Pediatric Annals

Craniosynostosis: Diagnosis and Management in the New Millennium

Robert F Keating, MD

Abstract

The diagnosis and management of craniosynostosis continue to evolve at an extraordinary pace as we approach the new millennium. Although the etiology remains unclear, greater insight is being made through the discovery of genetic markers, plus a better understanding of the pathophysiology of the affected suture and forces involved in the growth of the developing calvarium. Most remarkable have been significant advances in the arena of surgical therapy. New approaches to threedimensional radiographic diagnosis, improved pediatric anesthesia, better hardware and biomaterials, and refined surgical techniques all have contributed to making this surgery safe and effective. Although numerous controversies may continue, a majority of clinicians now appreciate the need for early diagnosis and release or modification of the affected sutures.

OVERVIEW

Craniosynostosis is defined as the premature closure of a calvaría! suture, which in turn may lead to a characteristic head shape, secondary to restriction of growth perpendicular to the suture, first outlined by Virchow in 185 1.1 Prior recognition of the importance of the skull sutures and overall head shape was recognized by many, including Hippocrates, Galen, and Celsus.

Ultimately, final head shapes are directed by the underlying rapid cerebral development. The infant's brain doubles in volume in the first 6 months and again by age 2 years. Any restriction of skull growth will be met by compensatory overgrowth elsewhere. When craniosynostosis is caused by pathology at an involved suture, it is called primary. Alternately, should the brain or cortical regions fail to develop, the ensuing microcephaly will allow premature closure of various sutures and is known as secondary erari' iosynostosis. Children with secondary synostosis are generally not surgical candidates; therefore it is imperative to discern between the two types.

Our institutional experience over the past decade53 involved 57 patients whose ages at surgery ranged from 3 to 33 months (mean, 10 months). These were followed for an average of 8 months (12 months recently) prior to surgery. We experienced no mortality and minimum morbidity (one leptomeningeal cyst required surgical correction: four patients needed removal of prominent wires or screws). There were no infections, cerebral injuries, or deficits, and no child required secondary surgery. Eventual cosmesis was excellent in 79%. The remaining 21% were considered significantly improved by the family although the surgeon's perspective was less enthusiastic. Nevertheless, results for all patients were satisfactory. Improvement in the facial and frontal symmetry was also satisfactory. The greatest improvement was demonstrated in children operated on at an early age.

CORONAL SYNOSTOSIS (PLAGIOCEPHALY/BRACHYCEPHALY)

Premature closure of a single coronal suture (Figure 4A) may lead to anterior plagiocephaly (versus posterior plagiocephaly secondary to pathophysiology of the lambdoid suture). The incidence of unilateral coronal synostosis (premature fusion) is 1 per 10 000 live births and represents approximately 20% to 25% of all craniosynostosis. Once again, it is important to differentiate deformational plagiocephaly from true coronal synostosis. Deformational plagiocephaly is common. It occurs in one fifth to as high as one half of live births and is the result of positional molding in utero or postpartum. This predominantly involves the left side of the forehead and is frequently associated with other congenital conditions, secondary to inhibited fetal growth: talipes equinovarus, genovarus, congenital hip dysplasia, micrognathia, and torticollis. Premature fusion of the involved suture is not visualized, and the child usually improves with time.

True coronal craniosynostosis will present with a unilateral flattening of the involved forehead with posterior and superior distortion of the lateral orbital wall and forehead (Figure 8A). In extreme examples, the ear will be anteriorly displaced. The forehead flattening is often associated with contralateral compensatory frontal bossing. No gender predilection is apparent and…

The diagnosis and management of craniosynostosis continue to evolve at an extraordinary pace as we approach the new millennium. Although the etiology remains unclear, greater insight is being made through the discovery of genetic markers, plus a better understanding of the pathophysiology of the affected suture and forces involved in the growth of the developing calvarium. Most remarkable have been significant advances in the arena of surgical therapy. New approaches to threedimensional radiographic diagnosis, improved pediatric anesthesia, better hardware and biomaterials, and refined surgical techniques all have contributed to making this surgery safe and effective. Although numerous controversies may continue, a majority of clinicians now appreciate the need for early diagnosis and release or modification of the affected sutures.

OVERVIEW

Craniosynostosis is defined as the premature closure of a calvaría! suture, which in turn may lead to a characteristic head shape, secondary to restriction of growth perpendicular to the suture, first outlined by Virchow in 185 1.1 Prior recognition of the importance of the skull sutures and overall head shape was recognized by many, including Hippocrates, Galen, and Celsus.

