Cephalometric investigation of craniomaxillofacial structures during the prenatal period: a cadaver study

INTRODUCTION

We aimed to investigate the morphometric development of the cranial base and its related structures, and their growth rate changes from the ninth gestational week to full term in a large group of human fetuses.

METHODS

We selected 203 (109 male, 94 female) fetuses between 9 and 40 weeks of gestation and without any external anomalies. From each fetus, standard lateral and posteroanterior cephalometric images were taken using a dental digital panoramic and cephalometric x-ray machine. Fourteen linear and 9 angular parameters were measured.

RESULTS

The cranial base angle showed a statistically significant increase between the groups from only the second to the third trimester periods. The sagittal translation of the maxilla increased during the prenatal period, whereas the mandibular sagittal relation grew at a steady rate. The vertical plane angles of the maxilla and the mandible did not show any significant changes. The maxillary length to mandibular length ratio remained stable.

CONCLUSIONS

The cranial base angle increased, especially in the second through the third trimesters. The maxilla and the mandible demonstrated different growth patterns in the sagittal direction. The findings of this study could be a guide for interpreting the relationships among the craniofacial structures.

Embryology of the internal carotid artery dural crossing: apropos of a continuous series of 48 specimens

The aim of this study was to describe the embryologic and foetal development of the anterior paraclinoid region and more precisely the relationship of the internal carotid artery to the dura mater. This has been done by examining a collection of histological sections, representing a continuous series of 48 embryologic and foetal specimens, covering the period of the first 6 months of intra-uterine life. Neurological and vascular elements develop during the embryologic period; the internal carotid artery is recognizable in the various sections of its course and acquires a histological adult parietal constitution. The foetal period corresponds to the development of the meningeal structures. The superior, medial and lateral walls appear on the fifteenth week of amenorrhoea and do not change after that. The internal carotid artery enters subarachnoid space accompanied by a sleeve of mesenchymatous cells, which fixes it to the anterior clinoid process. The constitution of this sleeve, arising from the superior wall of the lateral sellar compartment, remained independent of the principle vascular part, which allows the formation of a plan of cleavage. The foetal relations of the dura mater and the internal carotid artery were seen to be different from those of adult subjects described in the literature, suggesting an existence of period of maturation postnatally.

The prenatal development of the human cerebellar field in Down syndrome

OBJECTIVES

To describe the development of the osseous field enclosing the cerebellum and part of the brain stem (the neuro-osteological cerebellar field) in Down syndrome, and compare the development with normal developmental standard of the field.

DESIGN

Radiographic, cephalometric and histologic examination of 58 legally or spontaneously aborted Down syndrome prenatal human fetuses; crown-rump length of 80-255 mm and approximate gestational age from 13 to 26 weeks.

RESULTS

The growth of the Down syndrome cerebellar field is smaller in the sagittal and vertical directions than in normal fetuses.

CONCLUSION

In the present study the pathological development of the cerebellar field was described in a genotypic sample. In combining normal and pathological development of neural and osseous tissues a better understanding of the genotype/phenotype interactions is attainable and fields of common gene expression maybe defined.

Cranial base growth and morphology in second-trimester normal human fetuses and fetuses with cleft lip

OBJECTIVE

The present radiographic study describes the size and shape of the cranial base from the sagittal aspect for a sample of 77 second-trimester "normal" control fetuses (n = 61) and fetuses (n = 16) exhibiting isolated, unilateral clefts of the lip (CL), ranging in fertilization age from 10 to 22 weeks.

METHODS

Fetuses were placed in a cephalostat, and standardized, lateral head radiographs were taken. The radiographs were traced, and 15 cephalometric landmarks were identified and digitized for analysis. Growth curves for cranial base lengths, angles, and areas were compared between control and CL groups. Also, cranial base triangles were constructed and shape comparisons were made using tensor biometric analysis.

RESULTS

No significant differences (p >.05) in regression line slopes were noted for any comparisons between the control and CL samples. Tensor biometric analysis also revealed no significant differences in the shapes of various cranial base triangles between the control and CL samples.

