Development of the facial midline

In Utero Exposure to Maternal Electronic Nicotine Delivery System use Demonstrate Alterations to Craniofacial Development

OBJECTIVE

Develop a model for the study of Electronic Nicotine Device (ENDS) exposure on craniofacial development.

DESIGN

Experimental preclinical design followed as pregnant murine dams were randomized and exposed to filtered air exposure, carrier exposure consisting of 50% volume of propylene glycol and vegetable glycine (ENDS Carrier) respectively, or carrier exposure with 20 mg/ml of nicotine added to the liquid vaporizer (ENDS carrier with nicotine).

SETTING

Preclinical murine model exposure using the SciReq exposure system.

PARTICIPANTS

C57BL6 adult 8 week old female pregnant mice and exposed in utero litters.

INTERVENTIONS

Exposure to control filtered air, ENDS carrier or ENDS carrier with nicotine added throughout gestation at 1 puff/minute, 4 h/day, five days a week.

MAIN OUTCOME MEASURES

Cephalometric measures of post-natal day 15 pups born as exposed litters.

RESULTS

Data suggests alterations to several facial morphology parameters in the developing offspring, suggesting electronic nicotine device systems may alter facial growth if used during pregnancy.

CONCLUSIONS

Future research should concentrate on varied formulations and exposure regimens of ENDS to determine timing windows of exposures and ENDS formulations that may be harmful to craniofacial development.

Hemifacial microsomia: a scoping review on progressive facial asymmetry due to mandibular deformity

PURPOSE

This scoping review explores various parameters of the mandible in progressive facial asymmetry (FA) in hemifacial microsomia (HFM) patients, highlighting its relationship with sex, population, and age group.

METHODS

The review was based on a comprehensive search of PubMed, EBSCOhost, and Web of Science. Eligible studies that met the inclusion criteria form part of the selection study. The included studies were appraised using screening and quantitative criteria of mixed-method appraisal tools. The authors utilised a pre-set data extraction form to obtain information from the included studies.

RESULTS

Eleven studies met the inclusion criteria. The mandible parameters used were angular measurements, chin point, ramal height, body length, and total length. There was no relationship between FA and sex in HFM patients in the included studies. Most of the studies were comprised of European participants (55%), followed by Americans (36%) and Chinese (9%). The age groups included in the selected studies were categorised as dentition age (18%), early-to-middle childhood (18%), and varied ages (64%). The data presented in this review only pertains to the anomalous characteristics recorded on the affected side in HFM patients. No concomitant control data was recorded in this review.

CONCLUSION

An assessment of the included studies revealed that FA does not increase with age in HFM. Hence, FA is non-progressive in HFM patients. This information is relevant to diagnosing and managing HFM patients. More reports are needed on the progression of FA in HFM patients.

Computer-vision analysis of craniofacial dysmorphology in 22q11.2 deletion syndrome and psychosis spectrum disorders

BACKGROUND

Minor physical anomalies (MPAs) are congenital morphological abnormalities linked to disruptions of fetal development. MPAs are common in 22q11.2 deletion syndrome (22q11DS) and psychosis spectrum disorders (PS) and likely represent a disruption of early embryologic development that may help identify overlapping mechanisms linked to psychosis in these disorders.

METHODS

Here, 2D digital photographs were collected from 22q11DS (n = 150), PS (n = 55), and typically developing (TD; n = 93) individuals. Photographs were analyzed using two computer-vision techniques: (1) DeepGestalt algorithm (Face2Gene (F2G)) technology to identify the presence of genetically mediated facial disorders, and (2) Emotrics-a semi-automated machine learning technique that localizes and measures facial features.

RESULTS

F2G reliably identified patients with 22q11DS; faces of PS patients were matched to several genetic conditions including FragileX and 22q11DS. PCA-derived factor loadings of all F2G scores indicated unique and overlapping facial patterns that were related to both 22q11DS and PS. Regional facial measurements of the eyes and nose were smaller in 22q11DS as compared to TD, while PS showed intermediate measurements.

