Human Foramen Magnum Area and Posterior Cranial Fossa Volume Growth in Relation to Cranial Base Synchondrosis Closure in the Course of Child Development.

BACKGROUND: To date, no study has compared the evolution of the foramen magnum area (FMA) and the posterior cranial fossa volume (PCFV) with the degree of cranial base synchondrosis ossification. OBJECTIVE: To illustrate these features in healthy children. METHODS: The FMA, the PCFV, and the ossification of 12 synchondroses according to the Madeline and Elster scale were retrospectively analyzed in 235 healthy children using millimeter slices on a computed tomography scan. RESULTS: The mean FMA of 6.49 cm in girls was significantly inferior to the FMA of 7.67 cm in boys (P < .001). In both sexes, the growth evolved in a 2-phase process, with a phase of rapid growth from birth to 3.75 years old (yo) followed by a phase of stabilization. In girls, the first phase was shorter (ending at 2.6 yo) than in boys (ending at 4.33 yo) and proceeded at a higher rate. PCFV was smaller in girls (P < .001) and displayed a biphasic pattern in the whole population, with a phase of rapid growth from birth to 3.58 yo followed by a phase of slow growth until 16 yo. In girls, the first phase was more active and shorter (ending at 2.67 yo) than in boys (ending at 4.5 yo). The posterior interoccipital synchondroses close first, followed by the anterior interoccipital and occipitomastoidal synchondroses, the lambdoid sutures simultaneously, then the petro-occipital and spheno-occipital synchondroses simultaneously. CONCLUSION: The data provide a chronology of synchondrosis closure. We showed that FMA and PCFV are constitutionally smaller in girls at birth (P ≤ .02) and suggest that a sex-related difference in the FMA is related to earlier closure of anterior interoccipital synchondroses in girls (P = .01). ABBREVIATIONS: AIOS, anterior interoccipital synchondrosesFMA, foramen magnum areaLS, lambdoid suturesOMS, occipitomastoidal synchondrosesPCFV, posterior cranial fossa volumePIOS, posterior interoccipital synchondrosesPOS, petro-occipital synchondrosesSOS, spheno-occipital synchondrosisyo, years old.

Cranial base growth in adolescence assessed through cone-beam computerized tomographies--pilot study.

OBJECTIVE: To assess growth of the middle/posterior cranial base during adolescence based on landmarks located on serial three-dimensional cone-beam computerized tomography (CBCT) images. MATERIALS AND METHODS: CBCT scans from 62 adolescents (11 to 17 years) at baseline and 12 months were used. Eleven landmarks in the cranial base were identified. Linear landmark distances were compared over the two time points using basic descriptive statistics. Shape analysis was carried out using R (R Foundation for Statistical Computing, Austria). Discrete curves were obtained and aligned via a Procrustes transformation and examined for group dimorphism and longitudinal change. RESULTS: Mean differences between linear distances in the cranial base were within 1mm, apart from the difference between the right and left auditory external meatuses, which was 2.25 mm. No statistically significant longitudinal differences in shape were found in relation to the peak growth period. CONCLUSION: Cranial base growth was minimal over the observation period. There were no differences in terms of the amount and pattern of growth. The cranial base is said to complete most of its growth by age 12, but this has only been verified through two-dimensional studies. Our findings using CBCT confirm this, and support the use of the cranial base as a stable anatomical reference structure for superimpositioning.

The formation of the foramen magnum and its role in developing ventriculomegaly and Chiari I malformation in children with craniosynostosis syndromes.

