Jugular foraminal stenosis in Crouzon syndrome

Speech and Language Development, Hearing, and Feeding in Patients With Genetically Confirmed Crouzon Syndrome With Acanthosis Nigricans: A 36-Year Longitudinal Retrospective Review of Patients at the Oxford Craniofacial Unit

OBJECTIVE

Crouzon syndrome with acanthosis nigricans (CAN) is caused by the specific mutation c.1172C>A (p.Ala391Glu) in the fibroblast growth factor receptor 3 gene, and has an estimated prevalence of 1:1,000,000 births. Most cases occur de novo; however, autosomal dominant inheritance may occur. The clinical presentation typically includes craniosynostosis, midface and maxillary hypoplasia, choanal atresia/stenosis, hydrocephalus, and intracranial hypertension. Patients develop acanthosis nigricans, a hyperkeratotic skin disorder. The authors present the first known study to investigate the speech, language, hearing, and feeding of patients with CAN.

METHODS

A retrospective case-note review of patients with a genetically confirmed diagnosis of CAN attending the Oxford Craniofacial Unit during a 36-year period (1987-2023) was undertaken.

RESULTS

Participants were 6 patients with genetically-confirmed CAN (5 females, 1 male), all cases arose de novo. All patients had craniosynostosis (n = 5/6 multisuture synostosis, n = 1/6 left unicoronal synostosis). Hydrocephalus was managed through ventriculoperitoneal shunt in 67% (n = 4/6) of patients, and 67% (n = 4/6) had a Chiari 1 malformation. Patients had a complex, multifactorial feeding history complicated by choanal atresia/stenosis (100%; n = 6/6), and significant midface hypoplasia. All patients required airway management through tracheostomy (83%; n = 5/6); and/or continuous positive airway pressure (67%; n = 4/6). All patients underwent adenotonsillectomy (100%; n = 6/6). Initial failure to thrive, low weight, and/or height were seen in 100% (n = 6/6) patients; 80% (n = 4/5) had reflux; 100% (n = 6/6) had nasogastric, or percutaneous endoscopic gastrostomy based feeding during their treatment journey. All patients had hearing loss (100%; n = 6/6). Early communication difficulties were common: receptive language disorder (50%; n = 3/6); expressive language disorder (50%; n = 3/6); and speech sound disorder in 50% (n = 3/6)-necessitating the use of Makaton in 80% of patients (n = 3/5).

CONCLUSIONS

Patients with CAN experience significant respiratory, neurological, and structural obstacles to hearing, speech, language, and feeding. The authors present a recommended pathway for management to support patients in these domains.

Venous anomalies in hypoplastic posterior fossa: unsolved questions

INTRODUCTION

Anomalous intracranial venous anatomy is described in patients with syndromic craniosynostosis and is of significant importance when it comes to surgical morbidity. However, it is still controversial its origin, type of circulation in each syndrome, how it behaves over time, when it can be interrupted and wether it needs to be studied. The purpose of this paper is to discuss these issues by reviewing the literature.

METHODS

A literature search was performed using the PubMed database with a focus on papers including detailed descriptions of the venous outflow in complex and syndromic craniosynostosis. Search details used were the following: ("veins"[MeSH Terms] OR "veins"[All Fields] OR "venous"[All Fields]) AND ("abnormalities"[Subheading] OR "abnormalities"[All Fields] OR "anomalies"[All Fields]) AND syndromic[All Fields] AND ("craniosynostoses" [MeSH Terms] OR "craniosynostoses"[All Fields] OR "craniosynostosis"[All Fields]). Studies that exposed details of venous anomalies found in syndromic or complex craniosynostosis were selected.

RESULTS

Of a total of 211 articles found, 11 were selected for this review. Of these, 5 were case reports, 5 retrospective studies, and only 1 prospective study. From the 6 series of cases presented, 5 discussed the relationship between jugular foramen stenosis (JFS) and collateral venous drainage. The authors discuss data from the literature for each leading question presented: 1-collateral circulation: is it an intrinsic trouble, a consequence of stenosis of the cranial base foramina or related to raised intracranial pressure (ICP)?; 2-what venous anomalies should we search for, and what is the best exam to study them?; 3-collateral circulation changes with time?; 4-can neurosurgeons interrupt the collateral circulation?; 5-should we study all complex types of craniosynostosis?

