Lambdoid synostosis. Part 1. The lambdoid suture: normal development and pathology of "synostosis"

Atypical sagittal suture craniosynostosis: pathological considerations for early closure of the anterior part of the sagittal suture

Sagittal suture synostosis is one of the most common craniosynostoses and is often diagnosed by characteristic narrow and long skull shape, scaphocephaly. However, some patients with sagittal suture synostosis do not present with typical scaphocephaly, making early diagnosis difficult. In this study, five cases of characteristic skull deformity showing a narrowing of the cranium posterior to the coronal suture on computed tomography (CT) are presented. The three older children presented with papilledema and intellectual disability and a closed sagittal suture on CT. The two infant cases were diagnosed with the characteristic cranial deformities with aggravation of the deformity over time, but sagittal suture closure was not evident on CT. All patients underwent cranial remodeling surgery. In the two infant cases, the histopathological findings showed that the anterior part of the sagittal suture was firmly fused with fibrous tissue without bony fusion. These findings suggested that narrowing of the cranium posterior to the coronal suture might be due to functional fusion of the anterior portion of the sagittal suture prior to bony fusion. In an infant presenting with such a deformity that shows aggravation of the deformity over time, surgical treatment should be considered.

Positional cranial deformation in children: A plea for the efficacy of the cranial helmet in children

BACKGROUND

Cranial deformations have historically aroused the interest of people worldwide. One of the more debated points about positional plagiocephaly is the choice of the treatment. In this article, the senior author (CM) shares his experience on almost 30 years of use of the helmet molding therapy in children with deformation plagiocephaly.

METHODS AND POPULATION

We retrospectively and systematically reviewed the cases of 2188 patients (75% males and 25% females) presenting positional head deformity and treated between 1991 and 2013 with a cranial helmet. To assess the effectiveness of the helmet, we compared the cranial index in bilateral plagiocephaly and the Cranial Diagonals Difference (CDD) in unilateral plagiocephaly at the beginning and at the end of the treatment.

RESULTS

The cranial indexes ranged between 94.4% and 124.2% before the treatment and decreased significantly between 86.8% and 121.4% after the treatment (P<0.01). The CDD ranged between 0.3 cm and 4.5 cm with an average of 1.50±0.54 cm before the treatment and decreased significantly between 0.1 cm and 2.5 cm with an average of 0.72±0.37 cm after the treatment (P<0.01). For unilateral plagiocephaly, at the beginning of the treatment, 2.5% children presented a mild plagiocephaly, 19.6% a moderate plagiocephaly and 77.9% a severe plagiocephaly. At the end of the treatment, the deformation was classified as mild in 40.2% children, moderate in 44.3% children and severe in 15.5% children with significantly less children in the most severe subgroups (P<0.01) Facial symmetry pre-existed before the treatment in 13.7% of children. This rate was significantly increased at the end of the treatment to 66.7% (P<0.01). In only 8 cases (0.2%), the helmet therapy did not allow to obtain correct clinical results and a surgical posterior cranial remodeling was performed.

CONCLUSIONS

The results observed in this series confirms that cranial helmet is a simple and well tolerated alternative which bring satisfying results. Its success implies a good collaboration with parents and a management both by orthoptist, physiotherapist and doctor. Nevertheless, it remains many controversies in the literature concerning in particular long-term cosmetic and functional outcomes. A long-term multicentric prospective study could enable to remove doubts.

The Morphological Grading and Comparison of Sutural Patency Among Cranial Sutures in Dry Human Skulls

OBJECTIVE

To investigate the degree of fusion (patency) among cranial sutures in human dry skulls in the Anatolia.

METHODS

One-hundred fifty-eight human dry skulls that were accepted as adults according to the teeth eruption were macroscopically examined and photographed with Canon 400B (55 mm objective). The grades of fusion of coronal, sagittal, and lambdoid were quantitatively analyzed by using the modified grading scale. According to the extent of patency, the sutures were graded as grade-0 (open), grade-1 (fused but not obliterated), grade-2 (50%< obliterated), grade-3 (50% > obliterated), and grade-4 (100% obliterated). The authors determined and compared the rate for each grade of sutural patency on coronal, sagittal, and lambdoid sutures.