Ultimately, final head shapes are directed by the underlying rapid cerebral development. The infant's brain doubles in volume in the first 6 months and again by age 2 years. Any restriction of skull growth will be met by compensatory overgrowth elsewhere. When craniosynostosis is caused by pathology at an involved suture, it is called primary. Alternately, should the brain or cortical regions fail to develop, the ensuing microcephaly will allow premature closure of various sutures and is known as secondary erari' iosynostosis. Children with secondary synostosis are generally not surgical candidates; therefore it is imperative to discern between the two types.

Figure 1. Restriction of growth at specific sutures will lead to compensatory overgrowth at the remaining open sutures, and thus account for the characteristic head shapes seen with each type of craniosynostosis.

Figure 1. Restriction of growth at specific sutures will lead to compensatory overgrowth at the remaining open sutures, and thus account for the characteristic head shapes seen with each type of craniosynostosis.

Figure 2. Lateral and vertex views of the infant calvarium demonstrating the major sutures involved in craniosynostosis.

Figure 2. Lateral and vertex views of the infant calvarium demonstrating the major sutures involved in craniosynostosis.

Table

TABLE 1Classification of Synostoses

TABLE 1

Classification of Synostoses

In the developing infant's skull, there are six principal sutures involved with the clinical manifestation of craniosynostosis (Figure 2). Classification of craniosynostosis is predominantly dictated by the overall head shape after premature closure of one or more sutures. Children with single suture synostosis are catalogued as simple types (Table 1), whereas those with multiple sutural pathology and other associated morphologies (eg, Crouzon's, Pfeiffer's, Apert's syndromes; Table 2) are considered to have compound craniosynostosis. The majority of terms are Greek or Latin derivatives and are often confusing. Brachycephaly refers to a skull that is short and wide. It occurs with bilateral premature closure of the coronal or lambdoid suture. The sutures extend to the skull base, so the growth of the skull and face are both affected. Unable to grow in an anteroposterior direction, the skull disproportionately expands laterally.

Dolichocephaly (long-headed) and scaphocephaly (keel-shaped) are used interchangeably to describe a skull that is long (Figure 3), and occurs with premature closure of the sagittal suture. Unable to grow in width, the skull grows into a narrow, keel-shaped form.

Acrocephaly and turricephaly are often seen with severe brachycephaly and scaphocephaly, respectively. Acrocephaly is a pointed head and turricephaly is a tower head. Plagiocephaly is caused by unilateral abnormal coronal or lambdoid pathophysiology, resulting in an asymmetric head flattened on one side.

The incidence of craniosynostosis varies from 0.25 to 0.60 per 1000 births,2"4 although higher clinical estimates have been proposed by Tessier (1/1000)5 and Anderson and Geiger (1.6/1000)6 from their surgical experience. The frequency appears equal in all ethnic populations but gender predilection varies among different types of synostosis. The most common synostosis is principal involvement of the sagittal suture, accounting for 56% to 58% of all individuals with craniosynostosis, with males outnumbering females by 2-3: 1.2·6·7 This is followed by closure of the coronal suture (unilateral of bilateral) in 18% to 29%.2·6·7 Metopic synostosis occurs in 4% to 10% of patients with craniosynostosis, and true lambdoid fusion (versus the current endemic of positional plagiocephaly due to long durations of supine head position) is a relatively rare event in children (2% to 4%). There is no significant sex preponderance for coronal or lambdoid synostosis, whereas males slightly outnumber females with trigonocephaly (metopic synostosis). The majority of isolated craniosynostoses are sporadic, although there have been occasional familial patterns. Hunter and Rudd2 found a familial incidence in 8% of their patients with coronal synostosis and in 2% of those with sagittal synostosis. Both autosomal-dominant and recessive transmission has been observed with simple craniosynostosis, although the former is more common. The usual sporadic nature of transmission makes it difficult to predict risk for subsequent craniosynostosis, but if one parent and child are affected, subsequent siblings are likely to be affected 50% of the time. Conversely, if both parents are unaffected and two siblings are affected, the subsequent risk approaches 25%.

Table

TABLE 2Craniofacial Dysostoses Syndromes

TABLE 2

Craniofacial Dysostoses Syndromes

More complex syndromic craniosynostoses, such as Crouzon's, Apert's, and Pfeiffer's syndromes, are associated with multiple sutural closures and systemic manifestations (Table 2). They are much rarer and some are often inherited by an autosomal-dominant mode of transmission.8

Figure 3A. Lateral view of 5-year-old boy with severe scaphocephaly who failed to have corrective surgery at an earlier date. Note the prominent occipital shelf.

Figure 3A. Lateral view of 5-year-old boy with severe scaphocephaly who failed to have corrective surgery at an earlier date. Note the prominent occipital shelf.

The etiology is likely to remain elusive due to its heterogeneous pathogenesis. The calvarium and skull base arise from neural crest cells that surround the rapidly enlarging brain. Dural condensations are first observed at 5 to 6 weeks' gestation with subsequent development of islands of cartilage over the dura. These are transformed into ossification centers that coalesce at defined regions, and as brain growth slows, calvarial bones come together to form sutures.