CONCLUSION

The importance of the study of the venous outflow in patients with complex craniosynostosis is evident in the literature. The real relationship between intracranial hypertension, hypoplastic skull base foramen, Chiari I malformation, hydrocephalus, and venous collateral circulation remains unknown. Prospective studies focusing on molecular biology analysis will possibly solve all of these leading questions.

Dural sinus volume in children with syndromic craniosynostosis and intracranial hypertension

OBJECTIVE

Intracranial hypertension is a major concern in children with syndromic craniosynostosis (sCS). Cerebral venous hypertension caused by cerebral venous outflow obstruction is believed to contribute to intracranial hypertension. The authors therefore hypothesized that cerebral venous volume would be increased in those children with sCS and intracranial hypertension.

METHODS

In a case series of 105 children with sCS, of whom 32 had intracranial hypertension, cerebral MRI techniques were used to quantify the volume of the superior sagittal sinus, straight sinus (StrS), and both transverse sinuses.

RESULTS

Linear regression showed that total cerebral venous volume increased by 580.8 mm3 per cm increase in occipitofrontal head circumference (p < 0.001). No significant difference was found between the intracranial hypertension group and the nonintracranial hypertension group (p = 0.470). Multivariate ANOVA showed increased StrS volume (as a proportion of total volume) in the intracranial hypertension group (8.5% vs 5.1% in the nonintracranial hypertension group, p < 0.001). Multivariate logistic regression showed that a 100-mm3 increase in StrS volume is associated with increased odds of having intracranial hypertension by 60% (OR 1.60, 95% CI 1.24-2.08).

CONCLUSIONS

Although intracranial hypertension was not associated with total cerebral venous volume increase, it was associated with an isolated increase in StrS volume. Hence, it is unlikely that general cerebral venous outflow obstruction is the mechanism of intracranial hypertension in sCS. Rather, these findings indicate either a central cerebral vulnerability to intracranial hypertension or a mechanism involving venous blood redistribution.

Intracranial Venous Hypertension in Craniosynostosis: Mechanistic Underpinnings and Therapeutic Implications

Patients with complex, multisutural, and syndromic craniosynostosis (CSO) frequently exhibit intracranial hypertension. The intracranial hypertension cannot be entirely attributed to the craniocephalic disproportion with calvarial restriction because cranial vault expansion has not consistently alleviated elevated intracranial pressure. Evidence has most strongly supported a multifactorial interaction, including venous hypertension along with other pathogenic processes. Patients with CSO exhibit marked venous anomalies, including stenosis of the jugular-sigmoid complex, transverse sinuses, and extensive transosseous venous collaterals. These abnormal intracranial-extracranial occipital venous collaterals might represent anomalous development, with persistence and subsequent enlargement of channels normally present in the fetus, either as a primary defect or as nonregression in response to failure of the development of the jugular-sigmoid complexes. It has been suggested by some investigators that venous hypertension in patients with CSO could be treated directly via jugular foraminoplasty, venous stenting, or jugular venous bypass, although these options are not in common clinical practice. Obstructive sleep apnea, occurring as a consequence of midface hypoplasia, can also contribute to intracranial hypertension in patients with syndromic CSO. Thus, correction of facial deformities, as well as posterior fossa decompression, could also play important roles in the treatment of intracranial hypertension. Determining the precise mechanistic underpinnings underlying intracranial hypertension in any given patient with CSO requires individualized evaluation and management.

Clinical Significance of Venous Anomalies in Syndromic Craniosynostosis

Background

The pattern of cranial venous drainage in syndromic craniosynostosis is unpredictable and not adequately understood. Collateral channels substitute for stenotic venous sinuses and pose potential risk for surgical intervention. The purpose of this study was to analyze the patterns of venous drainage in patients with syndromic craniosynostosis and their influence on operative planning and morbidity.

