Recent advances in trigonocephaly

Nonsyndromic Craniofacial Disorders

We describe the investigation and management of select pediatric craniofacial disorders their recent advances. Positional plagiocephaly: The incidence of positional plagiocephaly has increased since the institution of the "safe to sleep" campaign to reduce sudden infant death syndrome. Positional plagiocephaly may be associated with underlying developmental delay. Nonsyndromic craniosynostosis: Treatment of nonsyndromic craniosynostosis depends on the age of the patient and the suture involved. Pediatric skull lesions: Management of skull lesions depends on histologic diagnosis. Some benign skull lesions are managed conservatively, whereas erosive and malignant lesions may require surgical excision, radiotherapy, chemotherapy, or multimodality treatment.

Clinical interest of molecular study in cases of isolated midline craniosynostosis

In some cases of infants with apparently isolated single-suture synostosis, an underlying variant can be found. We aimed to determine the molecular substratum in isolated sagittal and metopic craniosynostosis. To this end, we included all infants who presented isolated midline synostosis (sagittal or metopic) and had undergone surgery at the craniosynostosis national reference center of Lyon University Hospital. All infants were examined by a multidisciplinary team including neurosurgeons, clinical geneticists and neuropsychologist. Among 101 infants tested, 13 carried a total of 13 variants; that is, 12.9% of the infants carried a variant in genes known to be involved in craniosynostosis. Seven infants carried SMAD6 variants, 2 in FGFR2, 1 in TWIST1, one in FREM1, one in ALX4 and one in TCF12. All variants were detected at the heterozygous level in genes associated with autosomal dominant craniosynostosis. Also, neurodevelopmental testing showed especially delayed acquisition of language in children with than without variants in SMAD6. In conclusion, a high percentage of young children with isolated midline craniosynostosis, especially in isolated trigonocephaly, carried SMAD6 variants. The interpretation of the pathogenicity of the genes must take into account incomplete penetrance, usually observed in craniosynostosis. Our results highlight the interest of molecular analysis in the context of isolated sagittal and/or metopic craniosynostosis to enhance an understanding of the pathophysiology of midline craniosynostosis.

Trigonocephaly: Quantitative Comparison of the Complete Vault Reconstruction and Minimally Invasive Suturectomy

OBJECTIVE

The objective of the study was to present and compare outcomes and complications of conventional open reconstruction and minimally invasive correction of metopic synostosis in patients who underwent treatment of trigonocephaly in our center between 2015 and 2019.

METHODS

The hospital database was searched for hospitalization and surgical information, as well as imaging of individuals with trigonocephaly. Postoperative evaluation of the patients was performed during the follow-up sessions. The radiological evaluation was based on brain computed tomography scans taken 2 years following the operation.

RESULTS

Sixty-four patients (19 females and 45 males) had their trigonocephaly corrected surgically. Thirty-five patients (9 females and 26 males) had complete vault reconstruction surgery, while 29 patients (10 females and 19 males) had minimally invasive suturectomy (MIS). The postoperative cephalic width/intercoronal distance ratio and interpupillary distance/interfrontozygomatic distance ratio assessment showed no differences in the outcome of both groups (P value > 0.05). Minimally invasive techniques resulted in less intraoperative bleeding, a shorter stay in the intensive care unit and hospital, and a shorter surgery and anesthesia duration (P value < 0.05).

CONCLUSIONS

Surgical treatment of trigonocephaly can result in a satisfactory correction of the deformity. MIS delivers a comparable result to complete vault reconstruction with less invasiveness and hospitalization and can be considered a reasonable option for patients in their early months of life. Patients must, however, undergo long-term cosmetic, behavioral, and developmental evaluations.

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.

A Diffusion Tensor Imaging Analysis of Frontal Lobe White Matter Microstructure in Trigonocephaly Patients

BACKGROUND

Children with trigonocephaly are at risk for neurodevelopmental disorders. The aim of this study is to investigate white matter properties of the frontal lobes in young, unoperated patients with metopic synostosis as compared to healthy controls using diffusion tension imaging (DTI).