Several studies have shown that sutures are sites of bony "adaptation" rather than primary growth centers. Bone growth at a suture can be induced by expansion of the suture. This can be demonstrated experimentally after raising intracranial pressure. At first, the fibrous sutural ligament is separated and a layer of osteoid is deposited along the suture margin. This mineralizes and is transformed into bone. Successive replication of this process normally results in enlargement of the calvarial bones. On the other hand, compression of a suture can cause bone resorption along the suture margin rather than suture closure. This can be demonstrated experimentally by external mechanical suture compression.

There is some indirect evidence that mechanical compression can contribute to suture closure in humans. There is an increased incidence of craniosynostosts with intrauterine breach positioning and with twins. Some believe external compression from intrauterine crowding can cause fibrosis or ischemia at a suture and that this can contribute to premature closure. Postnatal positioning may also have a singular effect: currently, this is felt to be the pathogenesis of lambdoid positional plagiocephaly. Some clinicians recommend changing a child's position during sleep to help mold the head and improve suture mobility in the first few months of life. Others advocate "helmet therapy" in which a rigid external mold is applied to the skull of a neonate to redirect calvarial growth. Such therapies may be beneficial; however, because they are used on mild cases, some have argued that the improvement simply represents spontaneous resolution.

Figure 3B. Vertex view of same child demonstrating the elongated nature of his head as well as the narrow width. Premature closure of the midline sagittal suture will prevent any cerebral growth in a biparietal (ear to ear) direction and thus force the brain to grow in an anterior to posterior direction as well as towering of the overall skull.

Figure 3B. Vertex view of same child demonstrating the elongated nature of his head as well as the narrow width. Premature closure of the midline sagittal suture will prevent any cerebral growth in a biparietal (ear to ear) direction and thus force the brain to grow in an anterior to posterior direction as well as towering of the overall skull.

There are also components of craniosynostosts that represent arrested embryological development rather than abnormal compensatory growth as well as types that are not directly or mechanically linked to suture closure. These include systemic fibrocartilagenous disorders, which also include other abnormalities such as syndactyly, renal, skeletal, and cardiac anomalies.

DIAGNOSTIC EVALUATION

Significant craniosynostosis is often apparent at birth, but it may also be noted during infancy. Severe calvarial and facial deformation may be seen in conjunction with perisutural ridging. If an involved suture has calcified sufficiently, it may be detectable at the calvarial surface by a prominent ridge of bone. The calvarial shape will likely be asymmetric unless all sutures are involved uniformly (eg, severe microcephaly due to secondary craniosynostosis). Craniosynostosis remains predominantly diagnosed during the physical examination, with radiographic investigation used for corroboration.

Figure 4A. Three-dimensional CT depicting fusion of the left coronal suture with mild elevation of the involved orbit.

Figure 4A. Three-dimensional CT depicting fusion of the left coronal suture with mild elevation of the involved orbit.

The role of radiologic work-up varies among clinicians. Many patients arrive with skull radiographs that fail to demonstrate any sutural fusion. Computed tomography (CT) studies remain the most sensitive barometer of bony fusion, although it is important to obtain bone windows as well as appropriate thin slices through the involved suture. Presently, the advent of three-dimensional CT has simplified the diagnosis, providing an excellent view of the suture as well as overall head shape (Figure 4A). However, CT is usually reserved for patients with multiple or complicated suture pathology or for when the diagnosis is in question. The absence of bony fusion does not preclude the possibility of sutural pathophysiology. Microcalcification at the suture has been proposed, by Burke and colleagues,12 as a reason for restricted calvarial growth without overt bony fusion. The threedimensional studies are also vital to demonstrate the skull base, especially for syndromic patients, and to evaluate the underlying brain for abnormalities as well as to rule out increased intracranial pressure. A small number of patients may have hydrocephalus (more common with Crouzon's syndrome), partial agenesis of the corpus callosum, holoprosencephaly (seen in patients with trigonocephaly), or focal cortical dysplasias. Boop and colleagues' J noted that up to 5% of their patients with sagittal synostoses had unappreciated underlying intracranial pathology. It is very common to see expanded subarachnoid spaces in all types of craniosynostoses14 (Figure 4B). This usually spontaneously resolves and is usually not associated with increased intracranial pressure. Increases in intracranial pressure remain uncommon in isolated suture synostosis. However, Renier and colleagues15 documented that a subset of children (up to 13% depending on the sutures involved) will have elevated intracranial pressure, demonstrated by intracranial monitoring at surgery. Few children will manifest clinical symptoms of increased intracranial pressure (eg, headache, vomiting, visual changes, and so on), but it is not uncommon to visualize erosion of the inner calvarial table on CT scan (see Figure 4C). The clinical significance of this finding remains unclear. However, when it is seen, the clinician should look for other symptoms of increased pressure. If the child has any other evidence of elevated pressure, surgical correction should be expedited. This is especially vital in patients with syndromic synostosis (eg, Crouzon's, Apert's, Pfeiffer's) because they are at a greater risk for increased intracranial pressure.