CONCLUSIONS

The extent to which craniofacial dysmorphology 22q11DS and PS overlapping and evident before the impairment or distress of sub-psychotic symptoms may allow us to identify at-risk youths more reliably and at an earlier stage of development.

Embryonic Development of the Orbit

The embryonic and fetal development of the orbit comprises a series of sequential events, starting with the fertilization of the ovum and extending until birth. Most of the publications dealing with orbital morphogenesis describe the sequential development of each germinal layer, the ectoderm with its neuroectoderm derivative and the mesoderm. This approach provides a clear understanding of the mode of development of each layer but does not give the reader a general picture of the structure of the orbit within any specified time frame. In order to enhance our understanding of the developmental anatomy of the orbit, the authors have summarized the recent developments in orbital morphogenesis, a temporally precise and morphogenetically intricate process. Understanding this multidimensional process of development in prenatal life, identifying and linking signaling cascades, as well as the regulatory genes linked to existing diseases, may pave the way for advanced molecular diagnostic testing, developing minimally invasive interventions, and the use of progenitor/stem cell and even regenerative therapy.

Insight Into the Ontogeny of GnRH Neurons From Patients Born Without a Nose

CONTEXT

The reproductive axis is controlled by a network of gonadotropin-releasing hormone (GnRH) neurons born in the primitive nose that migrate to the hypothalamus alongside axons of the olfactory system. The observation that congenital anosmia (inability to smell) is often associated with GnRH deficiency in humans led to the prevailing view that GnRH neurons depend on olfactory structures to reach the brain, but this hypothesis has not been confirmed.

OBJECTIVE

The objective of this work is to determine the potential for normal reproductive function in the setting of completely absent internal and external olfactory structures.

METHODS

We conducted comprehensive phenotyping studies in 11 patients with congenital arhinia. These studies were augmented by review of medical records and study questionnaires in another 40 international patients.

RESULTS

All male patients demonstrated clinical and/or biochemical signs of GnRH deficiency, and the 5 men studied in person had no luteinizing hormone (LH) pulses, suggesting absent GnRH activity. The 6 women studied in person also had apulsatile LH profiles, yet 3 had spontaneous breast development and 2 women (studied from afar) had normal breast development and menstrual cycles, suggesting a fully intact reproductive axis. Administration of pulsatile GnRH to 2 GnRH-deficient patients revealed normal pituitary responsiveness but gonadal failure in the male patient.

CONCLUSIONS

Patients with arhinia teach us that the GnRH neuron, a key gatekeeper of the reproductive axis, is associated with but may not depend on olfactory structures for normal migration and function, and more broadly, illustrate the power of extreme human phenotypes in answering fundamental questions about human embryology.

Topographical variations of the incisive canal and nasopalatine duct in human fetuses

The incisive canal for nerves and vessels is generally thought to run along a suture between the incisive bone (IN) and maxilla. In contrast, there was a report saying the canal passes through the IN or primary palate in human fetuses. Examination of sagittal and frontal sections from 69 fetuses (31 of gestational age [GA] 9-15 weeks and 38 of GA 26-34 weeks) showed that the canal often penetrated the IN at the nasal half of its course and that, in other fetuses, the canal penetrated the IN along its entire course, irrespective of involvement of the nasopalatine duct. Canals developing in and corresponding to parts of the suture resulted in partial enlargement of the thin and tight sutures, which contained loose tissue, vessels, nerves and even a duct. Small processes of the IN were identified as upper irregular parts continuous with inferior main masses of bone in frontal sections but as bone fragments in sagittal sections. In some sections, a thin layer of the maxilla along the canal covered the medial or inferior aspect of the IN. Therefore, the incisive canal with or without duct exhibited a spectrum of variations in topographical relation to the IN-maxillary border. Because the primitive oronasal communication passes through the suture, the nasopalatine duct may have originated from the secondary developed elongation of the nasal epithelium at midterm. A large incisive fossa along the midline on the oral surface of the palate might make a macroscopic finding of variants difficult even in adults.

