Cephalic index correlates poorly with intracranial volume in non-syndromic scaphocephalic patients

Creation of the Scaphocephalic Index: Measurement of Global and Regional Severity in Scaphocephaly

BACKGROUND

The recently described frontal bossing index (FBI) and occipital bullet index (OBI) allow for quantification of scaphocephaly. A similar index examining biparietal narrowing has not been described. Addition of such an index measuring width would allow for direct evaluation of the primary growth restriction in sagittal craniosynostosis and the formation of an optimized global width/length measure.

METHODS

Computed tomography scans and three-dimensional photographs were used to recreate scalp surface anatomy. Equidistant axial, sagittal, and coronal planes were overlaid, creating a Cartesian grid. Points of intersection were analyzed for population trends in biparietal width. Using the most descriptive point coupled with the sellion protrusion to control for head size, the vertex narrowing index is formed. By combining this index with the FBI and OBI, the scaphocephalic index (SCI) is created as a tailored width/length measure.

RESULTS

Using 221 controls and 360 individuals with sagittal craniosynostosis, the greatest difference occurred superiorly and posteriorly at a point 70% of the head's height and 60% of the head's length. This point had an area under the curve of 0.97 and sensitivity and specificity of 91.2% and 92.2%, respectively. The SCI has an area under the curve of 0.9997, sensitivity and specificity greater than 99%, and interrater reliability of 0.995. The correlation coefficient between computed tomography imaging and three-dimensional photography was 0.96.

CONCLUSIONS

The vertex narrowing index, FBI, and OBI evaluate regional severity, while the SCI is able to describe global morphology in patients with sagittal craniosynostosis. These measures allow for superior diagnosis, surgical planning, and outcome assessment, independent of radiation.

Long-term results of minimally invasive strip craniectomy without helmet therapy for scaphocephaly - a single-centre experience

Scaphocephaly is the most common type of craniosynostosis and various surgical techniques are used for treatment. Due to late postoperative changes of the head shape, long-term outcome data is important for evaluating any new surgical technique. At our institution, minimally invasive strip craniectomy without regular helmet therapy is the standard treatment in scaphocephalic patients. Between October 2021 and February 2023, we retrospectively examined the skull shape of patients who underwent minimally invasive strip craniectomy for scaphocephaly using a 3D surface scan technique. The cephalic index (CI), the need for helmet therapy and additional cosmetic outcome parameters were investigated. We included 70 patients (72.5% male). The mean follow-up time was 46 (10-125) months and the mean CI was 75.7 (66.7-85.2). In 58 patients, the final cosmetic result was rated as "excellent/good" (mean CI: 76.3; 70.4-85.0), in 11 as "intermediate" (mean CI: 73.3; 66.7-77.6), and in one case as "unsatisfactory" (CI 69.3). The presence of a suboccipital protrusion was associated with a "less than good" outcome. The CI correlated significantly with the overall outcome, the presence of frontal bossing, and the interval between scan and surgery (age at scan). Minimally invasive strip craniectomy is an elegant and safe method to correct scaphocephaly. Our data show good cosmetic results in the long term even without regular postoperative helmet therapy.

Sagittal Craniosynostosis: Comparing Surgical Techniques Using 3D Photogrammetry

BACKGROUND

The aim of this study was to compare three surgical interventions for correction of sagittal synostosis-frontobiparietal remodeling (FBR), extended strip craniotomy (ESC), and spring-assisted correction (SAC)-based on three-dimensional (3D) photogrammetry and operation characteristics.

METHODS

Patients who were born between 1991 and 2019 and diagnosed with nonsyndromic sagittal synostosis who underwent FBR, ESC, or SAC and had at least one postoperative 3D photogrammetry image taken during one of six follow-up appointments until age 6 were considered for this study. Operative characteristics, postoperative complications, reinterventions, and presence of intracranial hypertension were collected. To assess cranial growth, orthogonal cranial slices and 3D photocephalometric measurements were extracted automatically and evaluated from 3D photogrammetry images.

RESULTS

A total of 322 postoperative 3D images from 218 patients were included. After correcting for age and sex, no significant differences were observed in 3D photocephalometric measurements. Mean cranial shapes suggested that postoperative growth and shape gradually normalized with higher occipitofrontal head circumference and intracranial volume values compared with normal values, regardless of type of surgery. Flattening of the vertex seems to persist after surgical correction. The authors' cranial 3D mesh processing tool has been made publicly available as a part of this study.

