This article provides an overview of etiology, epidemiology, pathology, diagnosis, and treatment of nonsyndromic craniosynostosis, including sagittal, metopic, coronal, lambdoid, and complex synostosis. Detailed discussion is presented regarding indications for surgical intervention and management options, including frontoorbital advancement, cranial vault reconstruction, endoscopic strip craniectomy, spring-assisted strip craniectomy, and cranial vault distraction osteogenesis. Deformational plagiocephaly is also presented with treatment options including repositioning, physical therapy, and helmet therapy.
Key points
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The incidence of infant head shape abnormalities is increasing. Physicians should be able to identify these patients and distinguish between deformational plagiocephaly and craniosynostosis.
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Deformational plagiocephaly does not have a known negative impact on the brain; however, early diagnosis and treatment is needed to correct the dysmorphic head.
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Most craniosynostoses are nonsyndromic and include sagittal, metopic, coronal, lambdoid, and multisuture synostosis. Surgeons should be able to make a diagnosis based on clinical findings.
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Surgical indications for craniosynostosis are to correct the abnormal craniofacial appearance, prevent negative effects of increased intracranial pressure on the brain and optic nerves, and protect the globe of the eye.
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Cranial vault reconstruction immediately corrects both the fused suture and cranial abnormality; minimally invasive procedures allow for improvement of the cranial shape over time.
Introduction
A persistent abnormal head shape is a concerning finding in an infant and can be from craniosynostosis (intrinsic) or deformational plagiocephaly (DP; extrinsic) causes. It is imperative the treating physician can differentiate between the 2 abnormalities to initiate appropriate treatment and avoid any long-term sequela. Craniosynostosis is the premature fusion of 1 or more cranial sutures, causing an abnormal head shape. This early fusion of the cranial sutures restricts normal skull growth, causing not only a dysmorphic head shape but also possible increased intracranial pressure leading to neurocognitive impairment. Deformational plagiocephaly , in contrast, is an atypical head shape caused by extrinsic forces pushing on the soft, malleable skull bones. The cranial sutures remain open and functional, with no risk for increased intracranial pressure causing impairment to the developing brain.
Introduction
A persistent abnormal head shape is a concerning finding in an infant and can be from craniosynostosis (intrinsic) or deformational plagiocephaly (DP; extrinsic) causes. It is imperative the treating physician can differentiate between the 2 abnormalities to initiate appropriate treatment and avoid any long-term sequela. Craniosynostosis is the premature fusion of 1 or more cranial sutures, causing an abnormal head shape. This early fusion of the cranial sutures restricts normal skull growth, causing not only a dysmorphic head shape but also possible increased intracranial pressure leading to neurocognitive impairment. Deformational plagiocephaly , in contrast, is an atypical head shape caused by extrinsic forces pushing on the soft, malleable skull bones. The cranial sutures remain open and functional, with no risk for increased intracranial pressure causing impairment to the developing brain.
Deformational plagiocephaly
Also termed positional plagiocephaly or nonsynostotic plagiocephaly , this asymmetric head shape abnormality has increased in incidence over the past 2 decades and is the leading cause for atypical head shapes. The cause of DP is asymmetric external forces on the soft infant calvarium, which are typically created by gravity pushing the infants head against the crib mattress with an equal but opposite force pushing back on the head ( Fig. 1 ). In 1992, the American Academy of Pediatrics initiated the Back to Sleep Campaign in which infants were placed on their backs during sleep to reduce the risk of sudden infant death syndrome. This campaign dramatically deceased the incidence of sudden infant death syndrome, but resulted in a significant increase in DP. A recent study in Canada found that nearly 47% of infants between 7 and 12 weeks of age had some degree of DP. Children with torticollis are at increased risk for DP, because they have limited head movement and lie with their head turned to only 1 side. Any preference of head position should be viewed as an early manifestation of torticollis and a high risk for DP. Other risk factors for DP include prematurity, developmental delay, multiple gestation pregnancy, male gender, assisted delivery, primaparity, uterine abnormalities, oligohydramnios, and breech presentation. Each of these factors cause intrauterine deformation and/or increase the risk of limited head movement during the first months of life. Deformational changes of the skull can lead to various head shapes, depending on what part of the head is positioned against the surface of the bed ( Box 1 ).
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Deformational plagiocephaly refers to asymmetry of the head, typically with a flattening of 1 side of the occiput. In more severe cases, the ipsilateral ear, forehead and cheek are also deviated forward. From a vertex view, this creates a parallelogram shape to the head (see Fig. 1 ).
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Deformational brachycephaly denotes flatness of the midline of the occiput with widening of the biparietal region of the skull.
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Deformational dolichocephaly results in a long, narrow head with flattening on either side. This deformity is found most commonly in premature infants who spent time in the neonatal intensive care unit and were positioned on the sides of their head because they lacked sufficient neck control to sleep on the back of their head.