OBJECT: Craniosynostosis syndromes are characterized by prematurely fused skull sutures, however, less is known about skull base synchondroses. This study evaluates how foramen magnum (FM) size, and closure of its intra-occipital synchondroses (IOS) differ between patients with different craniosynostosis syndromes and control subjects; and whether this correlates to ventriculomegaly and/or Chiari malformation type I (CMI), intracranial disturbances often described in these patients. METHODS: Surface area and anterior-posterior (A-P) diameter were measured in 175 3D-CT scans of 113 craniosynostosis patients, and in 53 controls (0-10 years old). Scans were aligned in a 3D multiplane-platform. The frontal and occipital horn ratio was used as an indicator of ventricular volume, and the occurrence of CMI was recorded. Synchondroses were studied in scans with a slice thickness ≤1.25 mm. A generalized linear mixed model and a repeated measures ordinal logistic regression model were used to study differences. RESULTS: At birth, patients with craniosynostosis syndromes have a smaller FM than controls (p < 0.05). This is not related to the presence of CMI (p = 0.36). In Crouzon-Pfeiffer patients the anterior and posterior IOS fused prematurely (p < 0.01), and in Apert patients only the posterior IOS fused prematurely (p = 0.028). CONCLUSION: The FM is smaller in patients with craniosynostosis syndromes than in controls, and is already smaller at birth. In addition to the timing of IOS closure, other factors may influence FM size.

Foramen magnum size and involvement of its intraoccipital synchondroses in Crouzon syndrome.

BACKGROUND: Cranial sutures and synchondroses tend to close prematurely in patients with Crouzon syndrome. This influences their skull vault and skull base development and may involve in common disturbances such as increased intracranial pressure and cerebellar tonsillar herniation. The authors' hypothesis was that Crouzon patients patients have a smaller foramen magnum than controls because of premature fusion of the intraoccipital synchondroses, putting them at risk for cerebellar tonsillar herniation. Therefore, foramen magnum size and time of intraoccipital synchondroses closure were evaluated and were related to the presence and degree of cerebellar tonsillar herniation. METHODS: The foramen magnum surface area and anteroposterior diameter were measured on three-dimensional computed tomographic scans of 27 Crouzon patients and 27 age-matched controls. Scans had a slice-thickness between 0.75 and 1.25 mm and were aligned in a three-dimensional reformatting platform. The t test was used to study size differences. Synchondroses were graded as described by Madeline and Elster and studied with ordinal logistic regression analysis. RESULTS: Crouzon patients had a smaller foramen magnum surface area (602 mm versus 767 mm, p < 0.001) and anteroposterior diameter (31 mm versus 35 mm, p < 0.001) compared with controls. Differences stayed constant over time. Intraoccipital synchondroses closed 3 to 9 months earlier in Crouzon patients than in controls (p < 0.05). CONCLUSIONS: Since intraoccipital synchondroses close earlier in Crouzon patients, from early life on their foramen magnum is smaller compared with controls. Within Crouzon patients, the presence of cerebellar tonsillar herniation could not be related to foramen magnum size. CLINICAL QUESTION/LEVEL OF EVIDENCE: Risk, II.

The growth of the foramen magnum in Crouzon syndrome.

BACKGROUND: Though the craniovertebral junction is often abnormal in children with Crouzon's syndrome, no study had measured accurately the size of their foramen magnum (FM). PATIENTS AND METHODS: We compared the FM size (area, diameters) on computed tomography examination in 21 children with a genetically confirmed Crouzon's syndrome prior to any surgery and in 23 control children without craniofacial abnormalities. We extrapolated the growth pattern in both groups. RESULTS: We found a statistically significant smaller FM area (p=0.0228), FM sagittal diameter (p=0.0287), and FM sagittal posterior diameter (p=0.0023) in children with Crouzon's syndrome. No differences were detected with regard to the transversal diameter. Hydrocephalus in children with Crouzon's syndrome was associated with a small FM area (p=0.05), small sagittal diameter (p=0.023), small sagittal posterior diameter (p=0.0173), and reduced transversal diameter (p=0.03985). No association of the aforementioned findings was found with the position of the cerebellar tonsils or the lambdoid suture functional state (open or fused). Comparable results were observed among the two genetic forms (exon 8 or 10 mutations). Concerning the growth pattern, a first phase of rapid increase and a second phase of slow increase could be recognized in all the measurements in both populations, though with some significant differences. DISCUSSION AND CONCLUSIONS: The growth of FM follows a biphasic pattern in both Crouzon's and control children. The sagittal diameter and the global size of the FM are mostly affected in children with Crouzon's syndrome. The small FM, especially its posterior part, is likely to play a key role in the physiopathology of hydrocephalus.