Methods

A retrospective study of patients with syndromic craniosynostosis from 2000 to 2013 was performed. Demographic data were collected including phenotype and associated pathologies. Pre- and/or postoperative venous imaging was reviewed for venous sinus stenosis, collateral emissaries, and persistent fetal sinuses. Categorization of anomalous venous drainage was performed, and the relationship with surgical morbidity was assessed.

Results

Forty-one patients were identified. Anomalies were present in 31 patients (76%) consisting of dural sinus stenosis in 28 (68%), dilated emissaries in 26 (63%), and fetal sinuses in 7 (17%). Pfeiffer syndrome was most commonly associated with anomalous drainage (100%). Venous anomalies were associated with elevated intracranial pressure (ICP), shunted hydrocephalus, Chiari malformations, and sleep apnea. In 5 cases, the surgical plan was adjusted based on anomalous anatomy. No mortalities occurred. Intraoperative complication rate was 7.3%, all with anomalous drainage. Median estimated blood loss was 1,100 cc for patients with anomalies versus 400 cc without anomalies (P = 0.181).

Conclusion

Cranial venous anomalies are commonly detected in patients with syndromic craniosynostosis and may affect surgical morbidity and outcome with a higher estimated blood loss, alteration of procedure, and postoperative morbidity. Detailed preoperative imaging of the venous drainage is therefore recommended in cases of syndromic synostosis.

Skull base morphology in fibroblast growth factor receptor type 2-related faciocraniosynostosis: a descriptive analysis

BACKGROUND

Children with faciocraniosynostosis present skull base abnormalities and may develop hydrocephalus or cerebellar tonsils ectopia (CTE). Several pathophysiological hypotheses were formulated in the past decades to explain these associations. However, no study has described in a genetically homogeneous population with confirmed fibroblast growth factor receptor type 2 (FGFR2) mutation eventual correlations between skull base abnormalities and hydrocephalus or CTE.

OBJECTIVE

To illustrate these features in children <2 years of age with a genetically confirmed FGFR2-related faciocraniosynostosis.

METHODS

We measured the foramen magnum area (FMA) and its sagittal and transversal components: the right, left, and mean area of the jugular foramen; the posterior fossa volume; and the cerebellar volume on preoperative millimetric computed tomography scan slices in 31 children with an FGFR2 mutation (14 with Crouzon syndrome, 11 with Apert syndrome, and 6 with Pfeiffer syndrome). They were compared with 17 children without synostosis. All children were <24 months of age. We correlated all these measures with the presence of hydrocephalus or CTE.

RESULTS

We observed a significantly small FMA in children with Crouzon (P = .03) and in children with Pfeiffer (P = .05) resulting from a reduced sagittal diameter (P = .02 for Crouzon and P = .002 for Pfeiffer). Hydrocephalus was associated with small FMA (P = .02). The jugular foramen area, posterior fossa volume, and cerebellar volume were not associated with hydrocephalus or CTE. Hydrocephalus and CTE were statistically associated (P = .002).

CONCLUSION

Hydrocephalus in FGFR2-related Crouzon and Pfeiffer syndromes is statistically associated with a small FMA. Hydrocephalus is statistically associated with CTE.

Spring-assisted cranial vault expansion in the setting of multisutural craniosynostosis and anomalous venous drainage: case report

