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Overview of craniosynostosis

Overview of craniosynostosis
Literature review current through: Jan 2024.
This topic last updated: May 04, 2021.

INTRODUCTION — Interruption of normal embryologic craniofacial differentiation can produce a wide variety of craniofacial abnormalities. Many of the more profound craniofacial deformities occur secondary to craniosynostosis or premature fusion of one or more cranial sutures. Reconstruction of craniofacial structure is typically required when physical or mental well-being becomes affected.

The pathogenesis, diagnosis, and surgical management of craniosynostosis are reviewed here. Specific syndromes associated with craniofacial abnormalities are discussed separately. (See "Craniosynostosis syndromes" and "Syndromes with craniofacial abnormalities".)

CRANIAL ANATOMY — The newborn infant's skull is composed of bony plates separated by sutures. This arrangement accommodates transient skull distortion during birth and permits future growth of the brain, the volume of which quadruples during the first two years of life. There are four major sutures: the metopic, coronal, sagittal, and lambdoid. Three additional sutures that contribute to calvarial development are considered minor: the frontonasal, temporosquamosal, and frontosphenoidal. The sagittal, coronal, and metopic sutures meet at the anterior of the skull to form the anterior fontanelle, palpable just behind the forehead at the midline. The posterior fontanelle is formed by the intersection of the sagittal and lambdoid sutures (figure 1).

The osseous cranial base is embryologically derived from a cartilaginous framework (endochondral bone) that undergoes a proliferative growth pattern. In contrast, the calvarium consists of membranous bone, which has no cartilaginous phase. The calvarium grows by depositing new bone along suture lines in response to the distending forces of the rapidly growing brain. During the first two years after birth, the brain increases in size to 75 percent of its adult volume (figure 2). The remaining 25 percent of growth occurs during the next 18 years.

Fontanelle and suture closure occurs in a specific pattern (table 1 and table 2). At two months of age, the posterior fontanelle closes, followed by anterior fontanelle closure at approximately two years. The anterolateral and posterolateral fontanelles close at three months and one year, respectively. While the metopic suture typically closes at two years of age, all remaining patent sutures close in adulthood following completion of craniofacial growth.

PATHOGENESIS — Craniosynostosis results from premature fusion of one or more cranial sutures (table 2 and figure 1) and affects 1 in every 2000 to 2500 births worldwide [1]. Premature fusion restricts the growth of the skull perpendicular to the affected suture [2]. In order to accommodate the growing brain, compensatory skull growth occurs parallel to the affected suture. The resulting skull deformity is dependent upon which suture(s) is/are affected (figure 3).

Craniosynostosis may involve any of the sutures in isolation or multiple sutures, although the sagittal suture is affected most often. In a review of 519 subjects, the sagittal suture was affected in 56 percent, the coronal suture in 25 percent, the metopic suture in 4 percent, and the lambdoid suture in 2 percent of cases [3]. Multiple sutures were affected in only 13 percent of cases. In general, craniosynostosis involving a single suture occurs sporadically and as an isolated defect. There is an increased incidence of craniosynostosis in multiple pregnancies and in the presence of uterine abnormalities, such as bicornuate uterus, implying that compression of the fetal skull during pregnancy can contribute to craniosynostosis. In contrast, craniosynostosis involving multiple sutures is often part of a genetic syndrome with additional anomalies [4]. (See "Craniosynostosis syndromes".)

Several additional hypotheses regarding the mechanisms underlying premature closure of cranial sutures in nonsyndromic craniosynostosis have been proposed. According to Moss's dural hypothesis, abnormal dural attachments exert restrictive tensile forces that arrest bone growth and lead to premature suture closure [5]. An alternative theory is that an intrinsic abnormality in the cranial base produces early fusion. This theory is supported by data from laboratory studies of osteoblasts retrieved from craniosynostotic tissues. In culture, these cells demonstrate prolonged doubling time and are inhibited by exposure to osteoblast growth factor [6]. In addition, craniosynostosis is associated with endocrine abnormalities, such as hyperthyroidism, and warfarin or valproate use during pregnancy [7,8].

