The brain is contained in the neurocranium, which comprises the skull base and cranial vault. Each of these two components of the neurocranium develops in different ways. The calvarial vault develops via intramembranous ossification as fibrous membrane (ectomeninx) over the brain, while the skull base develops through endochondral ossification. After the second month of gestation, ossification centers in the ectomeninx differentiate into an outer periosteum and inner dura. These ossification centers eventually expand or fuse to form the frontal, parietal, and occipital bones (Lemire 1986; Pritchard et al. 1956) (Fig. 3.1). The edges of these sutures contain special cells called the osteogenic front (Decker and Hall 1985). At 16 weeks gestation, sutures form as these osteogenic fronts approach each other (Vermeij-Keers 1990).

Sutures allow the infant’s head to reshape during the birth process and accommodate the expanding brain during rapid growth. Open sutures may also absorb stresses from trauma (Cohen and MacLean 2000). The dura (membrane covering the brain) is essential for suture and calvarial bone growth. The site of suture formation is related to the location of major dural reflections. Dural reflections are bands of dural attachment to the skull base that conform to the early recesses of the brain (Sun and Persing 1999). In infants with brain malformations, these early recesses may be absent and the suture will not form.

Removing the skull in a neonate with intact dura results in the dura regenerating the skull with sutures placed as dictated by the dura (Drake et al. 1993; Mabutt and Kokick 1979). In other words, neonates and young infants can have portions of or their entire skull removed, and an intact dura will regrow the skull bone with appropriate suture locations. This ability to reossify the skull diminishes as the infant ages.

As the brain grows, overall calvarial bone growth occurs from the expanding brain. New bone is deposited at the osteogenic fronts of the open sutures, and this bone deposition at the suture margins is driven by the expanding brain (Sun and Persing 1999). The skull is 35 % of adult size at birth, two thirds of adult size by 2 years of age, and reaching adult size between 6 and 10 years of age (Ohman and Richtsmeier 1994; Zollikofer 2009). The metopic suture can fuse normally in infants by as early as 2 months of age, but the other sutures remain open to accommodate brain growth into adulthood. A layer of capsular fibrous tissue surrounding the osteogenic fronts normally keeps the other sutures from fusing (Sun and Persing 1999). Even partial closure of one or more sutures during the period of rapid cranial growth can cause significant skull deformities (Fig. 3.2).

A discussion of the characteristics of each of the four most common single suture closures follows. Bicoronal synostosis and a multiple suture condition known as Mercedes Benz are also discussed, but other combinations involving multiple sutures can occur.

The most common type of craniosynostosis is sagittal, characterized by a scaphocephalic or “boatlike” shape to the skull, various degrees of bitemporal narrowing, frontal bossing, occipital cupping, and a palpable sagittal ridge (Fig. 3.3). Sometimes, the scaphocephalic shape, and especially the occipital cupping, is so prominent that when the infant is lying supine with the back of the head on the mattress, the head is flexed in a way that causes the airway to be compromised. The degree of scaphocephaly is determined by measuring cranial index. Using spreading cranial calipers (GPM Instruments, Switzerland), the distance is measured from euryon to euryon, divided by glabella to opisthocranion and multiplied by 100 (Fig. 3.4). A cephalic index between 75 and 85 would be normal, with higher numbers indicating a rounder head and lower numbers indicating a more scaphocephalic shape (Proctor 2014). A special laser scanner can also be used to get measurements and a 3D picture of the skull.

Mercedes-Benz syndrome, also known as craniofacial dyssynostosis in the genetics literature, results in a characteristic head shape with frontal bossing, turribrachycephaly, biparietal narrowing, occipital concavity, and inferior displacement of the ears (Hing et al. 2009). The term “Mercedes-Benz” is derived from the appearance of the bilateral lambdoid and sagittal synostosis (BLSS) as seen on 3D CT (Fig. 3.5). Although development in these children can be normal, some have short stature, developmental delays, and chromosomal abnormalities. Genetic testing is recommended in these patients as well as any patient with multiple suture synostosis.

Coronal synostosis, or anterior plagiocephaly, is characterized by vertical dystopia, nasional deviation to the ipsilateral (affected or same) side, flattening of the frontal bone on the ipsilateral side, and bulging of the frontal bone on the contralateral (opposite) side (Figs. 3.6 and 3.7). The tips of the nose and chin point to the contralateral side in some cases. Strabismus from ipsilateral superior oblique paresis and compensatory contralateral head tilt is present in 50–65 % of unilateral coronal synostosis (Gosain et al. 1996; O’Daniel et al. 1993). It is recommended that the patient see an ophthalmologist familiar with craniofacial disorders for preoperative evaluation. Strabismus surgery is usually needed, as it rarely improves after craniofacial reconstruction (Sun and Persing 1999). However, strabismus surgery corrects or improves the head tilt (Gosain et al. 1996). MacKinnon et al. (2013) found a significant improvement in strabismus after endoscopic strip craniectomy and postoperative helmet therapy. These patients also had fewer strabismus surgeries than those who underwent a fronto-orbital advancement. An anteroposterior (AP) skull film shows a harlequin appearance to the ipsilateral orbit as the superior orbital rim is elongated (Fig. 3.8).

