You are in: eMedicine Specialties > Radiology > PEDIATRICS CraniosynostosisArticle Last Updated: Jun 1, 2007AUTHOR AND EDITOR INFORMATIONSection 1 of 10
  Author: Majid A Khan, MD, Consulting Neuroradiologist, Department of Diagnostic Radiology, GV(Sonny) Montgomery VA Medical Center Majid A Khan, MD, is a member of the following medical societies: American College of Radiology and American Society of Neuroradiology Coauthor(s): David I Weltman, MD, Consulting Staff, S & D Medical, LLP; Director, Department of Radiology, Southside Hospital; Brian J Webber, DO, Staff Physician, Department of Radiology, Nassau University Medical Center; Dvorah Balsam, MD, Chief, Division of Pediatric Radiology, Nassau University Medical Center; Professor, Department of Clinical Radiology, State University of New York at Stony Brook Editors: Charles M Glasier, MD, Professor, Departments of Radiology and Pediatrics, University of Arkansas for Medical Sciences; Chief, Magnetic Resonance Imaging, Vice-Chief, Pediatric Radiology, Arkansas Children's Hospital; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Marta Hernanz-Schulman, MD, FAAP, Professor, Radiology, Radiological Sciences, and Pediatrics, Director, Department of Pediatric Radiology, Radiologist-in-Chief, Director, Department of Diagnostic Imaging, Vanderbilt University Medical Center, Vanderbilt Children's Hospital; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Eugene C Lin, MD, Consulting Staff, Department of Radiology, Virginia Mason Medical Center Author and Editor Disclosure Synonyms and related keywords: premature fusion of cranial sutures, cranial sutures, simple craniosynostosis, compound craniosynostosis, cranial synostosis, synostosis, suture synostosis, sagittal synostosis, coronal synostosis, metopic synostosis, lambdoid synostosis, combined synostosis, scaphocephaly, dolichocephaly, brachycephaly, plagiocephaly, oxycephaly, trigonocephaly, kleeblattschädel deformity, Cloverleaf deformity, Crouzon disease, Chotzen syndrome, Apert syndrome INTRODUCTIONSection 2 of 10
  BackgroundCraniosynostosis is the premature fusion of the cranial sutures. Craniosynostosis can occur as an isolated defect or as part of a syndrome and is recognized in 2 forms: simple and compound. In simple craniosynostosis, only 1 cranial suture is involved; compound craniosynostosis involves 2 or more sutures. PathophysiologyIn the recent literature, mutations have been reported in gene coding for fibroblast growth factor receptors (FGFRs) in affected families with craniosynostosis. The receptors mediate the effects of the fibroblast growth factors that modulate cellular processes, such as growth, differentiation, migration, and survival. Mutations of the FGFR2 gene, located on chromosome 7, have been recognized in Crouzon disease and in Apert, Jackson-Weiss, and Pfeiffer syndromes. Some cases of Pfeiffer syndrome and Crouzon disease involve mutations of both the FGFR1 and FGFR3 genes. These mutations account for a small fraction of cases of craniosynostosis; most cases have an unclear etiology.1 With the use of immunocytochemistry techniques, abnormal osteoblastic activity has been observed within the synostotic bone, along with decreased growth rate and alkaline phosphatase production. Histopathologic examinations of resected sutures have demonstrated new bone formation at various stages. These stages range from trabecular interdigitation across the fibrous tissue to complete bony fusion. FrequencyUnited StatesThe estimated incidence of simple or compound craniosynostosis is approximately 1 case per 2000 live births. Approximately 80-90% of cases involve isolated defects, while the remaining cases are part of a recognized syndrome. In the isolated cases, the sagittal suture is affected most often, followed by the coronal, lambdoid, and metopic sutures. Mortality/MorbidityIn most patients with craniosynostosis involving a single suture, the primary concern is cosmetic. Early diagnosis and surgical therapy are essential to prevent lifelong craniofacial deformity. Patients with diffuse craniosynostosis are at risk of developing increased intracranial pressure (ICP). Patients can have airway problems because of a hypoplastic maxilla or ophthalmologic problems related to shallow orbits. Patients with Apert, Pfeiffer, or Carpenter syndromes also have significant surgical issues related to fusion anomalies of the digits. RaceNo racial predilection exists. SexSeveral forms of craniosynostosis have sex predilections. A slight male predominance is observed in cases of sagittal synostosis, and a female predominance is noted in cases of coronal synostosis. AgeMost cases are evident during the neonatal period. AnatomyThe bones of the cranium (frontal, parietal, temporal, and occipital) are well developed by the fifth month of gestation. The membranous skull bones are joined by connective tissue at the sagittal, coronal, metopic, lambdoid, and squamous sutures. The anterior fontanelle is at the junction of the frontal and parietal bones, and it represents the intersection of the metopic, coronal, and sagittal sutures. It normally closes in children by the age of 20 months. The posterior fontanelle, located at the junction of the lambdoid and sagittal sutures, closes by the age of 3 months. Mature suture closure occurs by the age of 12 years, but completion of fusion continues into the third decade of life and beyond. Clinical DetailsSkull growth is restricted in the plane perpendicular to the prematurely fused suture and enhanced in the plane parallel to it. Synostosis of the sagittal suture produces a long and narrow skull, called scaphocephaly or dolichocephaly. The anteroposterior diameter of the skull is increased, whereas the transverse diameter is decreased. Sagittal synostosis is most commonly seen in men. Although the biparietal diameter is low, the actual head volume is normal; therefore, no