Mutations in specific genes have been identified in most of the common autosomal dominant craniosynostosis syndromes [9]. Most mutations affect genes that code for members of the fibroblast growth factor receptor (FGFR) family [10]. Mutations in these genes may also be found in patients with nonsyndromic craniosynostosis. In a study of 57 patients with bilateral coronal synostosis, mutations in FGFR2 or FGFR3 were identified in all patients with a phenotypic diagnosis (Apert, Crouzon, or Pfeiffer syndrome) [11]. Mutations in these genes also were found in 14 of 19 patients who could not be classified clinically. In another series, the most commonly mutated genes were FGFR2, FGFR3, TWIST1 (encodes the transcription factor twist homologue 1), and EFNB1 (encodes ephrin-B1, a protein involved in cell recognition) [12]. Single gene disorders accounted for 86 percent of the molecular defects identified in this study, whereas chromosome abnormalities occurred in only 14 percent (one patient had both). Syndromic craniosynostosis is discussed in greater detail separately. (See "Craniosynostosis syndromes".)

CATEGORIZATION OF CRANIAL DEFORMITIES — The cranial deformation is categorized as scaphocephaly, plagiocephaly, trigonocephaly, kleeblattschädel, or acrocephaly, depending upon which suture(s) is/are involved (figure 3).

Scaphocephaly — Scaphocephaly (dolichocephaly), also known as hull-shaped skull, is caused by premature fusion of the sagittal suture, which results in decreased width and elongation of the anteroposterior (AP) axis of the cranium (picture 1). Scaphocephaly accounts for approximately 50 percent of craniosynostosis cases, occurring with an estimated incidence of 1 in 2000 live births [13].

Plagiocephaly — Plagiocephaly, or twisted skull, is the result of unilateral coronal or lambdoidal synostosis.

Premature closure of a unilateral coronal suture, anterior plagiocephaly, occurs in 1 in 10,000 live births. Anterior plagiocephaly is characterized by flattening of the forehead and elevation of the eyebrow on the affected side. The contralateral forehead becomes excessively prominent as a result of compensatory overgrowth, and the ear on the affected side is displaced anteriorly and superiorly. The chin and nose deviate to the unaffected side. In AP radiographs of the face, the affected orbit has a Mardi Gras mask-like appearance referred to as harlequin eye deformity.

Premature closure of a unilateral lambdoid suture results in ipsilateral occipitoparietal flattening or posterior plagiocephaly (figure 4). The forehead on the contralateral side bulges forward, while the forehead on the ipsilateral side is set back. The ear is low set on the affected side. Ear placement is anterior, symmetric, or posterior in relation to the contralateral ear.

Trigonocephaly — Trigonocephaly is caused by premature closure of the metopic suture and accounts for approximately 10 percent of craniosynostosis cases. Trigonocephaly is characterized by a narrow, triangle-shaped forehead with a prominent midline ridge, resembling a keel, and superior-lateral orbital depression and hypotelorism [14,15]. Affected patients also have compensatory occipital-parietal calvarial changes, such as recessed lateral orbits [14,15].

Kleeblattschädel — Kleeblattschädel, also known as cloverleaf deformity, occurs when multiple sutures fuse prematurely. The coronal, lambdoid, and metopic sutures are most frequently affected. Bulging of the skull through the open sagittal and temporosquamosal sutures produces a trilobate skull. Kleeblattschädel is a rare anomaly, with fewer than 130 cases reported in the literature. Kleeblattschädel is the most severe form of cranial dysostoses. Nearly all affected patients have hydrocephalus and intellectual disability.

Acrocephaly — Acrocephaly, also known as tower skull, results from combined sagittal, coronal, and lambdoid synostosis. The anterior cranium is elevated relative to the posterior cranium, causing the vault to slant from front to back. Acrocephaly is often seen in Crouzon or Apert syndromes. (See "Craniosynostosis syndromes".)

Other deformities

Brachycephaly results from bilateral coronal synostosis. The cranium is shortened in length and increased in both width and height. Mild, transient brachycephaly can also occur as a positional deformity without sutural synostosis in normal babies who are placed in the "back to sleep" position to minimize the risk of sudden infant death syndrome. This form is also especially common in babies who suffer from hypotonia in infancy. (See 'Positional flattening (positional plagiocephaly)' below.)

Oxycephaly or turricephaly refers to a tall cranium with diminished growth in the AP and lateral dimensions. The nasofrontal angle is obtuse or blunted. Oxycephaly may occur when treatment of bicoronal synostosis is delayed or inadequate. In other words, it may be a natural progression of brachycephaly if bicoronal synostosis is untreated. This presentation is often found in syndromic craniosynostosis and may be associated with abnormalities in sutures other than the coronal sutures. (See "Craniosynostosis syndromes".)

