Craniosynostosis and Craniofacial Syndromes

Chapter 5

Craniosynostosis and Craniofacial Syndromes

General Craniosynostosis Nomenclature and Information

1. Craniosynostosis: Abnormal fusion of cranial sutures leading to abnormal head shape

• May lead to increased intracranial pressure (ICP) and developmental delay

▪ Increased ICP can be diagnosed by papilledema and “thumb printing” on radiographic studies.

• Prevalence: ~1:2500 live births

• Most common synostosis: Sagittal, followed by unilateral coronal, bilateral coronal, metopic, and lambdoid

• Most infants with single-suture synostosis are nonsyndromic, whereas most with multisuture synostosis do have a syndrome.

• Most syndromic craniosynostoses are related to fibroblast growth factor receptor (FGFR) genes and present with bilateral coronal craniosynostosis in isolation or in association with other suture synostoses.

• Syndromic craniosynostoses and their related gene mutations

▪ Apert syndrome: FGFR-2

▪ Crouzon syndrome: FGFR-2

▪ Pfeiffer syndrome: FGFR-2

▪ Saethre-Chotzen syndrome: TWIST 1

2. Cranial sutures (see Figure 5.1)

• Act as growth centers for the cranium and allow skull deformation for passage through the birth canal

• With an open suture, the bone grows perpendicular to the suture line.

• When the suture is fused, compensatory bone growth occurs parallel to the suture line (see Table 5.2).

Figure 5.1 Normal sutures and fontanels. Posterior and lateral views of a three-dimensional (3D) CT of a newborn. (Left) Posterior view of the skull, demonstrating the posterior fontanel (blue), the sagittal and the paired lambdoid sutures (white lines). The sagittal suture contains an incidental wormian bone. (Right) Right lateral view demonstrating the mastoidal fontanel posteriorly, the sphenoidal fontanel anteriorly, and at the vertex the anterior fontanel (blue), which is only partially seen. The right coronal, squamosal, and right lambdoid sutures are patent (white lines). (Reprinted from Kirmi, O., Lo, S.J., Johnson, D., et al., 2009. Craniosynostosis: a radiological and surgical perspective. Sem. Ultrasound CT MRI 30 (6), 492–512.)

3. Suture closure (see Figure 5.2)

• Order of closure: Metopic suture (8-9 months), sagittal suture (22 years of age), coronal suture (24 years), lambdoid suture (26 years), and squamosal suture (>60 years)

Figure 5.2 Fusing sutures. 3D CT: Normal suture (left), fusing suture (middle) that has lost its architecture, and bone bridging of a fused suture (right). (Reprinted from Kirmi, O., Lo, S.J., Johnson, D., et al., 2009. Craniosynostosis: a radiological and surgical perspective. Sem. Ultrasound CT MRI 30 (6), 492–512.)

4. Common craniofacial terms

• Hypertelorism: Abnormal increase in the distance between the bony orbits

• Hypotelorism: Decreased distance between the bony orbits

• Telecanthus: Increased distance between the medial canthi

• Exorbitism: Protrusion of the globe due to decreased volume of orbit

Craniosynostoses

See Figure 5.3.

1. Metopic craniosynostosis

• Also known as trigonocephaly (“triangular-shaped” head)

• Characterized by

▪ Keel-shaped forehead

▪ Metopic ridge (in mild cases)

▪ Bitemporal narrowing

▪ Parietal expansion

▪ Hypotelorism

• Most likely to be associated with midline brain abnormalities

2. Sagittal craniosynostosis

• Also known as scaphocephaly (“boat-shaped head”) or dolichocephaly

• Characterized by

▪ Bilateral frontal and occipital bossing

▪ Elongated head in the anteroposterior direction

▪ Decreased biparietal width

Figure 5.3 Characteristic skull shape depending on sutural involvement in craniosynostosis. (Reprinted from Neligan, P.C., Losee, J. [Eds.], 2013. Plastic Surgery, 3rd ed. Elsevier, 726–748.)

• Treatment: Endoscopic resection of the sagittal suture with postoperative helmet molding can often safely be performed on patients at 3 months of age.

