Size of the anterior fontanelle: three-dimensional measurement of a key trait in human evolution

Anterior fontanelle closure and diagnosis of non-syndromic craniosynostosis: a comparative study using computed tomography

OBJECTIVE

Suspicion of early anterior fontanel (AF) closure is a common reason for referral to a pediatric neurosurgeon because of the suspected increased risk of developing craniosynostosis (CS) in spite of the absence of evidence in the literature. The aim of this study was to analyze the association between AF closure and the diagnosis of non-syndromic CS in Brazilian children.

METHODS

An observational and case-cohort study was conducted to compare the incidence of closed AF between healthy children (group 1) and children diagnosed with non-syndromic CS (group 2) at a pediatric neurosurgery referral center. The accuracies of completely closed AF and diagnosis of CS were assessed.

RESULTS

High-resolution three-dimensional reconstruction computed tomography scans were obtained for 140 children aged < 13 months, of whom 62.9% were boys and 37.1% were girls (p < 0.001). The most common types of non-syndromic CS were trigonocephaly (34, 48%) and scaphocephaly (25, 35.7%). Closed fontanel (27, 38.6%) was observed in both groups, and a sensitivity of 36.1%, specificity of 72%, the positive predictive value of 59%, and negative predictive value of 51% were observed in the patients diagnosed with CS when AF closure occurred before the age of 6 months.

CONCLUSION

The results of this comparative study of AF closure and CS diagnosis suggest that early AF closure does not imply a diagnosis of CS. Pediatricians should be aware of the risk of misdiagnosis of CS in cases with a widely open AF in spite of the presence of CS.

Anterior Fontanel Size Among Term Newborns: A Systematic Review and Meta-Analysis

Background: Anterior fontanel is an integral element of an infant craniofacial system. There are six fontanels in the newborn skull, namely anterior, posterior, two mastoid, and two sphenoid fontanels. The anterior fontanel is the largest, prominent, and most important for clinical evaluation. Sex, race, genetics, gestational age, and region are the principal factors that influence anterior fontanel size. There exist inconclusive findings on the size of anterior fontanel in newborns. Therefore, this systematic review and meta-analysis aimed to determine the pooled mean size of anterior fontanel among term newborns and to identify the pooled mean difference of anterior fontanel size between males and females.

Methods: PubMed/Medline, Google Scholar, Science Direct, JBI Library, embase, and Cochrane Library databases were systematically searched. All essential data were extracted using a standardized data extraction format. The heterogeneity across studies was assessed using the Cochrane Q test statistic, I² test statistic, and p-values. A fixed-effect model and random effect model were used to estimate the pooled mean size of anterior fontanel and the pooled mean difference between male newborns and female newborns, respectively. To deal with heterogeneity, sub-group analysis, meta-regression analysis, and sensitivity analysis were considered. JBI quality appraisal checklist was used to evaluate the quality of studies.

Results: In this meta-analysis, 8, 661 newborns were involved in twenty-six studies. Among studies, 13 conducted in Asia, 7 in Africa, 5 in America, and 1 in Europe. The pooled mean size of anterior fontanel was 2.58 cm (95% CI: 2.31, 2.85 cm). The pooled mean size of anterior fontanel for Asia, Africa, America, and Europe region was 2.49, 3.15, 2.35, and 2.01 cm, respectively. A statistically significant mean difference was detected between male and female newborns (D + L pooled MD = 0.15 cm, 95% CI: 0.02, 0.29 cm).

Conclusion: The pooled estimate of this review does provide the mean value of the anterior fontanel size in the newborns. There was a statistically significant mean fontanel size difference between male and female newborns. Therefore, male newborns had a significantly larger mean size than female newborns.