DIAGNOSIS — The diagnosis of craniofacial deformity is primarily based upon physical examination (see 'Categorization of cranial deformities' above). Radiographic studies, such as plain radiographs and computed tomography (CT), may further characterize the structural abnormality. However, making a specific diagnosis can be complicated when features overlap two known syndromes or otherwise fail to fit into a defined clinical category [16]. Radiographic studies are best performed at a center with a craniofacial team. Molecular diagnosis is available for syndromic forms, including Muenke, Apert, Crouzon, Saethre-Chotzen, and Pfeiffer syndromes. (See 'Categorization of cranial deformities' above and "Craniosynostosis syndromes" and 'Management' below.)

Computed tomography — CT can identify the sutures more accurately than can plain radiographs and can be used to assess the extent of fusion and its effect on adjacent bones. The brain can be examined for abnormalities, including hydrocephalus. Asymmetry and deformities of the cranial base can be seen. CT also is used to evaluate the spatial and geometric relationships between the bony orbit and its soft tissue contents (the globe and extraocular muscles) [17,18].

Three-dimensional surface reconstructions using CT can assist in the classification of craniofacial disorders [19,20]. These images, together with cephalometric and anthropometric data, can be used to quantitate the skeletal deformity and plan surgical treatment of complex craniofacial reconstructions [21-23].

Changes in intracranial volume can be calculated in children with craniosynostosis using CT, although these measurements typically are within normal limits [24,25].

Ultrasound has been studied as a lower-cost alternative to CT. While results from one study look promising [26], there are several potential drawbacks to this diagnostic tool. Ultrasound is much more dependent upon the technician performing the study than CT, and inconclusive results require the patient to undergo further studies. In addition, CT allows for evaluation of more than just the affected suture. Minor cranial sutures, brain anatomy, and any concerning anomalous vascular structures are also assessed.

Cephalometrics — Cephalometry is the precise measurement of the dimensions of the head. Cephalometric radiography is a standardized technique that enables accurate longitudinal studies of head growth. Standardization is achieved by a constant orientation of the radiograph axis, the patient's head, and the film. The orienting device, called a cephalometer, stabilizes the patient's head with a pair of ear rods that enter the external auditory meatus and a third rod, which rests on the nasofrontal suture, thereby preventing sagittal rotation of the head. The radiographic film is held at a constant distance from the midline of the head and the radiograph source. Lateral and frontal views are obtained. Skeletal landmarks are identified in order to compare lengths and angles with normal values or in the same patient over time.

Genetics — Early screening for genetic mutations can be performed in affected newborns with suspected syndromic forms of craniosynostosis [27]. Genes screened include those encoding for members of the fibroblast growth factor receptor (FGFR) family and TWIST (a helix-loop-helix transcriptional regulator). Causative mutations are more commonly identified in children with unicoronal or bicoronal, rather than sagittal or metopic, nonsyndromic craniosynostosis [12]. (See 'Pathogenesis' above and "Craniosynostosis syndromes".)

DIFFERENTIAL DIAGNOSIS OF FACIAL ASYMMETRY — Several conditions can result in facial asymmetry and must be differentiated from craniosynostosis. They include positional deformities and congenital muscular torticollis.

Positional flattening (positional plagiocephaly) — Posterior plagiocephaly caused by craniosynostosis (figure 4) may be confused with positional skull flattening (or deformational plagiocephaly) [28]. The frequency of the latter condition has increased, in part because of supine sleep positioning to prevent sudden infant death syndrome [29-31]. Guidelines for the diagnosis and treatment of positional plagiocephaly are available and are largely consistent with our approach outlined below [32].

Localized lateral or occipital cranial flattening at birth is common and may be a precursor to posterior deformational plagiocephaly. In one study of healthy newborns, localized cranial flattening and other unusual head shapes (eg, dolichocephalous or protruding occiput) occurred in 13 and 11 percent, respectively, of singletons [33]. Localized flattening was more common in twins, occurring in 56 percent. Findings shared by localized flattening at birth and posterior deformational plagiocephaly that becomes apparent at two to three months of age suggested that the former may lead to the latter. These included boys affected more than girls, right side affected more than left, twins affected more than singletons, increased incidence of other deformations (eg, club feet) and cephalohematoma, primiparity, long labor, and assisted delivery. Positional plagiocephaly was also associated with developmental delay, particularly motor delay, in one systematic review [34].