Treatment of Deformational Plagiocephaly
Parental education about the etiology of DP and the importance of alternating the sleeping position by placing the infant supine and turning the head to either side will help to prevent the deformity from developing. Infants with torticollis, or any evidence of head position preference, should undergo physical therapy to allow full range of motion of the neck. The underlying goal of repositioning therapy is to keep the infant from lying on the flat part of the head. This includes monitored tummy time during the day, avoiding a car seat when not in a vehicle, and encouraging free and spontaneous movements of the infant. If the infant is young (<3 months) and the deformity is mild, repositioning of the infant to prevent lying on the flattened portion of the head may be all that is required. Often a wedge or rolled up blanket can be placed under the torso on 1 side to appropriately position the child. If the infant is older (>4–6 months) with failed repositioning therapy, orthotic helmets are often required to mold the cranium back to a normocephalic appearance. Helmet molding is possible owing to an infant’s malleable skull and rapid brain growth. The helmet is custom fit to the infant’s head with close approximation at the overexpanded areas of the skull, and the flat areas are left with excess space. As normal cranial growth occurs, the helmet redirects skull growth into the excess spaces to allow normalization of the head shape. There is no restriction of brain expansion. The skull grows into the ideal shape and the rate of correction is proportionate to the rate of head growth. Younger infants will correct faster than older infants. If the deformity is severe in an older child, there may not be sufficient cranial growth remaining to completely normalize the head shape. The helmet is worn 23 hours a day and requires monthly adjustments by an orthotist ( Fig. 2 ).
Craniosynostosis
Craniosynostosis, or early fusion of 1 or more cranial sutures, is typically an intrauterine event. The infant presents with an abnormal head shape at the time of birth or shortly thereafter. A human skull has 6 major cranial sutures, or dense fibrous connections that separate the individual cranial bones ( Fig. 3 ). In the normal skull, these sutures allow for compression of the cranial bones during passage through the birth canal and enable rapid skull growth during the first few years of life as the brain triples in size. Craniosynostosis restricts skull growth perpendicular to the affected suture. Continued brain enlargement leads to compensatory overgrowth of the skull at the remaining patent sutures, causing progressive deformity that typically parallels the fused suture. This is known as Virchow’s law and allows us to predict the characteristic dysmorphic head shape associated with each type of sutural fusion.
Epidemiology, Etiology, and Diagnosis
The incidence of craniosynostosis is 1 in 2000 to 2500 children. The etiology of craniosynostosis is multifactorial, involving environmental factors, genetic mutations, and intrinsic bone abnormalities with only 8% of cases being familial or syndromic. Diagnosis of most craniosynostosis can be performed typically with physical examination alone owing to Virchow’s Law. Each type of craniosynostosis will have a characteristic dysmorphic head shape. Three-dimensional computed tomography scanning is reserved for atypical findings, to confirm the diagnosis, and to assist in surgical planning.
Classification
Craniosynostosis can be classified into syndromic or nonsyndromic. Nonsyndromic craniosynostosis is further classified as either isolated or complex fusions. In isolated fusions, a single cranial suture is affected and includes the sagittal, metopic, coronal, or lambdoid sutures. Complex craniosynostosis indicates fusion of multiple sutures. Complex craniosynostoses have a higher risk of being associated with a genetic syndrome and an increased risk of elevated intracranial pressure with each additional suture that is fused.
Isolated craniosynostosis
Sagittal craniosynostosis
Sagittal craniosynostosis ( Fig. 4 ) is the most common type of synostosis, occurring 1 in 2000 births and has a male-to-female ratio of 3.5 to 1. The dysmorphic head shape created by fusion of the sagittal suture is termed scaphocephaly , meaning boatlike, or dolichocephaly , meaning long. The overall head shape is long and narrow with a decreased posterior skull width and height compared with the rest of the skull, owing to decreased growth perpendicular to the sagittal suture. Compensatory growth causes elongation of the head, through the lambdoid sutures, and variable frontal bossing of the forehead, from the coronal and metopic suture overgrowth. These children typically present with an increased head circumference, 98th percentile or greater.
Metopic craniosynostosis
Premature fusion of the metopic suture results in a triangular-shaped head, termed trigonocephaly ( Fig. 5 ). This condition presents with a prominent ridge along the metopic suture associated with narrowing of the bitemporal region and forehead, creating a triangular appearance to the forehead. Hypotelorism is a common finding with supraorbital retrusions and deficient lateral orbital rims. The occipitoparietal region widens with compensatory growth, enhancing the triangular shape of the head. The incidence of premature metopic fusion has been increasing and is now the second most common type of craniosynostosis. The current incidence is 1 in 5200 with males more commonly affected than females. The metopic suture is the first suture to close physiologically, occurring between 3 and 8 months of age. Metopic ridging can be encountered without the sequela of trigonocephaly or hypotelorism. In these patients, no surgical intervention is needed and the ridge typically softens as the child grows.
Coronal craniosynostosis
Unilateral coronal synostosis creates an asymmetric anterior head shape, or anterior plagiocephaly . The affected coronal suture growth is restricted, causing the dysmorphic head shape shown in Fig. 6 . This synostosis is more common in females than males, and the right side is more often affected than the left.
Lambdoid craniosynostosis
Posterior plagiocephaly means asymmetry of the posterior skull, which is caused by either unilateral lambdoid synostosis or DP. Unilateral lambdoid fusion is the least common type of isolated craniosynostosis, with an incidence of 1 in 40,000. The deformity will be noted at the time of birth and worsens progressively over time. These infants present with the findings listed in Fig. 7 . These abnormalities result in a trapezoid appearance when viewed from above, whereas DP has a parallelogram shape ( Fig. 8 ).
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