CONCLUSIONS

The findings suggest that until age 6, there are no significant differences among the FBR, ESC, and SAC in their ability to correct sagittal synostosis with regard to 3D photocephalometric measurements. Therefore, efforts should be made to ensure early diagnosis so that minimally invasive surgery is a viable treatment option.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Intracranial Volume Measured and Correlated to Cephalic Index in Syndromic and Nonsyndromic Anterior Brachycephaly

BACKGROUND

Premature fusion of both coronal sutures (anterior brachycephaly) alters skull shape and potentially affects intracranial volume (ICV). Currently little is known about preoperative ICV in anterior brachycephaly. Aim is to measure preoperative ICV and compare this with normative data. Additionally, ICV will be correlated to most used clinical method of quantification: cephalic index (CI).

METHODS

Preoperative patients with anterior brachycephaly (age, ≤12 months) were included and categorized by syndrome (when present). Computed tomography scans were used for ICV measurement by manual segmentation (OsiriX (Fondation OsiriX, Geneva, Switzerland)). Intracranial volume of each subgroup was compared with Lichtenberg normative cranial volume growth curves for controls. Cephalic index was calculated and correlated to ICV using Pearson correlation coefficient.

RESULTS

Thirty-four patients with both syndromic and nonsyndromic anterior brachycephaly were included: 17 with Apert syndrome, 6 with Muenke syndrome, 5 with Saethre Chotzen syndrome, 3 with Crouzon, 1 with craniofrontonasal dysplasia, and 2 nonsyndromal. Mean age at preoperative computed tomography scan was 4 months (1-10 months). Mean ICV was 847.31 cm3 (473.91-1459.22 cm3). Nineteen of 34 patients had skull volumes between ±2 SD curves of Lichtenberg, none of the patients had an ICV smaller than -2 SD and 15 of 34 had an ICV larger than +2 SD. Mean ICV in Apert syndrome was 829.85 cm3 (473.91-1061.53 cm3), in Muenke syndrome 942.06 cm3 (768.02-1136.75 cm3), in Saethre Chotzen syndrome 779.72 cm3 (609.21-1002.95 cm3), in Crouzon syndrome 700.57 cm3 (652.31-784.32 cm3), in craniofrontonasal dysplasia 738.97 cm3, and in the nonsyndromal group 1154.64 cm3 (850.07-1459.22 cm3). Apert had a mean greater than +2SD above the mean, the other subgroups had a mean within normal ranges (±2 SD). Correlation between severity of brachycephaly and overall ICV was low (r = 0.42).

CONCLUSIONS

Mean preoperative ICV in both syndromic and nonsyndromic anterior brachycephaly was 847.31 cm3. Intracranial volume in anterior brachycephaly is in 55.9% between normal ranges (±2 SD). In 44.1% ICV was greater than +2 SD, especially in Apert syndrome (11/16 Apert patients). None of the included patients had a deviant small ICV of less than -2 SD. Additionally, low correlation between ICV and CI (r = 0.42) was found and therefore CI is not suitable for estimating ICV in anterior brachycephaly.

Does Coronal Suturectomies and Occipital Barrel Staves Make a Difference in Early Reconstruction for Sagittal Craniosynostosis?

BACKGROUND

Various surgical methods are used for early treatment of nonsyndromic sagittal craniosynostosis. The craniofacial centers in Uppsala and Helsinki fundamentally both use the H-Craniectomy: Renier's technique. However, the Helsinki group systematically adds coronal suturectomies to prevent secondary coronal synostosis and posterior barrel staves to address posterior bulleting. The effects of these additions in early treatment of sagittal craniosynostosis are currently unknown.

METHODS

Thirty-six patients from Uppsala and 27 patients from Helsinki were included in the study. Clinical data and computed tomography scans were retrieved for all patients.

RESULTS

The Helsinki patients had a smaller preoperative Cranial index (CI) (65 vs 72) and a smaller preoperative width (10.1 vs 11.2). There was no difference in postoperative CI, corresponding to a difference in change in CI. Regression analysis indicated that the larger change in CI in the Helsinki group was mainly due to a lower preoperative CI allowing for a larger normalization. The Helsinki patients had less growth in length (1.5 vs 2.1 cm) and more growth in width (2.3 vs 1.9 cm). There were no differences in head circumference or surgical complications. Secondary coronal synostosis was present in 43% of the Uppsala group at 3 years of age, while calvarial defects located at sites of previous coronal suturectomies and posterior barrel staving were seen in the Helsinki group 1 year postoperatively.