In a prospective cohort study of 200 infants, the prevalence of nonsynostotic plagiocephaly and/or brachycephaly at six weeks and at 4, 8, 12, and 24 months was 16, 20, 9, 7, and 3 percent, respectively [30]. Risk factors for nonsyndromic plagiocephaly included limited head rotation, supine sleep position, and decreased activity levels. In another prospective cohort study of 440 infants, the incidence of positional plagiocephaly at 7 to 12 weeks was 47 percent [31]. (See 'Congenital torticollis' below and "Sudden infant death syndrome: Risk factors and risk reduction strategies", section on 'Other measures'.)

The position of the ear is the most reliable indicator of the correct diagnosis, but computed tomography (CT) studies have shown that ear position is not completely reliable in this matter [35-37]. The ear is displaced away (anteriorly) from the flattened region in posterior positional plagiocephaly [35,38]. In contrast, the ear placement may be symmetric in posterior synostotic plagiocephaly, displaced away from the affected side (anteriorly) or displaced toward the affected side (posteriorly) [36]. In addition, the head has a parallelogram shape on posterior view in patients with synostotic plagiocephaly, but the posterior view is normal in patients with positional plagiocephaly [38]. As expected, anterior positional plagiocephaly is very uncommon since children rarely experience prolonged pressure to the anterior aspects of the head. If the diagnosis of positional plagiocephaly is uncertain, a plain radiograph or ultrasound of the skull may be obtained to confirm that the sutures are patent.

In most cases, positional plagiocephaly can be treated by change in positioning [39]. A custom-fitted cranial molding orthosis (helmet) designed to relieve pressure on the flattened side is often used in the rare case of a severe deformity that does not respond to conservative treatment or that presents later in infancy since most studies suggest that the degree and speed of correction are greater with helmet therapy than repositioning [35,40,41]. A set of systematic reviews and evidence-based guidelines published by the Congress of Neurological Surgeons in 2016 regarding the management of positional plagiocephaly is consistent with this approach with one primary exception [42-46]. The data reviewed suggest that the addition of physical therapy to repositioning education is more effective than repositioning alone; therefore, the combined treatment approach is suggested.

Congenital torticollis — Congenital torticollis may result in anterior positional plagiocephaly. Affected infants maintain their external ear close to the shoulder on one side with the face turned to the other side, which may lead to positional deformation of the skull. In one review, all infants who presented with torticollis had craniofacial asymmetry, which typically was not striking [47]. Affected patients had anterior plagiocephaly consisting of recession of the ipsilateral zygoma and forehead and reduction of the vertical facial height on the affected side. Treatment of the torticollis alone was sufficient in most cases, although surgical intervention was needed to correct the skull deformity in severely affected children who presented later in childhood. (See "Congenital muscular torticollis: Clinical features and diagnosis".)

Other causes of facial asymmetry — Other causes of facial asymmetry include Parry-Romberg disease, craniofacial microsomia, and congenital facial paralysis. Unilateral tumors, such as juvenile hemangioma, neurofibromatosis, fibrous dysplasia, lymphangioma, osteoma, and embryonal rhabdomyosarcoma, can result in abnormal craniofacial appearance [48].

COMPLICATIONS — Complications associated with craniosynostosis include the following:

Increased intracranial pressure (ICP) and inhibition of brain growth. Brain growth is inhibited by prolonged uncorrected restriction of cranial growth. Compression of the underlying brain is more likely when multiple sutures are affected.

Associated impairments in cognitive and neurodevelopment function, including global developmental delay, poor feeding, and weight gain.

Deficits in vision, hearing, and speech due to cranial nerve involvement.

Poor self-esteem and social isolation due to the abnormal appearance.

Increased intracranial pressure — Increased ICP occurs more frequently in untreated craniosynostosis involving multiple sutures [49]. Acquired Chiari malformations that often require decompression are also more common in children with nonsyndromic, multi-sutural craniosynostosis [50]. The elevated incidence of Chiari malformations is thought to be related to the compromised skull growth from craniosynostosis, resulting in decreased intracranial volume and a subsequent increase in the ICP. The brain is displaced inferiorly due to the increase in ICP and decrease in intracranial volume.

