Craniosynostosis is the premature and abnormal fusion of 1 of the 6 suture lines that form the living skull (see the images below). This abnormal fusion results in an abnormal head shape from aberrant bone growth patterns and, if uncorrected, can lead to increased intracranial pressure (ICP) and abnormalities in the shape and symmetry of the craniofacial skeleton.  This article should familiarize the reader with the pathology of craniosynostosis, its manifestations, its diagnosis, and its surgical treatment.
Most of the modern understanding of craniosynostosis is referenced from the 1851 writings of Virchow. His understanding and descriptions of irregular calvarial growth patterns were the basis of the law of Virchow. According to his observations, the abnormal cranial growth observed in persons with craniosynostosis occurs perpendicular to the involved calvarial sutures. Therefore, if a suture line is prematurely ossified, no growth is present in the direction perpendicular to that suture. The law was too simplistic in its explanation of the growth patterns of the skull; later studies demonstrated conflicting data.  The presence of compensatory growth patterns in patients with craniosynostosis was described later. [3, 4]
Surgical treatment for craniosynostosis was initially advocated by Lannelongue in 1890.  His patients had microcephaly from craniosynostosis and were thought to be imbeciles. These patients accordingly underwent craniectomy to remove the involved suture line and to "release the brain".  Soon after, in 1891, linear craniectomy was introduced. As with any new procedure, this one met with much resistance. However, the resistance to a surgical intervention was slowly put to rest with mounting evidence. Several studies indicated that craniosynostectomy was the treatment of choice for the release of fused suture lines in the skull. [6, 7, 8, 9]
Although strip craniectomy was used often, it lost much support with the advent of cranial vault reconstruction, in which the calvarial bones were excised, reshaped, and trimmed. Studies showed that, over time, cranial suture areas excised during strip craniectomy still became fused and led to an abnormal cranial contour.  Strip craniectomy was easier and involved less blood loss compared with the newer cranial vault reconstruction. Strip craniectomy also did not address the frontal bossing and associated abnormalities in calvarial shape and relied on the rapid growth of the brain to correct it. Strip craniectomy was optimal only in the first few months of infancy, while surgeons could use cranial vault reconstruction throughout infancy. Consequently, strip craniectomy lost favor, and the surgical treatment has been modified to include cranial vault remodeling. [11, 12]
Recently, with the advent of endoscopy, attention has returned to endoscopic strip craniectomy. The endoscopic technique has only been tried over the last several years, but it offers the advantages of a shorter and safer operation, less cost, less in-hospital time, and less blood loss. The operation was shown to be a success in a study of 12 patients, all younger than 8 months.  Critical to this success and a departure from the standard strip craniosynostectomy was the extensive use of a postoperative remodeling helmet. Although first introduced by Persing et al in 1986, helmet therapy has not been used as extensively as a postoperative therapeutic intervention.  Following the endoscopic technique, helmets were used for several months and showed promising early results.
Rivero-Garvia et al concluded that endoscopy-assisted surgery for correction of craniosynostosis in children younger than 4 months represents a valid and safe management option that may help prevent the development of associated ventriculomegaly and Chiari I malformation. 
The neonate calvarium is composed of the frontal, parietal, temporal, sphenoid, and occipital bones. A suture separates each of these bones. The metopic suture separates the frontal bones; the coronal, the frontal, and parietal bones; the squamosal, parietal, and squamosal temporal bones; and the lambdoid, parietal, and occipital bones. The sagittal suture lies between the 2 parietal bones. The patent suture lines allow for continuous separation of the calvarial bones in the prenatal and the early perinatal period. They also allow for collapse of the head shape to facilitate the passage of the head through the birth canal.
If fused prematurely, growth is restricted predominantly in a direction perpendicular to the fused suture. However, growth does not completely stop. In response to a prematurely closed suture, the remaining sutures undergo compensatory growth in patterns that are now well documented.  As the suture lines fuse, they act as a single growth plate but with decreased growth potential. Suture lines that are contiguous with the fused growth plate undergo symmetric bony deposition along both edges of the suture line. Other unaffected suture lines at the perimeter of the fused suture also undergo increased bony deposition. In this way, the living skull attempts to compensate for the altered growth potential caused by the premature suture fusion.
As the rapidly growing brain expands, it does so in a direction unrestricted by the sutures that are fused. This results in characteristic morphologic features, specific for each type of suture fusion.
Scaphocephaly or "boat skull" occurs following fusion of the sagittal suture (see the images below). The calvarium continues to expand in the anteroposterior direction, with growth restricted in the transverse direction. Associated frontal bossing and occipital bathrocephaly (occipital bullet) are observed, which compound the scaphocephaly. With progression of the deformity, a typical hourglass deformity of the calvarium occurs. If the sagittal craniosynostosis is not corrected, the bizygomatic diameter narrows and the intercanthal and interdacryon distance decrease.