Patients with multisutural craniosynostosis can develop anomalous venous connections between the intracranial sinuses and cutaneous venous system through enlarged emissary veins. Cranial vault remodeling in this subset of patients carries the risk of massive intraoperative blood loss and/or occlusion of collateral draining veins leading to intracranial venous hypertension and raised intracranial pressure, increasing the morbidity of cranial expansion. The authors report the use of spring-mediated expansion as a technique for cranial reconstruction in which the collateral intracranial venous drainage system can be preserved. A patient with bilateral lambdoid, sagittal, and unicoronal synostosis presented for cranial reconstruction. A tracheostomy and ventriculoperitoneal shunt were placed prior to intervention. At the time of reconstruction, a Luckenschadel skull abnormality and Chiari malformation Type I were present. A preoperative CT venogram demonstrated large collateral superficial occipital veins, small bilateral internal jugular veins, and hypoplastic jugular foramina. Collateral flow from the transverse and sigmoid sinuses through large occipital emissary veins was seen. Spring-mediated cranial vault expansion was performed with care to preserve the large collateral veins at the occipital midline. Four springs were placed at each lambdoid and the posterior and anterior sagittal sutures following 1-cm strip suturectomies. Removal of the springs was performed 2 months postoperatively. Cranial vault expansion was performed without disturbing the aberrant intracranial/extracranial venous collateral system. Estimated blood loss was 150 ml. A CT scan obtained 3 months postoperatively showed resolution of the Luckenschadel deformity and a 40% volumetric increase in the skull compared with the preoperative CT. Patients with anomalous venous drainage patterns and multisutural synostosis can undergo spring-mediated cranial vault expansion while preserving the major emissary veins draining the intracranial sinuses. Risks of blood loss, intracranial venous hypertension, and increased intracranial pressure may be decreased compared with traditional techniques of repair.

A unifying theory for the multifactorial origin of cerebellar tonsillar herniation and hydrocephalus in osteopetrosis

OBJECT

Osteopetrosis is a rare congenital metabolic bone disease. There are very few reports in the literature associating cerebellar tonsillar herniation (CTH) and hydrocephalus requiring neurosurgical attention. The authors present cases of osteopetrosis requiring neurosurgical intervention from their practice and offer a detailed account of the literature.

METHODS

A retrospective review was conducted at the authors' institution, and all children with osteopetrosis requiring neurosurgical attention were identified. Medical charts and radiographic studies were reviewed. Data including age at presentation, sex, symptoms at presentation, age at follow-up, the presence of any neurological comorbidities, and surgical procedures performed were recorded.

RESULTS

Four patients were identified as having osteopetrosis requiring neurosurgical attention at the authors' institution between January 1, 2005, and January 1, 2014. There were 3 females and 1 male with an average age at presentation of 11.1 years; patients were observed for a mean of 4.4 years. All of the patients were identified as harboring jugular foraminal stenosis and CTH. Seventy-five percent of these patients developed hydrocephalus, and in those cases a triventricular pattern of dilation was noted. One patient developed syringomyelia. Three of the 4 patients underwent neurosurgical procedures. Cerebrospinal fluid diversion was performed in 2 patients via a ventriculoperitoneal shunt in one case and an endoscopic third ventriculostomy (ETV) in the other. The former patient required a proximal revision at 2 years for bony overgrowth at the site of the bur hole. Two patients underwent a suboccipital decompression. In patients undergoing CSF diversion, there was improvement in ventricle size.

CONCLUSIONS

Variable degrees of hindbrain crowding and/or CTH are mentioned throughout the literature, suggesting that this entity is nearly always present in this patient population. The progressive triventricular hydrocephalus seen in these cases results from a complex combination of both communicating and noncommunicating pathology, which may depend on the type of osteopetrosis, age at presentation, and the presence and degree of venous collateralization, and it appears that the hydrocephalus is more prevalent and more likely to be treated in infants and in the younger, school-aged population. The acquired hindbrain fullness in conjunction with the triventricular pattern of hydrocephalus has kept the authors enthusiastic regarding the use of ETV in these complicated cases.

Associated disorders of Chiari Type I malformations: a review

A single pathophysiological mechanism of Chiari Type I malformations (CM-I) has been a topic of debate. To help better understand CM-I, the authors review disorders known to be associated with CM-I. The primary methodology found among most of them is deformation of the posterior cranial fossa, usually with subsequent decrease in volume. Other mechanisms exist as well, which can be categorized as either congenital or acquired. In understanding the relationship of such disorders with CM-I, we may gain further insight into the process by which cerebellar tonsillar herniation occurs. Some of these pathologies appear to be true associations, but many appear to be spurious.