In a review of 1727 cases of craniosynostosis, cerebrospinal fluid (CSF) hydrodynamics were abnormal in 8 percent, and approximately 4 percent required shunts [3]. Subsequent smaller-scale studies showed elevated ICP in 15 to 20 percent of children with isolated single-suture craniosynostosis [51,52]. Abnormalities in CSF hydrodynamics included progressive hydrocephalus with ventricular dilation, nonprogressive ventriculomegaly, and dilation of the subarachnoid spaces. Importantly, elevated ICP does not correlate well with cranial volume as measured by computed tomography (CT) [53,54].

Hydrocephalus occurred in all patients with kleeblattschädel [3]. It was more frequent in patients with syndromic than isolated craniosynostosis (12 versus 0.3 percent) and in Crouzon syndrome than in other syndromes. Ventricular dilation occurred frequently in Apert syndrome but typically was nonprogressive. Venous sinus obstruction and/or chronic tonsillar herniation were evident in most cases of syndromic craniosynostosis.

Development — Children with nonsyndromic craniosynostosis demonstrate an increased incidence of speech language, cognitive, behavioral, and neurodevelopmental abnormalities [50,55-58]. The exact relationship between structural and developmental abnormalities remains unclear. To date, the relationship between surgical correction of craniosynostosis and changes in neurodevelopment remains equally nebulous [57,59].

In one study, 15 children <1 year of age with single-suture, nonsyndromic craniosynostosis were evaluated by the Bayley Scales of Infant Development two months before and one year after surgical correction [60]. The mean score for mental development index was unchanged before and after surgery (82 versus 79); however, there was improvement in psychomotor development indices (79 versus 89). In contrast, a literature review of 17 studies concluded that there was little evidence that surgery affects the risk of neurodevelopmental impairment [56].

MANAGEMENT — Optimal care of patients with craniofacial anomalies requires a multidisciplinary approach. This approach has been supported by a consensus conference of the American Cleft Palate-Craniofacial Association [61]. The recommendations emphasize management by an interdisciplinary team [62]. The team consists of specialists from anesthesiology, audiology, cardiology, dermatology, radiology, genetic counseling, medical genetics, neurology, neurosurgery, nursing, ophthalmology, oral and maxillofacial surgery, microsurgery, nutrition, orthodontics, orthopedics, otolaryngology, pediatrics, pediatric dentistry, physical anthropology, plastic surgery, prosthodontics, psychiatry, psychology, social work, and speech-language pathology [62].

A patient whose abnormal cranial shape prompts concern when evaluated by their primary care clinician should be referred to a craniofacial team for evaluation. If such a team is not available in the local community, the patient can be referred to a specialist with craniofacial training, such as a plastic surgeon or neurosurgeon, for management advice or to a clinical geneticist for diagnosis of the underlying cause. Clinical expertise in diagnosis and treatment is maintained by a large volume of patients. Immediate referral to a craniofacial team for evaluation and imaging at a specialized children's hospital saves time and increases the efficiency of resource utilization. Patients should be evaluated as soon as possible, preferably within the first few weeks after birth [63]. However, referral is appropriate at any age.

Imaging need not be performed before referral. Plain radiographs and computed tomography (CT) performed by inexperienced personnel may be substandard and need to be repeated. Three-dimensional CT reconstructions are not typically performed at centers without a craniofacial team. If they are performed at such centers, they may not be reformatted correctly.

The craniofacial team develops and implements the treatment plan and provides coordination of care, which should be provided at the local level whenever possible. The team monitors short- and long-term outcomes, including the satisfaction and psychosocial well-being of the patient [64-66], as well as effects on growth, function, and appearance [67]. Efforts are made to assist the families of craniofacial patients in adjusting to the demands and stress placed upon them.

SURGICAL APPROACH — Surgical repair of craniosynostosis is performed to prevent intracranial hypertension and improve socialization by normalizing the appearance of the face and head [68-70].

Surgical planning — As noted above, three-dimensional surface reconstructions using computed tomography (CT) is used to plan surgical treatment of complex craniofacial reconstructions [21-23]. Interactive techniques have been developed that simulate osteotomies and skeletal movements in three dimensions on computer-generated surface images [71-73]. The ocular globes are marked to position the orbital segments, and then the osteotomized segments are transposed into normal anatomic relationship with respect to the eyes using animation. The measurements from the computer-graphic simulation then are used intraoperatively to establish the correct position of the skeletal segments [74].