CONCLUSIONS

Lower preoperative CI appears to be the main factor in determining the amount of normalization in CI. Prophylactic coronal suturectomies do not seem to benefit preservation of coronal growth function since the modification correlates to less sagittal growth and more growth in width.

Dental Age, Agenesis, and Morphology in Patients With Operated Single-Suture Craniosynostoses

OBJECTIVE

The aim of this study was to evaluate the dental age, agenesis, and morphology of children with surgically operated single-suture craniosynostoses from orthopantomographs.

DESIGN

A single-centered cross-sectional observational archival study.

PATIENTS

A sample of 196 Finnish patients with single-suture craniosynostosis without additional birth defects or syndromes (excluding Muenke syndrome) was included in this study.

MAIN OUTCOME MEASURES

Dental age was assessed using the method developed by Demirjian et al. and modified by Nyström et al. for the Finnish population. Methods described by Tulensalo et al. and Oehlers et al. were used to study taurodontism and dens invaginatus, respectively.

RESULTS

The study sample of 149 patients was divided into 3 groups: patients with sagittal synostosis (n = 103), coronal synostosis (n = 25), and metopic synostosis (n = 21). Orthopantomographs taken on average at ages 8.20 to 8.33 were used. The dental ages in different groups were on average 0.37, 0.60, and 0.66 years ahead of normative values, for sagittal, coronal, and metopic groups, respectively. Tooth agenesis, taurodontism, and invaginated teeth were found in all groups with invaginations having a high prevalence. Peg-shaped upper lateral incisors and one geminated lower lateral incisor were also found.

CONCLUSIONS

These descriptive data may help improve dental care in patients with single-suture craniosynostosis.

A systematic quantitative morpho-volumetric analysis in infants with sagittal craniosynostosis and relationship with the severity of scaphocephalic deformity

PURPOSE

Among patients with isolated sagittal synostosis (ISS), the head shape varies considerably in relation to the severity of the abnormality. This study aimed to quantify skull base morphometry and intracranial volume to investigate their relationships with the severity of scaphocephaly.

METHODS

We studied 66 infants with ISS identifying three groups according to the morphological severity of cranial deformity (group I: mild deformity; group II: moderate deformity; group III: severe deformity), by combining two scaphocephaly severity indices as descriptors of the relation of three morphological measurements (length, width and height) We perform a quantitative analysis using high-resolution CT images calculating following parameters: cranial fossae dimensions, supratentorial (ICV) and infratentorial (PCFV) cranial volume, supratentorial (WBV) and infratentorial (PCFBV) brain volume, ICV/WBV, PCFV/PCFBV, supratentorial and infratentorial cerebrospinal fluid (CSF).

RESULTS

In all subgroups, anterior and middle skull base lengths were increased, while posterior hemifossae lengths were unchanged. In mild subgroup, ICV/WBV was significantly different and ICV, WBV and CSF supratentorial volume increased (p < 0.05). In moderate and severe subgroups, FCPV/FCPBV was significantly different and CSF infratentorial volume was reduced (p < 0.05); FCPBV was increased only in the severe subgroup (p < 0.05).

CONCLUSION

This morpho-volumetric study provides new insights in understanding the compensatory changes occurring in infants at different stages of scaphocephaly severity. In particular, our study suggests that patients with severe deformity might have an earlier depletion of reserve mechanisms with a reduced compliance of the overall skull during encephalic growth and these patients might require early surgical cranial expansion.

Comparing Cephalic Index and Midsagittal Vector Analysis in Assessing Morphology in Sagittal Synostosis: A CT-Based Morphometric Analysis

INTRODUCTION

Assessment of cranial dysmorphism in sagittal synostosis is often subjective but objective measures can be applied. These include cephalic index (CI) and midsagittal vector analysis (MSVA).

OBJECTIVE

To assess discriminant validity, construct validity, and responsiveness of CI and MSVA measured from computed tomography (CT) in patients with sagittal synostosis.

METHODS

Patients with nonsyndromic isolated sagittal synostosis with complete preoperative (n = 30) and postoperative (n = 13) CT data were included. Age-matched control group (n = 24) comprised of normocephalic patients who underwent CT for reasons related to trauma.