Foramen magnum ontogeny in Homo sapiens: a functional matrix perspective.

Historically, the foramen magnum (FM) has been an integral component of studies on skull ontogeny and evolutionary transformations of cranial form. Although this foramen has been considered a single entity, we hypothesize that it comprises two functional matrices, a ventral matrix and a dorsal matrix. In general, the ventral matrix is related to locomotor functions, whereas the dorsal matrix is related to neurological functions and fluid flow dynamics. To test our hypothesis, we used a large ontogenetic sample of modern human crania (seventh fetal month to adult) to (1) delineate bony size and shape ontogeny for both the foramen and its dorsal and ventral units; (2) delineate the role of synchondroses in the observed growth patterns and rates; and (3) explore the relationship between FM and cranial size, shape, and growth. Detailed growth patterns and rates are established for the bony FM and its ventral and dorsal skeletal units. These data are supplemented by literature and observational data on embryonic and fetal FM ontogeny, soft tissue relationships, anomalous/pathological extremes of size, and craniocervical anatomy and locomotor functions. The hypothesis that the FM is composed of a ventral and a dorsal functional matrix is supported by observed ontogenetic differences between ventral and dorsal skeletal units, as well as by the soft tissue anatomy of these matrices. Further documentation of these matrices has the potential to significantly enhance our understanding of the ontogenetic and evolutionary transformations of skull base morphology.

Quantification of cranial base growth during pubertal growth.

OBJECTIVE: To quantify longitudinal cranial base growth from prepubertal through postpubertal stages of development, as defined by biological indicators of individual skeletal maturity (cervical vertebral maturation - CVM) method and to determine if there is sexual dimorphism resulting from cranial base growth. DESIGN: A longitudinal cephalometric study. SETTING: The Dental School of Paulista University, Brazil. PARTICIPANTS: 36 subjects (21 females, 15 males) who were part of a longitudinal growth study and exhibited normal facial and normal vertical growth patterns. METHODS: Growth maturation of cervical vertebrae stages was assessed by two examiners independently. Cranial base measurements were carried out by one individual and repeated after one month. The growth increments over time were assessed with the one-way repeated-measures analysis of variance and post hoc Tukey multiple comparisions. RESULTS: There were no significant gender differences. There was a significant increase in all cephalometric measures between the different time points. Ba-Na showed the greatest amount of growth (mean change=2.8 mm). From T2-T3, the greatest amount of growth was found for Se-Na (mean change=3.4 mm) and the lowest for CC-Na (mean change=1.4 mm). Comparing overall changes (T1-T3) all the measurements showed statistically significantly increases (P<0.05). For all comparisons of between-stage changes the cranial base grew more than 2.0 mm during the pubertal growth. CONCLUSIONS: Linear variables of cranial base showed significant growth during pubertal stages (pre-peak, peak and post-peak). No significant differences.

Sexual dimorphism in the foramen magnum dimensions / Dimorfismo sexual en las dimensiones del foramen magno

The purpose of this study is to assess the presence of sexual dimorphism in the foramen magnum size. We analyzed 211 human skulls from the collection of the Universidade Federal de Sao Paulo, with a record of sex and age determined using anteroposterior and transverse diameters of foramen magnum, and their differences by gender (p<0.05) were ascertained. Fischer linear discriminant function was calculated and the value for the classification of these variables was determined. All the dimensions were found to be higher, and in men's skulls, the foramen magnum size had low discriminating power and were accurately classified only in 66.5 percent skulls. Our results show that this quantitative indicator is of limited practical value and should be supplemented with qualitative indicators of sexual dimorphism in the occipital bone to improve the accuracy in the sex diagnosis.