RESULTS

The cranial sutures of 4 cranii (4/158; 2.53%) had grade-4 fusion, whereas there were no any cranii with sutures of grade-0 fusion. The number of each grade of fusion among cranial sutures of 158 skulls, in descending order, was as follows: 171 (grade-3), 145 (grade-1), 133 (grade-2), and 25 (grade-4). The grade-4 fusion was significantly less observed than the others. The grade-1 and grade-4 fusion of lambdoid sutures were established as the most (66/41.8%) and least (5/3.2%) common fusions among cranial sutures, respectively. The frequencies of each grade of fusion for each cranial suture were determined in a descending order: coronal (grade-3 > 2 > 1 > 4), sagittal (grade-3 > 2 > 1 > 4), and lambdoid sutures (grade-1 > 3 > 2 > 4). The frequency of grade-1 fusion of lambdoid suture (66/41.8%) was significantly different when compared with coronal (39/24.7%) and sagittal sutures (40/25.3%), respectively.

CONCLUSION

The grades of fusion (or sutural patency) vary among cranial sutures.

Comparative histology of some craniofacial sutures and skull-base synchondroses in non-avian dinosaurs and their extant phylogenetic bracket

Sutures and synchondroses, the fibrous and cartilaginous articulations found in the skulls of vertebrates, have been studied for many biological applications at the morphological scale. However, little is known about these articulations at the microscopic scale in non-mammalian vertebrates, including extant archosaurs (birds and crocodilians). The major goals of this paper were to: (i) document the microstructure of some sutures and synchondroses through ontogeny in archosaurs; (ii) compare these microstructures with previously published sutural histology (i.e. that of mammals); and (iii) document how these articulations with different morphological degrees of closure (open or obliterated) appear histologically. This was performed with histological analyses of skulls of emus, American alligators, a fossil crocodilian and ornithischian dinosaurs (hadrosaurids, pachycephalosaurids and ceratopsids). Emus and mammals possess a sutural periosteum until sutural fusion, but it disappears rapidly during ontogeny in American alligators. This study identified seven types of sutural mineralized tissues in extant and extinct archosaurs and grouped them into four categories: periosteal tissues; acellular tissues; fibrous tissues; and intratendinous tissues. Due to the presence of a periosteum in their sutures, emus and mammals possess periosteal tissues at their sutural borders. The mineralized sutural tissues of crocodilians and ornithischian dinosaurs are more variable and can also develop via a form of necrosis for acellular tissues and metaplasia for fibrous and intratendinous tissues. It was hypothesized that non-avian dinosaurs, like the American alligator, lacked a sutural periosteum and that their primary mode of ossification involved the direct mineralization of craniofacial sutures (instead of intramembranous ossification found in mammals and birds). However, we keep in mind that a bird-like sutural microstructure might have arisen within non-avian saurichians. While synchondroseal histology is relatively similar in archosaurs and mammals, the microstructural differences between the sutures of these two clades are undeniable. Moreover, the current results suggest that the degree of sutural closure can only accurately be known via microstructural analyses. This study sheds light on the microstructure and growth of archosaurian sutures and synchondroses, and reveals a unique, undocumented histological diversity in non-avian dinosaur skulls.

Craniosynostosis of the lambdoid suture

Craniosynostosis affecting the lambdoid suture is uncommon. The definition of lambdoid craniosynostosis solely applies to those cases demonstrating true suture obliteration, similar to other forms of craniosynostosis. In patients presenting with posterior plagiocephaly, true lambdoid craniosynostosis must be differentiated from the much more common positional molding. It can occur in a unilateral form, a bilateral form, or as part of a complex craniosynostosis. In children with craniofacial syndromes, synostosis of the lambdoid suture most often is seen within the context of a pansynostotic picture. Chiari malformations are commonly seen in multisutural and syndromic types of craniosynostosis that affect the lambdoid sutures. Posterior cranial vault remodeling is recommended to provide adequate intracranial volume to allow for brain growth and to normalize the skull shape. Although many techniques have been described for the correction of lambdoid synostosis, optimal outcomes may result from those techniques based on the concept of occipital advancement.

Pathology in metopic synostosis

Premature closure and subsequent ossification of the metopic suture results in triangular head shape called trigonocephaly and is characterized by a midline metopic ridge, frontotemporal narrowing, and an increased biparietal diameter. Trigonocephaly is the second most frequent type of craniosynostosis. It can be isolated and associated with other congenital anomalies without any known syndrome, or occurs as part of a multiple malformation syndrome. Improvement in treatment is directed by a thorough understanding of the basic pathology of this condition. This review aims to provide an overview of metopic synostosis by correlating what is known about pathogenesis and pathology of this entity.

Fetal transient occipital bone protuberance during early pregnancy

OBJECTIVE

To describe the prenatal sonographic findings and pregnancy outcome of fetuses with transient occipital bone protuberance (TOBP).