Brachycephaly or "short skull" occurs secondary to fusion of both coronal sutures (see the images below). Fusion of both coronal sutures prevents anteroposterior growth of the calvarium and the anterior cranial fossa. The calvarium tends to grow vertically, leading to turricephaly, and laterally, leading to an increase in the bizygomatic and bitemporal diameter.
Unlike brachycephaly, unicoronal synostosis involves only one of the coronal sutures (see the image below). This results in a discrepancy in growth of the calvarium. The restriction of the anterior growth on the involved (ipsilateral) side leads to a dorsal position of the frontoorbital bar and a ventral, more anterior position of the contralateral frontoorbital bar. Understanding this physiology is critical before attempting a corrective procedure. Once operative correction is instituted, both the ipsilateral and contralateral bones must be corrected in their position; this is essential. Moreover, one must understand that the fused suture restricts the growth of the sphenoid bone, resulting in a reduction of the anteroposterior dimension of the anterior cranial fossa. Consequently, the anterior endocranial base deviates toward the fused ipsilateral side.
In similar fashion, the ectocranium also deviates to the ipsilateral side and, if not corrected, leads to a deviation of the face and the occlusal cant. The roof of the orbit, which is formed by the greater wing of the sphenoid, is raised. The shape of the ipsilateral orbit is more vertical and the shape of the contralateral orbit is more horizontal. Throughout this process, the posterior cranial base is unaffected.
Trigonocephaly or "triangular skull" is seen in a pathologically fused metopic suture wherein the transverse growth of the forehead is compromised (see the images below). This results in a narrowed, triangular forehead and a decrease in the interdacryon and intercanthal distances.
Lambdoid synostosis is one of the most rare types of craniosynostosis. The fused lambdoid suture leads to ipsilateral occipital flattening and enlargement of the ipsilateral mastoid process. The posterior ectocranial and endocranial base is deviated toward the fused lambdoid suture, and the petrous part of the temporal bone is deviated ipsilaterally; this is associated with external auditory meatus (and external ear) deviation dorsally toward the fused suture.
Lambdoid craniosynostosis is easily mistaken for deformational plagiocephaly, which occurs secondary to an external deforming force (vide infra). The external deforming force flattens the soft, malleable calvarium, resulting in ipsilateral occipital bone flattening, ipsilateral frontal bossing, contralateral occipital bossing, and contralateral frontal flattening (typical parallelogram-shaped head). The cranial base is not significantly deviated in deformational plagiocephaly.
Another very rare type is oxycephaly (turricephaly or "towering skull"). A combination of coronal and other types of early suture fusions can occur. In kleeblattschãdel or cloverleaf skull, all cranial sutures except the metopic and squamosal sutures fuse prematurely, giving the skull the appearance of a cloverleaf. 
Frequency and Etiology
In the United States, the frequency rate of craniosynostosis is 0.04-0.1% and the prevalence is 3-5 cases per 10,000 live births. Commonly, the male-to-female ratio is reported to be 3:1. The most common type is sagittal synostosis, with a frequency rate of 50-58% of synostotic patients and a prevalence of 1 case in 4200 live births. The next most common type is coronal craniosynostosis, with a prevalence of 1 case in 10,000 live births and an overall frequency rate of 20-29%. Less common are metopic craniosynostosis at 4-10% and lambdoid craniosynostosis at 2-4%. Other forms of craniosynostosis (eg, oxycephaly) are rare. Associated syndromic conditions such as Apert syndrome or Crouzon syndrome are uncommon (approximately 4.5% of all craniosynostoses or approximately 1 case in 160,000 births).
The calvarial sutures serve 2 important functions. The first is maintenance of head malleability during passage through the birth canal, and the second is continuance of the separation of the calvarial bones during intrauterine and early perinatal life. The sutures serve as growth sites where new bone is deposited in response to continuing separation of the osteogenic fronts between the opposing bones. 
Premature closure of any of the calvarial sutures prevents separation of the calvarial bones and produces a restriction on growth vectors leading to a morphologic change in calvarial shape. These changes are specific and characteristic for every type of craniosynostosis, as is described in Pathogenesis. [18, 16, 19] However, the sequence of events leading to premature ossification of sutures is unknown. Biomechanical forces and genetically determined local expression of growth factors have been implicated in the etiology of craniosynostosis. [20, 21, 22, 23, 16]
The cranial base was proposed as the primary locus of the abnormality in children with craniosynostosis, and the altered cranial base was suggested to transmit the tensile forces through the dura, which led to premature closure of the calvarial suture.  To study the changes in cranial base, suturectomy was performed in rabbits with and without dural transection. Findings suggested that suturectomy and transection of the dura did not affect growth more than suturectomy alone.  This evidence indicated that the dura played a less important role than previously thought.