METHODS

Preoperative DTI data sets of 46 patients with trigonocephaly with a median age of 0.49 (interquartile range: 0.38) years were compared with 21 controls with a median age of 1.44 (0.98) years. White matter metrics of the tracts in the frontal lobe were calculated using FMRIB Software Library (FSL). The mean value of tract-specific fractional anisotropy (FA) and mean diffusivity (MD) were estimated for each subject and compared to healthy controls. By linear regression, FA and MD values per tract were assessed by trigonocephaly, sex, and age.

RESULTS

The mean FA and MD values in the frontal lobe tracts of untreated trigonocephaly patients, younger than 3 years, were not significantly different in comparison to controls, where age showed to be a significant associated factor.

CONCLUSIONS

Microstructural parameters of white matter tracts of the frontal lobe of patients with trigonocephaly are comparable to those of controls aged 0-3 years.

Cerebral Blood Flow of the Frontal Lobe in Untreated Children with Trigonocephaly versus Healthy Controls: An Arterial Spin Labeling Study

BACKGROUND

Craniofacial surgery is the standard treatment for children with moderate to severe trigonocephaly. The added value of surgery to release restriction of the frontal lobes is unproven, however. In this study, the authors aim to address the hypothesis that the frontal lobe perfusion is not restricted in trigonocephaly patients by investigating cerebral blood flow.

METHODS

Between 2018 and 2020, trigonocephaly patients for whom a surgical correction was considered underwent magnetic resonance imaging brain studies with arterial spin labeling to measure cerebral perfusion. The mean value of cerebral blood flow in the frontal lobe was calculated for each subject and compared to that of healthy controls.

RESULTS

Magnetic resonance imaging scans of 36 trigonocephaly patients (median age, 0.5 years; interquartile range, 0.3; 11 female patients) were included and compared to those of 16 controls (median age, 0.83 years; interquartile range, 0.56; 10 female patients). The mean cerebral blood flow values in the frontal lobe of the trigonocephaly patients (73.0 ml/100 g/min; SE, 2.97 ml/100 g/min) were not significantly different in comparison to control values (70.5 ml/100 g/min; SE, 4.45 ml/100 g/min; p = 0.65). The superior, middle, and inferior gyri of the frontal lobe showed no significant differences either.

CONCLUSIONS

The authors' findings suggest that the frontal lobes of trigonocephaly patients aged less than 18 months have a normal cerebral blood flow before surgery. In addition to the very low prevalence of papilledema or impaired skull growth previously reported, this finding further supports the authors' hypothesis that craniofacial surgery for trigonocephaly is rarely indicated for signs of raised intracranial pressure or restricted perfusion for patients younger than 18 months.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Risk, II.

Fetal Trigonocephaly (Strawberry Skull) in Early Pregnancy

Trigonocephaly was previously described prenatally in association with severe abnormalities, mostly observed after 18 weeks of gestation. We describe our experience with this finding in early pregnancy, between 14 and 17 weeks of gestation. Our series includes 18 cases of trigonocephaly with several etiologies; trisomy 18, de novo translocation, thanatophoric dysplasia, and open spina bifida without hydrocephalus. Two fetuses had no other significant abnormalities and a spontaneous normalization of the skull shape was observed on follow-up. Both had normal genetic testing and postnatal outcome. These two cases represent a new phenomenon of an isolated transient form with normal outcome.

Trigonocephaly and Cranium Bifidum Occultum Treated Simultaneously Using the Split-Bone Technique and Piezosurgery

Cranium bifidum occultum (CBO) is a rare congenital disease characterized by the anomalous ossification of parietal bones, which presents with a midline bone defect with no extrusion of intracranial content. Its association with craniosynostosis has been reported only a few times to date. The aim of this case report was to describe, for the first time, the association between presumed non-syndromic trigonocephaly and CBO, as well as the treatment of both conditions using the same surgical approach. This was done by performing fronto-orbital advancement and the split-bone technique using piezosurgery, in order to achieve an autologous sample to cover the bone defect. To the best of our knowledge, this approach was proven to be safe and able to treat both diseases without a heterologous bone graft.

