Bilateral squamosal suture synostosis: A rare form of isolated craniosynostosis in Crouzon syndrome

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.

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.

Classification of Subtypes of Crouzon Syndrome Based on the Type of Vault Suture Synostosis

BACKGROUND

Patients with Crouzon syndrome develop various types of anatomic deformities due to different forms of craniosynostosis, yet they have similar craniofacial characteristics. However, exact homology is not evident. Different pathology then may be best treated by different forms of surgical technique. Therefore, precise classification of Crouzon syndrome, based on individual patterns of cranial suture involvement is needed.

METHODS

Ninety-five computed tomography (CT) scans (Crouzon, n = 33; control, n = 62) were included in this study. All the CT scans are divided into 4 types based on premature closure of sutures: class I = coronal and lambdoidal synostosis; class II = sagittal synostosis; class III = pansynostosis; and class IV = "Others." The CT scan anatomy was measured by Materialise software.

RESULTS

The class III, pansynostosis, is the most prevalent (63.6%). The classes I, III, and IV of Crouzon have significantly shortened entire anteroposterior cranial base length, with the shortest base length in class III. The external cranial measurements in class I show primarily a decreased posterior facial skeleton, while the class III presented with holistic facial skeleton reduction. Class II has the least severe craniofacial malformations, while class III had the most severe.

CONCLUSION

The morphology of patients with Crouzon syndrome is not identical in both cranial base and facial characteristics, especially when they associated with different subtypes of cranial suture synostosis. The classification of Crouzon syndrome proposed in this study, summarizes the differences among each subgroup of craniosynostosis suture involvement, which, theoretically, may ultimately influence both the timing and type of surgical intervention.

The Significance of Squamosal Suture Synostosis

The squamosal suture is one of the lateral minor skull sutures, separating the parietal and squamous temporal bones. While the phenotypic appearances and sequelae of synostosis of the major cranial vault sutures are well documented, little is reported concerning synostosis of the squamosal suture (SQS). The aim of this study was to determine the frequency of squamosal suture synostosis, and to document the significance of this entity.A retrospective review of the diagnostic imaging for all new pediatric patients (aged ≤16 years) referred to the Oxford Craniofacial Unit between January 2008 and February 2013 was completed to identify patients with SQS. Computed tomography (CT) imaging was available in 422 patients and the axial and three-dimensional reconstructed images reviewed.Squamosal suture synostosis was confirmed in 38 patients (9%). It was present in conjunction with major suture synostosis in 33 patients and in isolation in 5. The incidence increased with age. It was more common in patients with syndromic craniosynostosis (18%) and associated syndromic conditions (36%) than in those with isolated major suture synostosis (6%). It was found to occur with coronal, lambdoid, and sagittal synostosis, but was most frequent with multisuture fusion patterns. Squamosal suture synostosis was not associated with a consistent calvarial deformity either in isolation or when associated with a major suture fusion. No patient underwent surgery specifically to correct SQS.In conclusion, contrary to previous reports, squamosal suture synostosis is a relatively frequent finding in the general case mix of a typical craniofacial unit, but is of limited clinical significance.

Squamosal Craniosynostosis: Defining the Phenotype and Indications for Surgical Management

BACKGROUND

Squamosal craniosynostosis is seldom reported in the craniofacial literature. Given that this is an uncommon diagnosis, phenotype and management remain unclear. The authors present a case series and review the literature to define the phenotype and management of these patients.

METHODS

We retrospectively reviewed 7 patients from our institution and systematically reviewed all published cases of squamosal craniosynostosis. Demographics, medical history, imaging, clinical presentation, subsequent workup, and treatment were examined and analyzed.

RESULTS

A comprehensive review of the literature yielded a total of 31 cases (including our new series) of squamosal craniosynostosis. Average age of presentation was 25.3 months, 52% of female patients, 74% of cases with bilateral squamosal involvement, 44% syndromic, 39% isolated squamosal (vs 61% multisutural). Overall, 56% of cases were handled surgically, whereas 44% were managed conservatively. Thirty-three percent of surgical cases required multiple operations. One patient with isolated bilateral squamosal craniosynostosis developed elevated intracranial pressure, requiring cranial vault remodeling.