Hydrocephalus and Chiari type I malformation

INTRODUCTION

[corrected] Hydrocephalus has been related to Chiari type I malformation (CIM) for a long time. The pathogenesis of this association is complex and still debated.

DISCUSSION

A supratentorial hypertensive hydrocephalus may cause CIM, exerting pressure from above. Another pathogenetic hypothesis is based on the clinical and radiological data from patients affected by complex craniosynostosis, in which this association is more commonly observed as the consequence of a "cephalo-cranial disproportion" ultimately leading to a secondary hydrocephalus. In some cases, the concomitant presence of a stenosis of the jugular foramina would determine a condition of upward venous hypertension, resulting in the development of CIM and an associated hydrocephalus due to cerebellar parenchyma turgor.

CONCLUSIONS

The radiological association of ventricular enlargement and hindbrain herniation would be the result of heterogeneous pathogenetic mechanisms which would then require specific therapeutic approaches. In this context, the endoscopic third ventricle-cisternostomy is gaining an increasing interest because of its more physiologic correction of the altered CSF dynamics and its minor interference on the developmental processes responsible for the association of hydrocephalus and CIM.

Crouzon syndrome with acanthosis nigricans: a case-based update

BACKGROUND

Crouzon syndrome with acanthosis nigricans also named Crouzono-dermo-skeletal is a clinically and genetically distinct entity. It associates a craniofacial phenotype to anomalies of the skin and long bones. This syndrome is due to a specific mutation in FGFR3 gene that can be identified by genetic testing.

ILLUSTRATIVE CASES

As in our two patients, not all these features might be present and some will be patent only in the infancy or early childhood. Moreover, other organs such as the kidneys might be affected.

DISCUSSION

Because several organs might be affected the recognition of such syndrome is important for a correct management of the patient as well as a proper information and genetic counseling of the families.

Abnormal venous drainage in syndromic craniosynostosis and the role of CT venography

OBJECTIVE

Venous hypertension is emerging as a significant contributor to intracranial pressure in children with syndromic craniosysnostosis. This is associated with jugular foramen stenosis or atresia and with the development of collateral emissary veins. We demonstrate how computed tomography venography can document the prevalence of these emissary veins and how their visualisation plays an important role in operative planning.

MATERIALS AND METHODS

Patients with known syndromic craniosynostosis underwent computed tomography venography as part of their routine pre-operative evaluation. The venous drainage pattern was examined in these patients, with a special note of the presence of abnormal venous pathways.

RESULTS

Eleven patients were recruited into the study from ages 3 months to 22 years. All had a diagnosis of syndromic craniosynostosis with six Crouzon's, four Pfeiffer's and one patient with Crouzon's and acanthosis nigricans. Nine of 11 patients had demonstrable evidences of transosseous venous drainage through an identifiable abnormal emissary vein. Four of 11 had a transosseous route as the main mechanism of drainage for the cerebral venous system.

CONCLUSIONS

Patients with syndromic craniosynostosis often demonstrate abnormal venous anatomy, which can have serious consequences on craniofacial surgery, especially when a posterior decompression is being considered. Based on these findings, the authors assert that those children with some syndromic craniosynostosis being considered for surgery should undergo venographic studies as part of their pre-operative evaluation.

Crouzon with acanthosis nigricans. Further delineation of the syndrome

Patients with Crouzon and acanthosis nigricans syndrome show craniofacial features similar to those observed in patients with classic Crouzon syndrome, in addition to acanthosis nigricans with peculiar characteristics. More severe physical manifestations, such as Chiari malformation, hydrocephalus, and atresia or stenosis of the choanas, which are unusual in individuals with classic Crouzon syndrome, are reported in these patients. The molecular abnormality associated with Crouzon syndrome with acanthosis nigricans (CAN) is a transition in the transmembrane domain of the FGFR3 gene that results in an Ala391Glu mutation. We describe two unrelated patients showing this mutation and compare their clinical features with those of other patients with CAN reported in the literature. In addition to craniosynostosis with crouzonoid facies and acanthosis nigricans (present in all patients), melanocytic nevi, choanal atresia or stenosis, hydrocephalus, Chiari malformations and oral abnormalities were observed in the majority of the 35 patients analyzed. Vertebral anomalies and conductive hearing loss were present with less frequency. Some characteristics considered typical of this condition (jaw cementomas, acanthomas and finger abnormalities) were absent in most of the patients.