El propósito de este estudio fue evaluar la presencia de dimorfismo sexual en las dimensiones del foramen magno. Se analizaron 211 cráneos humanos de la colección de la Universidade Federal de Sao Paulo, con registro de sexo y edad, se determinaron los diámetros anteroposterior y transverso máximo del foramen magno y se establecieron las diferencias por sexo (p<0,05), se determinaron las funciones lineales discriminantes de Fischer y se calculó la utilidad para la clasificación de estas variables. Todas las dimensiones resultaron mayores y significativas en cráneos de hombres, las dimensiones del foramen magno presentaron un bajo poder discriminante y clasificaron correctamente el 66,5 por ciento de los cráneos. Nuestros resultados muestran que este indicador cuantitativo es de limitada utilidad práctica y debe ser complementado con los indicadores cualitativos de dimorfismo sexual en el hueso occipital para mejorar la exactitud en el diagnóstico del sexo.

Morphometric analysis of the skull of the Sahel goat breed: basic and clinical anatomy.

The work reports morphometric analysis of the skulls of the Sahel breed of goat. The calculated metric data (mean +/- SD) included the condylobasal length, 16.94 +/- 1.39 cm, while the orbital circumference was 11.30 +/- 0.48 cm. The foramen magnum height and width were 1.82 +/- 0.11 cm and 1.85 +/- 0.15 cm respectively while the foramen magnum index was 89.81 +/- 8.71. Animals above one year of age had significantly higher values for orbital length including horizontal and vertical diameters, overall skull length, basal length, and neurocranium height than animals aged one year and below. The cornual process length, maximum orbital circumference and horizontal diameter obtained in this study were higher than those reported for other Nigerian goat breeds in the literature. The data for the distances from the facial tuberosity to the infraorbital canal, from the mental foramen to the lateral extent of the alveolar root of the lower incisor, as well as from the mandibular foramen to the base of the mandible and that from the mental foramen to the caudal border of the mandible, which are important clinically in the estimation of craniofacial measurements that will aid regional anaesthesia, were however similar to those reported earlier for the Red Sokoto and West African Dwarf breeds implying that a uniform craniometric estimation for associated regional nerve blocks can be attempted for these goat breeds.

Posterior fossa dimension and volume estimates in pediatric patients with Chiari I malformations.

INTRODUCTION: Chiari I malformations (CMI) involve pathological hindbrain abnormalities reported to be correlated with a hypoplastic posterior fossa. CMI was traditionally characterized by the downward herniation of the cerebellar tonsils with a descent of 5 mm or more below the foramen magnum. The fullness of the cisterna magna and CSF flow at the level of the cervicomedullary junction have been shown to be more useful in selecting symptomatic patients for surgical decompression. The present study calculates posterior fossa dimension and volume estimates in pediatric patients using magnetic resonance imaging. The combination of neuroradiological and clinical findings is used to re-examine the criteria used for diagnosis and treatment of pediatric CMI patients. MATERIALS AND METHODS: A retrospective chart review was conducted on patients who were admitted to the Division of Neurosurgery of the Children's hospital of Eastern Ontario between 1990 and 2007. Clinical and radiological assessments were performed on all patients. Posterior fossa volumes (PFV) and intracranial volumes (ICV) were measured from sagittal head magnetic resonance imaging scans using the Cavalieri method. RESULTS: Sixty-one CMI patients were identified. There were 32 male and 29 female patients with a mean age of 10 years (range: 8 weeks-18 years). Thirty-four (55%) of these patients were symptomatic with scoliosis (38%), suboccipital headaches (29%), and motor/sensory deficits (26%) being the most prominent symptoms. The mean PFV/ICV ratio for all the CMI patients (0.110) was found to be statistically smaller than that of the control patients (0.127, p=0.022). Mean PFV/ICV ratios for asymptomatic and symptomatic CMI patients were found to be similar for children aged 0-9 years (p=0.783) but different for children aged 10-18 years (p=0.018). DISCUSSION: Mean PFV values were found to be smaller in pediatric CMI patients than control patients; this complements earlier studies in adults and supports the present theory concerning the pathophysiological mechanism of CMI. Subtle morphometric differences among asymptomatic and symptomatic patients aged 0-9 years stress the importance of monitoring asymptomatic patients for the onset of symptoms in their adult years. Symptom development in CMI is likely multifactorial and is much more extensive than the degree of cerebellar tonsillar herniation.

On the variability of skull shape in German shepherd (Alsatian) puppies.