METHODS

Five fetuses with TOBP were identified at routine 14 to 15 weeks ultrasound. The sonographic examination was repeated during pregnancy and the neonates were examined after birth.

RESULTS

The occipital bone protuberance disappeared by 24 weeks in all five cases, and the postnatal examination of the skull was normal.

CONCLUSIONS

Isolated TOBP is rare during early pregnancy. Ultrasound follow-up is suggested and disappearance of the lesion can be expected in most, if not all the cases with normal skull at birth.

The earliest evidence of true lambdoid craniosynostosis: the case of "Benjamina", a Homo heidelbergensis child

BACKGROUND

The authors report the morphological and neuroimaging findings of an immature human fossil (Cranium 14) diagnosed with left lambdoid synostosis.

DISCUSSION

The skull was recovered at the Sima de los Huesos site in Atapuerca (Burgos, Spain). Since the human fossil remains from this site have been dated to a minimum age of 530,000 years, this skull represents the earliest evidence of craniosynostosis occurring in a hominid. A brief historical review of craniosynostosis and cranial deformation is provided.

Unravelling the molecular control of calvarial suture fusion in children with craniosynostosis

BACKGROUND

Craniosynostosis, the premature fusion of calvarial sutures, is a common craniofacial abnormality. Causative mutations in more than 10 genes have been identified, involving fibroblast growth factor, transforming growth factor beta, and Eph/ephrin signalling pathways. Mutations affect each human calvarial suture (coronal, sagittal, metopic, and lambdoid) differently, suggesting different gene expression patterns exist in each human suture. To better understand the molecular control of human suture morphogenesis we used microarray analysis to identify genes differentially expressed during suture fusion in children with craniosynostosis. Expression differences were also analysed between each unfused suture type, between sutures from syndromic and non-syndromic craniosynostosis patients, and between unfused sutures from individuals with and without craniosynostosis.

RESULTS

We identified genes with increased expression in unfused sutures compared to fusing/fused sutures that may be pivotal to the maintenance of suture patency or in controlling early osteoblast differentiation (i.e. RBP4, GPC3, C1QTNF3, IL11RA, PTN, POSTN). In addition, we have identified genes with increased expression in fusing/fused suture tissue that we suggest could have a role in premature suture fusion (i.e. WIF1, ANXA3, CYFIP2). Proteins of two of these genes, glypican 3 and retinol binding protein 4, were investigated by immunohistochemistry and localised to the suture mesenchyme and osteogenic fronts of developing human calvaria, respectively, suggesting novel roles for these proteins in the maintenance of suture patency or in controlling early osteoblast differentiation. We show that there is limited difference in whole genome expression between sutures isolated from patients with syndromic and non-syndromic craniosynostosis and confirmed this by quantitative RT-PCR. Furthermore, distinct expression profiles for each unfused suture type were noted, with the metopic suture being most disparate. Finally, although calvarial bones are generally thought to grow without a cartilage precursor, we show histologically and by identification of cartilage-specific gene expression that cartilage may be involved in the morphogenesis of lambdoid and posterior sagittal sutures.

CONCLUSION

This study has provided further insight into the complex signalling network which controls human calvarial suture morphogenesis and craniosynostosis. Identified genes are candidates for targeted therapeutic development and to screen for craniosynostosis-causing mutations.

Cell fate specification during calvarial bone and suture development

In this study we have addressed the fundamental question of what cellular mechanisms control the growth of the calvarial bones and conversely, what is the fate of the sutural mesenchymal cells when calvarial bones approximate to form a suture. There is evidence that the size of the osteoprogenitor cell population determines the rate of calvarial bone growth. In calvarial cultures we reduced osteoprogenitor cell proliferation; however, we did not observe a reduction in the growth of parietal bone to the same degree. This discrepancy prompted us to study whether suture mesenchymal cells participate in the growth of the parietal bones. We found that mesenchymal cells adjacent to the osteogenic fronts of the parietal bones could differentiate towards the osteoblastic lineage and could become incorporated into the growing bone. Conversely, mid-suture mesenchymal cells did not become incorporated into the bone and remained undifferentiated. Thus mesenchymal cells have different fate depending on their position within the suture. In this study we show that continued proliferation of osteoprogenitors in the osteogenic fronts is the main mechanism for calvarial bone growth, but importantly, we show that suture mesenchyme cells can contribute to calvarial bone growth. These findings help us understand the mechanisms of intramembranous ossification in general, which occurs not only during cranial and facial bone development but also in the surface periosteum of most bones during modeling and remodeling.