Neuroimaging findings in macrocephaly-capillary malformation: a longitudinal study of 17 patients

Here, we report the neuroimaging findings and neurological changes in 17 unpublished patients with Macrocephaly-Capillary Malformation (M-CM). This syndrome has been traditionally known as Macrocephaly-Cutis Marmorata Telangiectatica Congenita (M-CMTC), but we explain why M-CM is a more accurate term for this overgrowth syndrome. We analyzed the 17 patients with available brain MRI or CT scans and compared their findings with features identified by a comprehensive review of published cases. White matter irregularities with increased signal on T2-weighted images were commonly observed findings. A distinctive feature in more than half the patients was cerebellar tonsillar herniation associated with rapid brain growth and progressive crowding of the posterior fossa during infancy. In four such cases, we confirmed that the tonsillar herniation was an acquired event. Concurrently, with the development of these findings, ventriculomegaly (frequently obstructive) and dilated dural venous sinuses were observed in conjunction with prominent Virchow-Robin spaces in many of those in whom cerebellar tonsil herniation had developed. We postulate that this constellation of unusual features suggests a dynamic process of mechanical compromise in the posterior fossa, perhaps initiated by a rapidly growing cerebellum, which leads to congestion of the venous drainage with subsequently compromised cerebrospinal fluid reabsorption, all of which increases the posterior fossa pressure and leads to acquired tonsillar herniation. We make a distinction between congenital Chiari I malformation and acquired cerebellar tonsil herniation in this syndrome. We also observed numerous examples of abnormal cortical morphogenesis, including focal cortical dysplasia, polymicrogyria which primarily involved the perisylvian and insular regions, and cerebral and/or cerebellar asymmetric overgrowth. Other findings included a high frequency of cavum septum pellucidum or vergae, thickened corpus callosum, prominent optic nerve sheaths and a single case of venous sinus thrombosis. One patient was found to have a frontal perifalcine mass resembling a meningioma at age 5 years. This is the second apparent occurrence of this specific tumor in M-CM.

Anomalous venous drainage preventing safe posterior fossa decompression in patients with chiari malformation type I and multisutural craniosynostosis. Report of two cases and review of the literature

The authors report on two children in whom an anomalous posterior fossa venous drainage pattern prevented safe posterior fossa decompression. Both patients had Chiari malformation Type I, multisutural craniosynostosis, and crowded posterior fossa structures. Both patients had been treated with ventriculoperitoneal shunts for hydrocephalus. Pfeiffer syndrome had been diagnosed in one of the patients, and the other was suspected to have osteogenesis imperfecta. Although both patients were believed to have symptoms resulting from brainstem compression, posterior fossa decompression was not offered due to profound venous anomalies noted on imaging studies that greatly increased the expected risks associated with surgery. These cases are presented to alert neurosurgeons to carefully evaluate the posterior fossa venous anatomy prior to considering posterior fossa decompression with or without occipitocervical fusion or calvarial vault remodeling procedures in patients with multisutural craniosynostosis.

Venous hypertension and craniosynostosis

INTRODUCTION

This article addresses the relevance of venous hypertension to children born with, in particular, the "syndromic" forms of craniosynostosis. The development of the human cerebral venous system is summarised and the patterns of anomalous venous drainage seen in children with complex forms of craniosynostosis associated with raised intracranial pressure are described.

AETIOLOGY

The aetiology of these abnormal patterns is discussed under the general headings of "The constriction theory", "A primary role for FGFR mutations" and "Persistence of the foetal pattern of intracranial venous drainage."Venous hypertension (along with hydrocephalus, cranio-cerebral disproportion and airway obstruction) has an important role in the aetiology of raised intracranial pressure in severely affected children.

