Morphology of the foramen magnum in syndromic and non-syndromic brachycephaly

Re-imagining early cloverleaf skull deformity management from front to back approach-30 years on

The cloverleaf skull deformity remains among the most complicated craniofacial conditions to successfully manage. Many cases achieve largely unsatisfactory outcomes due to the requirement for frequent reoperation on the cranial vault and failure to deal with all the elements of the craniofaciostenosis in a timely fashion. Early cranial vault surgery without addressing the cranial base deformity and its attendant cerebrospinal fluid flow changes is invariably challenging and disappointing. A recent focus on the expansion of the posterior cranial vault as a primary procedure with the greater volume change allows a delay in fronto-orbital advancement and reduced need for repeat surgery. We herein describe three cases of complex multisuture craniosynostosis with cloverleaf skull deformity who underwent neonatal posterior cranial vault decompression along with foramen magnum decompression. Our report examines the safety and rationale for this pre-emptive surgical approach to simultaneously deal with the cranial vault and craniocervical junction abnormalities and thus change the early trajectory of these complex cases.

What We Know About Intracranial Hypertension in Children With Syndromic Craniosynostosis

OBJECTIVE

A scoping review of literature about mechanisms leading to intracranial hypertension (ICH) in syndromic craniosynostosis (sCS) patients, followed by a narrative synopsis of whether cognitive and behavioral outcome in sCS is more related to genetic origins, rather than the result of ICH.

METHODS

The scoping review comprised of a search of keywords in EMBASE, MEDLINE, Web of science, Cochrane Central Register of Trials, and Google scholar databases. Abstracts were read and clinical articles were selected for full-text review and data were extracted using a structured template. A priori, the authors planned to analyze mechanistic questions about ICH in sCS by focusing on 2 key aspects, including (1) the criteria for determining ICH and (2) the role of component factors in the Monro-Kellie hypothesis/doctrine leading to ICH, that is, cerebral blood volume, cerebrospinal fluid (CSF), and the intracranial volume.

RESULTS

Of 1893 search results, 90 full-text articles met criteria for further analysis. (1) Invasive intracranial pressure measurements are the gold standard for determining ICH. Of noninvasive alternatives to determine ICH, ophthalmologic ones like fundoscopy and retinal thickness scans are the most researched. (2) The narrative review shows how the findings relate to ICH using the Monro-Kellie doctrine.

CONCLUSIONS

Development of ICH is influenced by different aspects of sCS: deflection of skull growth, obstructive sleep apnea, venous hypertension, obstruction of CSF flow, and possibly reduced CSF absorption. Problems in cognition and behavior are more likely because of genetic origin. Cortical thinning and problems in visual function are likely the result of ICH.

Morphology of the Occipital Bones and Foramen Magnum Resulting From Premature Minor Suture Fusion in Crouzon Syndrome

To identify skull-base growth patterns in Crouzon syndrome, we hypothesized premature minor suture fusion restricts occipital bone development, secondarily limiting foramen magnum expansion.

Skull-base suture closure degree and cephalometric measurements were retrospectively studied using preoperative computed tomography (CT) scans and multiple linear regression analysis.

Evaluation of multi-institutional CT images and 3D reconstructions from Wake Forest's Craniofacial Imaging Database (WFCID).

Sixty preoperative patients with Crouzon syndrome under 12 years-old were selected from WFCID. The control group included 60 age- and sex-matched patients without craniosynostosis or prior craniofacial surgery.

None.

2D and 3D cephalometric measurements.

3D volumetric evaluation of the basioccipital, exo-occipital, and supraoccipital bones revealed decreased growth in Crouzon syndrome, attributed solely to premature minor suture fusion. Spheno-occipital (β = -398.75; P < .05) and petrous-occipital (β = -727.5; P < .001) suture fusion reduced growth of the basioccipital bone; lambdoid suture (β = -14 723.1; P < .001) and occipitomastoid synchondrosis (β = -16 419.3; P < .001) fusion reduced growth of the supraoccipital bone; and petrous-occipital suture (β = -673.3; P < .001), anterior intraoccipital synchondrosis (β = -368.47; P < .05), and posterior intraoccipital synchondrosis (β = -6261.42; P < .01) fusion reduced growth of the exo-occipital bone. Foramen magnum morphology is restricted in Crouzon syndrome but not directly caused by early suture fusion.

Premature minor suture fusion restricts the volume of developing occipital bones providing a plausible mechanism for observed foramen magnum anomalies.

The foramen magnum in scaphocephaly

PURPOSE

The foramen magnum (FM) presents various alterations in craniosynostoses, such as brachycephaly or Crouzon syndrome. However, to date, no study has been devoted to its morphology and morphometry in scaphocephaly, which is the most common of cranial deformities resulting from premature fusion of cranial sutures.

METHODS

We assessed the morphology and morphometry of FM using preoperative thin-cut CT scans of 107 children with non-syndromic sagittal craniosynostosis aged 1-12 months (mean age 5.38 months). A series of sagittal and transverse dimensions were taken and the FM area was calculated in each case. Obtained data were compared to the age-matched control group of 101 normocephalic children.

RESULTS

Dolichotrematous type of FM was dominant in the scaphocephaly group and observed in 63/107 cases (58.9%). The mean FM area in the scaphocephaly group was 519.64 mm² and was significantly smaller compared to the control group (p = 0.0011). The transverse diameter and anterior sagittal diameter were also significantly smaller (p = 0.0112 and p = 0.0003, respectively).