The new bone biology: Pathologic, molecular, and clinical correlates

Bone and cartilage and their disorders are addressed under the following headings: functions of bone; normal and abnormal bone remodeling; osteopetrosis and osteoporosis; epithelial-mesenchymal interaction, condensation and differentiation; osteoblasts, markers of bone formation, osteoclasts, components of bone, and pathology of bone; chondroblasts, markers of cartilage formation, secondary cartilage, components of cartilage, and pathology of cartilage; intramembranous and endochondral bone formation; RUNX genes and cleidocranial dysplasia (CCD); osterix; histone deacetylase 4 and Runx2; Ligand to receptor activator of NFkappaB (RANKL), RANK, osteoprotegerin, and osteoimmunology; WNT signaling, LRP5 mutations, and beta-catenin; the role of leptin in bone remodeling; collagens, collagenopathies, and osteogenesis imperfecta; FGFs/FGFRs, FGFR3 skeletal dysplasias, craniosynostosis, and other disorders; short limb chondrodysplasias; molecular control of the growth plate in endochondral bone formation and genetic disorders of IHH and PTHR1; ANKH, craniometaphyseal dysplasia, and chondrocalcinosis; transforming growth factor beta, Camurati-Engelmann disease (CED), and Marfan syndrome, types I and II; an ACVR1 mutation and fibrodysplasia ossificans progressiva; MSX1 and MSX2: biology, mutations, and associated disorders; G protein, activation of adenylyl cyclase, GNAS1 mutations, McCune-Albright syndrome, fibrous dysplasia, and Albright hereditary osteodystrophy; FLNA and associated disorders; and morphological development of teeth and their genetic mutations.

Nonsynostotic Occipital Plagiocephaly: Radiographic Diagnosis of the ???Sticky Suture???

BACKGROUND

While the clinical differences between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis have been described, the radiographic differentiation between the two remains obscure. The aim of this study was to characterize morphological differences in the lambdoid suture between nonsynostotic occipital plagiocephaly and lambdoid craniosynostosis.

METHODS

Computed tomography scans of children clinically diagnosed with nonsynostotic occipital plagiocephaly (n = 26) were compared with computed tomography scans from children diagnosed with lambdoid craniosynostosis (n = 7). Suture and cranial morphology, ear position, and endocranial base angles were qualitatively and quantitatively compared.

RESULTS

Nonsynostotic occipital plagiocephaly sutures demonstrated areas of focal fusion (25 percent), endocranial ridging (78 percent), narrowing (59 percent), sclerosis (19 percent), and changes from overlapping to end-to-end orientation (100 percent). No sutures demonstrated ectocranial ridging. All cases of nonsynostotic occipital plagiocephaly presented with ipsilateral occipital flattening, 85 percent with ipsilateral frontal, and 95 percent with contralateral occipital bossing producing parallelogram morphology. In contrast, a greater frequency of sutures in lambdoid craniosynostosis patients demonstrated nearly complete obliteration (p < 0.001) with ectocranial ridging (p < 0.001); significantly more of these patients presented with ipsilateral occipital flattening with compensatory ipsilateral mastoid (p < 0.001) and contralateral parietal (p < 0.01) bossing, producing a trapezoid morphology. Sutures from nonsynostotic occipital plagiocephaly patients showed endocranial ridging, focal fusions, and narrowing, previously reported as lambdoid craniosynostosis.

CONCLUSIONS

In contradiction to previous reports, lambdoid craniosynostosis is not radiographically unique among suture fusions. This work establishes the radiographic diagnosis of nonsynostotic occipital plagiocephaly.

Lambdoid synostosis and occipital plagiocephaly: clinical decision rules for surgical intervention

Lambdoid craniosynostosis has been regarded as one of the least common categories of premature fusion of the cranial sutures, yet reports have suggested the incidence may be increasing. To guide treatment decisions, the authors describe a set of rules based on radiographic indicators and clinical assessment in the child. Experience suggests that children can have abnormal-appearing cranial sutures with normal neurological status and normal-appearing sutures with neurological deficits or marked cerebral compression. Early evaluation and follow-up treatment is essential for children with suspected craniosynostosis.