The skulls of members of American Indian tribes who intentionally modified children's skull shapes by head binding have been examined.  The researchers concluded that a deformity of the cranial vault, either congenital or intentional, alters the morphology of the endocranial base and face and that mutability of the cranial base suggested that the endocranial base may not be the primary anomaly in persons with bicoronal or sagittal craniosynostosis.
Over the last decade, the role of the dura in maintaining sutural patency has been extensively studied. A series of experiments demonstrated that the dura initially plays an inductive role. Later, it assumes a permissive role in maintaining sutural patency through various signaling factors. [26, 27, 28, 21, 29, 30] The dura was studied in premature synostosis in rats, and researchers determined that the dura generates abnormal signals, which are blocked by a silastic sheet interposed between the dura and the overlying suture.  Other investigators also documented an increased level of transforming growth factor-beta and mRNA levels locally, indicating an interaction between the dura and overlying sutures at the time of closure. 
Later, dura mater transplanted from beneath normally patent sutures to sites of sutural fusion in a naturally occurring craniosynostotic rabbit model was proven to keep these sites from reobliteration.  Although the mechanism is not understood, the regional dura mater somehow determines the fate of the overlying suture. 
Sutures continue to remain as growth sites where cells undergo proliferation and later differentiate into osteoblasts. The calvarial sutures produce new bone at the suture front in response to the expanding neurocranium. As the brain expands, the sutures respond to this stimulus by adding new bone at the suture front. The addition of this new bone helps the suture width remain constant to accommodate the enlargement of the brain.  The interaction between the brain and the patency of the overlying sutures is amply proven by clinical evidence of a premature closing of the sutures in the presence of microcephaly and continuing patency in the presence of hydrocephalus.
Secondary craniosynostosis can also develop following placement of a shunt in a child with hydrocephalus (shunt-induced craniosynostosis) because of a drop in ICP and diminution of neural thrust.  Therefore, the neural thrust and the patency of overlying sutures may be closely integrated via the dura, which then serves as an intermediary source of signaling mediated through the TGF (transforming growth factor), FGFR (fibroblast growth factor receptor), TWIST, and MSX2 (muscle segment homeobox 2) genes. Genetic studies have now determined that mutations within these factors are responsible for a variety of craniosynostoses. [35, 22, 36, 37] The source of generation of these signals and gene amplification is not yet understood.
Until recently, brain function (neurodevelopmental analysis) had been considered normal in children with nonsyndromic craniosynostosis.  Abnormalities have been reported in the cortex of the brains of children with craniosynostosis.  Analyses of both cortical and subcortical structures have now revealed abnormalities in children with craniosynostosis.  Preliminary results also demonstrate that although the brain on the affected side continues to grow following surgery, it does not demonstrate compensatory growth but continues to remain morphologically different compared with the contralateral side. This ultimately calls into question the concept held by most craniofacial surgeons that the growing brain in children with craniosynostosis is only restricted or compressed by the overlying fused suture. 
Because the development of the brain and the overlying calvarial bones are closely interrelated, craniosynostosis may synchronously affect both the suture and the underlying brain. Alternatively, the brain may be the source of the abnormality and the diminution or reduction of neural thrust may lead to craniosynostosis.
Clinical Presentation and Diagnosis
Passage of the head through the birth canal deforms the head. This shape is retained for 2-3 weeks postnatally, making the diagnosis of craniosynostosis by a pediatrician difficult in the neonatal period. Therefore, most cases are detected in the perinatal period and occasionally during later infancy. Diagnosing craniosynostosis early in the perinatal period is important because the brain grows rapidly during this period and a delay only worsens the deformity of the head shape. The clinical diagnosis is not difficult because each suture fusion is characterized by a specific calvarial deformity. The recent increase in the incidence of deformational plagiocephaly secondary to sleeping in the supine position has compounded the ease of diagnosis.
Prior to surgical intervention, cranial deformity from synostosis must be differentiated from plagiocephaly without synostosis. Plagiocephaly can be caused by a number of factors, the most common of which is the normal variant, deformational plagiocephaly. Two mechanisms have been proposed for the development of deformational plagiocephaly. The first mechanism occurs in utero, where the cranial deformation is the result of an early descent of the fetus into the true pelvis with resultant pressure on the malleable head. The second mechanism occurs is in the perinatal period in which infant positioning is thought to cause the observed plagiocephaly. The positioning can be caused by an inherent restriction of the neck and its movement, similar to torticollis, or may simply be the result of the habitual practice of placing the child in a supine position. 
In 1992, the American Academy of Pediatricians recommended that infants sleep in a supine position to reduce the incidence of sudden infant death syndrome. Although the incidence of sudden infant death syndrome dropped dramatically, the supine position generated a dramatic increase in the incidence of posterior plagiocephaly.  This increased incidence has been proven to be directly related to children sleeping in the supine position.  For more information on neonatal conditions, see Medscape's Neonatal Medicine Resource Center.