In this study the skulls of 32 German shepherd puppies (40-107 days old) were examined. They were divided into three age groups (40-49, 50-69, and 70-107 days) and the variability of their shapes was determined. Some geometrical shapes were drawn by joining the measuring points. Angle measurements were made on these shapes, which comprised the whole skull, neurocranium, and viscerocranium. The skull index was further calculated in order to assess the correlation, if any, of this index with the angle measurements. It was found that the length of the skull increased more than the width, and, accordingly, the skull became narrower and longer with age. Furthermore, the AZP and AZN angles widened with age, while the ZAZ, ZPZ, NcANc, NcPNc, NcBrNc, SwNSw, and SwPSw angles decreased. The decrease in the skull index, which was not proportionate to the age, showed that the zygomatic width did not increase as much compared to the length of the skull.

Induced leukemia and antineoplastic agent carmustine cause permanent changes in craniofacial growth of immature rats.

OBJECTIVES: The purpose of the present study was to investigate the possible effects of untreated terminal leukemia on craniofacial growth (Study I), and also the effects of the antineoplastic agent carmustine on craniofacial growth in both leukemic and healthy rats (Study II). MATERIAL: A total of 367 inbred Piebald variegated rats was used. METHOD: Transmission of leukemic cells was carried out intraperitoneally at 30 days of age, and without treatment (Study I), the rats reached the terminal phase within 17 +/- 1 days. Rats with induced leukemia was cured with 10 mg/kg carmustine (BCNU) given on days 6 and 13 following cell transmission (Study II), the rats remaining in remission until they were killed at 100 days of age. Final weight was recorded and 12 craniofacial dimensions and tibial length were measured with a digital sliding caliper. RESULTS: The results showed that the effect of untreated terminal rat leukemia (Study I) on craniofacial growth differed between the genders. Male rats showed clearly reduced dimensions of facial structures and also retarded general body growth, whereas females showed differences mainly in general body growth. The effect of cured leukemia (Study II) as such was minor, while BCNU had a strong and permanent reducing effect on both craniofacial and general body growth in both genders. CONCLUSION: We suggest that the results in Study I came both from a direct effect of leukemia and an indirect effect of untreated terminal leukemia through malnutrition. The alkylating agent BCNU seemed to be the main cause of permanent craniofacial and general growth retardation in Study II.

Morphometric analysis of the foramen magnum in German shepherd dogs (Alsatians).

In this study, a total of 32 skulls from German Shepherd (Alsatian) puppies were used. These animals were divided into two groups and examined individually. Group 1 included the puppies of between 43-60 days old. Group 2 included the puppies of between 61-107 days old. We based our study on the changes in shape and size of the foramen magnum and the correlation of normal craniometric measurements in the German Shepherd puppies. In group 1, a maximum width of the foramen magnum of 15.55 mm, a height of the foramen magnum of 14.38 mm and a foramen magnum index of 92.67 were observed. In group 2, a maximum width of the foramen magnum of 17.49 mm, a height of the foramen magnum of 16.34 mm and a foramen magnum index of 93.51 were measured. A high positive correlation was found between the maximum width and height of the foramen magnum, the maximum width of the occipital condyles, the maximum width of the bases of the jugular processes, the skull height, the height of the occipital triangle, the skull length from prosthion to basion and the skull length from prosthion to the caudal borders of the occipital condyles. A negative correlation was observed between the width and height of the foramen magnum and indices. Although there was no relation between the foramen magnum index and the age of the animals, an important difference was found between groups 1 and 2. A negative correlation was observed between the foramen magnum index and the rate of increase in the cranial volume. In all the animals examined, the dorsal bone of the foramen magnum was closed, therefore any extension or dorsal notch was not seen. Such an extension or dorsal notch of the foramen magnum in the German Shepherd puppies may therefore be the result of a pathological condition.

Suture closure in the human chondrocranium: CT assessment.