Advances in the management of the craniosynostoses

The spectacular beginning of craniofacial surgery in the modern era involved a case of craniosynostosis. Progress from that time to the present in the development of our understanding of this disease process and its management reflects the wider progress in the development and institutionalization of the discipline of craniofacial surgery. Complex surgical interventions have led the way to multidisciplinary units that have developed a greater understanding of the pathology and natural history of the craniosynostoses. New technologies have been developed to further advance the surgical techniques and these can now be evaluated by the institutions that have spawned them. This paper deals with the development of the discipline, the current status of the management of craniosynostosis, both syndromal and non-syndromal, and discusses the technological advances including imaging, distraction osteogenesis and the current status of genetic investigations.

Metopic Synostosis: Defining the Temporal Sequence of Normal Suture Fusion and Differentiating It from Synostosis on the Basis of Computed Tomography Images

Only the metopic suture normally fuses during early childhood; all other cranial sutures normally fuse much later in life. Despite this, metopic synostosis is one of the least common forms of craniosynostosis. The temporal sequence of normal physiologic metopic suture fusion remains undefined and controversial. Therefore, diagnosis of metopic synostosis on the basis of computed tomography images alone can prove misleading. The present study sought to determine the normal sequence of metopic suture fusion and characterize both endocranial and ectocranial suture morphology. An analysis of computed tomography scans of 76 trauma patients, ranging in age from 10 days to 18 months, provided normative craniofacial data that could be compared to similar data obtained from the preoperative computed tomography scans of 30 patients who had undergone surgical treatment for metopic synostosis. Metopic suture fusion was complete by 6 to 8 months in all nonsynostotic patients, with initiation of suture fusion evident as early as 3 months of age. Fusion was found to commence at the nasion, proceed superiorly in progressive fashion, and conclude at the anterior fontanelle. Although an endocranial ridge was not commonly seen in synostotic patients, an endocranial metopic notch was virtually diagnostic of premature suture fusion and was seen in 93 percent of synostotic patients. A metopic notch was not seen in any nonsynostotic patient. The morphologic and normative craniofacial data presented permit diagnosis of metopic synostosis based on computed tomography images obtained beyond the normal fusion period.

Occipital plagiocephaly

The diagnosis of occipital plagiocephaly has remained a complex and controversial issue in the field of craniofacial surgery. Over the past 30 years, numerous studies have been published describing the management and treatment for 'posterior plagiocephaly', 'plagiocephaly without synostosis', 'deformational plagiocephaly' and 'occipital plagiocephaly', with surgical 'correction' being chosen as the primary modality of treatment irrespective of the patency status of the lambdoid sutures. Two hundred and four patients with unilateral occipital plagiocephaly have been seen at the Australian Craniofacial Unit over the past 16 years. Each patient was evaluated by a craniofacial surgeon, paediatric neurosurgeon and paediatric geneticist. All children underwent plain radiographs of the skull to define the sutural anatomy. In those patients where the sutural anatomy was equivocal, 2-D and 3-D CT scans were performed. Only two of the 204 patients (approximately 1%) manifested the clinical, radiographic and pathological features of true unilambdoid synostosis. There was radiographic evidence of sutural fusion on plain films, 2-D and 3-D CT scans. Pathology specimens showed bony sutural fusion. Two hundred and two patients presented with unilateral occipital deformities and patent sutures on radiography. These patients with occipital plagiocephaly in the absence of true synostosis were initially managed conservatively (head positioning, and physiotherapy in those patients with torticollis). Those patients who underwent surgical correction in infancy (21/204) included patients with severe plagiocephaly not responding to conservative therapy (19/204) and the two patients with true unilambdoid synostosis (2/204).One hundred and ninety-one of the total patients (94%) were noted by their parents to have acceptable improvement in their head shape. Thirteen patients were seen within the past year and are too early to assess. Two surgical patients (one fronto-orbital advancement, one occipital craniectomy) and one patient followed conservatively were judged by their parents to be without notable improvement. In our series it is apparent that the majority of cases of occipital plagiocephaly are not secondary to true synostosis and can be managed by conservative positional measures.

Occipital plagiocephaly: a critical review of the literature

OBJECT

The literature on occipital plagiocephaly (OP) was critically reviewed to determine the feasibility of establishing treatment recommendations.

METHODS

Using standard computerized search techniques, medical literature databases containing peer-review articles dating from 1966 were queried for key words related to OP. The titles of all articles were scanned for relevance, and copies of potentially relevant articles published in English were reviewed. Articles in which treatment was discussed were categorized according to their weight of evidence as Class I (prospective randomized controlled trials), Class II (clinical studies in which data are collected prospectively or retrospective analyses based on clearly reliable data), and Class III (most studies based on retrospectively collected data) to evaluate their contribution to developing a consensus on the treatment of OP. Of the 4308 articles identified, all but 89 were excluded. Based on the review of these articles, the actual incidence of OP is unknown, and no population-based studies of its incidence or prevalence exist. The reported incidence of lambdoid craniosynostosis ranges from 3 to 20% with differences in diagnostic criteria accounting for the variability. With the possible exception of a lambdoid suture that is replaced by a dense ridge of bone, no other diagnostic criteria have been agreed on. There were no Class I studies and only one Class II study provided comparisons of outcomes in more than one treatment group with outcomes in an untreated group. Recommended treatment options included observation only, mechanical interventions, and a variety of surgical techniques.