The calvarial bones are soft and malleable in the early perinatal period. Thus, a persistent deforming external force can produce ipsilateral occipital flattening, frontal bossing, contralateral occipital bulging, and frontal recession.  This produces a typical parallelogram-shaped head, which simplifies the diagnosis of deformational plagiocephaly. The side on which the occiput is flattened has frontal bossing and ventral translocation of the external auditory meatus when viewed from the top of the head. The other side has occipital bossing, frontal flattening, and dorsal translocation of the external auditory meatus.
To confirm the diagnosis of craniosynostosis, take a careful history and complete a thorough physical examination. Take a detailed history of the birth, and document the sleeping position of the child in the early perinatal period. Head tilt and the inability of the head to turn in a particular direction suggest torticollis, making the diagnosis of deformational plagiocephaly more likely. Because some craniosynostoses are syndromic and familial, a detailed family history is absolutely essential. A family history of abnormal head shape or multiple systemic problems (eg, cardiac, genitourinary, musculoskeletal) is consistent with syndromic craniosynostosis. 
An increase in the anteroposterior length (scaphocephaly) is caused by a sagittal synostosis. A transverse narrowing of the anterior skull (trigonocephaly) is associated with metopic synostosis. In trigonocephaly, the intermedial-canthal distance is decreased; however, these children do not have true hypotelorism because the interorbital distance is normal. The orbital rims are commonly hypoplastic. Bicoronal synostosis results in shortening of the skull in the anteroposterior direction but with widening at the bitemporal region. The frontoorbital rims are recessed bilaterally, leading to exorbitism and possible exposure keratitis.
Unilateral asymmetry or plagiocephaly can result from coronal or lambdoid synostosis. Unilateral coronal synostosis results in a recessed forehead and frontoorbital rim. Contralateral bossing of the forehead and the frontoorbital rim are present. The eyebrow on the ipsilateral side is raised, and the palpebral fissure is increased in vertical height. The globe is occasionally raised along with the pupil, resulting in vertical dystopia. Lambdoid synostosis is rare and must be differentiated from deformational plagiocephaly or plagiocephaly without synostosis.
As part of the examination, the head circumference is measured to rule out microcephaly or macrocephaly and associated hydrocephalus. The range of neck movements is documented to rule out torticollis. Examination of the face should include measurement of the distance between the medial canthi of the eyes (intermedial-canthal distance) and the interpupillary distance. The interpupillary distance is increased in children with hypertelorism.
The examination is then extended to include an appropriate neurologic examination with a focus on visual acuity and cranial nerves. In addition, pay particular attention to any signs and symptoms of elevated ICP. The fundi must be examined, and parents must be questioned regarding persistent vomiting or lethargy. If elevated ICP is suggested, neurosurgical assistance must be immediately obtained. Once a thorough neurological examination is completed, the face and its contour are examined for evidence of midface, orbital, or craniofacial abnormalities. Midface retrusion is associated with Apert or Crouzon syndrome.
Examination of toes and digits is critical to diagnose Apert syndrome that is associated with compound syndactyly. Transverse ridging is associated with craniofrontonasal dysplasia.
Plain skull radiographs serve as an initial screening tool to visualize sutures and diagnose craniosynostosis. The test is simple and inexpensive, but the accuracy of the findings is less than desired. The efficacy of plain films is questionable because they cannot be used to differentiate certain pathologies such as lambdoid synostosis and deformational plagiocephaly (plagiocephaly without synostosis). In addition, to visualize all the sutures, special Waters views must be taken.
As a noninvasive, nonradiologic modality, ultrasound has been used as a diagnostic tool in the area of craniosynostosis. It has been shown to be more effective than plain skull radiographs in detecting fused sutures, yet its use requires and its accuracy depends on a reliable and experienced operator.
A three-dimensional CT (3D CT) scan now serves as the diagnostic criterion standard for the complete visualization of the skull and cranial sutures. In the past, a standard, 2-dimensional CT (2D CT) scan was routinely used for the initial diagnosis of craniosynostosis. However, 2D CT failed to provide a complete assessment of the overall associated deformities. This made preoperative planning difficult, surgeries unpredictable, and outcomes unreliable. For these reasons, the standard 2D CT was abandoned in favor of the more reliable 3D CT scan.
With the 3D CT scan, specific views and protocols (eg, frontal, right or left profile, ectocranial or endocranial) can be used to allow for comparisons between the preoperative, perioperative, and postoperative courses. A tomographic scale of the various bony landmarks of the skull and face can be easily constructed. This, combined with available software analysis, allows for planning of possible osteotomies; thus, a more accurate preoperative plan can be completed and a more meaningful outcome analysis can be performed. [39, 42]
Because the sagittal suture is fused and any growth in a transverse direction is restricted, the anteroposterior skull length is increased (see the image below). Frontal bossing and an exaggerated occiput (occipital bathrocephaly) are present. The cephalic index (maximum transverse width/maximum anteroposterior length) is reduced. The severity of the ensuing scaphocephaly can be indexed because normograms for cephalic indices are available.  However, the cephalic indices only measure 2-dimensional distances and fail to accurately account for the frontal bossing or the exaggerated occipital bulging. At this point, even though these measurements are crude, they are the most accurate and most widely available.