Anatomic approximation approach to correction of transverse facial clefts

Transverse clefts of the oral cavity have significant impacts on both appearance and function. Many methods of repair have been described, but there is no consensus on optimal approach. In addition, dissatisfaction with scars, distortion of appearance, and recurrent deformity have led to complex surgical designs that are difficult to understand and reproduce. We describe a simple approach to repair that is based upon anatomic approximation of lip components and accurate repair of the muscle. Twenty patients underwent repair by the senior author, who devised the approach, and the corresponding author, who adopted it. Eight (62%) patients had right-sided clefts, three (23%) patients had left-sided clefts, and two (15%) patients had bilateral clefts. One patient had an associated branchial cleft remnant, two patients had multiple branchial cleft remnants and tragus deformities, one patient had craniofacial microsomia with microtia, and one patient had a contralateral Tessier 1 cleft. Mean age of the patients at repair was 23 months. All patients achieved normal oral competence, have favorable scars and commissure appearance, and have had no recurrent deformity. None of the patients have required revision. The described surgical approach is reproducible, easy to understand, and can produce favorable outcomes.

Maxillary and Sella Turcica Morphology in NewbornsWith Cleft Lip and Palate

Objective

The first aim was to examine maxillary developmental fields by analyzing bone size parameters within the maxillary bone complex in newborns with unilateral cleft lip (UCL) and unilateral cleft lip and palate (UCLP). The second aim was to evaluate sella turcica morphology in unilateral cleft lip and unilateral cleft lip and palate.

Subjects and Methods

Axial and profile radiographs from 40 newborns (boy–girl, 1:1) in each group (20 unilateral cleft lip and 20 unilateral cleft lip and palate) were randomly selected among radiographs taken for optimizing treatment planning. Analysis of maxillary bone size was performed on axial radiographs and size parameters were measured. Furthermore, analysis of sella turcica morphology was performed on profile radiographs. The results were divided into groups with normal morphology and severe deviations in the morphology.

Results

The maxillary areas were significantly shorter and broader in unilateral cleft lip and palate than in unilateral cleft lip. A profound asymmetry in the maxillary areas was seen in unilateral cleft lip and palate, but not in unilateral cleft lip. In both cleft types, approximately half of the individuals had deviations in sella turcica morphology. The most severe deviations occurred in newborns with unilateral cleft lip and palate.

Conclusions

In newborns with unilateral cleft lip and palate, the maxillary areas are significantly shorter, broader, and more asymmetric than in newborns with unilateral cleft lip. The present study showed that bone structures are a suitable parameter for characterizing the craniofacial developmental fields. Additionally, a high incidence of deviations in sella turcica morphology might indicate that this area is affected in individuals with clefts.

Congenital nasal pyriform aperture stenosis: A case with accompanying short lingual frenulum

Congenital nasal pyriform aperture stenosis (CNPAS) is a rare cause of nasal obstruction. We presented a case of CNPAS with accompanying short lingual frenulum. Surgical dilatation without osteotomy was used, and the infant had normal growth and development. In these cases, the less invasive surgical methods can be effective.