Heterozygous intragenic deletions of FREM1 are not associated with trigonocephaly

Recessive mutations in FRAS1-related extracellular matrix 1 (FREM1) are associated with two rare genetic disorders, Manitoba-oculo-tricho-anal (MOTA) and bifid nose with or without anorectal and renal anomalies (BNAR). Fraser syndrome is a more severe disorder that shows phenotypic overlap with both MOTA and anorectal and renal anomalies and results from mutations in FRAS1, FREM2 and GRIP1. Heterozygous missense mutations in FREM1 were reported in association with isolated trigonocephaly with dominant inheritance and incomplete penetrance. Moreover, large deletions encompassing FREM1 have been reported in association with a syndromic form of trigonocephaly and were designated as trigonocephaly type 2. Trigonocephaly results from premature closure of the metopic suture and typically manifests as a form of nonsyndromic craniosynostosis. We report on 20 patients evaluated for developmental delay and without abnormal metopic suture. Chromosomal microarray analysis revealed heterozygous FREM1 deletions in 18 patients and in 4 phenotypically normal parents. Two patients were diagnosed with MOTA and had homozygous FREM1 deletions. Therefore, although our results are consistent with the previous reports of homozygous deletions causing MOTA, we report no association between heterozygous FREM1 deletions and trigonocephaly in this cohort.

Craniometric Measurements and Surgical Outcomes in Trigonocephaly Patients Who Underwent Surgical Treatment

Objective

The aim of this study was to discuss the results of craniometric measurements and surgical treatments in patients operated for isolated trigonocephaly (TC) in light of the current literature.

Methods

A total of 18 cases who underwent surgery for isolated TC were included in the study. Age, gender, family history, follow-up time, complications, duration of surgery, surgical blood loss, and amount of blood replacement in these patients were recorded. Craniometric measurements such as metopic angle (MA), cephalic index (CI), interparietal distance (IPD), intercoronal distance (ICD), and their ratio to each other were evaluated according to pre-and postoperative parameters. Photographs of the patients were taken before and after the operation. The Whitaker classification and Kampf "aesthetic outcome staging" were used in the evaluations.

Results

The mean MA values after the operation increased to reach above 147 degrees in all cases. The average CI did not change. ICD measurement averages increased significantly. The average IPD/ICD ratio decreased due to the increase in ICD and the enlargement of the anterior fossa after the operation. According to the Whitaker classification and Kampf “aesthetic outcome staging” scale, 17 of our cases were at stage I, rated as perfect, and one was at stage II, rated as good.

Conclusion

Surgery performed at the appropriate time for TC yields cosmetically satisfactory results. Since potential neurological and cognitive morbidities occur mostly in school-age patients, long-term follow-up of the cases is required. Performing craniometric measurements enables patients to be evaluated with objective and measurable numerical data.

Distinguishing craniomorphometric characteristics and severity in metopic synostosis patients

The decision about which metopic synostosis patients should undergo surgery remains controversial. Multiple measures for radiographic severity have been developed in order to determine the optimal criteria for treatment. The aim of this study was to perform an extensive craniomorphometric analysis of patients who underwent surgery for metopic synostosis to validate and compare the various severity scales developed for this non-syndromic craniosynostosis. A comparative morphometric analysis was performed using computed tomography scans of preoperative metopic synostosis patients (n=167) and normal controls (n=44). Measurements included previous and newly developed metopic severity indices. Volumetric and area analyses were used to determine the degree of anterior cranial area and potential volume restrictions. Of the severity indices measured, the frontal angle, endocranial bifrontal angle (EBF), adjusted EBF (aEBF), anterior cranial fossa angle, horizontal cone angle, and bitemporal/biparietal distance ratio were significantly different in the metopic subjects relative to controls overall. However, metopic index, orbital rim angle, foramen ovale distance, and cranial volume exhibited no significant difference from controls. Only the frontal angle and aEBF correlated with the changes in anterior cranial dimensions observed in metopic synostosis. In conclusion, the frontal angle and aEBF provide the most accurate measures of severity in metopic synostosis.