CONCLUSION

This report presents second-trimester baseline growth curves for various cranial base components in CL human fetal specimens, and these data suggest that CL fetuses may also be used as an appropriate control sample for prenatal growth comparison studies of cleft lip and palate and cleft palate.

Aspects of skeletal development in fragile X syndrome fetuses

The purpose of the present investigation was to describe the skeletal development in prenatal fragile X syndrome. We studied fetuses (4 males, 2 females), with gestational ages (GA) 12-14 weeks, from 5 unrelated, different, known carrier mothers. Because of trauma to the fetus during abortion, different parts of the 6 fetuses were available for investigation. The vertebral column and the facial skeleton of all the fetuses were examined, the feet and hands of 5 fetuses, and the cranial base of 3 fetuses. The tissue remnants were examined radiographically and histochemically, and the results compared with previously published normal findings. Radiographic findings included normal ossification sequence, except for 1 fetus where there was an abnormal sequence in the first finger; normal morphology of ossification centres; and nasal bones were absent in the 5 fetuses and present in 1 (14 weeks of gestation). The histological study suggests presence of an acid mucopolysaccharide malfunction in the supporting tissue, because the normal cartilage resorption and orthochromatic cartilage reactions do not appear during the initial enchondral ossification. In addition, the apoptosis of ectodermally derived cells (notochord and palatal epithelial layers) appears delayed or abnormal. The sella turcica was malformed in the 2 fetuses investigated for sella turcica morphology.

The prenatal pituitary gland--hidden and forgotten

The sella turcica and pituitary gland in a human fetus (18 weeks gestation) with unilateral oro-ocular cleft combined with unilateral cleft lip and palate are described histologically. In this fetus the sella turcica was not a normal sella but a caudally open funnel. The adenopituitary gland tissue was positioned ectopically within the funnel canal and in the pharyngeal submucosa.

Postnatal structure of the sella turcica in Down syndrome

The purpose of this study was to analyze the shape of the sella turcica in a group of patients with Down syndrome and compare the findings with those made earlier in human fetuses with Down syndrome. Profile radiographs from 78 patients (age 4 months to 50 3/12 years) were analyzed. A tracing was made of each sella turcica, and the shape was compared with that of a normal sella, including the normal growth pattern from childhood to adulthood. Sella turcica structure could be classified into three morphological types, defined as: type I, almost normal appearance; type II, deviations in the anterior wall; and type III, deviations in the floor of the sella turcica. Compared with previously registered prenatal structural deviations in the sella turcica, it can be concluded that the postnatal radiographic material reflects the prenatal findings, because type I, both prenatally and postnatally, is by far the most common, whereas the remaining types are uncommon, both prenatally and postnatally. The study confirms the relevance of prenatal investigations for postnatal diagnostics as previously documented in sella turcica analyses of prenatal and postnatal myelomeningocele cases.

Malformations of cranial base structures and pituitary gland in prenatal Meckel syndrome

The sella turcica region, including the clivus and the pituitary gland, was studied histologically in five human fetuses with Meckel syndrome (MS). All cases had malformed sella turcica and malformed clivus with irregularly shaped notochordal remnants. We consider that these three characteristics are constant phenotypic traits in MS. The adenohypophysis was present in three cases. In one of these, ectopia of the gland occurred with adenopituitary tissue overlying the dorsum sella, and in another remnants were found in the pharyngeal submucosa. In two fetuses the neurohypophysis was not found. The findings in the region were compared to normal findings and to findings in trisomy 18, where cranial base structures radiographically appeared similar to those in MS. We conclude that in MS specific characteristics are found in the cranial base region and that radiographic analysis needs to be supplemented by histological analysis when studying this specific region.

