The Significance of Squamosal Suture Synostosis

Squamosal Craniosynostosis Associated with Rickets

Rickets results from defective bone mineralization, leading to skeletal deformities. Among those deformities, rickets has been associated with craniosynostosis, the premature closure of cranial sutures. Most of these patients have fusion of major sutures. Rarely, squamosal craniosynostosis in association with rickets has been described. Squamosal craniosynostosis is noted as lacking a definitive head abnormality and difficult visualization on standard imaging modalities, leading to poor recognition. Careful attention should be given to rickets patients to monitor for these unusual suture closures. Additionally, craniosynostosis could be a presenting feature of rickets, and further rickets evaluation of the patient is indicated.

Surgical Management in Isolated Squamosal Craniosynostosis: A Systematic Review

BACKGROUND

Although craniosynostoses involving the major sutures have been well described, the frequency of isolated minor suture craniosynostoses is much lower. Squamosal craniosynostosis (SQS) is a rare form of cranial synostosis, and the paucity of literature has made the creation of a standardized treatment plan difficult. We present a systematic review of the literature on isolated SQS to identify disease characteristics that lead to a need for operative intervention and to delineate patterns in surgical management.

METHODS

A systematic literature review was performed using the electronic databases of PubMed, Scopus, and MEDLINE and the key words "squamosal AND craniosynostosis," "squamous AND craniosynostosis," "squamosal craniosynostosis, "squamosal suture craniosynostosis," and "isolated squamosal craniosynostosis." Only human studies that described presentation and management of SQS were included. A blinded, 2-reviewer analysis of the articles was performed. Data collected included patient and disease characteristics, imaging workup, and treatment specifics, which were analyzed by descriptive statistics.

RESULTS

A total of 19 studies examining 119 patients with SQS were reviewed, with 97 (82%) multisutural cases and 22 isolated cases (18%). Of the isolated cases, 6 (27%) required surgical craniosynostosis repair, of which 1 (17%) had unilateral sutural involvement and 5 (83%) had bilateral involvement. Of the patients with isolated SQS, 7 (32%) had a congenital syndrome and comprised 33% of patients who required surgical intervention. The nonsyndromic patients with isolated SQS who required surgery presented with a wide array of phenotypic findings; 3 patients underwent some form of cranial vault remodeling, whereas 1 patient underwent ventriculoperitoneal shunt only. Of the 4 nonsyndromic patients with isolated SQS who underwent surgical repair, half required operative intervention because of elevated intracranial pressure and the other half because of dysmorphic head shape.

CONCLUSION

The findings of this updated systematic review suggest a trend toward surgical management in bilateral SQS versus unilateral SQS, and that patients with isolated SQS, previously considered to be a nonsurgical finding, should be carefully monitored, as there remains risk of increased intracranial pressure. Pooled systematic review data suggest isolated SQS has a 27% operative intervention rate, with the presence of coexisting syndromic diagnoses increasing that risk.

Squamosal Suture Synostosis: An Under-Recognized Phenomenon

INTRODUCTION

The squamosal suture (SQS) joins the temporal to the parietal bones bilaterally and is a poorly described site of craniosynostosis. SQS fusion is thought to occur as late as the fourth decade of life and beyond; however, we have incidentally noted its presence among our pediatric patients and hypothesize that it may occur earlier in life and more frequently than previously believed.

METHODS

A retrospective review of imaging performed on pediatric patients was completed to identify patients with SQS synostosis. This included a review of clinical notes as well as computed tomography (CT) images obtained by our craniofacial clinic. Relevant patient data and imaging were reviewed.

RESULTS

Forty-seven patients were identified with SQS synostosis, 21 were female (45%). Age at the time of radiographic diagnosis was 10.1 ± 8.4 years (range 17 days to 27 years). A majority of patients had bilateral SQS synostosis (57%), with a relatively even distribution of unilateral right (23%) versus left (19%). SQS was an isolated finding (no other suture involvement) in 15 patients (32%), all of whom were normocephalic and did not require surgical intervention. Thirty-two patients (68%) had concomitant craniosynostosis of other sutures, most commonly sagittal and coronal. Nine patients (19%) underwent surgery to correct cranial malformations-all these patients had multi-suture synostosis (P = 0.012). Twenty-seven patients (57%) had SQS synostosis diagnosed incidentally compared to 20 (43%) who were imaged with suspicion for synostosis. In those who were symptomatic, common findings included developmental delay, elevated intracranial pressure, hydrocephalus, seizures, and visual/hearing impairments. Ten patients (21%) were syndromic, the most frequent of which was Crouzon syndrome. No single pattern of calvarial malformation could be definitively described for SQS synostosis.