Diseases of the nose and paranasal sinuses in child

Diseases of the pediatric nose and nasal sinuses as well as neighboring anatomical structures encompass a variety of pathologies, especially of inflammatory nature. Congenital disease, such as malformations and structural deviations of the nasal septum, as well as systemic metabolic pathologies affecting the nose and sinuses, rarely require medical therapy from an Otolaryngologist. The immunological function of the mucosa and genetic factors play a role in the development of disease in the pediatric upper airway tract, especially due to the constantly changing anatomy in this growth phase. Disease description of the nose and nasal sinuses due to mid-facial growth must also take developmental age differences (infant, toddler, preschool, and school age) into account. Epidemiological examinations and evidence based studies are often lacking in the pediatric population. The wide range of inflammatory diseases of the nose and paranasal sinuses, such as the acute and chronic rhinosinusitis, the allergic rhinitis, and adenoid disease, play a role in the susceptibility of a child to infection. The susceptibility to infection depends on the pediatric age structure (infant, young child) and has yet to be well defined. The acute rhinosinusitis in children develops after a viral infection of the upper airways, also referred to as the "common cold" in the literature. It usually spontaneously heals within ten days without any medical therapy. Antibiotic therapy is prudent in complicated episodes of ARS. The antibiotic therapy is reserved for children with complications or associated disease, such as bronchial asthma and/or chronic bronchitis. A chronic rhinosinusitis is defined as the inflammatory change in the nasal mucosa and nasal sinus mucosa, in which the corresponding symptoms persist for over 12 weeks. The indication for CT-imaging of the nasal sinuses is reserved for cases of chronic rhinosinusitis that have been successfully treated with medication. A staged therapeutic concept is followed in CRS based on conservative and surgical methods. Nasal sinus surgery is considered nowadays as effective and safe in children. Based on the assumption that adenoids are a reservoir for bacteria, from which recurrent infections of the nose and nasal sinus originate, the adenoidectomy is still defined as a cleansing procedure in rhinosinusitis. 69.3% of the children had benefit from adenoidectomy. Comorbidities, such as pediatric bronchial asthma, presently play an even more important role in the therapy of rhinosinusitis; therefore, it is often wise to have the support of pediatricians. In western European countries 40% of children presently suffer from allergic rhinitis, in which pronounced nasal obstruction can cause disturbed growth in facial bones. An early therapy with SIT may prevent the development of bronchial asthma and secondary sensitization to other allergens. Therefore, SIT is recommended in treatment of allergic rhinitis whenever, if possible. The assessment of diagnostic tools is for the examiner not often possible due to the lack of evidence. Rhinosurgical approaches are often described in study reports; however, they lack the standard prospective randomized long-term study design required nowadays and can only be evaluated with caution in the literature.

Effects of the val(158)met catechol-O-methyltransferase gene polymorphism on olfactory processing in schizophrenia

The catechol-O-methyltransferase (COMT) val158met polymorphism has received attention in schizophrenia due to its role in prefrontal dopamine catabolism. Given the rich dopaminergic innervations of the olfactory bulb and the influence of dopamine on the transmission of olfactory signals, the authors examined the influence of COMT genotype status on the olfactory processing impairment observed in schizophrenia. The University of Pennsylvania Smell Identification Test was administered unirhinally to individuals with schizophrenia (n = 42) and a demographically matched sample of healthy controls (n = 30). Individuals were genotyped for the COMT val158met polymorphism. A statistically significant interaction of diagnosis and COMT genotype was observed, such that schizophrenia heterozygotes and Met homozygotes showed impaired odor identification accuracy relative to Val158 homozygotes. These findings could not be explained by factors such as antipsychotic medication status, clinical symptomatology, or demographic and illness characteristics. Notably, the schizophrenia Val158 homozygotes' odor identification performance was comparable to that of the control group. These data indicate that odor identification impairments observed in schizophrenia are influenced by the COMT val158met polymorphism. This relationship is consistent with specific dopaminergic modulation of primary olfactory sensory afferents, rather than a broader effect on cognitive processes. Future studies that examine the olfactory processing deficit in schizophrenia with respect to other olfactory measures and COMT haplotypes is warranted.