As the metopic suture separates the frontal bones, its fusion restricts the transverse growth of the frontal bones and results in narrowing of the anterior cranial fossa (see the images below). In the resulting trigonocephalic skull, the intermedial-canthal distance (ie, distance between medial canthi) and the interdacryon distance (ie, distance between lacrimal crests) are reduced. In addition, the orbital rims may be affected and hypoplastic depending on the severity of disease. Physiologically, the metopic suture is the first suture line to close. The commonly accepted theory is that the metopic suture fuses between the first and second years of life. However, as more CT scans are being completed on neonates, the metopic suture has been demonstrated to actually close much earlier, possibly as early as the third month of postnatal life. 
A normal physiologic closure of the metopic suture is not associated with deformity of the anterior cranial fossa. However, the medial-intercanthal distances should still be measured and compared with an available normogram.
Brachycephaly results when premature fusion of both coronal suture lines occurs, restricting the anteroposterior growth of the anterior cranial fossa (see the images below). This premature fusion restricts the anteroposterior dimension but allows for temporal growth, resulting in an increased bitemporal diameter. In addition, the frontoorbital bar is recessed; consequently, the supraorbitale is more posterior to the corneal plane. Normally, the supraorbitale is 2 mm ventral to the corneal plane.  This abnormality leads to exorbitism and other complications.
Unicoronal synostosis is characterized by a single fused coronal suture, differentiating it clearly from brachycephaly (see the images below). In these patients, the ipsilateral frontoorbital bar is recessed while the contralateral frontoorbital bar continues to grow, making it more ventral. Because anteroposterior growth cannot occur, compensatory changes occur along the unaffected contralateral suture line. This is critical to understand because in these patients, both the ipsilateral and the contralateral suture lines must be surgically corrected to allow for a smooth and symmetric correction. The fused suture also affects the growth of the sphenoid bone, reducing the anterior cranial fossa and altering the contour of the roof of the orbit.
As a consequence of these interactions, the anterior endocranial base and the ectocranium both deviate toward the ipsilateral involved side. If not corrected, this changes the shape of the face and the occlusal cant. Because of the position of the abnormal suture line in these patients, the posterior cranial base remains unaltered and grows normally. 
This synostosis is characterized by a fused lambdoid suture (see the image below). The fused lambdoid suture alters the dimensions of the posterior cranial fossa. The posterior cranial base deviates to the ipsilateral side. As expected, the contralateral suture line then protrudes. On the affected side, the mastoid process bulges and is considered pathognomonic for lambdoid synostosis. Unlike with the other synostoses, the diagnosis of lambdoid synostosis is difficult because it shares similar features with deformational plagiocephaly (plagiocephaly without synostosis).
For this same reason, care must be taken to understand each unique feature. In lambdoid synostosis, growth is restricted on the side of the fused suture, while in deformational plagiocephaly, the skull is pushed ventrally. In lambdoid synostosis, the petrous part of the temporal bone and the external auditory canal are pulled towards the fused suture. In deformational plagiocephaly, the temporal bone and the external auditory canal are pushed anteriorly (ventrally). Also in deformational cases, ipsilateral frontal bossing is common; however, it is almost never seen in a true lambdoid synostosis.
Even though MRI affords much more specific information about the anatomy of the brain (see the images below), it is not commonly used to assess craniosynostosis. MRI is able to effectively and clearly catalogue the cortical patterns of the sulci and the gyri of the brain underneath fused suture lines; however, it does not provide information about cortical function.
Currently, the relevance of the abnormal patterns of gyri and sulci observed in patients with craniosynostosis is intensely debated. Whether these abnormal patterns are the result of the overlying fused sutures or whether they are the primary event causing the fusion of the suture lines remains unknown. Although this question should seemingly be effectively answered by comparing preoperative and 1-year postoperative MRIs, this has proven much more difficult because of the lack of normal MRIs for comparison and the lack of software that can objectively measure alterations in the underlying sulci and gyri.