CONCLUSIONS

Controlled clinical trials are needed before any form of intervention can be recommended for the treatment of OP. If surgery, which is expensive and potentially dangerous, is to continue to play a role in the management of this condition, efforts should be made to determine if patients with untreated OP have suffered from lack of treatment.

Posterior skull surgery in craniosynostosis

In 1984, two young infants with unusual "clover-leaf" patterns of skull deformity were treated by posterior skull-releasing surgery that dramatically improved their overall skull shape, to the extent that further operative intervention was not required. This focused our attention on the posterior skull and its role in craniosynostosis. In cases of multi-suture craniosynostosis and craniofacial syndromes severely raised intracranial pressure is frequent, demanding early surgery. One of the problems identified with such surgery undertaken before 6 months of age is recurrent craniosynostosis needing later re-operation. This occurred in 15 (5%) of 275 patients treated between 1978 and 1994. Since 1986, in the presence of significant raised intracranial pressure it has been our policy to do an initial posterior skull release or decompression. This takes the pressure of the growing brain away from the orbits, allowing us to defer fronto-orbital advancement until the age of 12 months or later. Three patients managed in this way completely avoided anterior surgery, while in another 9 patients re-operation for recurrent anterior deformity has not been required. The exception to this policy has been the presence of severe exorbitism posing a threat to vision. Under these circumstances early fronto-orbital advancement is mandatory, and an additional posterior skull release may be helpful later. Debate continues especially on the management of unilateral lambdoid synostosis. The recent increase in positional posterior plagiocephaly. possibly related to supine nursing of newborns, has emphasised the need to differentiate between a fixed deformity, which might require surgical correction, and positional moulding of the occiput, which improves spontaneously. This paper reports our experience with 22 patients treated by posterior skull surgery, either alone or as an additional procedure, which we believe has a definitive role in the management of craniosynostosis.

The differential diagnosis of posterior plagiocephaly: true lambdoid synostosis versus positional molding

The diagnosis and treatment of posterior plagiocephaly is one of the most controversial aspects of craniofacial surgery. The features of true lambdoid synostosis versus those of deformational plagiocephaly secondary to positional molding are inadequately described in the literature and poorly understood. This has resulted in many infants in several craniofacial centers across the United States undergoing major intracranial procedures for non-synostotic plagiocephaly. The purpose of this study was to describe the detailed clinical, imaging, and operative features of true lambdoid synostosis and contrast them with the features of positional plagiocephaly. During a 4-year period from 1991 to 1994, 102 patients with posterior plagiocephaly were assessed in a large multidisciplinary craniofacial program. During the same period, 130 patients with craniosynostosis received surgical treatment. All patients were examined by a pediatric dysmorphologist, craniofacial surgeon, and pediatric neurosurgeon. Diagnostic imaging was performed where indicated. Patients diagnosed with lambdoid synostosis and severe and progressive positional molding underwent surgical correction using standard craniofacial techniques. Only 4 patients manifested the clinical, imaging, and operative features of unilambdoid synostosis, giving an incidence among all cases of craniosynostosis of 3.1 percent. Only 3 among the 98 patients with positional molding required surgical intervention. All the patients with unilambdoid synostosis had a thick ridge over the fused suture, identical to that found in other forms of craniosynostosis, with compensatory contralateral parietal and frontal bossing and an ipsilateral occipitomastoid bulge. The skull base had an ipsilateral inferior tilt, with a corresponding inferior and posterior displacement of the ipsilateral ear. These characteristics were completely opposite to the findings in the 98 patients who had positional molding with open lambdoid sutures and prove conclusively that true unilambdoid synostosis exists as a specific but rare entity. Awareness of the features of unilambdoid synostosis will allow more accurate diagnosis and appropriate treatment of posterior plagiocephaly in general and in particular will avoid unnecessary surgical intervention in patients with positional molding.

