilla and sphenoid bone. The mandible, posterior cranial bones, cranial nerves and blood vessels were normal. A synophthalmic eye with two lenses was found. The prosencephalon was a single small protrusion above the diencephalon. No nasal cavity was present. Above the single eye a proboscis was found.

Conclusion

The absence of the facial midline bones above the maxilla and the presence of a proboscis as a nose-like structure above the cyclopic eye both mean that there was a developmental defect in the fronto-nasal facial process of this fetus.

Lobar holoprosencephaly with a median cleft: case report

Holoprosencephaly is a congenital abnormality of the prosencephalon associated with median facial defects. Its frequency is 1 in 250 pregnancies and 1 in 16,000 live births. The degree of facial deformity usually correlates with the severity of brain malformation. Early mortality is prevalent in severe forms. This report presents a child with lobar holoprosencephaly accompanied by median cleft lip and palate. The treatment and 9 months' follow-up are presented. This unique case shows that holoprosencephaly may present different manifestations of craniofacial malformations, which are not always parallel to the severity of brain abnormalities. Patients with mild to moderate brain abnormalities may survive into childhood and beyond.

Development of the meniscus of the knee joint in human fetuses

Discoid meniscus of the knee joint occurs at a higher incidence in the lateral than in the medial menisci. Although its developmental origin has been suggested, it remains unclear. To verify the developmental etiology, we examined the meniscus of the knee joint in 41 human fetuses (from 14 to 30 weeks of gestation) and 14 adults (from 56 to 91 years of age) comparatively. The articular surfaces of the tibia and meniscus of the left knees in 40 fetuses and 14 adults were photographed and each area was measured by Scion Image (Scion; http://www.scioncorp.com). Morphometric analyses revealed that the proportion of the area of meniscus to that of the plateau was continuously higher in the lateral side than in the medial side. The right knee joints of seven fetuses were histologically observed, and the layered structure of fibers developed earlier in the lateral meniscus than in the medial in fetuses. The observed differential development of lateral and medial sides of the meniscus may be involved in the etiology of discoid meniscus.

Morphometric study on the characteristic external features of normal and abnormal human embryos

The embryonic period is characterized by organogenesis and accompanying dynamic changes in external features. The measurement of human embryos has been limited to whole body dimensions, such as crown-rump length. More detailed measurements would add quantitative information about these characteristic events and provide a better understanding of normal and abnormal embryonic development. In the present study, we defined axes, landmarks, and measurements for human embryos, and measured 250 externally normal human embryos at Carnegie stages 14-23 (6.5-29.3 mm in crown-rump length, approximately 5-8 weeks of estimated ovulation age) that were fixed in Bouin's solution and preserved in 10% formalin solution. The axes, landmarks, and measurements defined for human embryos are corresponding to those in human and primate fetuses. The whole body, head, face, and extremities were measured using a scale attached to a dissecting microscope. Axial length, head height plus ear-shoulder length plus trunk height, was designated as a new measurement of the whole body, which is comparable with crown-rump length. Approximate standards of these measurements were obtained. The ratios of some measurements to trunk height and between the different parts were also obtained, and several different developmental patterns were recognized. The reproducibility of each measurement was evaluated by measuring 50 specimens three times each at intervals of one or two months. As a pilot study for the application of the proposed measurements, 84 human embryos with external anomalies, including holoprosencephaly, anomalies of extremities, and pharyngeal arch anomalies, were measured using the same method, and a few tendencies characteristic to holoprosencephaly were noticed.