The purpose of neurodevelopmental testing is to obtain information about the cortical functioning prior to and after cranial vault remodeling. The Bayley Scales of Infant Development–II (BSID-II) are commonly used to procure this information.  A longitudinal assessment is essential to perform a meaningful analysis. These tests compare the child's mental and psychomotor scales with a normogram and thus help in quantifying whether the child is delayed and whether the surgery will help reduce the severity of the delay. Children with syndromic craniosynostosis characterized by multisystem involvement are often delayed. This delay can be severe, and the child may be classified as mentally retarded. However, children with single-suture craniosynostosis do not commonly have significant delays. [50, 51, 52, 53]
A more detailed assessment with more sophisticated analyses has demonstrated delays in patients with single-suture craniosynostosis. [38, 54] Children with metopic and sagittal craniosynostosis also have minor delays in learning and speech, which were not previously recognized in this population. [55, 56]
The greatest difficulty with neurodevelopmental testing is the lack of accuracy in measuring cortical function in an infant at age 3-6 months. Children considered at risk who showed delays at 12 months did correlate with scores of development at age 4.5 years.  Similarly, at-risk children assessed at 6 months had scores predictive of intelligence scores at 24 and 48 months.  Understandably, an infant aged 3 months cannot be tested for language delays, but the BSID-II is a comprehensive test of various aspects of an infant's developmental skills and does not produce isolated findings. These factors make BSID-II the most reliable assessment tool for infants.
Indications and Contraindications to Intervention
The absolute indications for surgical intervention in persons with craniosynostosis include (1) prevention of intracranial hypertension and its associated sequelae that occur in some patients with uncorrected synostosis, (2) prevention of progression of the calvarial deformity, (3) prevention of progression of the facial deformity, and (4) optimization of the growth potential of the brain in the early perinatal period.
Uncorrected synostosis may be associated with an increase in ICP. This has been documented in animal models and in humans. As the suture lines fail to yield, growth of the calvarium is restricted. The continuing growth of the underlying brain parenchyma exerts an expansile force leading to an increase in ICP. In a study in which the ICP of children with synostosis was measured, 47% of the children with multiple synostosis and 14% of the children with single synostosis had elevated ICP.  In these same patients, ICP dropped significantly following surgical correction.
Surgical intervention corrects possible intracranial hypertension and corrects facial skeletal asymmetry if the surgery is performed before age 9 months. [60, 61] The ensuing asymmetry of the orbit leads to ocular dystopia and consequent strabismus. The asymmetry in the maxilla and mandible leads to malocclusion.
Almost as important as the decision to operate is the optimum age at operation. Surgery is advocated in early infancy because most brain growth occurs in the first year of life. Therefore, if the deformed sutures are not released, the deforming vectors of the continually growing brain result in progression of the deformity with increasing age. The osseous defects following surgery undergo reossification more completely if surgery is performed in those younger than 1 year compared with later. The calvarium in an infant aged 3-9 months is much more malleable, making it easier to shape and providing a better outcome.
The only absolute contraindication to surgical intervention is the presence of microcephaly. Calvarial sutures close secondary to the lack of expansile force from the underlying brain. Surgical intervention just to release the fused sutures is associated with high rate of re-fusion and thus is not appropriate.
Although surgery for craniosynostosis improves calvarial shape, it should not be considered cosmetic. For reasons mentioned earlier, delay in surgery leads to continuing deformity of the craniofacial skeleton. In addition, increased ICP adversely affects the development of the child. This has been demonstrated in recent studies in which exposure to prolonged ICP has been associated with a delay in brain development. 
Treatment and Complications
Although surgical intervention remains the primary treatment modality, one must keep in mind the role of medical (nonsurgical) treatment. Limited to nonsyndromic deformational plagiocephaly, molding helmets serve an important role in the correction of cranial deformities. Customized molding helmets are an adjunct to preventive measures such as frequent posture change. Helmets must be worn 23 h/d until age 1 year. Early intervention is important because molding therapy is not very effective after age 1 year.
A survey of 53 surgeons by Alperovich et al examined management patterns in cases of craniosynostosis, finding that 100% of the physicians finish repair of the condition before the patient reaches age 1 year and that most operate at ages 4-8 months. The study also found that 68.8% of the surgeons have preoperative imaging performed on every patient, with 83% of these respondents preferring the use of CT scanning, and that 28% of the surveyed physicians routinely prescribe a course of antibiotics lasting more than 24 hours. In addition, 93.6% of the surgeons stated that they routinely send their patients to the intensive care unit postoperatively. 
A study by Nguyen et al indicated that using transfusion algorithms and blood-sparing surgical techniques reduces the amount of intraoperative blood product needed during primary open craniosynostosis surgery without increasing the need for postoperative transfusion. Comparing results from 39 patients who were treated with the algorithm/blood-sparing strategy with those from 41 patients who were not managed with this protocol, the study found that the intraoperative transfusion volume of packed red blood cells was reduced by 17.7 mL/kg, fresh-frozen plasma transfusion volume was reduced by 25.3 mL/kg, and estimated blood loss was reduced by 11.9 mL/kg. 