Coronal suture pathology and synostotic progression in rabbits with congenital craniosynostosis

The purpose of the present study was to describe coronal suture pathology and cross sectional synostotic progression in an inbred strain of rabbits with congenital craniosynostosis. Calvaria from 102 perinatal rabbits (39 unaffected; 63 bilateral or unilateral synostosis) were collected at fetal days 21 (n = 12), 25 (n = 20), 27 (n = 22), 30 (term) (n = 32), and 3 days post-term (n = 16) for gross morphologic and histologic examination. Synostotic foci, the extent of relative bony bridging, and suture morphology were evaluated qualitatively and quantitatively. Of the 204 coronal sutures examined, 91 sutures were synostosed, and 113 were patent. All synostosed sutures showed similar foci by day 25, which originated as bony bridges in the middle of each suture on the ectocortic surface. Bony bridging width increased significantly (p < .001) from day 25 through 3 days post-term, and was best described by a linear regression equation. Osteogenic front areas of synostosed sutures were up to 2.5 times greater than patent sutures in term fetuses. Findings demonstrate that coronal suture synostosis in the congenital rabbit model (1) begins early during suture morphogenesis (before 25 days of gestation); (2) consistently radiates from a single focus corresponding to a normal interdigitating region (i.e., a high-tension environment); (3) varies in onset and rate as evidenced by low R2 value between age and extent of bony bridging; and (4) is the result of early hyperostosis of the osteogenic fronts and sutural agenesis. A number of possible pathogenetic mechanisms are discussed.

Quantitative analysis of cerebrospinal fluid spaces in children with occipital plagiocephaly

The etiology of occipital plagiocephaly (OP) is not fully understood. The authors have observed that many infants with this condition have external hydrocephalus. This study was undertaken to quantify cerebrospinal fluid (CSF) space caliber in children with OP and to compare these measurements to those derived from normal age-matched controls to further elucidate the pathogenesis of this condition. Thirty-one infants with isolated unilateral OP (mean age 6 months) were studied. Infants with multiple cranial suture abnormalities, impaired neurological function, developmental delay, and associated craniofacial anomalies were excluded. Twenty normal infants were evaluated as controls. The volumes of the sylvian fissures, frontal and occipital subarachnoid spaces, as well as the cross-sectional areas of the suprasellar and perimesencephalic cisterns, were calculated from computerized tomography (CT) studies. Ventricular size was also assessed. Generalized subarachnoid space dilation was observed in 29 (93.5%) of the 31 children with OP. Head circumference was significantly greater in the case group (71.4 vs. 50.8 percentile; p = 0.0002 by analysis of variance). The sylvian fissure volume was significantly larger in the case group (5.8 ml vs. 0.7 ml in controls, p < 0.0001). The volume of the contralateral sylvian fissure was greater than that ipsilateral to the side of OP (7.1 ml vs. 4.5 ml, p = 0.001). Frontal subarachnoid space volume was greater in infants with OP (27.5 ml vs. 0.6 ml in controls, p < 0.0001). Both the suprasellar and perimesencephalic cisterns were of greater caliber in the case group (p = 0.007 and p < 0.0001, respectively). No difference in ventricular size or occipital subarachnoid space volume was noted between groups. The extraventricular CSF spaces in neurologically unimpaired infants with OP are significantly larger than those in age- and sex-matched controls. Enlarged subarachnoid spaces may increase the compliance and malleability of the calvaria and sutures, predisposing to positional deformity. External hydrocephalus may be a fundamental etiological factor in OP.

Factitious lambdoid perisutural sclerosis: does the "sticky suture" exist?

We report a patient with occipital flattening attributed to lambdoid synostosis on the basis of perisutural sclerosis. The lambdoid suture was patent at surgery and by histology. Specimen radiography showed no perisutural sclerosis. This case questions the validity of peri- sutural sclerosis as a radiographic indicator of impending lambdoid synostosis.

Recurrent lambdoid synostosis within two families

We report on 2 families with multiple members who have proven or suspected lambdoid craniosynostosis. In one family the lambdoid suture was unilaterally involved in one sib, and bilaterally in the other. In the second family the propositus had unilateral lambdoid synostosis and his twin sisters each had bilateral lambdoid synostosis. Both families had another distant relative, a maternal grandmother in the first and paternal uncle in the second, who were also reported to have posterior plagiocephaly. We report these families as evidence for genetic transmission of a craniosynostotic trait which has only been rarely reported previously.