OUTCOME MEASURES

Retrospective CT evaluation of CI and MSVA was conducted and correlated with a dysmorphism numeric rating scale (D-NRS) that measured surgeon-rated severity of sagittal synostosis. Responsiveness of CI and MSVA was evaluated using dysmorphism global rating of change (D-GRC).

RESULTS

Thirty patients with sagittal synostosis were demographically similar to 24 normocephalic patients. The difference in CI and MSVA was statistically significant between normocephalic and scaphocephalic patients. Cephalic index had a good correlation with D-NRS (r = -0.665, ρ = -0.667), but not with MSVA (r = 0.250, ρ = 0.203). Change in CI (r = 0.738, ρ = 0.657) was well correlated with D-GRC, but not with MSVA (r = -0.409, ρ = -0.301).

CONCLUSION

Cephalic index appears to quantify the severity of sagittal synostosis better than MSVA. Cephalic index also has better responsiveness than MSVA to measure a reduction in severity of disease; however, MSVA is a better descriptive craniometric measurement. Midsagittal vector analysis was able to quantify the shift in morphology in sagittal synostosis following surgical treatment.

Length of synostosis and segmented intracranial volume correlate with age in patients with non-syndromic sagittal synostosis

PURPOSE

The aim of this study is to compare the length of synostosis and segmented intracranial volume (SIV) with age in children with non-syndromic sagittal synostosis.

METHODS

Thirty-three consecutive patients (22 boys) who had been operated by cranial vault remodeling because of sagittal synostosis were compared retrospectively from 3D-CT imaging data sets obtained from volumetric CT. The mean age of the patients at preoperative CT imaging was 0.49 (range 0.13-1.3) years and at 1-year postoperative imaging 1.8 (range 1.3-3) years. The mean interval between preoperative CT imaging and surgery was 0.25 (range 0-0.8) years. Pearson's correlation and Student's t test were used in the statistical analyses.

RESULTS

Length of sagittal synostosis correlated positively with age at preoperative CT (r = 0.688, p < 0.01). Children with total synostosis (n = 9) were significantly older (mean age 0.74 vs. 0.4 years, p < 0.01) than those with partial synostosis. Of partial synostoses, 9 were located anteriorly, 3 in the middle, and 12 posteriorly. The mean synostosis ratio (synostosis length/total sagittal suture length × 100) was 83%. Preoperative SIV correlated positively with age at preoperative CT (r = 0.788, p < 0.01), whereas the 1-year postoperative SIV did not correlate with age at operation. The older the child at the time of the operation, the less the percentage SIV increased.

CONCLUSIONS

Length of sagittal synostosis and SIV increased with age.

The value of three-dimensional photogrammetry in isolated sagittal synostosis: Impact of age and surgical technique on intracranial volume and cephalic index─a retrospective cohort study

PURPOSE

The aim of this study was to compare the outcome of intracranial volume (ICV) and cephalic index (CI) between two different techniques for surgical therapy of sagittal synostosis.

MATERIAL AND METHODS

Between 2011 and 2015, all patients scheduled for surgical therapy of sagittal synostosis were consecutively enrolled. All patients younger than 6 months underwent early extended strip craniectomy (ESC group), and patients older than 6 months underwent late modified pi-procedure (MPP group). To measure ICV and CI, data acquisition was performed via three-dimensional photogrammetry, 1 day before (T0) and between 10 and 12 weeks after surgery (T1). Results were compared with an age-matched reference group of healthy children. Perioperative parameters, as duration of surgery and the amount of blood loss of both surgical procedures were analyzed.

RESULTS

A total of 85 patients were enrolled. Of the patients, 48 underwent an extended strip craniotomy with parietal osteotomies and biparietal widening and 37 patients underwent a late modified pi-procedure. There was no significant difference between the ESC group and the MPP group regarding the efficacy of improving CI (p > 0.05). Both techniques were able to normalize CI and to improve head shape. ICV was normal compared to age-matched norm-groups with both techniques, pre- and postoperatively. However, duration of the surgical procedure and calculated blood loss were significantly lower in the ESC group (p < 0.05).

CONCLUSION

ESC and MPP were effective techniques to normalize cephalic index (CI) and improve head shape at their recommended time of surgery. Measurement of ICV and CI with 3D photogrammetry is a valid method to objectively evaluate patients before and after surgery without exposing pediatric patients to ionizing radiation.