A case of Kallmann syndrome

Kallmann syndrome (KS), a rare genetic disorder, refers to the association between hypogonadotropic hypogonadism and anosmia or hyposmia due to abnormal migration of olfactory axons and gonadotropin-releasing hormone producing neurons. The authors report a case of a 26-year-old Filipino male who presented with eunuchoid body proportion, absence of facial and axillary hair and sparse pubic hair, micropenis and bilaterally descended prepubertal testes. Associated findings were hyposmia, high pitched voice, absence of puncta and smooth philtrum. Hormonal assay showed hypogonadotropic hypogonadism. He has normal male karyotype. Ultrasonography revealed no renal abnormalities. MRI of the brain showed hypoplastic left olfactory bulb and aplastic right olfactory bulb. These findings are characteristic of KS. Androgen replacement with testosterone was started to induce virilisation. Our patient is now on regular follow-up to monitor response to treatment.

Neuroembryology and functional anatomy of craniofacial clefts

The master plan of all vertebrate embryos is based on neuroanatomy. The embryo can be anatomically divided into discrete units called neuromeres so that each carries unique genetic traits. Embryonic neural crest cells arising from each neuromere induce development of nerves and concomitant arteries and support the development of specific craniofacial tissues or developmental fields. Fields are assembled upon each other in a programmed spatiotemporal order. Abnormalities in one field can affect the shape and position of developing adjacent fields. Craniofacial clefts represent states of excess or deficiency within and between specific developmental fields. The neuromeric organization of the embryo is the common denominator for understanding normal anatomy and pathology of the head and neck. Tessier's observational cleft classification system can be redefined using neuroanatomic embryology. Reassessment of Tessier's empiric observations demonstrates a more rational rearrangement of cleft zones, particularly near the midline. Neuromeric theory is also a means to understand and define other common craniofacial problems. Cleft palate, encephaloceles, craniosynostosis and cranial base defects may be analyzed in the same way.

Facial and pituitary morphology are related in Dutch patients with GH deficiency

OBJECTIVE

Classical GH deficiency (GHD) is associated with typical phenotypic features. We have analysed standardized photographs of 137 Caucasian patients with GHD, in order to examine the relations between auxological, biochemical, pituitary and facial morphometric features.

PATIENTS AND MEASUREMENTS

We analysed pictures of 137 patients: 73 (55 Males/18 Females) with Isolated GHD and 64 (48 M/16 F) with multiple pituitary hormone deficiency (MPHD). Of each patient, standardized frontal and lateral digital pictures were taken and analysed using Adobe Photoshop 5.0.

RESULTS

Canthal index (CI), the relative distance between the eyes, was related to pituitary morphology. Patients with an ectopic posterior pituitary (EPP) had significantly higher CI values than patients without EPP. We found CI > 39 to be a good cut-off value to select children with highest probability of having EPP. The combination of CI > 39 with the presence of hormonal deficiencies additional to GHD strongly predicted EPP: 93% of the patients with a CI > 39 and additional hormonal deficiencies had EPP, in contrast to 77% of the patients with additional hormonal deficiencies but a CI < 39, and 29% of the patients with none of these criteria (P = 0.0001).

CONCLUSION

CI, measured on digital pictures, is associated with ectopia of the posterior pituitary and this might be caused by an altered midline development, affecting both the pituitary and the facial structures of GHD patients.

Nonmuscle myosin II generates forces that transmit tension and drive contraction in multiple tissues during dorsal closure

BACKGROUND

The morphogenic movements that characterize embryonic development require the precise temporal and spatial control of cell-shape changes. Drosophila dorsal closure is a well-established model for epithelial sheet morphogenesis, and mutations in more than 60 genes cause defects in closure. Closure requires that four forces, derived from distinct tissues, be precisely balanced. The proteins responsible for generating each of the forces have not been determined.

RESULTS

We document dorsal closure in living embryos to show that mutations in nonmuscle myosin II (encoded by zipper; zip/MyoII) disrupt the integrity of multiple tissues during closure. We demonstrate that MyoII localization is distinct from, but overlaps, F-actin in the supracellular purse string, whereas in the amnioserosa and lateral epidermis each has similar, cortical distributions. In zip/MyoII mutant embryos, we restore MyoII function either ubiquitously or specifically in the leading edge, amnioserosa, or lateral epidermis and find that zip/MyoII function in any one tissue can rescue closure. Using a novel, transgenic mosaic approach, we establish that contractility of the supracellular purse string in leading-edge cells requires zip/MyoII-generated forces; that zip/MyoII function is responsible for the apical contraction of amnioserosa cells; that zip/MyoII is important for zipping; and that defects in zip/MyoII contractility cause the misalignment of the lateral-epidermal sheets during seam formation.