increase in ICP, no hydrocephalus, and no neurologic deficits are usually present. Synostosis of the coronal suture can occur bilaterally (brachycephaly) or unilaterally (plagiocephaly). Brachycephaly results in a short, wide skull, with a shortened anteroposterior diameter and a flattened occiput and forehead. Brachycephaly is seen more commonly in females and is associated with a higher incidence of neurologic complications, including increased ICP, optic atrophy, and mental retardation, than sagittal synostosis, which is usually associated with normal intellectual function. A higher incidence of anomalies is also associated with coronal craniosynostosis: in plagiocephaly, the incidence rate is 33%; in brachycephaly, the incidence can be as high as 59%. Synostosis of the lambdoid sutures is less common than sagittal and coronal synostosis. A marked flattening and underdevelopment of the posterior fossa are present with lambdoid synostosis, and overgrowth of the bregma may occur, resulting in a tall cranial shape called oxycephalic or turricephalic skull. Synostosis of the metopic suture, which occurs in utero, is rare. Called trigonocephaly, it results in a pointed forehead and hypotelorism, with an increased risk for associated anomalies of the forebrain. Other anomalies often encountered with metopic synostosis include cleft palate, coloboma, and a wide array of urinary tract abnormalities. A combined synostosis of the coronal and sagittal sutures results in a severe form of craniosynostosis termed oxycephaly, which can lead to microcephaly. In addition, increased ICP is associated with significant neurologic complications. The most severe form of craniosynostosis is called the kleeblattschädel deformity, or cloverleaf skull, in which the coronal, sagittal, and lambdoid sutures are all affected. The skull resembles a cloverleaf shape, and patients typically have a bulging forehead, proptotic eyes, and severe neurologic impairment. The most common syndrome-associated synostoses are Crouzon disease and Chotzen and Apert syndromes, which account for more than two thirds of syndrome-related craniosynostosis.
Increased ICP is frequently caused by abnormalities of cerebral venous drainage as a result of maldevelopment of the foramina at the skull base. Preferred ExaminationPatients in whom craniosynostosis is suggested should undergo a careful clinical examination, with the clinician looking for abnormalities of the skull and extremities. Plain radiography is the first radiologic step. Plain radiography quickly and simply identifies skull-shape abnormalities, which are seen in most patients with craniosynostosis. With this simple and inexpensive examination, usually all cranial sutures can be surveyed for patency. Conventional cranial CT scans with bone windows or 3-dimensional (3D) CT scans are frequently obtained to confirm bony abnormalities and to delineate any associated intracranial anomalies. Three-dimensional CT is the criterion standard for the evaluation of craniosynostosis. Limitations of TechniquesThe entire length of each suture is not always visible on plain radiographs, and some patients have only a small bony bar limiting growth at a particular suture. If the skull shape is entirely normal, craniosynostosis is unlikely. DIFFERENTIALSSection 3 of 10
Other Problems to Be ConsideredThe conditions listed below are associated with secondary synostosis: Metabolic conditions leading to premature fusion RADIOGRAPHSection 4 of 10
FindingsPlain radiographs are obtained easily and demonstrate osseous anatomy well. At a minimum, views should include anteroposterior (AP), Townes, and bilateral lateral films. Plain radiographs are useful for identifying the abnormalities of head shape (dolichocephaly, brachycephaly, and plagiocephaly) that are characteristic of the various forms of craniosynostosis. Plain radiographs can be used for the following:
Degree of ConfidenceVisualizing the length of all sutures is not always possible, and suture closure may be difficult to detect unless it is accompanied by an abnormal head shape. False Positives/NegativesCT SCANSection 5 of 10
FindingsCT scans provide a more detailed method for visualizing intracranial pathology and detailed anatomy of the calvaria and brain parenchyma. In contrast to plain radiographs, the skull base is visualized well, and hard and soft tissues of the craniofacial skeleton can be studied in detail.
Degree of ConfidenceThe sensitivity of CT scans, when combined with physical examination and plain radiography, approaches 100%. False Positives/NegativesEven on CT scans, the entire length of every suture may not be clearly visible. Once again, normal variations in skull shape may pose a problem. MRISection 6 of 10
FindingsMRI shows better definition of intracranial soft-tissue structures than CT. In addition, MRI is useful in the detection of hydrocephalus and cerebral developmental defects, such as myelination defects and deformities of the maxilla resulting in airway compromise. False Positives/NegativesMRI is not a strong modality for evaluating bony abnormalities and thus cannot be used as the primary method of evaluating craniosynostosis. MRI is used primarily for assessing associated brainstem and soft tissue abnormalities. ULTRASOUNDSection 7 of 10
FindingsThe recent literature has shown some advancement in the prenatal detection of craniosynostosis by using 3D versus 2D ultrasonography. A case was reported by Degree of ConfidenceResearch is ongoing to determine the usefulness of ultrasonography as a tool in diagnosing craniosynostosis. False Positives/NegativesUltrasonography is user dependent, and therefore, inexperienced personnel can miss the diagnosis of craniosynostosis. INTERVENTIONSection 8 of 10
Medical/Legal Pitfalls
MULTIMEDIASection 9 of 10
REFERENCESSection 10 of 10
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