Temporal mapping of the closure of the anterior fontanelle and contiguous sutures using computed tomography, in silico models of modern infants

The aim of this study is to quantify and statistically model the age-related decline in the fibrous connective tissue interface of the anterior fontanelle in modern Australian infants, using three-dimensional, semi-automated computed-assisted design protocols. Non-linear regression with variance models, using power functions, combined with quantile regression of the 5th and 95th population percentiles, were utilised to assess absolute anterior fontanelle surface area (AFSA) as a function of age, using multi-slice cranial computed tomography scans obtained from 256 infants aged < 30 months (males: n = 126, females: n = 109) from Brisbane children's hospitals. Normalised AFSA (NFSA), standardised for variation in cephalic size, followed a progressive decline from birth, the greatest velocity change occurring between the 3-6 and 6-9 month cohorts. Growth of the neurocranium is the most significant within the first 8 months postpartum, with a mean increase of 19.03 mm in maximum cranial length and 10.04 mm in breadth. Directionality of fontanelle closure, quantified using spline curves refutes fundamental assumptions that the anterior fontanelle is consistent with a quadrilateral, and contiguous sutures exhibit constant velocity of closure. The present study provides normative values for fontanelle size and diameters as well as new predictive non-linear models for age substantiation, screening of developmental abnormalities and indicators of suspected child maltreatment in modern infants aged birth to 30 months.

Modeling the effect of brain growth on cranial bones using finite-element analysis and geometric morphometrics

PURPOSE

Brain expansion during ontogeny has been identified as a key factor for explaining the growth pattern of neurocranial bones. However, the dynamics of this relation are only partially understood and a detailed characterization of integrated morphological changes of the brain and the neurocranium along ontogeny is still lacking. The aim of this study was to model the effect of brain growth on cranial bones by means of finite-element analysis (FEA) and geometric morphometric techniques.

METHODS

First, we described the postnatal changes in brain size and shape by digitizing coordinates of 3D semilandmarks on cranial endocasts, as a proxy of brain, segmented from CT-scans of an ontogenetic sample. Then, two scenarios of brain growth were simulated: one in which brain volume increases with the same magnitude in all directions, and other that includes the information on the relative expansion of brain regions obtained from morphometric analysis.

RESULTS

Results indicate that in the first model, in which a uniform pressure is applied, the largest displacements were localized in the sutures, especially in the anterior and posterior fontanels, as well as the metopic suture. When information of brain relative growth was introduced into the model, displacements were also concentrated in the lambda region although the values along both sides of the neurocranium (parietal and temporal bones) were larger than under the first scenario.

CONCLUSION

In sum, we propose a realistic approach to the use of FEA based on morphometric data that offered different results to more simplified models.

Closure of the anterior and posterior fontanelle in the New Zealand population: A computed tomography study

AIM

Significant ethnic variation has been demonstrated in the closure of the anterior fontanelle (AF); however, to date, this has not been investigated in the Māori/Pasifika population.

METHODS

The computed tomography scans of 163 individuals (116 Māori/Pasifika and 47 New Zealand (NZ) European) aged between birth and 4 years were retrospectively analysed to investigate the surface area (SA) and time of closure of the anterior and posterior fontanelles in New Zealand.

RESULTS

The Māori/Pasifika group showed clinical AF closure (SA < 114 mm² ) rates of 25% at 4-6 months, increasing to 47% at 10-12 months and 80% at 13-18 months. The posterior fontanelle was clinically unfused in 17% of the Māori/Pasifika group aged <1 month and in 7% of the 1-3-month-old group. No cases of posterior fontanelle non-fusion were identified in the NZ European population.

CONCLUSION

This study establishes normal values for AF size and closure frequency for the first time in the paediatric Māori/Pasifika population.

Anterior Fontanelle Size in Healthy Indian Late Preterm and Full Term Newborns

OBJECTIVE

To measure the size of the anterior fontanelle (AF) in healthy late-preterm and term newborns and correlate it with birth weight, gestational age, gender, occipito-frontal circumference, small for gestational age status and birth weight z-score.

METHODS

This was an observational study carried out from October 2013 through April 2015 at a tertiary care hospital. Newborns ≥ 34 wk gestation were enrolled. Fontanelle edge was palpated with index finger and size calculated by adding anterior-posterior and transverse diameters and dividing by two.