TREATMENT

The inter-relationship between these factors is explained and then the treatment of those children whose raised intracranial pressure is considered to be due predominantly to venous hypertension is described.

Cutaneous manifestations and the Chiari I malformation

This article presents a child with Chiari I malformation and cutis marmorata telangiectatica congenita and reviews the medical literature regarding Chiari I malformation and other cutaneous disorders. In addition to cutis marmorata telangiectatica congenita and Chiari I malformation, our patient exhibited hemihypertrophy, Tourette's syndrome, scoliosis, obsessive-compulsive disorder, and seizures. Other associated findings seen in patients with Chiari I malformation include basilar invagination, Klippel-Feil syndrome, atlantoaxial assimilation, scoliosis from an underlying syrinx, and hydrocephalus.

CT imaging of craniofacial malformations

Because of its superior depiction of bone detail, CT is a useful tool in the characterization of CF deformities and presurgical planning. Modern CT scanners and workstations provide 2D techniques such as multiplanar reformats and 3D techniques, such as MIP and volume renderings, which may be used effectively in the diagnosis and management of patients with CF malformations.

Costello syndrome and Chiari I malformation: apropos of a case with a review of the literature regarding a potential association

We report a child with Costello syndrome and Chiari I malformation. The medical literature has several case reports of findings peculiar for each of these two clinical entities that, when investigated, can actually be found in both processes. Recent reports have shown additional medical coincidences for the Chiari I malformation, which, unlike the Chiari II malformation, was once thought not to have many additional associations. We propose that both Costello syndrome and other clinical entities that have potential mesodermal or ectodermal deficiencies (eg, Chiari I malformation and phakomatoses, respectively) could have common dysgeneses. Further case reports from other institutions regarding Costello syndrome and Chiari I malformation are now necessary to confirm our findings. Our hope is that these data will potentially add to our knowledge of the etiology of both Costello syndrome and Chiari I malformation and potentially aid in the definition of a genetic locus for both entities.

Midface anomalies in children

A variety of congenital midface anomalies occur in children. High-resolution computed tomography (CT) and magnetic resonance (MR) imaging have proved helpful in determining the nature and extent of dysplasia, thereby facilitating treatment planning. A classification system has been developed that groups these anomalies into four categories based on embryogenesis and anatomic location. These categories comprise anomalies that are related to the nasal cavity, nasofrontal region, nasolacrimal apparatus, and craniofacial syndromes. CT is the imaging modality of choice in children with possible choanal atresia, pyriform aperture stenosis, or anomalies of the nasolacrimal duct (eg, nasolacrimal duct stenosis, dacryocystoceles). MR imaging is the modality of choice in patients with congenital midface masses (eg, dermoid and epidermoid cysts, nasal gliomas, encephaloceles) and craniofacial syndromes (eg, Apert syndrome, Crouzon syndrome, Treacher Collins syndrome). In many cases, however, both CT and MR imaging are required to adequately evaluate midface anomalies. Familiarity with the characteristic imaging features of these anomalies along with knowledge of midface embryogenesis and normal developmental anatomy is essential to prevent misinterpretation of anatomic variations that may simulate disease.

The molecular and genetic basis of fibroblast growth factor receptor 3 disorders: the achondroplasia family of skeletal dysplasias, Muenke craniosynostosis, and Crouzon syndrome with acanthosis nigricans

Achondroplasia, the most common form of short-limbed dwarfism in humans, occurs between 1 in 15,000 and 40,000 live births. More than 90% of cases are sporadic and there is, on average, an increased paternal age at the time of conception of affected individuals. More then 97% of persons with achondroplasia have a Gly380Arg mutation in the transmembrane domain of the fibroblast growth factor receptor (FGFR) 3 gene. Mutations in the FGFR3 gene also result in hypochondroplasia, the lethal thanatophoric dysplasias, the recently described SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans) dysplasia, and two craniosynostosis disorders: Muenke coronal craniosynostosis and Crouzon syndrome with acanthosis nigricans. Recent evidence suggests that the phenotypic differences may be due to specific alleles with varying degrees of ligand-independent activation, allowing the receptor to be constitutively active. Since the Gly380Arg achondroplasia mutation was recognized, similar observations regarding the conserved nature of FGFR mutations and resulting phenotype have been made regarding other skeletal phenotypes, including hypochondroplasia, thanatophoric dysplasia, and Muenke coronal craniosynostosis. These specific genotype-phenotype correlations in the FGFR disorders seem to be unprecedented in the study of human disease. The explanation for this high degree of mutability at specific bases remains an intriguing question.