CONCLUSION

The area of FM in scaphocephaly is smaller compared to normal individuals. This is associated with a significant reduction of the width of FM in children with sagittal craniosynostosis. FM in scaphocephaly is larger than in other reported series of children with brachycephaly or Crouzon syndrome.

Morphometric Analysis of the Posterior Cranial Fossa in Syndromic and Nonsyndromic Craniosynostosis

Posterior cranial fossa (PCF) anatomy can be abnormal in craniosynostosis, and hindbrain herniation may occur. This study analyzed PCF anatomy in single suture and complex craniosynostosis.Children with craniosynostosis and age-matched controls were identified. Cephalic index (CI) for cranial vault and PCF as well as tentorial (TA) and occipital angles (OA) were measured on preoperative imaging.Children with syndromic (N = 6), bicoronal (N = 4), sagittal (N = 12), and metopic synostosis (N = 4) as well as controls (N = 10) were enrolled. Mean CI for cranial vault was 0.89, 0.93, 0.65, 0.74, and 0.78, respectively. Corresponding CI for PCF was 0.81, 0.93, 0.62, 0.74, and 0.78. Mean TA and OA were 45.4° and 96.6° in syndromic, 39.7° and 87.0° in bicoronal, 34.0 and 75.0° in sagittal, 39.7° and 87.0° in metopic synostosis, and 42.9° and 88.3° in controls.While CI, TA, and OA in metopic synostosis were similar to controls, abnormalities were found in syndromic, bicoronal, and sagittal synostosis. Syndromic and bicoronal craniosynostosis patients had a higher CI for both cranial vault and PFC as well as larger TA and OA, indicating a brachycephalic skull with steep tentorium and narrow PCF. In sagittal synostosis, CI for cranial vault and PCF were lower and TA and OA smaller, reflecting scaphocephalic deformity also at PCF, with a flat tentorium. This study provides basic PCF morphometry in craniofacial conditions.

Reduced Intercarotid Artery Distance in Syndromic and Isolated Brachycephaly

INTRODUCTION

The morphology of the skull base can be altered in craniosynostoses. The objective of this study is to evaluate the reduced intercarotid artery distance in the lacerum segment in patients with syndromic and isolated brachycephaly.

MATERIALS AND METHODS

The distances between the inner walls of the carotid canal at the lacerum segment were measured on high-resolution CT scans in children with Crouzon (25), Pfeiffer (21), Apert (26), Saethre-Chotzen (7) syndromes, isolated bicoronal synostosis (9), and compared to an age-matched control group (30).

RESULTS

A significantly smaller mean distance between carotid canal walls was observed in Crouzon (11.1 ± 4.9 mm), Pfeiffer (9.6 ± 5.1 mm), Apert (12.3 ± 4.3 mm), Saethre-Chotzen (14.8 ± 3.0 mm) syndromes, and isolated bicoronal synostosis (14.9 ± 3.7 mm) as compared to the control group (19.7 ± 2.4 mm, P < 0.001, P < 0.001, P < 0.001, P = 0.005, and P = 0.002, respectively). There was no statistically significant difference in intercarotid canal distance among the Apert, Saethre-Chotzen and isolated bicoronal synostosis groups. Overall, the brachycephalic group showed reduced intercarotid canal distance comparing to controls (P < 0.001).

DISCUSSION AND CONCLUSIONS

There is significant reduction of the distance between carotid canals in brachycephalic patients. This distance is more significantly altered in FGFR-related brachycephaly syndromes (especially Crouzon and Pfeiffer syndromes), than Saethre-Chotzen syndrome (TWIST1 mutation) and isolated non-syndromic bicoronal synostosis. This study highlights the importance of FGFRs in shaping the skull base. Altered vascular course of the internal carotid arteries can have important implications in planning skull base surgery in brachycephalic patients.

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.

Central nervous system and cervical spine abnormalities in Apert syndrome

PURPOSE

Apert syndrome characterized by acrocephalosyndactyly is a rare autosomal dominant congenital malformation with a prevalence of 1/65,000 births. With an extensive range of phenotypic and developmental manifestations, its management requires a multidisciplinary approach. A variety of craniofacial, central nervous system (CNS), and cervical spine abnormalities have been reported in these patients. This study aimed to determine the incidence of these CNS abnormalities in our case series.

METHODS

Retrospective review of Australian Craniofacial Unit (ACFU) database for Apert patients was performed. Data collected that included demographics, place of origin, age at presentation, imaging performed, and images were reviewed and recorded. Where available, developmental data was also recorded.

RESULTS

Ninety-four patients seen and managed at the ACFU had their CNS and cervical spine abnormalities documented. The main CNS abnormalities were prominent convolutional markings (67 %), ventriculomegaly (48 %), crowded foramen magnum (36 %), deficient septum pellucidum (13 %), and corpus callosum agenesis in 11 %. Major C-spine findings were present in 50.8 % of patients and included fusion of posterior elements of C5/C6 (50 %) and C3/4 (27 %). Multilevel fusion was seen in 20 %. Other abnormalities were C1 spina bifida occulta (7 %) and atlanto-axial subluxation (7 %).

CONCLUSION

Multiple CNS and cervical spine (c-spine) abnormalities are common in Apert syndrome. The significance of these abnormalities remains largely unknown. Further research is needed to better understand the impact of these findings on growth, development, and treatment outcomes.