Pituitary gland and sella turcica in human trisomy 21 fetuses related to axial skeletal development

The purpose of the present investigation was to study the sella turcica/pituitary gland region in trisomy 21 fetuses and to relate the findings in the region to the ossification pattern in the axial skeleton formed by the cranial base and spine. Material from 22 human fetuses with trisomy 21, CRL 80 mm to CRL 190 mm, corresponding to gestational ages from 14 to 21 weeks, was examined and compared with material from gestation-matched normal controls. After radiography, tissue blocks from the cranial base, including the pituitary gland, were examined and compared with those of normal fetuses. Four different types of sella turcica/ pituitary gland morphology were observed. Thirteen fetuses (Type I) were morphologically normal. Minor abnormalities occurred in the sella turcica and pituitary gland (adenopituitary gland tissue pharyngeally) in six fetuses (Types II and III). There was agreement between the histologically recorded deviations in the sella turcica and the radiographic observations of the basisphenoid bone. In three cases (Type IV) out of 22, more pronounced structural abnormalities occurred in the sella turcica, and radiographically the basisphenoid bone appeared cleft. All sella turcica changes observed in trisomy 21 were situated anteriorly in the base of the sella. In all cases the basilar part of the occipital bone was normal. Minor changes in the sella turcica region were mainly accompanied by cervical vertebral abnormalities, while the most severe abnormalities occurred in association with malformations in the lumbar vertebrae. There was no association between sella turcica malformations and the absence or presence of the nasal bone.

Prenatal traces of aberrant neurofacial growth

The interrelation between the development of the brain/peripheral nerves and that of the surrounding bone tissue is termed neuro-osteology. In orthodontic and pediatric practice the development of the hard tissues is evaluated radiographically, but the development of the neural tissue within the bone tissue is not evaluated. In this review the emphasis is placed on two neuro-osteologic interrelations that can be observed on profile radiographs and orthopantomograms, respectively. One is the connection between the pituitary gland of the central nervous system and the sella turcica (profile radiograph), and the other is the association between the peripheral nerves and the development of the dentition (orthopantomogram). Pituitary gland/sella turcica: The correlation between prenatal malformation in the pituitary gland/sella turcica and the postnatal morphology of the sella turcica in holoprosencephaly, spina bifida/myelomeningocele, and cri-du-chat syndrome is demonstrated. Peripheral nerves/dentition: The prenatal innervation of the dentition is presented. Agenesis and tooth malformation occur in constant patterns within the dental arch fields that share the same innervation. The findings demonstrate that in postnatal diagnosis of the cranium and the teeth, traces of prenatal aberrations can be found that are important for neurofacial growth.

Is there a dural wall between the cavernous sinus and the pituitary fossa? Anatomical and MRI findings

We compared MRI studies of the sellar area and embryological and adult histological studies of the cavernous sinuses and pituitary fossa. MRI studies were performed in 50 normal subjects with coronal sections using a fast inversion-recovery sequence to demonstrate the dural walls of the cavernous sinus and pituitary fossa. With this sequence, dura mater appears as a high-signal linear structure. The lateral and superior walls of the cavernous sinus was easily identified on all studies, but demonstration of a dural wall separating the cavernous sinus from the pituitary fossa was not possible. These results correlated well with embryological and adult histological studies obtained from 14 specimens. The absence of a strong separation between the pituitary fossa and the cavernous sinus explains the high incidence of extension of pituitary tumours to the cavernous sinuses and vice versa.

Neuro-osteology

Neuro-osteology stresses the biological connection during development between nerve and hard tissues. It is a perspective that has developed since associations were first described between pre-natal peripheral nerve tissue and initial osseous bone formation in the craniofacial skeleton (Kjaer, 1990a). In this review, the normal connection between the central nervous system and the axial skeleton and between the peripheral nervous system and jaw formation are first discussed. The early central nervous system (the neural tube) and the axial skeleton from the lumbosacral region to the sella turcica forms a unit, since both types of tissue are developmentally dependent upon the notochord. In different neurological disorders, the axial skeleton, including the pituitary gland, is malformed in different ways along the original course of the notochord. Anterior to the pituitary gland/sella turcica region, the craniofacial skeleton develops from prechordal cartilage, invading mesoderm and neural crest cells. Also, abnormal development in the craniofacial region, such as tooth agenesis, is analyzed neuro-osteologically. Results from pre-natal investigations provide information on the post-natal diagnosis of children with congenital developmental disorders in the central nervous system. Examples of these are myelomeningocele and holoprosencephaly. Three steps are important in clinical neuro-osteology: (1) clinical definition of the region of an osseous or dental malformation, (2) embryological determination of the origin of that region and recollection of which neurological structure has developed from the same region, and (3) clinical diagnosis of this neurological structure. If neurological malformation is the first symptom, step 2 results in the determination of the osseous region involved, which in step 3 is analyzed clinically. The relevance of future neuro-osteological diagnostics is emphasized.