CONCLUSIONS

Squamosal craniosynostosis frequently presents in a delayed fashion with nonsyndromic, bilateral involvement. In isolated bilateral squamosal cases, the associated phenotype is frontal prominence, occipital flattening, scaphocephalic tendency (low-end normocephalic cranial index), and superior parietal cornering. Evaluation of clinical signs and computed tomography imaging guides management, as evidence of increased intracranial pressure may indicate need for cranial vault expansion. Although previous literature suggests that nonsyndromic cases are nonsurgical, the majority of cases reviewed required surgical intervention, including our case of isolated bilateral squamosal craniosynostosis. We recommend vigilant management in patients with squamosal craniosynostosis, even those with isolated squamosal involvement.

Squamosal Suture Synostosis: Incidence, Associations, and Implications for Treatment

Squamosal suture craniosynostosis is thought to be a relatively rare entity. In the authors' experience, it is underreported in imaging examinations and the existing literature. The authors sought to determine the incidence of squamosal synostosis, whether it is increasing in frequency, and its relationship with synostosis of the major calvarial sutures.Patients undergoing computed tomography imaging for suspected craniosynostosis over a 15-year period were reviewed by a plastic surgeon and pediatric neuroradiologist. Patients with synostosis of the squamosal sutures were identified and involvement of additional sutures, gender, and the presence of a known syndromic diagnosis were recorded. Patients greater than 4 years of age or those with prior craniofacial surgery were excluded.One hundred twenty-five patients met inclusion criteria, 26 of whom had squamosal suture synostosis (26/125, 20.8%). Squamosal synostosis was found in isolation in 3 patients (3/26, 11.5%), with 1 additional major suture in 10 patients (10/26, 38.5%), and ≥2 major sutures in 13 patients (13/26, 50%). Squamosal synostosis was more common in patients with a syndromic diagnosis (11/26 syndromic, 15/99 nonsyndromic, P < 0.001). Eleven of 26 patients with squamosal synostosis were identified in the radiology report (42.3%).Craniosynostosis of the squamosal suture is much more common than previously reported and can contribute to abnormal head shape in isolation, or in combination with major sutures. Squamosal suture synostosis is underdiagnosed clinically and radiologically, although insufficient evidence exists to determine if its true incidence is increasing.

Squamous Suture Synostosis: A Review With Emphasis on Cranial Morphology and Involvement of Other Cranial Sutures

Squamosal suture synostosis has received little attention, potentially due to its rare nature. The authors present here a clinical report of isolated unilateral squamosal suture synostosis and a literature review, which produced 6 articles describing 33 patients of squamosal synostosis.Of the reported patients, 15 were associated with a craniofacial syndrome, 10 were nonsyndromic, and 8 were not specified. The cranial morphology varied greatly and only 1 patient was consistent with the morphology predicted by Virchow law-decreased vertical growth with compensatory ipsilateral longitudinal growth (manifesting as occipital and possibly frontal zygomatic bulging). Additional suture synostoses were observed in 36.3% of nonsyndromic and 80% of syndromic patients, suggesting that either squamosal synostosis may have an effect on other sutures, or more likely, only the most severe patients are recognized and reported.Surgical and nonsurgical interventions have found limited utility due to the subtle nature of the cranial defects and a lack of increased intracranial pressure, with a conservative follow-up course being the preferred treatment.

Paleodysmorphology and paleoteratology: Diagnosing and interpreting congenital conditions of the skeleton in anthropological contexts

Most congenital conditions have low prevalence, but collectively they occur in a few percent of all live births. Congenital conditions are rarely encountered in anthropological studies, not least because many of them have no obvious effect on the skeleton. Here, we discuss two groups of congenital conditions that specifically affect the skeleton, either qualitatively or quantitatively. Skeletal dysplasias (osteochondrodysplasias) interfere with the histological formation, growth and maturation of skeletal tissues leading to diminished postural length, but the building plan of the body is unaffected. Well- known skeletal dysplasias represented in the archeological record include osteogenesis imperfecta and achondroplasia. Dysostoses, in contrast, interfere with the building plan of the body, leading to e.g. missing or extraskeletal elements, but the histology of the skeletal tissues is unaffected. Dysostoses can concern the extremities (e.g., oligodactyly and polydactyly), the vertebral column (e.g., homeotic and meristic anomalies), or the craniofacial region. Conditions pertaining to the cranial sutures, i.e., craniosynostoses, can be either skeletal dysplasias or dysostoses. Congenital conditions that are not harmful to the individual are known as anatomical variations, several of which have a high and population-specific prevalence that could potentially make them useful for determining ethnic origins. In individual cases, specific congenital conditions could be determinative in establishing identity, provided that ante-mortem registration of those conditions was ensured. Clin. Anat. 29:878-891, 2016. © 2016 The Authors Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.