An Appraisal of the Cephalic Index in Sagittal Craniosynostosis, and the Unseen Third Dimension

BACKGROUND

The cephalic index is often used to evaluate sagittal craniosynostosis corrections; however, validation of this measure remains untested.

METHODS

A three-part study was designed to (1) determine the normal distribution of cephalic indices in untreated sagittal craniosynostosis; (2) examine index values in treated children, subsequently determined to require secondary surgery; and (3) explore the correlation between a photography-based assessment of scaphocephaly severity and the cephalic index.

RESULTS

Of 392 preoperatively measured patients (mean cephalic index, 70.7; 95 percent CI, 57.4 to 89.5), 343 (87.5 percent) had Z scores falling within 2 SD of the mean; only 49 (12.5 percent) fell more than 2 SD below the mean, whereas 13 percent exceeded the mean. For 10 patients requiring secondary surgery (mean cephalic index, 74.8; 95 percent CI, 68.1 to 83.4), the mean Z score was -0.5 (range, -2.5 to 1.6). The polled results of 10 observers revealed no significant correlation between subjectively ranked severity scores and cephalic indices.

CONCLUSIONS

Although the average preoperative cephalic index in children with sagittal craniosynostosis was below normal, the majority of measurements fell within a statistically normal distribution. Furthermore, many children requiring secondary corrections were found to have relatively normal indices, suggesting that normal values are not necessarily predictive of satisfactory outcomes. We also found no correlation between this index and a subjective assessment of severity. These findings suggest that the cephalic index is not a reliable outcome measure, perhaps because of the inability for this ratio to capture the amount of correction of the reduced posterior skull height associated with sagittal craniosynostosis.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Diagnostic, IV.

A Systematic Approach to Predicting Spring Force for Sagittal Craniosynostosis Surgery

Spring-assisted surgery (SAS) can effectively treat scaphocephaly by reshaping crania with the appropriate spring force. However, it is difficult to accurately estimate spring force without considering biomechanical properties of tissues. This study presents and validates a reliable system to accurately predict the spring force for sagittal craniosynostosis surgery. The authors randomly chose 23 patients who underwent SAS and had been followed for at least 2 years. An elastic model was designed to characterize the biomechanical behavior of calvarial bone tissue for each individual. After simulating the contact force on accurate position of the skull strip with the springs, the finite element method was applied to calculating the stress of each tissue node based on the elastic model. A support vector regression approach was then used to model the relationships between biomechanical properties generated from spring force, bone thickness, and the change of cephalic index after surgery. Therefore, for a new patient, the optimal spring force can be predicted based on the learned model with virtual spring simulation and dynamic programming approach prior to SAS. Leave-one-out cross-validation was implemented to assess the accuracy of our prediction. As a result, the mean prediction accuracy of this model was 93.35%, demonstrating the great potential of this model as a useful adjunct for preoperative planning tool.

Intracranial volume (ICV) in isolated sagittal craniosynostosis measured by 3D photocephalometry: A new perspective on a controversial issue

BACKGROUND

There are still controversies regarding the intracranial volumes in patients with isolated sagittal craniosynostosis compared to a healthy population. This study aimed to compare the intracranial volume of children with sagittal synostosis and scaphocephaly to an age- and gender-matched control cohort using three-dimensional (3D) photogrammetry.

METHODS

62 boys and nine girls with sagittal craniosynostosis were included in this study. The intracranial volume was measured at the first clinical presentation. However, 3D photogrammetry was performed at children not younger than 3 months. The 3D photogrammetric data of 547 healthy boys and 287 healthy girls between the ages of 3-10 month was analyzed to establish an age- and gender-matched control group.

RESULTS

Male patients with sagittal synostosis showed a significantly reduced intracranial volume compared to the reference group. For female patients, the intracranial volume was slightly lower compared to the norm group, but not significantly.

CONCLUSIONS

Male children with sagittal synostosis showed significantly decreased intracranial volume between the age of 3 and 10 months compared to an age- and gender-matched control group. Female patients in the same age group presented a lower intracranial volume compared to the norm group. Measuring intracranial volume using 3D photogrammetry is a comparable and valuable alternative to CT scans that leads to a significant reduction of radiation exposure to the growing brain.