Positioning and access
Patient position on the operating table depends on which fused suture needs correction. The supine position with the head supported on a neurosurgery horseshoe allows access to the anterior cranium and the frontoorbital region. This position is frequently used for correction of metopic and unicoronal craniosynostoses. The prone position gives access to the occipital area and thus is used to correct lambdoid craniosynostosis. If access to both the anterior and the posterior cranium is needed, then a modified prone position with the cervical spine extended allows access to both the frontoorbital area and the occipital area (see the image below). This position is used for correction of sagittal and bicoronal craniosynostoses. This position can be dangerous if the patient is accidentally extubated during the procedure. Great care should be taken to ensure proper fixation of the endotracheal tube to prevent this occurrence.
A zigzag bicoronal incision is routinely used for access. The zigzag incision prevents parting of the hair along a straight line, and the scar tends to spread less because of redistribution of the forces. Incision begins slightly anterior and superior to the helix of the ear. Care must be taken to not extend incisions too far anterior or inferior for fear of injury to the temporal branch of the facial nerve. Electrocautery is used cautiously in order to prevent damage to the hair follicles and subsequent visible scarring resulting from a lack of hair in the incision line.
Dissection is performed in the subgaleal plane. Flaps are developed anteriorly and posteriorly if needed. As the orbital rims are reached, the incision through the periosteum is completed. Care is taken to not injure the supraorbital neurovascular bundle, exiting from the supraorbital foramen or notch, in the medial aspect of the superior orbital rim. The bundle is then subsequently translocated forward and out of the foramen or notch with the coronal flap. The temporalis muscle is dissected from the bone and reflected inferiorly. This allows access to the lateral wall of the orbit.
High-speed craniotomes with small burs are used for the initial craniotomy. Constant irrigation is necessary to prevent thermal injury to the cranial bones. The craniotomy is then extended. Using periosteal elevators, the calvarium is carefully elevated from the dura. Dural tears are identified and repaired immediately after removal of the bones. If orbital osteotomies are needed, the periorbitum is separated carefully and the ocular globe is retracted with a malleable retractor. Intracranial and transorbital approaches are performed to create the osteotomy of the supraorbital ridge (frontoorbital bar).
Rigid fixation is critical to maintain the shape following correction. Although titanium plates were used in the past, they were associated with migration from the ectocranium to the endocranium. Some of the plates and screws came in contact with the dura and the brain. Over the last decade, these plates have been replaced by absorbable plates made of a combination of polyglycolic and polylactic acid. These plates variably absorb by hydrolysis in 1-3 years. Their strength and safety have been well documented. [65, 66]
Following are descriptions of the techniques used by the authors to correct craniosynostosis. The described techniques are not the only effective methods; other methods have been used successfully, but a complete description of all procedures is beyond the scope of this article.
Treatment objectives include correction of scaphocephaly and correction of the frontal bossing and occipital protrusion associated with this deformity. Initial surgical procedures included a narrow-strip craniectomy, which was associated with a high prevalence of resynostosis.  A wider and more extensive craniectomy was performed and became the norm. This procedure did not address the frontal bossing and occipital bathrocephaly and relied on the growing brain to correct these deformities. Dissatisfaction amongst craniofacial surgeons led to a more extensive cranial vault remodeling with barrel-stave osteotomy to correct the scaphocephaly and associated deformities. 
A recent retrospective comparison between the extended-strip craniectomy and cranial vault remodeling has shown that the extent of improvement in the cephalic index was significantly higher with the latter procedure, even if the extended-strip craniectomy was performed in the first 4 months of postnatal life.  With the advent of endoscopes in neurosurgery, extended-strip craniectomy is performed and the patient is placed in a custom-made molding helmet to correct the frontal bossing and bathrocephaly. [69, 13] Although this procedure has become more popular in recent years because of the rapid recovery of the child and diminished need for blood transfusion, no prospective long-term studies are currently comparing the results of extended-strip craniectomy with molding-helmet therapy versus cranial vault remodeling.
Another approach described in the literature is the use of springs. Described by Lauritzen et al, this approach has compared favorably with the standard craniofacial procedures for the correction of cranial synostosis.  A study of spring-mediated cranioplasty noted its application in treating scaphocephaly in patients younger than 9 months because of its improved morbidity profile.  Ririe et al described changes in anesthetic management for this approach. 
Based on current evidence, the authors prefer to perform cranial vault remodeling (see the images below). The frontal, parietal, and occipital bones are removed and transferred to the side assembly table. Radial osteotomies are performed on each bone to normalize the contours. Shortening of the anteroposterior dimension is accomplished by ostectomy of the sagittal suture. Out-fracturing the base of the temporal bones aids in increasing the lateral dimension of the calvarium. The bones are molded into shape and subsequently replaced into position. Fixation of the bones is accomplished with absorbable plates and resorbable sutures.