CONCLUSIONS

We establish that zip/MyoII is responsible for generating the forces that drive cell-shape changes in each of the force-generating tissues that contribute to closure. This highly conserved contractile protein likely drives cell-sheet movements throughout phylogeny.

Tissue fusion and cell sorting in embryonic development and disease: biomedical implications

Throughout embryonic development, segregated epithelial and/or mesenchymal cell populations make contact and fuse to shape new tissue units. This process, known as tissue fusion, is a key event in many essential morphogenetic mechanisms and its disruption can lead to congenital malformations. Another mechanism whereby complex tissues can arise involves a cell sorting process in which originally intermixed cells de-mix to generate distinct phases or layers. Different organisms use a combination of tissue fusion and cell sorting to acquire shape. Although the two processes appear to differ mechanistically, they are intricately linked inasmuch as they both involve the same molecular determinants and contribute to the same body plan. We aim to discuss the role of adhesion molecules and cell dynamics in tissue fusion and cell sorting, providing examples of their impact in embryonic development. Finally, we will advance the concept that malignant invasion may be viewed as cell sorting in reverse. Supplementary material for this article can be found on the BioEssays website (http://www.interscience.wiley.com/jpages/0265-9247/suppmat/index.html).

Reconstruction of #7 facial cleft with distraction-assisted in situ osteogenesis (DISO): role of recombinant human bone morphogenetic protein-2 with Helistat-activated collagen implant

A case involving concomitant presentation of a #7 lateral facial cleft with a complete cleft of the ipsilateral lip, alveolus, and palate is presented. The mandibular defect was Pruzansky III with a foreshortened body, absent ramus and absent masseter. Taking advantage of developmental field theory, reconstruction of the osseous defect was undertaken using the autogenous periosteum as a source of mesenchymal stem cells. Expansion of the periosteum was followed by implantation of Helistat (Integra Life Sciences, Plainsboro, NJ) collagen sponge saturated with recombinant human bone morphogenetic protein-2. Stimulation of this distraction-induced envelope by rhBMP-2 resulted in abundant production of bicortical membranous bone in situ within 12 weeks. The neoramus was subsequently suspended from the cranial base, and a temporalis muscle transfer was used to provide motor control of the jaw. Synthesis of bone in this manner is termed DISO (distraction-assisted in situ osteogenesis). The biologic rationale and clinical implications of DISO are discussed.

Noses and neurons: induction, morphogenesis, and neuronal differentiation in the peripheral olfactory pathway

Non-axial mesenchymal/epithelial (M/E) induction guides peripheral olfactory pathway differentiation using cellular and molecular mechanisms similar to those in the developing limbs, aortic arches, and branchial arches. At each of these bilaterally symmetric sites off the midline axis, a thickened ectodermal epithelium is apposed to a specialized mesenchyme derived largely, but not exclusively, from the neural crest. The capacity of M/E interaction in the olfactory primordia (the combined olfactory placodal epithelium and adjacent mesenchyme) to induce a distinct class of sensory receptor neurons-olfactory receptor neurons-suggests that this mechanism has been modified to accommodate neurogenesis, neurite outgrowth, and axon guidance, in addition to musculoskeletal differentiation, chondrogenesis, and vasculogenesis. Accordingly, although the olfactory primordia share signaling molecules and transcriptional regulators with other bilaterally symmetric, non-axial sites such as limb buds, their activity may be adapted to mediate distinct aspects of cellular differentiation and process outgrowth during the initial assembly of a sensory pathway-the primary olfactory pathway-during early forebrain development.