Although bicoronal synostosis can occur sporadically, there is a much higher association in syndromic patients as compared to single suture craniosynostosis (Proctor 2014). Patients with bicoronal synostosis have turribrachycephaly or a “tower-shaped” head with flattening of the frontal area. Although all children with craniosynostosis should have genetic screening, these patients need to be referred to a geneticist because of the high association with genetic mutations (MacKinnon et al. 2009) (Fig. 3.9).

Metopic synostosis is characterized by a trigonocephalic or triangular shape to the head when viewed from above. There are various degrees of bitemporal narrowing, parietal bossing, hypotelorism (close-set eyes), and ridging of the metopic suture that can resemble a keel (Fig. 3.10). The metopic suture is the only suture that truly fuses, usually by 2 years of age. When it closes in utero, the baby can be born with the characteristic trigonocephalic head shape (Proctor 2014). If the suture fuses in infancy, a common variation can occur, characterized by a normal shape to the skull, absence of hypotelorism, slight ridging of the metopic suture, and radiographic evidence of a fused metopic suture. This ridge will usually disappear over 2–3 years as the frontal bones thicken (Proctor 2014). Surgery is not necessary in this instance and the head shape remains normal. The ridge can be “burred down” at a later date if it is still prominent (Fig. 3.11).

Lambdoid synostosis or occipital plagiocephaly is characterized by a trapezoid shape to the head when viewed from above, tilted skull base (ipsilateral side displaced inferiorly), and ipsilateral ear displaced inferiorly and posteriorly. The fused lambdoid suture has a palpable ridge, and there is an ipsilateral occipitomastoid bulge. When viewed from behind, the skull base appears tilted (Fig. 3.12). Care must be taken not to confuse true lambdoid synostosis with positional plagiocephaly (Table 3.2). Radiographically, a Towne’s view skull film or CT scan will show a closed lambdoid suture.

Deformational forces, such as the prenatal head on the mother’s pelvic bone or the birth process itself, can shape the skull. The infant brain grows rapidly during the first several months after birth, and it is this growth that expands the skull into its normocephalic shape. Infant head circumference increases 9 centimeters (cm) during the first 6 months and grows approximately 12 cm during the first year. In comparison, the head circumference increases by only 2.25 cm during the second year after birth and just 0.75 cm between the second and third years. Therefore, deformational forces encountered when an infant head lies on a mattress; against a car seat, swing, or stroller; or on any firm surface for prolonged periods of time can have a significant influence during the period of rapid skull growth.

Most babies are born with normocephaly, but their skulls may become progressively more misshapen during the first several weeks after birth because of deformities from unrelieved pressure on the occipital bone. By 2 months of age, a baby may have spent approximately 700 h sleeping. If the baby lies supine with the head turned to one side, either from preference or the head has not been rotated to redistribute the deformational forces of gravity, positional plagiocephaly (PP) can result. This condition can be further aggravated by torticollis, which is a tightening of the sternocleidomastoid or cervical muscles that prevent the infant from turning the head 180° (Rekate 1997).

There has been a significant increase in “deformational” or “positional” plagiocephaly since 1992, when the American Academy of Pediatrics initiated the “Back to Sleep” (BTS) campaign and recommended that infants sleep on their backs or sides to decrease the incidence of sudden infant death syndrome (SIDS) (Kane et al. 1996; Majnemer and Barr 2006; Moon et al. 2011). One referral center reported a tenfold increase in referrals for occipital plagiocephaly compared with 1991 (Carson et al. 1997). Positional plagiocephaly occurs in 18–19.7 % of healthy infants, depending on age. Thirteen percent of newborns present with PP, and the incidence increases to 16 % and 19 % at 6 weeks and 4 months of age, respectively (Hutchinson et al. 2004; Peitsch et al. 2002). There is much controversy in the literature regarding the association between positional plagiocephaly and developmental delays (Collett et al. 2005; Majnemer and Barr 2006).

It is important to differentiate positional plagiocephaly from craniosynostosis, as the treatment for craniosynostosis is surgery and the treatment for plagiocephaly is, with rare exception, nonsurgical. A thorough history and physical examination will help differentiate between the two. Parents of infants with plagiocephaly frequently report that the head shape was normal at birth and that the occipital flattening was noticed later, often by the pediatrician at the 2-month well-baby exam. They also recall their baby preferred to sleep in one position with the head turned to one side. Some babies may prefer to sleep with the back of the head on the mattress, not turning it to either side. These infants can have flattening of the entire occipital bone, which causes the face to appear very round when viewed from the front.