Treatment objectives include the correction of asymmetry within the frontoorbital bar, frontal bone, and orbits.  The frontal bone is removed by performing a craniotomy 10 mm above the supraorbital rim, thus separating it from the orbital bar. Advancement of the ipsilateral frontoorbital bar is accomplished by first creating an osteotomy across the floor of the anterior cranial fossa and the roof of the orbit. The osteotomy begins at the pterion and extends across the midline anterior to the crista galli and onto the pterion on the other side. Externally, the osteotomy is made across the lateral wall of the orbit and onto the frontozygomatic suture. The frontoorbital bar is then excised. Each orbit is then remodeled and shaped to create symmetry. The bar is fixed at the nasion with absorbable plates. The frontoorbital bar is then advanced on the ipsilateral side. The objective is to position the rim approximately 3 mm ventral to the vertical plane of the cornea.
Small bone grafts may need to be used as interposition grafts if the overall advancement is large. The ipsilateral orbital rim is cephalad compared with the uninvolved side. Bone is removed from the frontozygomatic and frontonasal sutures to correct this asymmetry. In addition, bone is added to the contralateral side to aid in symmetry. Bone is also added to the ipsilateral orbit rim width and removed from the contralateral rim width to correct the transverse discrepancy. Symmetric replacement of the frontal bone, after molding, is completed.
Fixation is accomplished via absorbable plate fixation. The plates are positioned at the lateral orbital rim at its junction with the temporal bone, the frontonasal junction, and on the frontal bone at its junction with the frontoorbital bar, parietal bones, and temporal bones. Early intervention and appropriate remodeling aids in the prevention of long-term growth disturbances within the facial bones and jaws.
The images below illustrate unicoronal craniosynostosis.
The images below illustrate bicoronal craniosynostosis.
Objectives include an increase in width of the bifrontal diameter, an increase in volume of the anterior cranial fossa, and normalization of frontal bone shape.  The frontal bones and the frontoorbital bones are excised and transferred to the side assembly table (see the images below). The frontoorbital bar is advanced to create an appropriate brow position.
The interdacryon distance is increased by placing a bone graft between the 2 halves of the frontoorbital bars. The bone is placed in a tenon-and-mortise fashion to enhance stabilization. The lateral aspects of the orbital rims are also advanced. Fixation is accomplished via absorbable plates placed at the lateral orbital rims at their junction with the temporal bones. In addition, fixation is accomplished at the frontonasal junction. The frontal bones are fixed to one another so that the bifrontal diameter is increased.
After fixation of the bone segments, closure is undertaken. If the temporalis muscle was separated, it must be repositioned. The temporalis is resuspended using absorbable sutures secured to a previously placed fixation plate. This technique provides a cephalad suspension of the muscle as it heals in place. The coronal flaps must be reapproximated, and the galeal layer must be sutured. Hemostasis is paramount prior to closure to minimize blood loss. Resorbable sutures are used to close the skin layer. The placement of a suction drain is recommended to reduce the amount of subcutaneous blood collection. A firmly applied head dressing is secured in place with burn netting.
Admission to the pediatric intensive care unit for 24 hours is usually indicated. Hemodynamic and neurologic parameters are closely monitored. Considerable edema may be encountered, but it quickly resolves in the following days. The authors complete a perioperative 3D CT scan on the fourth postoperative day. This allows for comparison of the preoperative skull morphology with the immediate postoperative result. The child is discharged following the CT scan. Routine postoperative follow-up visits are made over the next 3 weeks, 6 weeks, 3 months, 6 months, and 1 year, with annual visits until age 6 years. Subsequent follow-up visits with a craniofacial team every 2-3 years are indicated for ongoing evaluation.
Associated complications inherent to surgical treatment and general anesthesia are anticipated. Although rare, mortality has been described.  Commonly, insufficient intraoperative blood replacement is the main cause. Wound infections likewise are rare but have been documented; prophylactic perioperative antibiotics are used to minimize this risk. Wound dehiscence is also intermittently encountered and treated locally as indicated; prevention, aided by meticulous closure, is of primary importance. Persistent cerebrospinal fluid leaks are extremely rare.
Minor asymmetries are occasionally encountered. Tolerance of the discrepancy is acceptable; however, hydroxyapatite paste is used to correct persistent deformities. Major asymmetries must be addressed with surgical alteration by osteotomy and repositioning. Reoperation rates approach 7%, with increased rates of reoperation for syndromic versus nonsyndromic craniosynostosis. 
Advances in research may one day eliminate the need for surgical intervention. Prevention and early identification may render surgical techniques obsolete. Until that time, advances are directed toward shortening surgical time and minimizing surgical trauma. Endoscopic strip craniectomies are now being performed. The results are interesting but more data are required to demonstrate the superiority of this technique over existing procedures. Improvement in surgical treatment planning, along with computer-aided or stereotactic procedures, may lead to improved accuracy in bone positioning. Lastly, advancements in medical therapeutics, anesthesia, monitoring, and management may improve the overall experience of the child and the families of these unique individuals.