In Situ Osteogenesis: Regeneration of 10-cm Mandibular Defect in Porcine Model Using Recombinant Human Bone Morphogenetic Protein-2 (rhBMP-2) and Helistat Absorbable Collagen Sponge

Traditional bone grafting relies upon the incorporation of a bone-cell bearing structure into a recipient site. The graft serves as a scaffold that is eventually replaced and remodeled. This process is known as osteoconduction. Recombinant human bone morphogenetic protein-2 (rhBMP-2) is commercially available as an acellular implant in which the protein is bound to an absorbable collagen sponge (ACS). The rhBMP-2/ACS implant converts undifferentiated mesenchymal stem cells into osteoblasts and promotes an intense local neovascular response. This process, known as osteoinduction, produces bone via membranous, chondroid, or endochondral ossification. The type of bone synthesis depends upon the mesenchymal substrate and the local cellular environment. Using this simple technique, bone defects can be resynthesized with good outcomes and a significant reduction in donor site morbidity. Repair of a critical-sized mandibular resection defect with ISO is described. Basic science concepts of rhBMP-2, relevant histopathologic findings, and clinical application are described.

Cross-sectional study of the length of the nasal bone in cleft lip and palate subjects

OBJECTIVE

The purpose of this study was to analyze the human nasal bone length in newborns and male adults with cleft lip (CL), cleft palate (CP), and unilateral cleft lip and palate (UCLP) and to compare the results to previous findings in prenatal material.

DESIGN

This study was a radiographic profile cephalometric cross-sectional analysis.

SUBJECTS AND METHODS

Profile radiographs from 60 newborns with a male-to-female ratio of 1:1 in each group (20 CL, 20 CP, and 20 UCLP) and 60 male adults (20 CL, 20 CP, and 20 UCLP) were randomly selected among radiographs, taken for optimizing the treatment planning. The nasal bone lengths (n-na) were measured with a digital caliper on the profile radiographs. To compare the nasal bone lengths in the different cleft groups, Student's t tests at a significant level at 5% were performed.

RESULTS

Nasal bone length was significantly shorter in male adult patients with CL compared with patients with CP. Furthermore, the nasal bone length was significantly shorter in newborns with CL (2 months) compared to newborns with UCLP (2 months). A borderline significance was seen in the comparison of patients with CL and UCLP in male adults. There was no significant difference in the nasal bone length between the patients with CP and UCLP, in either the newborns or the male adults.

CONCLUSIONS

Nasal bone length was significantly shorter in subjects with CL compared with subjects in whom the palate was clefted. The results show that the clefted lip in CL is associated with a subjacent skeletal deviation in the upper midface.

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.

Current concepts in the embryology and genetics of cleft lip and cleft palate

Many mechanisms underlying normal and abnormal craniofacial embryogenesis are well understood. The genetic factors that provoke abnormal development and result in orofacial clefts are not clear, but much progress has occurred in our understanding. Genes or chromosomal rearrangements on many chromosomes can lead to syndromes that include orofacial clefts. This diversity in the mechanisms that can lead to syndromic clefts highlights the fact that the processes leading to the development of the oral cavity and face are complex and sensitive to disturbances at multiple timepoints or within multiple genetic domains. As for nonsyndromic clefting, large-scale family studies are consistent with one or a few loci exerting major effects on phenotypic expression, although no single gene has been identified as a "necessary" locus for development of nonsyndromic clefts. Rather, the emerging consensus is that the genetic etiology of nonsyndromic clefting is complex, with several loci showing significant results in at least some studies. Some of these loci may be genes for susceptibility to environmental factors, some may be modifying loci, and some may be "necessary" loci. Mutations in genes that are now known to control early development are logical candidate genes for future studies of nonsyndromic orofacial clefting. Continued genetic analyses and developmental studies are crucial for eventual understanding of the complex etiology of these common congenital anomalies.