3. Coronal craniosynostosis

• Unilateral coronal craniosynostosis is also known as anterior plagiocephaly; bicoronal craniosynostosis is known as brachycephaly (“short, flat head”).

• Unilateral coronal synostosis is characterized by

▪ Flattening of the ipsilateral forehead and supraorbital rim

▪ Contralateral forehead bossing

▪ “Harlequin” eye deformity: Flattened supraorbital rim, raised eyebrow, widened palpebral opening, deficient lateral orbital rim, steep superior orbital fissure, and sphenoid wing

▪ Anterior displacement of the ipsilateral ear

▪ Deviation of the nasal root toward the affected side

• Bilateral coronal synostosis is characterized by

▪ Symmetric, flat forehead

▪ Increased biparietal width

▪ Decreased anteroposterior length

▪ Turricephaly or turribrachycephaly; can occur in certain patients in which there is a compensatory increase in parietal height leading to a “tall, flat head”

4. Lambdoid craniosynostosis

• Also known as posterior plagiocephaly; very rare

• Distinguished from deformational plagiocephaly by a “trapezoid”-shaped head

• Characterized by

▪ Flattening of the ipsilateral occiput

▪ Inferior displaced mastoid bulge on affected side

▪ Contralateral forehead bossing

▪ Inferior displacement of the ipsilateral ear

5. Multisuture craniosynostosis

• Involves premature fusion of multiple sutures

• In the most severe form (pansutural synostosis), patients can develop a “cloverleaf” skull deformity (also known as the kleeblattschädel skull deformity)

▪ Characterized by a “moth-eaten” appearance of bone on computed tomography (CT) imaging

▪ May lead to severe increases in ICP and airway anomalies

6. Treatment of craniosynostosis depends on severity, appearance, and functional concerns.

• Goals of surgery: Suture release to allow brain growth and development; normalization of head shape; reduction of functional deficits (e.g., increased intracranial pressure, developmental delay, etc.)

• Timing of surgery is often dependent on the severity of the abnormality, with the more severe or symptomatic (e.g., increased ICP) patient often requiring surgery between 6 and 12 months of age.

7. Surgical treatment options (see Table 5.1)

• Cranial vault remodeling: Multiple techniques have been described.

▪ Surgery is often performed between 6 and 12 months of age.

• Distraction osteogenesis

▪ Useful for advancements >1 cm

▪ Latency phase

○ The phase following osteotomy and application of the distractor device in which there is no bony movement

○ A typical latency phase lasts between 1 and 7 days.

▪ Activation phase

○ The phase following the latency period in which the distractor is moved at a set rate (e.g., 1 mm/day)

○ Encourages bone formation

▪ Consolidation phase

○ The distraction is completed, the device is left in place, and the new bone is allowed to consolidate and calcify.

○ A typical consolidation period is twice the duration of the active distraction.

• Midface advancement

▪ Often, LeFort I or III advancements

• Rhinoplasty

Table 5.1

Skull Deformity in Craniosynostosis and Operative Techniques Used for Correction

FUSED SUTURE	SKULL SHAPE	HYPOPLASTIC ELEMENTS	COMPENSATORY GROWTH	OPERATIVE TECHNIQUES
Sagittal	Scaphocephaly	Biparietal, bitemporal	AP lengthening, frontal bossing, occipital protrusion	Strip craniectomy, cranial vault remodeling, spring-assisted cranioplasty
Unicoronal	Plagiocephaly	Ipsilateral frontal flattening, orbital rim recession	Contralateral frontal and temporal bulging, ipsilateral facial sutures (facial scoliosis)	FOA
Bicoronal	Brachycephaly	Occipital flattening, AP shortening	Elevation in skull height	FOA
Lambdoid	Plagiocephaly	Ipsilateral parieto-occipital flattening	Bulging of contralateral parieto-occipital bone	Lambdoid strip craniectomy, biparietal occipital remodeling
Metopic	Trigonocephaly	Hypotelorism, superior orbital rim recession, bitemporal narrowing	Parietal flaring	FOA

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