With positional plagiocephaly, there is no bony ridge palpated along the lambdoid suture, and the base of the skull will be horizontal when viewed from behind. When viewed from above, there is occipitoparietal flattening on the affected side with anterior displacement of the ear, forehead, and malar eminence on the ipsilateral side. This appears to resemble the shape of a parallelogram as one side of the skull is shifted forward (Fig. 3.13). A Towne’s view x-ray or CT of the brain with bone windows will clarify the diagnosis by showing open lambdoid sutures. However, if a thorough history and physical examination clearly supports the diagnosis of positional plagiocephaly, imaging is often not necessary. The severity of cranial vault asymmetry can be evaluated by obtaining transcranial anthropometric measurements with a sliding caliper. Two oblique transverse cranial diameters are measured – from the midpoint of the supraorbital rim to the midpoint of the contralateral parieto-occipital scalp. The larger the difference between these two points, the greater the asymmetry (Mulliken et al. 1999; Farkas 1996; Dec and Warren 2011).

The prevention of positional plagiocephaly should begin at birth, with education provided by the postpartum nursing staff and continuing at each pediatric well-child care visit by the pediatrician or pediatric Advanced Practice Nurse (Table 3.3). Before leaving the hospital, parents should be instructed in principles of “back to sleep/tummy to play.” Although babies should be supine for sleep or naps, it is important to provide “tummy time” to allow strengthening of neck muscles and promote optimal development (Table 3.4). Parents should be taught to reposition their infant’s head when lying supine, starting from birth. Mild cases of flatness will resolve over weeks to months if the infant’s head is repositioned on a flat surface. Toys or objects of interest can be placed on the nonpreferential side to encourage the infant to turn his head in the nonpreferential direction. Alternating arms to hold the baby when feeding will also encourage head turning to both sides. “Tummy time,” or placing the baby prone while awake and observed, will decrease gravitational forces on the skull (Koren et al. 2010).

A cranial orthotic device such as a band or molding helmet may be used to correct moderate to severe cases of positional plagiocephaly (Kluba et al. 2014), but only after the parents have attempted all other repositioning strategies without significant improvement in the head shape (Fig. 3.14). Molding therapy is most effective between 4 and 12 months of age, during the time of rapid brain growth. The helmet helps to reshape the skull by restricting the growth in one direction, thus allowing it to expand in the other direction. It is critical to refer these patients to an orthotist experienced in cranial orthotic devices for positional plagiocephaly. The orthotist will closely monitor the patient for changes in head measurements and pressure points and instruct the parents in cleaning and caring for the helmet. Infants typically show significant improvement in head shape over the first several weeks, and significant correction is usually achieved by 3 months (Robinson and Proctor 2009). However, the helmet must be worn at least 23 h each day to get best results. Surgery may be considered in extremely rare cases where a severe deformity still exists despite repositioning, correction of torticollis, and use of a cranial orthotic device.

Torticollis, or unilateral shortening and fibrosis of the sternocleidomastoid, can prevent an infant from turning his head to the nonpreferential side and cause further deformity to the face. Congenital muscular torticollis is associated with PP in up to 90 % of infants (Rogers 2011). Static stretching exercises can be done to gently stretch the affected sternocleidomastoid muscle. Confirm that there is no cervical spine defect before doing these exercises. A pediatric physiotherapist should be consulted, though parents can be taught to do these exercises at home five to six times a day. With the infant lying supine on a flat surface and the head in midline position, the parent can slowly turn the head 90° toward the nonpreferential side, holding the stretched position for 10 s, and then slowly turn the head back to midline. A second person may need to hold the shoulders so they don’t turn with the head. If a head tilt is present, the parent should slowly tilt the head to the contralateral side and hold that position for 10 s (Fig. 3.15). Parents should be informed that these exercises should be done slowly to prevent trauma to the muscle and that the baby will cry the first few times. However, within a few days, the muscle will relax and it will be easier to turn the head. The torticollis should resolve within a couple of weeks.

In sternocleidomastoid tumor of infancy, a tumor is palpable in the muscle and can restrict the infant’s ability to turn the head. Stretching exercises may improve this condition, but surgery is usually necessary to remove the mass and lyse the muscle (Kane et al. 1996; Rekate 1997).

Although preventing positional plagiocephaly is ideal, treatment should be instituted as soon as the diagnosis is made. Early intervention during the period of rapid skull growth (first few months of age) will have the best results.

Infants with craniosynostosis “syndromes” or “conditions” present with a characteristic group of clinical findings. They have multiple cranial suture synostoses, including the sutures of the cranial base, which result in complex skull and forehead deformities (Bartlett and Mackay 1997). The cranial base abnormalities are manifested by hypoplasia of the midface and maxilla. These children often have hypertelorism, exorbitism, syndactyly, cleft palate, cardiac anomalies, and eye muscle abnormalities (e.g., strabismus). Depending on the degree of severity, there are frequently associated medical problems, including hydrocephalus, papilledema, respiratory distress, and failure to thrive.

The most common of these conditions are Crouzon, Apert, and Pfeiffer syndromes. Although their etiology is not totally clear and the majority of the reported cases are sporadic, it is known that they have an autosomal dominant mode of inheritance. An affected individual always has a 50 % chance of parenting a child who will be born with the same condition. Mutations in specific fibroblast growth factor receptor (FGFR) gene types for these syndromes have been identified (Ridgeway and Weiner 2004; Rossi et al. 2003).