Figure 4B. 9-month-old male infant with brachycephaly and expanded bifrontal subarachnoid spaces. This will invariably resolve spontaneously (even without surgery) and is not felt to represent any increase in intracranial pressure; nor does this by itself characterize chronic subdural collections/atrophy.

Figure 4B. 9-month-old male infant with brachycephaly and expanded bifrontal subarachnoid spaces. This will invariably resolve spontaneously (even without surgery) and is not felt to represent any increase in intracranial pressure; nor does this by itself characterize chronic subdural collections/atrophy.

THERAPEUTIC CONSIDERATIONS

It must be kept in mind that the majority of children with simple craniosynostosis have no neurologic compromise. Thus, surgical intervention is primarily for cosmetic reasons. Patients with complex synostoses (syndromic variants) frequently have both neurologic and cosmetic concerns. In today's society, cosmetic issues remain of paramount importance. Children bom with an obvious deformity have a low likelihood of spontaneous resolution. For these children, early surgical release of the affected suture produces the best long-term results and minimizes secondary midfacial deformations. Timing of surgery remains controversial and depends on the severity and location of the synostosis,. Most surgeons prefer to operate when the patient is 3 to 6 months of age, with a window up to 18 months of age.

When children present with mild to moderate craniosynostosis, the decision to operate is less clear. The age of the child and the severity of calvarial asymmetry will dictate the rationale for corrective surgery. If the calvarial deformation is mild and the child is approaching 12 to 18 months, they will probably not need surgery. The most rapid portion of cerebral and skull growth occur during the first 12 months. Thus, a mild deformity at 12 months is unlikely to become significantly more pronounced. However, the asymmetry is also likely to remain unchanged as the child grows older. The family's discomfort with the degree of calvarial deformation and psychosocial issues that will be encountered in the school setting are to be considered. It is usually prudent to follow the growth and shape of the calvarium before surgical decisions are made.

The role of orthotic molding remains controversial. Proponents911 argue that helmet therapy offers a safer and effective alternative for mild to moderate craniosynostosis. This is perhaps best exemplified in patients with positional lambdoid plagiocephaly. Critics argue that this therapy is costly, may not be well -tolerated, and effectiveness is uncertam because studies lack any true controls. Cranioorthotics will provide little change for completely fused sutures and thus has the best chance of improvement in incompletely closed sutures. These same individuals can do equally well with simple modification of sleeping position (off the affected or flattened side), changing the direction of the crib toward doors or windows, and moving crib toys and mobiles. The use of helmet therapy can also delay objective evaluation of the calvarial shape till the surgical window of opportunity has been lost. In addition, orthotics may redirect calvarial growth forces and improve overall head shape but still leave the child with significant facial malformation.

SAGITTAL SYNOSTOSIS ( SC APHOCEPHALY/DOLICHOCEPHALY)

Children with premature closure of the sagittal suture will present with an elongated, narrow, often towering skull. Depending on the region of greatest premature fusion, the child may manifest frontal or occipital bossing (Figure 3A) or a combination. Perisutural ridging at areas of fusion is common as is premature (frequent) or delayed closure of the anterior fontanel. Severe scaphocephaly may be apparent at birth or progress later (up to 12 months). With a frequency of 1 per 1000 live births, sagittal synostosis represents 56% to 58% of single suture pathology6'7 and is seen 2 to 3 times more commonly in males than in females. Although the majority of cases occur sporadically, occasional familial patterns have been reported. Secondary sagittal closure may also be seen in children with significant ventriculomegaly following shunting for hydrocephalus23 (~-l%) as well as infants who have undergone serious chronic neonatal illness and immobility.

Figure 4C. 6-month-old female infant with mild lambdoid positional plagiocephaly manifesting resorption of the occipital inner calvarial table. The clinical significance remains unclear, but this is usually not associated with generalized increased intracranial pressure. This finding as well as the plagiocephaly subsequently resolved with conservative therapy (positional modification).

Figure 4C. 6-month-old female infant with mild lambdoid positional plagiocephaly manifesting resorption of the occipital inner calvarial table. The clinical significance remains unclear, but this is usually not associated with generalized increased intracranial pressure. This finding as well as the plagiocephaly subsequently resolved with conservative therapy (positional modification).