RESULTS

A total of 1010 neonates were enrolled. The mean AF size was 2.23 ± 0.52 cm (mean ± SD). There was a significant decrease in the size of the AF with advancing gestational maturity on one-way ANOVA (F = 31.30) (P < 0.001) and also by increasing birth weight (F = 20.34) (P < 0.001). There was no significant difference in the mean AF size between males; 2.21 ± 0.54 cm and females; 2.25 ± 0.55 cm (mean ± SD) (P = 0.575). There was a strong correlation between AF size with increasing birth weight; correlation (r) = 0.985. In small for gestational age neonates the AF was larger, 2.27 ± 0.55 (mean ± SD) and a strong correlation between birth weight z-score and AF size was noted (r = 1.012).

CONCLUSIONS

The mean AF size in late-preterm and term Indian newborns in a mixed community hospital was 2.23 ± 0.52. A strong correlation was found between AF size with increasing birth weight and with birth weight z-score in small for gestational age babies.

Anterior fontanelle size among term neonates on the first day of life born at University of Gondar Hospital, Northwest Ethiopia

Background

Anterior fontanelle is the largest, prominent and most important fontanelle, which is used for clinical evaluation. It is mainly characterized by its size and shape variation and is possibly influenced by gender, race and genetics. Understanding the variation of anterior fontanelle is used for recognition of different medical disorders and abnormal skeletal morphogenesis.

Objective

To determine the mean size of anterior fontanelle among term neonates on the first day of life born at University of Gondar Hospital, Gondar Town, Northwest Ethiopia, 2018.

Methods

Descriptive cross sectional study design was undertaken in 384 term and apparently healthy neonates, using standard methods. Descriptive analysis, student t-test, one way ANOVA and Pearson correlation coefficient were implemented.

Results

In this study, the mean size of anterior fontanelle in term neonates was 3.00 ± 0.62 cm (range 1.70–5.50 cm). The mean size of anterior fontanelle was 3.10 ± 0.66 cm for males, and 2.88 ± 0.57 cm for females. There was statistically significant difference in anterior fontanelle size in neonates of different genders (p<0.001), mode of delivery (p<0.001) and duration of labour (p = 0.006). However, the size of anterior fontanelle was not significantly affected by the birth order, onset of labour and socio-demographic variables of the mother except occupation of the mother (p = 0.01). There was a significant positive correlation between the mean size of anterior fontanelle with birth weight (r = 0.11; p = 0.04) and head circumference (r = 0.17; p = 0.001).

Conclusions

At term, male neonates had significantly larger anterior fontanelle than female neonates and anterior fontanelle size has a direct relationship with birth weight and head circumference.

A comprehensive review of the anterior fontanelle: embryology, anatomy, and clinical considerations

PURPOSE

Fontanelles are a regular feature of infant development in which two segments of bone remain separated, leaving an area of fibrous membrane or a "soft spot" that acts to accommodate growth of the brain without compression by the skull. Of the six fontanelles in the human skull, the anterior fontanelle, located between the frontal and parietal bones, serves as an important anatomical diagnostic tool in the assessment of impairments of the skull and brain and allows access to the brain and ventricles in the infant.

METHODS

Using a standard database search, we conducted a review of the anterior fontanelle, including its embryology, anatomy, pathology, and related surgical implications.

CONCLUSIONS

The diagnostic value of the anterior fontanelle, through observation of its shape, size, and palpability, makes the area of significant clinical value. It is important that clinicians are aware of the features and associated pathologies of this area in their everyday practice.

Primate pelvic anatomy and implications for birth

The pelvis performs two major functions for terrestrial mammals. It provides somewhat rigid support for muscles engaged in locomotion and, for females, it serves as the birth canal. The result for many species, and especially for encephalized primates, is an 'obstetric dilemma' whereby the neonate often has to negotiate a tight squeeze in order to be born. On top of what was probably a baseline of challenging birth, locomotor changes in the evolution of bipedalism in the human lineage resulted in an even more complex birth process. Negotiation of the bipedal pelvis requires a series of rotations, the end of which has the infant emerging from the birth canal facing the opposite direction from the mother. This pattern, strikingly different from what is typically seen in monkeys and apes, places a premium on having assistance at delivery. Recently reported observations of births in monkeys and apes are used to compare the process in human and non-human primates, highlighting similarities and differences. These include presentation (face, occiput anterior or posterior), internal and external rotation, use of the hands by mothers and infants, reliance on assistance, and the developmental state of the neonate.