CONCLUSION

Given that most isolated SQS synostosis cases were normocephalic, asymptomatic, and discovered incidentally, it is likely that there are many cases of unidentified SQS synostosis. The significance of SQS synostosis is currently unclear, and warrants further investigation into this phenomenon, its natural course, and its potential presence in the spectrum of normal development.

Fusion of Lateral Calvarial Sutures on Volume-Rendered Computed Tomography Reconstructions in Patients With Known Craniosynostosis

INTRODUCTION

After treating a child with familial sagittal craniosynostosis, clinocephaly, and bilateral parietomastoid/posterior squamosal suture fusion, the authors wondered if major-suture synostosis and clinocephaly were associated with abnormal fusion of minor lateral calvarial sutures.

METHODS

The authors reviewed all preoperative volume-rendered head computed tomography reconstructions performed for craniosynostosis at their institution from 2010 through 2014 and determined whether the sphenoparietal, squamosal, and parietomastoid sutures were open, partially fused, or fused. The authors determined whether any sutures were abnormally fused based upon a previous study from their center, in which abnormal fusion was defined as either 1 of 3 abnormal fusion patterns or abnormally-early fusion. The authors then determined the rate of abnormal fusion of these sutures and whether abnormal fusion was associated with (1) major-suture craniosynostosis, (2) type of craniosynostosis (sutures involved; single-suture versus multisuture; syndromic versus nonsyndromic), and (3) clinocephaly.

RESULTS

In 97 included children, minor lateral sutures were abnormally fused in 8, or 8.2%, which was significantly higher than in children without craniosynostosis from our earlier study. Abnormal minor lateral suture fusion was not associated with the type of single-suture synostosis or with multisuture synostosis but was associated with syndromic synostosis. Four of 8 children with abnormal minor lateral suture fusion had multisuture synostosis and 6 had syndromic synostosis. Lateral sutures were abnormally fused in 1 of 4 subjects with clinocephaly, which was not significant.

CONCLUSION

Abnormal minor lateral calvarial suture fusion is significantly associated with major-suture craniosynostosis, especially syndromic synostosis.

Management of Minor Suture Craniosynostosis

Although most reported cases of minor suture involvement include multiple sutures, isolated suture involvement has been reported. Morphologic differences such as scaphocephaly and anterior plagiocephaly have been reported. Management should involve proper identification and multidisciplinary treatment. Surgical treatment should involve the expansion of the cranial vault as well as the correction of the deformity.

Delayed Presentation of Sagittal Suture Craniosynostosis

BACKGROUND

Sagittal craniosynostosis typically presents as dolichocephaly or less frequently as clinocephaly, a "saddle-shaped" phenotype. This project aimed to characterize clinically relevant differences between sagittal synostosis phenotypes and examine the etiology of the delay in presentation.

METHODS

An institutional review board-approved retrospective review was performed from January 1999 to November 2018 at a single institution. Analyses examined correlations between subphenotype, time of presentation, minor suture fusion, developmental delay, and operative technique.

RESULTS

One hundred sixty patients diagnosed with single-suture sagittal craniosynostosis were identified. A total of 30.6% had a saddle phenotype (n = 49) and 69.4% had dolichocephaly (n = 111). Patients with the saddle phenotype were more likely to present with a developmental delay and to have at least 1 minor suture fused than patients with dolichocephaly were. Patients with the saddle phenotype presented for surgery at an older age and were more likely to undergo open cranial vault repair, with increased blood loss, higher transfusion volume, and longer time.

CONCLUSIONS

This study highlights clinical differences in sagittal craniosynostosis phenotypes and shows that developmental delay is an initial presentation of the saddle phenotype. The saddle phenotype also correlated with fusion of the minor squamous and sphenoid sutures. The link between developmental delay and minor suture fusion was notable and should be explored with a larger sample size. Patients with saddle synostosis present for surgery at an older age than patients with dolichocephaly and therefore are more likely to receive open cranial vault repair, with a taxing intraoperative experience characterized by increased blood loss, increased transfusions, and longer operation time.

Pediatric craniosynostosis computed tomography: an institutional experience in reducing radiation dose while maintaining diagnostic image quality

BACKGROUND

Children with craniosynostosis may undergo multiple computed tomography (CT) examinations for diagnosis and post-treatment follow-up, resulting in cumulative radiation exposure.

OBJECTIVE

To reduce the risks associated with radiation exposure, we evaluated the compliance, radiation dose reduction and clinical image quality of a lower-dose CT protocol for pediatric craniosynostosis implemented at our institution.

MATERIALS AND METHODS

The standard of care at our institution was modified to replace pediatric head CT protocols with a lower-dose CT protocol utilizing 100 kV, 5 mAs and iterative reconstruction. Study-ordered, protocol-utilized and radiation-dose indices were collected for studies performed with routine pediatric brain protocols (n=22) and with the lower-dose CT protocol (n=135). Two pediatric neuroradiologists evaluated image quality in a subset (n=50) of the lower-dose CT studies by scoring visualization of cranial structures, confidence of diagnosis and the need for more radiation dose.