Microanatomy of the hypophyseal fossa boundaries

OBJECT

The authors studied the heads of 17 adult cadavers and one fetus to clarify the anatomy of the sellar region, particularly the lateral boundaries of the hypophyseal fossa.

METHODS

Vascular injections and microdissection or histological techniques were used in this study. The roof of the cavernous sinuses and diaphragma sellae were part of a single horizontal dural layer that joined the two anterior petroclinoid folds. Laterally, the direction of this layer changed; it became the lateral wall of the cavernous sinus and joined the dura mater of the middle cerebral fossa. On the midline, this layer ballooned toward the sella through the diaphragmatic foramina, created a dural bag containing the hypophysis, and attached to the inferior aspect of the diaphragma sellae. As a consequence, no straight sagittal dural wall existed between the pituitary gland and cavernous sinus; the lateral border of the hypophyseal fossa was part of this anteroposterior and superoinferior convex bag. The authors stress the importance of the venous elements of the region and discuss the structure of the cavernous and coronary sinuses.

CONCLUSIONS

Invasion of the cavernous sinus makes surgery more risky and difficult and may necessitate modification of the surgical treatment plan. The preoperative diagnosis of cavernous sinus invasion is thus of great interest, but the possibility of normal lateral expansions of the pituitary gland must be kept in mind. A lateral expansion of this gland into the cavernous sinus was encountered in 29% of the specimens, and an adenoma that developed in such an expansion could easily mimic cavernous sinus invasion.

The association between prenatal sella turcica morphology and notochordal remnants in the dorsum sellae

The purpose of this study was to describe the location and morphology of notochordal remnants in the cranial base in normal and pathological conditions and to relate these findings to the morphological appearance of the sella turcica. Serially cut sagittal sections of paraffin-embedded sella turcica tissue blocks from 88 normal and pathological fetuses, 13 to 24 weeks of gestation, were examined. Twenty-seven specimens out of 88 had visible notochordal remnants in the cranial base, and these constituted the material available for this study. A straight notochordal course is always seen in normal sella turcica morphology, and a non-straight notochordal course is always seen in malformed sella turcica. Among the fetuses diagnosed at autopsy as "normal fetuses," both normal and pathological findings in the sella turcica regions were observed. The pathological findings were always found in the spontaneously aborted fetuses (five cases). Among the fetuses diagnosed at autopsy as "pathological fetuses," both normal and pathological findings were also observed in the sella region. Our conclusion is that the morphological appearance of the notochordal remnants in the dorsum sellae is associated with the morphology of the sella turcica. These structures ought to be analyzed on larger materials of both normal and pathological fetuses. One of the more obvious perspectives opened up by the present study is the probable disclosure of malformations in spontaneously aborted fetuses without external malformations.

Anatomy and embryology of the trigeminal nerve and its branches in the parasellar area

The cavum trigeminale (Meckel's cave) anatomy is still poorly understood. Many different descriptions are found in the literature. In order to clarify the relationship of trigeminal ganglion and its branches with dura and arachnoid, we underwent an embryological and adult microanatomical and histological study. Serial sections of human embryos and fetuses were used. For adult study, microdissections and histological serial sections were performed. We found that dura and arachnoid stop at the trigeminal ganglion and do not extend the three branches of the trigeminal nerve. These three branches are embedded into separate peripheral sheaths. These results are important for clear understanding of the anatomy of the parasellar lodge (cavernous sinus) lateral wall.