The majority of children, even those with severe scaphocephaly, do not manifest neurologic abnormalities if only a single suture is involved. However, if there are multiple areas of premature sutural closure, there may be an increased intracranial pressure. A subset of affected individuals (up to 13%) have increased intracranial pressure.15,24 Although most cases of sagittal synostosis remain strictly a cosmetic problem, the suggestion of increased intracranial pressure (vomiting, lethargy, and headaches) requires an expethent radiologic work-up. A CT scan with bone windows may demonstrate erosion of the inner table of the calvarium in early stages of elevated intracranial pressure and remains the most sensitive barometer of elevated pressure.

Figure 5A. Intraoperative photograph of bone removal (calvarectomies) for a Pi procedure. Bone is removed adjacent to the fused sagittal suture as well as behind the coronal sutures in a bilateral fashion. This will allow the head to expand in width and be shortened in an anterior-posterior direction (by releasing the bone circumferentially, across the midline, at the coronal suture).

Figure 5A. Intraoperative photograph of bone removal (calvarectomies) for a Pi procedure. Bone is removed adjacent to the fused sagittal suture as well as behind the coronal sutures in a bilateral fashion. This will allow the head to expand in width and be shortened in an anterior-posterior direction (by releasing the bone circumferentially, across the midline, at the coronal suture).

Figure 5B. Following removal of the Pi-shaped piece of bone in the previous example. It is not necessary to remove the fused sagittal suture in the midline (overlying the sagittal sinus). The calvarial defects will fill in by 2 to 3 months.

Figure 5B. Following removal of the Pi-shaped piece of bone in the previous example. It is not necessary to remove the fused sagittal suture in the midline (overlying the sagittal sinus). The calvarial defects will fill in by 2 to 3 months.

Controversy continues to surround the optimal timing and choice of surgical procedure for sagittal synostosis. Most pediatric neurosurgeons agree that earlier surgery provides a better long-term result for severely affected children. There is less agreement as to appropriate treatment for children presenting later than 3 to 6 months of age. As indications for operative intervention are predominantly cosmetic, anesthetic risks, recurrence rate, and complications are paramount issues.

A number of simple approaches that advocate removal of the pathologic sagittal suture have been proposed as early as 1892.25'27 More recently, areas of adjacent bone are also resected. The general consensus is that simple synostectomy (removal of the sagittal suture alone) may be sufficient under the age 2 to 3 months. However, criticism has been directed toward the overall cosmetic result, persistence of calvarial defects, and the possibility of restenosis of the sagittal suture.28"32 For those infants who will undergo a simple synostectomy, this is best performed by age 2 to 3 months.26

The older child (>3 months) with significant calvarial asymmetry, and including the well-established Pi technique, first introduced by Jane in 1978 to offer greater piparietal expansion anterior and/or posterior bossing may undergo modifications of a simple strip craniectomy25·33·34 to offer greater biparietal expansion (width) as well as more effective treatment of coexistent frontal or occipital prominences. An example is illustrated in Figures 5 A and 5 B. The overall success of this operation depends on initiation of surgical intervention prior to significant calvarial and mid-face changes. The extremely rapid cerebral growth in infants will help remodel the new calvarial reconfiguration. To date, multiple modifications of this approach have been proposed, including 12 different variations suggested by jane depending on the patient's clinical presentation.36

Older infants (>12 months) and those with significant frontal or occipital prominence often require more aggressive craniectomy and reconstruction. A number of approaches have been advocated (see Figure 5C for an example). The indications for more aggressive surgical intervention with its concomitant increase in morbidity and mortality remain controversial. Many pediatric neurosurgeons believe total calvarectomies (widespread removal of bone) and reconstruction should be done for severe or late presentation scaphocephaly.3743 When the child is beyond the period of maximal cerebral growth (>12 to 18 months of age), any correction of the cephalic index (width of head length of head X 100) will require substantial realignment of the calvarium and skull base. This may be accomplished by removal of frontal and occipital bones as well as both parietal bones with subsequent reconfiguration (Figure 5C). Rigid fixation is indispensable in these cases and may provide greater three-dimensional conformational stability, decreased intraoperative time and bleeding, and a decrease in postoperative infections.

Figure 5C. Total carvarectdrny in a child (2 years old) with late presentation scaphocephaly. It was necessary to remove a majority of the calvarium to foreshorten the anteriorposterior length of the skull as well as widen the head with interposition bone grafts. Although the cosmetic results are less satisfactory than that seen for early correction, one may still change the overall head shape considerably with minimal morbidity.

Figure 5C. Total carvarectdrny in a child (2 years old) with late presentation scaphocephaly. It was necessary to remove a majority of the calvarium to foreshorten the anteriorposterior length of the skull as well as widen the head with interposition bone grafts. Although the cosmetic results are less satisfactory than that seen for early correction, one may still change the overall head shape considerably with minimal morbidity.