Intervention — The preferred time for surgical intervention depends upon the type of craniosynostosis being treated and the surgical technique being used. Surgical treatment can be performed via the open approach or the endoscopic approach, but not all types of craniosynostosis can be corrected via the endoscopic approach.

The open approach requires a large incision across the scalp to obtain access to the cranial vault. It can be used to treat all kinds of craniosynostosis. It is preferentially used to treat patients who require a fronto-orbital advancement since is required to treat unicoronal or bicoronal craniosynostosis. Open techniques, especially for fronto-orbital reconstructions, are delayed until 9 to 12 months of age so that the bones are strong enough to build an enduring construct. In our experience, postoperative regression of cranial position is less likely to occur when surgery is performed at 9 to 12 months.

Endoscopic techniques require smaller incisions and are usually performed at a younger age to capture the rapid cranial growth that occurs in the first two years of age. In addition, the cranial bone is easier to remove, and there is typically less blood loss if this type of repair is performed before three months of age. Endoscopic techniques involve a wide craniectomy of the involved cranial suture with limited shaping maneuvers to allow for directed cranial growth postoperatively. This growth is usually guided by postoperative cranial orthotics. The most commonly treated craniosynostosis treated endoscopically are sagittal and metopic craniosynostosis.

Patients with syndromic craniosynostosis with multiple fused cranial sutures will require a specialized approach to cranial vault surgery, often requiring more than one operation to achieve the desired cranial expansion and shape. Details of syndromic craniosynostosis repair exceed the scope of this topic review.

Scaphocephaly — Scaphocephaly results from premature closure of the sagittal suture. This condition can be treated endoscopically or via the open approach. Patients treated endoscopically are corrected at two to three months of age. The operation normally takes an hour, and the children stay in the hospital for one day. These patients are usually not transfused, but they are prepared for one in case the blood loss is more than expected. Postoperatively, they are fitted with a helmet to assist with shaping. Helmets are used for three to six months. If the open approach is used, no helmet is required. This operation occurs between six to nine months of age and involves a middle and posterior cranial vault remodeling. These patients normally require a blood transfusion given the amount of reconstruction [75].

Plagiocephaly — Anterior and posterior plagiocephaly due to craniosynostosis is a result of unilateral coronal and lambdoid synostosis, respectively. Surgical intervention for anterior plagiocephaly for unicoronal craniosynostosis is undertaken at 9 to 12 months of age [76]. This allows for the cranial bone to become strong enough to undergo a durable reconstruction that does not need revisionary work. Correction of posterior plagiocephaly due to lambdoid craniosynostosis can occur at one of two time points. If the diagnosis is made in the first one to two months of life, surgical correction can be performed endoscopically via a wide stripe craniectomy and barrel stave osteotomies, with postoperative helmet therapy. This surgery is usually done at two to three months of life. If the diagnosis is made later, surgery is ideally performed between six to nine months of age. An open posterior cranial vault remodeling is performed, and postoperative helmet therapy is not required. Resorbable plates and screws made of polyglycolic acid are used for fixation after remodeling operations. This technology has proven invaluable to stabilize the remodeled cranium to prevent relapse.

Trigonocephaly — The surgical therapy for trigonocephaly is via the open or endoscopic technique. The open approach is done between 9 to 12 months of age, when the bone is strong enough for reconstruction. It usually requires a blood transfusion and three to four days of postoperative hospitalization. A full reconstruction of the forehead and fronto-orbital bar is performed. The endoscopic technique for metopic craniosynostosis occurs at two to three months of age and includes a suturectomy of the involved suture and osteotomies over the frontal areas to help with postoperative shaping. A helmet is used for three to six months postoperatively to help achieve the desired shape.

In one study, the outcomes of 76 children who underwent surgery for trigonocephaly were assessed at ≥3 years of age [77]. Approximately one-third had abnormal mental development. Factors associated with poor outcome were severe frontal stenosis, cranial reconstruction performed after one year of age, and associated extracranial malformations. Development was strongly influenced by the family environment but not by the presence of intracranial abnormalities.

Kleeblattschädel — Kleeblattschädel (also known as cloverleaf skull deformity) is caused by the fusion of multiple sutures, which usually results in hydrocephalus. Conventional surgical management advocates shunting prior to definitive craniotomy and bone remodeling [78]. Results from a small series suggest that staged cranial vault remodeling with initial ventriculoperitoneal shunting is a better alternative than early remodeling, which is associated with increased risk of pneumonia, meningitis, and excessive bleeding, that results in longer intensive care unit and hospital stays [79].