Functional matrix cleft repair: principles and techniques

As an application of developmental anatomy, functional matrix cleft repair has scientific value. It tests out many aspects of periosteal physiology, and it is based squarely on concepts central to orthodontics. The "molecular revolution" has melded together developmental anatomy and genetics to create a new and clinically relevant model of facial development. This article outlines the scientific rationale for cleft repair based on this model.

Anatomical consideration of the congenital nasal pyriform aperture stenosis: localized dysostosis without interorbital hypoplasia

Congenital nasal pyriform aperture stenosis may be isolated or associated with other midline anomalies. The aim of the study was to describe the measurements and features of the interorbital structure and midface in congenital nasal pyriform aperture stenosis. The computed tomography scans of eight patients (two girls and six boys) were retrospectively reviewed. Several distances were obtained at the orbital and midface levels and compared with normative data. The average width of the pyriform aperture was 5.5 mm +/- 1.6, and there was overgrowth of the pyriform aperture rim (nasal process of the maxilla). No skeletal anomalies were present other than the congenital nasal pyriform aperture stenosis. It was associated with a single median maxillary central incisor in two cases. The anterior and lateral interorbital distances were normal (17.4 mm and 65.4 mm, respectively). The midface was not hypoplastic. There was no brain malformation. Congenital nasal pyriform aperture stenosis is a localized dysostosis of the pyriform aperture rim without interorbital or midface hypoplasia. It may be associated with a single median maxillary central incisor but cannot be viewed as a minor form of holoprosencephaly.

Neural tube programming and craniofacial cleft formation. I. The neuromeric organization of the head and neck

This review presents a brief synopsis of neuromeric theory. Neuromeres are developmental units of the nervous system with specific anatomic content. Outlying each neuromere are tissues of ectoderm, mesoderm and endoderm that bear an anatomic relationship to the neuromere in three basic ways. This relationship is physical in that motor and sensory connections exist between a given neuromeric level and its target tissues. The relationship is also developmental because the target cells exit during gastrulation precisely at that same level. Finally the relationship is chemical because the genetic definition of a neuromere is shared with those tissues with which it interacts. The model developed by Puelles and Rubenstein is used to describe the neuroanatomy of the neuromeres. Although important details of the model are currently being refined it has immediate clinical relevance for practicing clinicians because it permits us to understand many pathologic states as relationships between the brain and the surrounding tissues. Relationships between the processes of neurulation and gastrulation have been presented to demonstrate the manner in which neuromeric anatomy is established in the embryo. We are now in a position to describe in detail the static anatomic structures that result from this system. The neuromeric 'map' of craniofacial bones, dermis, dura, muscles, and fascia will be the subject of the next part of this series.

Integrative classification of morphology and molecular genetics in central nervous system malformations

We propose a scheme to classify central nervous system (CNS) malformations that integrates morphology and genetics by using patterns of genetic expression as its basis. The precise genetic mutations are not necessary to know in all cases. The premises of this classification are (1) genetic expression in the neural tube follows gradients in the axes that are established at the time of gastrulation: vertical (dorsoventral and ventrodorsal); rostrocaudal; mediolateral. (2) Overexpression in one of these gradients generally results in duplication or hyperplasia of structures, or ectopic segmental (i.e., neuromeric) expression. (3) Underexpression in a gradient generally results in hypoplasia, noncleavage in the midline of paired structures or segmental deletion of neuromeres. These gradients may also affect the formation and migration of neural crest tissue, affecting non-neural structures such as the face in the case of the mesencephalic neural crest, or induction of paraxial mesodermal in the posterior fossa. Additional criteria of the new classification allow for other genetic influences on developmental processes, such as cellular lineage, exemplified by tuberous sclerosis, and hemimegalencephaly. It is essential that the CNS be considered as a whole and classification not be regionalized, as to the cerebral cortex, because the limit of the rostrocaudal gradient may account for variability in clinical manifestations.

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.