Figure 6A. 8-month-old child with metopic synostosis demonstrating a prominent "keel" forehead with recession of his lateral supraorbital rims.

Figure 6A. 8-month-old child with metopic synostosis demonstrating a prominent "keel" forehead with recession of his lateral supraorbital rims.

Figure 6B. Removal of the frontal bone and subsequent supraorbital bar (lower piece). Note the thickened midline in the region of the metopic suture.

Figure 6B. Removal of the frontal bone and subsequent supraorbital bar (lower piece). Note the thickened midline in the region of the metopic suture.

METOPIC SYNOSTOSIS (TRIGONOCEPHALY)

Premature closure of the metopic suture may lead to a triangular-shaped head, otherwise known as trigonocephaly. Not all children with premature closure of the metopic suture will develop trigonocephaly. In severe trigonocephaly (Figure 6A), the child's head will have a prominent "keel" forehead with recession of the lateral orbital rims, hypotelorism, and constriction of the anterior frontal fossa. The degree of severity is variable and will direct the need and type of surgical intervention.

Figure 6C. Removal of the supraorbital rim in one piece. This bone may then be fractured in the midline as well as laterally to allow shaping into a normal fronto-orbital contour. In young patients (<1 yr), the application of absorbable plates will facilitate this construct greatly.

Figure 6C. Removal of the supraorbital rim in one piece. This bone may then be fractured in the midline as well as laterally to allow shaping into a normal fronto-orbital contour. In young patients (<1 yr), the application of absorbable plates will facilitate this construct greatly.

Mild variants of metopic synostosis may represent familial inheritance, and have been associated with abnormalities of chromosomes 3, 9, and 11.16-18 At the other end of the spectrum lies the severe trigonocephaly. These infrequently have associated underlying frontal brain dysmorphology. Although single suture synostosis has a low incidence of associated mental retardation in general, trigonocephaly has the highest rate.19 This most likely is due to concomitant cerebral abnormalities.

The timing and extent of surgery will be directed by the severity of frontal changes. The goals of surgery will be normalization of the forehead with reconstitution of a normal surpraorbital rim if necessary. Patients with significant hypotelorism (closely set eyes) may also require lateral expansion of the orbits. Delashaw and colleagues20 proposed that metopic synostosis and trigonocephaly represent an embryological continuum and thus the surgical approach should deal with the various calvarial deficiencies. More recent modifications, advocated by Goodrich21 and Sadove,22 provide more radical treatment of the involved sphenoid bone as well as simultaneous correction of hypotelorism.

The essentials of surgical correction involve a standard bicoronal incision (ear to ear) which will provide adequate exposure of the fronto-orbital region as well as minimize any postoperative scar. Following exposure of the frontal and orbital regions, the frontal bone is removed. The supraorbital rim is then removed in one piece to facilitate reconstruction of a now flattened supraorbital bar (Figures 6B and 6C). Care is taken to remove sufficient bone in the region of the sphenoid bone to allow for growth at the midface and orbits. If the orbits require correction of the hypotelorism, it will be necessary to displace the lateral walls of the orbit as well as split the midline and interpose a calvarial bone graft. The patients do remarkably well despite the extensive nature of reconstruction.

Table

TABLE 3Potential Indications for Lambdoid Plagiocephaly Surgery

TABLE 3

Potential Indications for Lambdoid Plagiocephaly Surgery

LAMBDOID PLAGIOCEPHALY

There has been a recent explosion occurring in the posterior plagiocephaly, as demonstrated by numerous articles, the press (Wall Street Journal, February 23, 1996) and television ("20/20"). True lambdoid synostosis is relatively rare and represents 2% to 4% of all craniosynostosis. At present, some craniofacial surgeons are seeing 25% to 30% of their craniofacial volume presenting with lambdoid plagiocephaly (Figure 8A). Most investigators54,55 believe this sudden rise in the incidence of posterior plagiocephaly represents a transient calvarial deformation secondary to prolonged supine sleeping positions. This may be related to the American Academy of Pediatrics56,57 recommendation for supine sleeping position to decrease the risk of sudden infant death syndrome. The sleeping infant can lie comfortably in the same supine position for an extended period of time. This contrasts with the need for frequent head repositioning to breathe when prone. Thus, supine sleeping may promote posterior flattening of the occiput. The majority of these infants will improve spontaneously with simple positional modifications or through helmet orthotics. Personal experience has demonstrated that more than 93% of these children will do well with conservative measures.47 However, a certain subset (~7%) may eventually benefit from surgical intervention. The primary clinician should recognize children who will likely have failure of conservative treatment and be ready to refer for more aggressive intervention if necessary (Table 3).