Sutural biology and the correlates of craniosynostosis

The purpose of this paper is to provide a new perspective on craniosynostosis by correlating what is known about sutural biology with the events of craniosynostosis per se. A number of key points emerge from this analysis: 1) Sutural initiation may take place by overlapping, which results in beveled sutures, or by end-to-end approximation, which produces nonbeveled, end-to-end sutures. All end-to-end sutures occur in the midline (e.g., sagittal and metopic) probably because embryonic biomechanical forces on either side of the initiating suture tend to be equal in magnitude. A correlate appears to be that only synostosed sutures of the midline have pronounced bony ridging. 2) Long-term histologic observations of the sutural life cycle call into question the number of layers within sutures. The structure varies not only in different sutures, but also within the same suture over time. 3) Few, if any, of the many elegant experimental research studies in the field of sutural biology have increased our understanding of craniosynostosis per se. An understanding of the pathogenesis of craniosynostosis requires a genetic animal model with primary craniosynostosis and molecular techniques to understand the gene defect. This may allow insight into pathogenetic mechanisms involved in primary craniosynostosis. It may prove to be quite heterogeneous at the basic level. 4) The relationship between suture closure, cessation of growth, and functional demands across sutures poses questions about various biological relationships. Two conclusions are provocative. First, cessation of growth does not necessarily, or always lead to fusion of sutures. Second, although patent sutures aid in the growth process, some growth can take place after suture closure. 5) In an affected suture, craniosynostosis usually begins at a single point and then spreads along the suture. This has been shown by serial sectioning and calls into question results of studies in which the affected sutures are only histologically sampled. 6) Craniosynostosis is etiologically and pathogenetically heterogeneous. Known human causes are reviewed. Is craniosynostosis simply normal suture closure commencing too early?(ABSTRACT TRUNCATED AT 400 WORDS)

Endocranial suture closure in rhesus macaques (Macaca mulatta)

Endocasts from skulls of 330 rhesus monkeys (Macaca mulatta) of known age are scored for closure of nine bilateral and three unilateral sutures or segments of sutures. A variety of tests reveals a strong relationship between age and stages of suture closure, although increasingly broad confidence intervals prevent sutures from being very useful for precisely aging older macaques. The order in which endosutures begin to close, as well as that in which closure is finally achieved, is determined for macaques, and these sequences compared to those for endosutures of humans (Todd and Lyon, 1924). The basilar suture is the earliest to close, while the masto-occipital and rostral and caudal squamosal sutures achieve closure quite late in both species. On the other hand, humans and macaques differ in their schedules for the sphenofrontal suture and in the initiation of closure for the rostral portion of the squamosal suture. Two sutures close significantly sooner on the right than on the left side (the rostral squamosal and masto-occipital) and asymmetry favoring closure of the right lateral lambdoid suture also approaches significance at the 0.05 level. No sutures close significantly sooner on the left side. It is suggested that macaque sutures may close from the inside out, that endosutures are more sensitive than ectosutures for detecting sequences in which cranial sutures begin to close, and that directional asymmetries in suture closure of macaques may be related to minor asymmetries in brain/skull shape (petalias).

Calcified tissues involved in the ontogenesis of the human cranial vault

The cranial vault of fifteen human subjects varying in age from 20th week of gestational life to 9th month post-matum were submitted to microradiographic and histological analysis. Different phenomena such as cortical drift, bone cavitation and progressive substitution of different calcified tissues by lamellar bone are illustrated. Moreover, this study reveals in several areas the presence of chondroid tissue; it constitutes the edges of the sutures and is responsible for their growth till the post-natal period. Therefore, it can be supported that the role of chondroid tissue is essential for the harmonious development of the cranial vault.

Lambdoid synostosis. Part 2: Review of cases managed at The Hospital for Sick Children, 1972-1982

Seventy-four patients with premature union of the lambdoid suture were treated at The Hospital for Sick Children during the years 1972 through 1982. Lambdoid synostosis is considered to be a rare form of craniosynostosis, but this is more likely due to lack of recognition rather than to infrequent occurrence. The skull deformity resulting from lambdoid synostosis is often mistakenly attributed to positional molding rather than to actual synostosis. When the lambdoid suture closes, the occiput on the involved side is flat, the forehead on the same side tends to bulge forward, and the ear on this side adopts a low and forward position. Skull x-ray films may demonstrate obliteration of the lambdoid suture, but more frequently one sees sclerosis along one edge of the closing suture. Radionuclide bone scanning will show increased activity during the active phase of union and decreased or absent activity once union has occurred. Craniectomy performed during the neonatal period will correct the deformity and provide for normal cranial growth. Delay in surgery beyond 6 months will frequently necessitate a more extensive cranial repair.