PURPOSE: To chronicle the development of ossification centers, sutures, and synchondroses in the chondrocranium throughout childhood by using computed tomography (CT). MATERIALS AND METHODS: One hundred eighty-nine children (age range, newborn to 18 years; median age, 4.0 years) without skull base deformity were referred for cranial CT. The closure of 18 sutures and synchondroses was graded. RESULTS: In the occipital bone at birth, six components were identified. The Kerckring ossicle rapidly fused to the supraoccipital bone within the 1st month. At age 1-3 years, the posterior and anterior intraoccipital synchondroses began to fuse. The occipitomastoidal, petro-occipital, and spheno-occipital synchondroses remained partially open into the teenage years. In the sphenoid bone at birth, 13 ossification centers were identified; most assimilated into the sphenoidal body during the first 2 years. Pneumatization of the sphenoid sinus appeared at age 1-2 years and advanced posteriorly over the next 3-5 years. CONCLUSION: The complex process of skull base development is chronicled, which provides CT standards for judgment of the patterns and timing of sutural or synchondrosal closure.

Postnatal development of the central skull base: normal variants.

PURPOSE: To illustrate the normal variants and developmental anomalies of the skull base on computed tomographic (CT) scans. MATERIALS AND METHODS: One hundred eighty-nine children (age range, newborn to 18 years; median age, 4.0 years) without skull base deformity were referred for cranial CT. Normal developmental variants in the sphenoid and occipital bones were characterized. RESULTS: Sixteen normal variants of central skull base development were identified including anterior foramen in the presphenoid, remnant of the craniopharyngeal canal in the anterior portion of the postsphenoid, rounded defects in the central sphenoid, clefts and fissures along the basiocciput and basisphenoid, basioticum variants, notochordal remnant in the midline of the basiocciput, and fusion variants of the Kerckring ossicle with the supraoccipital portion of the occipital bone. CONCLUSION: The location and CT appearance of the 16 variants and anomalies are related to the known embryologic origin of this region. Recognition of such variants may prove necessary in evaluation of patients with skeletal dysplasias and disorders of skull base development.

Morphometric analysis of the foramen magnum in Pekingese dogs.

The size and shape of the foramen magnum were studied in skulls from 75 adult and 5 juvenile Pekingese dogs. After maceration of the skulls, the height, width, and area of each foramen magnum were measured, and various skull indices were determined. The shape of the foramen varied from ovoid to rectangular and had a dorsal notch in all but 2 skulls. Prolapse of cerebellum or brain stem through the enlarged opening was prevented by a fibrous membrane covering the dorsal notch. Mean +/- SD area of the foramen was 138.1 +/- 26.1 mm2; its mean total height was 15.0 +/- 2.9 mm, and its mean maximal width was 13.3 +/- 1.1 mm. Statistically, variability in the area of the foramen was mainly correlated with total height of the foramen, including the dorsal notch. Total height of the foramen was not correlated with age or gender. The degree of dysplasia, notch index, and occipital index of each foramen magnum were determined. To allow a more accurate evaluation of the morphology of the foramen, the foramen magnum index, defined as the ratio between the maximal width and the total height of the foramen, was also computed. Mean +/- SD foramen magnum index was 91.8 +/- 17.1 in the adult Pekingese dogs. Foramen magnum index was not significantly correlated with age, but was significantly larger in male than in female dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth of the foramen magnum in achondroplasia.

Foramen magnum growth curves in achondroplasia and in the general population are presented. The achondroplastic foramen magnum is small at birth, and during the first year it has a severely impaired rate of growth especially in the transverse dimension. This markedly diminished growth results not only from abnormal endochondral bone growth but also because of abnormal placement and premature fusion of the synchondroses. Evaluation of the foramen magnum in achondroplasia should address absolute size of the transverse and sagittal dimensions, shape, and growth centers to determine growth potential of this area.

Pseudo-iniencephaly. A case report.

A case of congenital webbing with other congenital abnormalities is presented. Initial examination of the features of the case made a diagnosis of iniencephaly seem likely. However, further examination of the radiographs and the physical abnormalities demonstrated too few of the typical features, and the term pseudo-iniencephaly has been used to describe the case. The various aetiological possibilities are discussed, but it is clear that further research into webbing and its concomitant abnormalities would be necessary to provide the answers to the questions posed by this case.