Lambdoid plagiocephaly will present as a flattening of the occipital bone with frequent compensatory bossing of the ipsilateral frontal region. Anterior displacement of the ipsilateral tragus and facial malrotation (scoliosis) in severe cases may shape the head like a parallelogram (see Figure 7). Positional plagiocephaly will rarely have perisutural ridging of the lambdoid suture and usually lacks bony fusion on radiologic work-up. This subset of children predominantly do well with conservative therapy (positional modification, helmet therapy). In contrast, the unique infant with true lambdoid synostosis may present with contralateral frontal bossing and unchanged position of the ipsilateral ear. In past personal experience,47 males outnumber females by 4:1 and the right side was affected 70% of the time. Approximately 65% of these children had expanded subarachnoid spaces, predominantly over the frontal regions. Torticollis was also frequent.

Figure 7. Head CT scan of infant with lambdoid positional plagiocephaly, demonstrating the classic parallelogram shape. The child's right occipital region is flat and there is a moderate degree of ipsilateral frontal compensatory bossing. The head normalized over 4 to 6 months with aggressive positional modifications.

Figure 7. Head CT scan of infant with lambdoid positional plagiocephaly, demonstrating the classic parallelogram shape. The child's right occipital region is flat and there is a moderate degree of ipsilateral frontal compensatory bossing. The head normalized over 4 to 6 months with aggressive positional modifications.

Figure 8A. 3-month-old male infant with severe right coronal plagiocephaly, demonstrating flattening of the right supraorbital and frontal regions as well as compensatory bossing of the contralateral forehead.

Figure 8A. 3-month-old male infant with severe right coronal plagiocephaly, demonstrating flattening of the right supraorbital and frontal regions as well as compensatory bossing of the contralateral forehead.

Figure 8B. Skull x-ray of above infant demonstrating elevation of the right orbital roof and classic appearance of a "Harlequin eye."

Figure 8B. Skull x-ray of above infant demonstrating elevation of the right orbital roof and classic appearance of a "Harlequin eye."

Surgical approaches vary from simple synostectomies (removal of the affected suture) to total calvarial reconstructions following removal of affected sutures and surrounding bones.48-52 The objective is to release the abnormal suture. Primary removal of the pathological lambdoid suture may be effective in the very young infant (<3 months) but is often insufficient in the older child with severe flattening of the occiput. Many of these children who eventually require surgery will benefit from more aggressive total calvarectomies (removal of large amounts of the calvarium followed by reconstruction).

Figure 8C. Vertex view of a 6-month-old patient after a bifrontal correction of his or her left coronal plagiocephaly. Note the anterior advancement of the new supraorbital rim on the patient's left side when compared to the right.

Figure 8C. Vertex view of a 6-month-old patient after a bifrontal correction of his or her left coronal plagiocephaly. Note the anterior advancement of the new supraorbital rim on the patient's left side when compared to the right.

Figure 8D. Lateral intraoperative view of this patient, demonstrating significant bone advancement on the affected side. A titanium plate was used to maintain final position of the new supraorbital-forehead construct.

Figure 8D. Lateral intraoperative view of this patient, demonstrating significant bone advancement on the affected side. A titanium plate was used to maintain final position of the new supraorbital-forehead construct.

Our institutional experience over the past decade53 involved 57 patients whose ages at surgery ranged from 3 to 33 months (mean, 10 months). These were followed for an average of 8 months (12 months recently) prior to surgery. We experienced no mortality and minimum morbidity (one leptomeningeal cyst required surgical correction: four patients needed removal of prominent wires or screws). There were no infections, cerebral injuries, or deficits, and no child required secondary surgery. Eventual cosmesis was excellent in 79%. The remaining 21% were considered significantly improved by the family although the surgeon's perspective was less enthusiastic. Nevertheless, results for all patients were satisfactory. Improvement in the facial and frontal symmetry was also satisfactory. The greatest improvement was demonstrated in children operated on at an early age.

CORONAL SYNOSTOSIS (PLAGIOCEPHALY/BRACHYCEPHALY)

Premature closure of a single coronal suture (Figure 4A) may lead to anterior plagiocephaly (versus posterior plagiocephaly secondary to pathophysiology of the lambdoid suture). The incidence of unilateral coronal synostosis (premature fusion) is 1 per 10 000 live births and represents approximately 20% to 25% of all craniosynostosis. Once again, it is important to differentiate deformational plagiocephaly from true coronal synostosis. Deformational plagiocephaly is common. It occurs in one fifth to as high as one half of live births and is the result of positional molding in utero or postpartum. This predominantly involves the left side of the forehead and is frequently associated with other congenital conditions, secondary to inhibited fetal growth: talipes equinovarus, genovarus, congenital hip dysplasia, micrognathia, and torticollis. Premature fusion of the involved suture is not visualized, and the child usually improves with time.