Surgical complications — The risks associated with surgery for craniosynostosis, as with all surgical procedures, include those related to general anesthesia, bleeding, infection, scarring, injury to underlying neurovascular structures, and possible need for additional surgical procedures [80-83]. All patients who undergo correction of craniosynostosis should be prepared for a blood transfusion, with appropriate perioperative planning (eg, having blood available, using a cell saver) based upon the surgical approach, given the potential risk of large blood loss. Patients undergoing the open approach almost always will require a transfusion given the amount of skin and bone that is cut or removed during the operation. Patients who have endoscopic approaches oftentimes do not need to be transfused, since the incisions are smaller and the amount of bone that is being removed and reshaped is less. There also is a risk of injury to underlying orbital or intracranial contents, including the brain and sagittal sinus. Injury to these structures may result in significant neurologic abnormalities, including blindness, weakness, seizures, cerebral edema, coma, and death [80-82].

Postoperatively, patients are admitted to either the intensive care unit (ICU) or the hospital floor depending upon their status in surgery and their postoperative stability. Normally, patients who have open operations will require a one-day stay in the ICU to manage fluid shifts, blood loss, and correct any electrolyte or coagulation abnormalities. If they stabilize overnight, they are transferred to the hospital floor for two to three additional days. Discharge occurs when their pain is controlled on oral medications, they are eating without issues, and the family is comfortable with wound management. Patients who have endoscopic surgery are usually admitted to the hospital floor for one day and discharged from the hospital the next day. They normally are sent to have a laser scan of their heads after discharge so that they can receive their helmet for postoperative molding within the same week.

SUMMARY AND RECOMMENDATIONS

Definition, terminology, and categorization – Craniosynostosis is the premature fusion of one or more cranial sutures (figure 1 and table 1 and table 2). The four major sutures are the metopic, coronal, sagittal, and lambdoid, and the three minor sutures are the frontonasal, temporosquamosal, and frontosphenoidal. The cranial deformation is categorized as scaphocephaly, plagiocephaly, trigonocephaly, or kleeblattschädel, depending upon which suture(s) is/are involved (figure 3). (See 'Introduction' above and 'Cranial anatomy' above and 'Categorization of cranial deformities' above.)

Pathogenesis – Premature fusion restricts the growth of the skull perpendicular to the affected suture (figure 2). Compensatory skull growth occurs parallel to the affected suture in order to accommodate the growing brain. (See 'Pathogenesis' above.)

Diagnosis – The diagnosis of craniofacial deformity is primarily based upon physical examination. Radiographic studies, such as plain radiographs and computed tomography (CT), may further characterize the structural abnormality. (See 'Diagnosis' above.)

Differential diagnosis – Several conditions can result in facial asymmetry, including positional flattening (positional plagiocephaly) (figure 4) and congenital torticollis. (See 'Differential diagnosis of facial asymmetry' above.)

Complications – Complications associated with craniosynostosis include increased intracranial pressure (ICP) and inhibition of brain growth, associated impairments in cognitive and neurodevelopment function, and poor self-esteem and social isolation due to the abnormal appearance. (See 'Complications' above.)

Management – The care of patients with craniofacial anomalies requires a multidisciplinary approach. (See 'Management' above.)

Referral – The primary care provider should refer every child whom he/she suspects has an abnormal head shape to a craniofacial team. The expertise of a plastic surgeon or neurosurgeon with craniofacial training and experience should be sought if an interdisciplinary team is not available in the local community. Patients should be evaluated as soon as possible, preferably within the first few weeks after birth.

Surgical repair – Surgical repair of craniosynostosis is performed to prevent intracranial hypertension and improve socialization by normalizing the appearance of the face and head. Three-dimensional surface reconstructions using CT is used to plan surgical treatment of complex craniofacial reconstructions. The preferred time for surgical intervention is 9 to 12 months of age. The different types of craniosynostosis require specific surgical approaches. (See 'Surgical approach' above.)

ACKNOWLEDGMENT — The UpToDate editorial staff acknowledges Patrick Cole, MD and Larry H Hollier, Jr, MD, who contributed to earlier versions of this topic review.

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Topic 2910 Version 26.0

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