Crouzon syndrome with acanthosis nigricans: case report and mutational analysis

OBJECTIVE

To describe the 22nd case of Crouzan syndrome with acanthosis nigricans, a hyperkeratotic skin disorder with hyperpigmentation.

METHODS

DNA analysis and sequencing of the FGFR3 gene were performed.

RESULTS

The 13-year-old Japanese boy described here also had dyspnea, facial palsy, sensorineural hearing loss, and skeletal and mental retardation. Examination of a skin biopsy specimen revealed the typical findings of acanthosis nigricans. Genetic analysis revealed the Ala391Glu mutation in one FGFR3 gene.

CONCLUSIONS

Crouzon syndrome with acanthosis nigricans is a distinct clinical entity different from classic Crouzon syndrome.

Molecular diagnosis of bilateral coronal synostosis

The authors performed a prospective study evaluating molecular diagnosis in patients with bilateral coronal synostosis. The patients were divided into two groups: (1) those clinically classified as having Apert, Crouzon, or Pfeiffer syndrome and (2) those clinically unclassified and labeled as having brachycephaly. Blood samples were drawn for genomic DNA analysis from 57 patients from 1995 to 1997. Polymerase chain reactions were performed using primers flanking exons in FGFR 1, 2, and 3. Each exon was screened for mutations using single-strand confirmation polymorphism, and mutations were identified by DNA sequencing. Mutations in FGFR2 or FGFR3 were found in all patients (n = 38) assigned a phenotypic (eponymous) diagnosis. All Apert syndrome patients (n = 13) carried one of the two known point mutations in exon 7 of FGFR2 (Ser252Trp and Pro253Arg). Twenty-five patients were diagnosed as having either Crouzon or Pfeiffer syndrome. Five patients with Crouzon syndrome of variable severity had mutations in exon 7 of FGFR2. Fifteen patients (12 with Crouzon, 3 with Pfeiffer) had a mutation in exon 9 of FGFR2, many of which involved loss or gain of a cysteine residue. A wide phenotypic range was observed in patients with identical mutations, including those involving cysteine. Two patients labeled as having Crouzon syndrome had the Pro250Arg mutation in exon 7 of FGFR3. All three patients with the crouzonoid phenotype and acanthosis nigricans had the same mutation in exon 10 of FGFR3 (Ala391Glu). This is a distinct disorder, characterized by jugular foraminal stenosis, Chiari I anomaly, and intracranial venous hypertension. Mutations were found in 14 of 19 clinically unclassifiable patients. Three mutations were in exon 9, and one was in the donor splice site of intron 9 on FGFR2. The most common mutation discovered in this group was Pro250Arg in exon 7 of FGFR3. These patients (n = 10) had either bilateral or unilateral coronal synostosis, minimal midfacial hypoplasia with class I or class II occlusion, and minor brachysyndactyly. No mutations in FGFR 1, 2, or 3 were detected in five patients with nonspecific brachycephaly. In conclusion, a molecular diagnosis was possible in all patients (n = 38) given a phenotypic (eponymous) diagnosis. Different phenotypes observed with identical mutations probably resulted from modulation by their genetic background. A molecular diagnosis was made in 74 percent of the 19 unclassified patients in this series; all mutations were in FGFR2 or FGFR3. Our data and those of other investigators suggest that we should begin integrating molecular diagnosis with phenotypic diagnosis of craniosynostoses in studies of natural history and dysmorphology and in analyses of surgical results.