Human fetal pituitary gland in holoprosencephaly and anencephaly

The normal prenatal development of the human pituitary gland and the gland-supporting sella turcica has recently been investigated. The sella turcica area constitutes a developmental boundary area in the cranial base. Posterior to the area the cranial base has developed close to the notochord, and anterior to the region the cranial base development is dependent chiefly on neural crest cell migrations. In the present study the sella turcica region was analyzed in two fetuses with holoprosencephaly (cyclopia and median cleft) and four fetuses with anencephaly combined with rachischisis in the neck region (GA 16-20 weeks). The sella turcica region was investigated radiologically and histologically. Adenohypohyseal gland tissue was localized by immunohistochemical hormonal marking. In both types of malformation an open craniopharyngeal canal was seen in the base of the sella turcica with adenohypophyseal glandular tissue located in the sella turcica, in the canal, and in the pharyngeal connective tissue at the external side of the cranial base. In conclusion, severe malformations of the pituitary gland occur in both holoprosencephaly, which is a polytopic field defect located anterior to the sella turcica, and in anencephaly associated with notochordal insufficiency posterior to the sella turcica. This might indicate that the sella turcica area, bounding different developmental fields, is involved in various craniofacial malformations. It is consequently recommended that examination of the pituitary gland should become a part of the routine autopsy of prenatal material when malformations in the face, brain, and cranial base occur.

Midline maxillofacial skeleton in human anencephalic fetuses

The purpose of this study was to describe the midline maxillofacial skeleton (the axial skeleton anterior to the sella turcica) in 15 human anencephalic fetuses (14-19 weeks of gestation) by radiography and histology, and to relate the findings to skeletal patterns in the remaining part of the axial skeleton. Four patterns in the maxillofacial skeleton were recognized: normal structures, slightly deformed (6 cases); cleft palate (3 cases); incomplete nasal septum (3 cases); multilocular ethmoid cartilage (3 cases). No association was found between skeletal patterns in the different parts of the axial skeleton. The study demonstrates the existence of a developmental borderline in the anencephalic axial skeleton in the region of the sella turcica. It is presumed that this borderline indicates the boundary between skeletal tissue developed around the notochord (posterior axial skeleton) and the anterior skeletal components derived from neural crest cells.

Relationship between the development of diaphragma sellae and the morphology of the sella turcica and its content

The impaired formation of the diaphragma sellae may lead to the development of the empty-sella syndrome. This structure, when fully formed, is a protective barrier against the pulsating action that the cerebrospinal fluid exerts on the sellar content. There are anatomical features which support this belief, but they also suggest that the development of the diaphragma sellae is a factor which determines the morphology of the sella turcica and its contents. Those human specimens which do not have diaphragma sellae or in which it is only partially developed, are characterized by a smaller hypophysis, always located at the inferior and/or posterior half of the sella, with a larger sellar volume and frequently greater fragility of its bony walls. These findings, although rare (5% of the cases), are indirect signs of the important role which the diaphragma sellae plays in the sellar region.

Anatomy and radiology of the sellar spine

Five anatomical and radiological observations of a spine protruding into the pituitary fossa are reported. This osseous spine, about 4 mm long, arises in the midline from the inferior part of the anterior aspect of the dorsum sellae and extends upward and forward. The possible origins of this malformation are discussed.

Structure and postnatal organization of heretofore uninvestigated and infrequent ossifications of the sella turcica region

A heretofore unreported spine, which protrudes into the pituitary fossa, has been described and recorded. Complete and incomplete 'sella bridges', their angle formations with the planes of the head, dimensions and sutures have been detailed and their origin postulated. The development and formation of the carotico-clinoid foramina have been exhibited and interpreted. Development stages of the ophthalmic canals have been elicited. An ossified trigeminus bridge has been measured and its origin elucidated. The supracochlear cartilages have been traced from their appearance in the new-born to their supposed fate (os suprapetrosum).

The different relationship of the sella point to growth sites fo the cranial base in fetal life

Histological observations of the fetal cranial base in 17 human specimens showed that the sella point was identified closely with the dorsum sellae, and occupied an intermediate position in relation to the growth sites of the spheno-occipital synchondrosis. The cancellous structure of the sphenoid bone clearly demonstrated that the pituitary fossa, and hence the sella, moved upward and backward during growth.