True coronal craniosynostosis will present with a unilateral flattening of the involved forehead with posterior and superior distortion of the lateral orbital wall and forehead (Figure 8A). In extreme examples, the ear will be anteriorly displaced. The forehead flattening is often associated with contralateral compensatory frontal bossing. No gender predilection is apparent and both sutures appear to be affected equally. Bilateral involvement of the coronal sutures (as well as the lambdoid sutures) may lead to increased width of the head known as brachycephdy. In extreme cases, this may lead to acrocephaly (pointed skull). Involvement of the orbits and face requires a full evaluation by a craniofacial panel. A harlequin orbit may be evident on skull radiograph (Figure 8B), and associated difficulties with ocular motility may be present.

The rationale for surgical correction is to restore normal anterior fossa intracranial volume (via advancement of the restricted fronto-orbital bone), repair the frontal and orbital deformities, and correct growth restriction at the coronal and anterior skull base sutures (frontosphenoidal, frontoethmoidal) (Figures 8C and 8D). This involves the face and orbits more than any other type of craniosynostosis surgery. As a result, the number and types of surgical intervention vary from the simple removal of the coronal suture to unilateral correction of the forehead, to more extensive bifronto-orbital reconstruction.

The timing of surgery remains controversial.58-60 Many advocate early intervention (by 3 to 4 months) for severe changes. Others believe waiting till die patient reaches 8 to 10 months of age a will lead to better long-term results with less surgical morbidity. Earlier surgical repair may be safely performed with experienced pediatric anesthesiologists and strict efforts to keep up with intraoperative blood losses. Personal experience has demonstrated better longterm head and facial symmetry following early bilateral surgical correction (3 to 6 months of age at time of surgery) of coronal synostosis. The greatest challenge facing the surgeon is the restoration of a "natural" supraorbital rim with attention to the lateral and superior aspects of the orbits. Most craniofacial surgeons61"64 believe this is best accomplished by the removal and reconfiguration of the entire (bilateral) orbital rim, replacement of the frontal region with a new forehead, and a build-up of bone over the pterional (temple) regions. These children frequently have the least satisfactory result over the long term because of the involvement of the adjacent facial structures. For this reason, an increasing number of craniofacial surgeons promote early surgical intervention to offer the best opportunity for the face to grow normally with the expansion of the calvarial vault. Regardless of which approach is taken, it is now possible to provide significant improvement in this previously challenging region with a minimum amount of surgical risk.

CONCLUSION

Over the past decade, advances in craniofacial surgery due to improved diagnosis, safer pediatric anesthesia, and refined surgical techniques have led to better overall long-term results. At the same time, these advances have contributed to decreasing perioperative risks. As a result, children are now being treated safely in an earlier fashion, with the majority of patients proceeding to live normal lives without needing further treatment. Although this approach is presently routine, with an increasing number of children being diagnosed by the primary care physician at birth or shortly thereafter, it must be remembered that this is a relatively recent phenomenon. Less than 20 years ago, many of these same individuals, who now undergo complicated surgery (often at less than 6 months of age) requiring significant blood transfusions, complete rearrangement of the calvarial vault, face, and orbits, and reconstruction employing absorbable plates and screws or a hydroxyapatite matrix with associated bone growth factors, would then require multiple, extensive operations. These surgeries were often associated with long hospital stays complicated by serious morbidity and even mortality. At present, the majority of children undergo a single operation, which is expected to routinely lead to an excellent cosmetic result with a minimum of morbidity and nearly nonexistent mortality. These children are discharged to home in 3 to 5 days despite the frequent complete reshaping of the entire head as well as face and orbits.

The future is likely to bring further refinements in the areas of pediatric anesthesia, blood and fluid management, and surgical technique. Endoscopic techniques have now been successfully applied to this arena and represent die progressive trend to minimalistic intervention. The use of more compatible biomaterials for rigid fixation (absorbable polylactic or glycolic plates and screws) and bone substitution materials (readily mixable hydroxyapatite paste) with the near-term institution of growth factors (BMP or bone morphogenic protein) will all contribute to providing a stronger and more accurate calvarial reconstruction. It is not inconceivable that genetic manipulation in the future will provide the ultimate microsurgical tool for the perfect restoration to a normal calvarium. Nevertheless, craniofacial surgeons will undoubtedly continue their quest to provide the ultimate repair of an asymmetric calvarium with the goal of zero morbidity and a perfect outcome. This journey will continue to stretch the limits of our knowledge and "push the technical envelope," but should ultimately be successful in the hands of the future craniofacial surgeon.

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TABLE 1

Classification of Synostoses

TABLE 2

Craniofacial Dysostoses Syndromes

TABLE 3

Potential Indications for Lambdoid Plagiocephaly Surgery

10.3928/0090-4481-19971001-07

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