RESULTS

During the 30-month period, the lower-dose CT protocol had high compliance, with 2/137 studies performed with routine brain protocols. With the lower-dose CT protocol, volume CT dose index (CTDI_vol) was 1.1 mGy for all patients (0-9 years old) and effective dose ranged from 0.06 to 0.22 mSv, comparable to a 4-view skull radiography examination. CTDI_vol was reduced by 98% and effective dose was reduced up to 67-fold. Confidence in diagnosing craniosynostosis was high and more radiation dose was considered unnecessary in all studies (n=50) by both radiologists.

CONCLUSION

Replacing the routine pediatric brain CT protocol with a lower-dose CT craniosynostosis protocol substantially reduced radiation exposure without compromising image quality or diagnostic confidence.

Bilateral squamosal synostosis: unusual presentation of chromosome 1p12–1p13.3 deletion. Illustrative case

BACKGROUND

Squamosal sutures are minor sutures of the human skull. Early isolated fusion of the sutures (squamosal synostosis) is rarely found.

OBSERVATIONS

The authors report a case of a girl who presented with an abnormal head shape and bilateral squamosal synostosis. Genetic testing revealed a chromosome 1p12–1p13.3 deletion. She has been managed with conservative treatment of the synostosis. She has global developmental delay and multiple anomalies due to the chromosome abnormality.

LESSONS

Isolated squamosal suture synostosis could be an uncommon feature of chromosome 1p12–1p13.3 deletion.

Squamous suture obliteration: frequency and investigation of the associated skull morphology

This study aimed to investigate the frequency of squamous suture (SqS) obliteration, to estimate the involvement of the major calvarial sutures and those surrounding the temporal squama, and to inspect the neuro- and basicranium for deformities. A series of 211 dry skulls of contemporary adult males were macroscopically observed. The skulls with closed SqS were scanned using an industrial µCT system. Digital morphometry of the skulls with obliterated SqS was performed by recording the 3D coordinates of anatomic landmarks and calculation of linear distances, angles and indices. Obliteration of SqS was observed in 3 (1.42%) skulls. One skull showed bilateral SqS obliteration. The other two cases were unilateral, one right-sided and one left-sided. SqS obliteration seems to be co-ordinated with the closure of the parietomastoid suture, partially related to the closure of the occipitomastoid, sphenoparietal and sphenofrontal sutures, and independent from the closure of the sphenosquamosal suture and the major calvarial sutures. No severe disproportions in the skull configuration were observed in the three investigated cases. The major differences in the complimentary hemicrania concern the parietal and occipital parts of the skull vault. Dorsum sellae erosion, an indicator for raised intracranial pressure, was observed in all three cases.

Late presenting bilateral squamosal synostosis

Premature fusion of one or other of the minor sutures can subtly influence the shape of the human skull. Although infrequently reported or not clinically recognized, it can such contribute to a variety of craniofacial dysmorphisms. We herein report a case of late presenting, isolated bilateral synostosis of the squamosal suture dysmorphologies whose presentation mimics aspects of sagittal synostosis.

Additional squamosal suture synostosis and segmented intracranial volume in patients with non-syndromic sagittal synostosis

PURPOSE

To evaluate the incidence of squamosal suture synostosis (SQS) in children with non-syndromic sagittal synostosis and to evaluate whether the additional SQS affects the intracranial volume (ICV).

METHODS

Thirty-four consecutive patients (23 boys) who had been operated by cranial vault remodelling 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 0.48 (range 0.13-1.3) years. Mann-Whitney U test was used in the statistical analyses.

RESULTS

Sagittal synostosis was combined with SQS in four children (11.7%) but the additional SQS did not affect the ICV. SQS was unilateral in all children, two were located on the right and two on the left side. The length of the SQS varied between 4 and 27 mm. The children with SQS had a shorter sagittal suture synostosis length ratio (length of synostosis / total sagittal suture length × 100) than those without SQS.

CONCLUSIONS

The incidence of SQS in non-syndromic sagittal synostosis was 11.7% but SQS did not affect the ICV.

Unilateral Pterional Polycraniosynostosis Treated with Craniectomy and Helmet Therapy

Supplemental Digital Content is available in the text.

Craniosynostosis is a condition in which one or more of the cranial sutures have fused prematurely, affecting the growth pattern and contours of the infant skull. The pterion is the junction of temporal, frontal, parietal, and sphenoid bones of the skull. We present a case of unilateral pterional craniosynostosis, which was treated with strip craniectomy and helmet therapy.