Craniosynostosis

What is the incidence of craniosynostosis?

1 in 2,000 births.

True/False: Facial sutures fuse before cranial sutures.

False.

When do the facial sutures fuse?

Facial sutures (except for the midpalatal suture) fuse in the seventh decade. Suture—time of fusion: frontonasal—68 years, frontozygomatic—72 years.

When do the cranial sutures fuse?

Cranial sutures fuse earlier than the facial sutures.

Suture—Time of fusion: metopic—2 years (may persist throughout life in 10%), sagittal—22 years, coronal—24 years, lambdoid—26 years, palatal—30 to 35 years.

What is the pattern of cranial suture fusion?

Front to back, lateral to medial.

What is the function of cranial and facial sutures?

Cranial: Bone overlap during birth, principal site of skull expansion, and shock-absorbing function in childhood.

Facial: Shock-absorbing function related to mastication.

What is Moss’s functional matrix theory?

Cranial bones enlarge as a result of growth and expansion of the underlying brain.

What role may osteoblast-derived growth factors have in craniosynostosis?

In vitro studies of craniosynostotic bone cells reveal a longer population doubling time, which suggests that suppression of osteoblastic-derived growth factors (IGF-I, IGF-II, TGF-b1, PDGF, and bFGF) may be a factor.

What is the genetic abnormality of Crouzon, Apert, and Jackson–Weiss syndromes?

Chromosome 10, mutation of fibroblast growth factor receptor 2 gene.

What is the genetic abnormality of Pfeiffer syndrome?

Chromosomes 8 and 10, mutation of the fibroblast growth factor receptor 1 or 2 gene.

Which form of suture synostosis has an increased frequency of mutation in the genetic loci for fibroblast growth factor receptor 3 (FGFR-3)?

Coronal.

What is the genetic transmission of Saethre Chotzen, Crouzon, Apert, and Pfeiffer syndromes?

Autosomal dominant.

What is the genetic transmission of Carpenter and Baller–Gerhold syndromes?

Autosomal recessive.

What is the cause of contralateral frontal bone bossing and bilateral temporal bulges in coronal suture craniosynostosis?

Bone growth occurs at the perimeter sutures with increased bone deposition directed away from the abnormally fused bone plate.

True/False: Virchow (1851) noted that skull growth is inhibited parallel to the synostosed suture.

False (inhibited perpendicular, compensatory expansion parallel).

What are the three types of forehead plagiocephaly (asymmetry of the head)?

Synostotic plagiocephaly, compensational plagiocephaly, deformational plagiocephaly.

What is the incidence of synostotic forehead plagiocephaly?

1 in 10,000 live births.

True/False: 79% of synostotic forehead plagiocephaly occurs in females.

True.

What are the distinguishing features of synostotic forehead plagiocephaly?

• Forehead flat on affected side.

• Eyebrow elevated on affected side.

• Ear on affected side rotated anterior-superiorly.

• Face C-shaped with nose and chin deviated to opposite side.

• Forehead prominence opposite side.

• Ipsilateral cheek forward.

What is the cause of head tilting in uncorrected unilateral synostosis?

Strabismus secondary to paresis of the ipsilateral superior oblique muscle.

What are the radiographic features of synostotic forehead plagiocephaly?

• Radiographs—perisutural sclerosis, absence of coronal suture, harlequin mask appearance of orbit.

• 3D CT scan—fused suture, extent of skull, and facial deformity.

What percentage of patients with synostotic forehead plagiocephaly have torticollis?

14%, usually contralateral side.

What is the cause of compensational plagiocephaly?

Premature fusion of the contralateral lambdoid suture. Uncommon condition, fused suture revealed on radiographs. Clinical distinguishing factor from deformational plagiocephaly, no improvement on follow-up.

What are the causes of deformational plagiocephaly?

Compressive forces in utero, by birth trauma and postnatal deformation by laying too much on one side.

What is the incidence of deformational forehead plagiocephaly?

1 in 300 live births.

What are the distinguishing features of deformational plagiocephaly?

• Superior orbital rim lower on the affected side.

• Eyebrow down.

• Ear rotated posterior-inferiorly on the flattened side.

• Malar eminence flattened ipsilaterally.

• Nose and chin rotated to affected side.

• Deformity not as severe as in synostosis.

What are the radiographic findings?

Patent sutures.

True/False: Torticollis is most commonly ipsilateral in deformational forehead plagiocephaly.

True.

True/False: Unlike synostotic forehead plagiocephaly, 76% of patients are male in deformational forehead plagiocephaly.

False.

True/False: On follow-up examination, physical findings in deformational plagiocephaly do not improve.

False.

What is the cause of brachycephaly?

Bilateral coronal suture craniosynostosis.

What are the clinical features of brachycephaly?

Reduced anterior–posterior distance, increased bitemporal distance.

What is the normal ratio of anterior–posterior to bitemporal distance? What is the ratio in brachycephaly?

3:2, 1:1.

What are the radiographic findings of brachycephaly?

• X-ray—bilateral fused coronal sutures and harlequin mask appearance.

• CT scan—fused sutures, abnormal shape of frontal bone.

• 3D CT scan—receding supraorbital borders, compensatory bulging of upper forehead.

What is the cause of trigonocephaly?

Metopic suture craniosynostosis.

What are the clinical features of trigonocephaly?

Triangular forehead with bilateral recession of lateral supraorbital borders and hypotelorism.

What are the radiographic findings of trigonocephaly?

• X-ray—hypotelorism.

• CT scan—triangular-shaped forehead.

• 3D CT scan—altered shape of forehead.

Which form of synostosis is most frequently associated with abnormalities of the corpus callosum and increased incidence of developmental delay?

Metopic synostosis, trigonocephaly.

What is the cause of scaphocephaly?

Sagittal suture craniosynostosis.

True/False: Scaphocephaly is the most common form of craniosynostosis, more than 50% of cases.

True.

What are the clinical features of scaphocephaly?

Dolichocephalic (scaphocephalic) cranial shape with biparietal narrowing and often frontal and/or occipital bossing. Palpable midline ridge. The cranial vault is long and narrow with a low posterior vault. Apex of the vault is anterior whereas under normal circumstances it is posterior.

What percentage of patients also have lambdoid synostosis?