68 Scaphocephaly

Case 68 Scaphocephaly

Abdulrahman J. Sabbagh, Jeff rey Atkinson, Jean-Pierre Farmer, and José Luis Montes

Clinical Presentation

A 3-month-old child presents with an abnormal head shape since birth.

He was born at term via a normal vaginal delivery.

The father has a similar but more accentuated head shape.

The physical examination is otherwise normal.

A computed tomography (CT) scan of the head is done and shown in Fig. 68.1.

Fig. 68.1 (A) Head photograph, (B,C) axial computed tomography (CT) scan, and (D) three-dimensional reconstructed CT scan, (E,F) of a child with craniosynostosis.

Questions

Describe the head shape and the CT scan. What is the diagnosis?
What is scaphocephaly?
How common is scaphocephaly?
What is the prognosis of scaphocephaly?
What is the risk of developing hydrocephalus in patients diagnosed with craniosynostosis? What is the risk for this patient?
What are some treatment options and their possible related morbidities?
What is the accepted hypothesis for the pathogenesis of deformities caused by craniosynostosis?
What is more clinically important, timing of head and brain growth or timing of normal sutural closure, and why?

Answers

Describe the head shape and the CT scan. What is the diagnosis?

The photograph, plain CT, and three-dimensional reconstructed CT scans show an elongated boatlike skull with a closed sagittal suture (Fig. 68.1).

Also seen is frontal and occipital bossing.

The diagnosis is scaphocephaly.
What is scaphocephaly?
- Scaphocephaly can be described as a boat-shaped head, caused by synostosis of the sagittal suture, leading to a long and thin skull.¹
- There is bifrontal and occipital symmetric compensatory bossing.
- There is usually a midline ridge, and there may be a saddle deformity where the synostosis began.
- It may be evident at birth and progresses to become more pronounced with time.
- It is the most common type of synostosis and is more common in males than females.
How common is scaphocephaly?
- Epidemiology of scaphocephaly is described below.
  - Incidence is 2–10 per 10,000 live births.²
  - It comprises 55–64% of synostosis surgical cases (most common type).
  - 70–85% of patients are male.¹
  - 6–10% of cases are familial.
  - It may follow an autosomal dominant inheritance pattern.²
  - There is 38% penetrance. ²
What is the prognosis of scaphocephaly?
- This deformity, like other forms of craniosynostosis, usually progresses with time and will have an important impact on the growing child’s social and psychological status.³
- These children usually would develop normally from a neurologic standpoint.
- There is a slight risk of increased intracranial pressure (ICP).³
What is the risk of developing hydrocephalus in patients diagnosed with craniosynostosis? What is the risk for this patient?
- Renier et al. in 1982 measured ICP using epidural sensor in 92 patients for 12–24 hours.⁴ He found the following results as they relate to ICP.
  - In one suture synostosis, 62% were normal, 24% were borderline and 14% were high.
  - In several sutures synostosis, 19% were normal, 34% were borderline and 47% were high.
- The incidence of hydrocephalus in sagittal craniosynostosis is remarkably rare (~0.3%), except in patients with prematurity or those who have been shunted.⁵
- On the other hand, in syndromic craniosynostosis (Crouzon syndrome, Pfeiff er syndrome, Apert syndrome, etc.), the incidence of hydrocephalus may range from 20 to 40%.^5–7 The former two are more likely to be associated with shunt dependent hydrocephalus than the latter.⁷
What are some treatment options and their possible related morbidities?
- Ideally, surgical repair should be done at 2–3 months of age. When done before 3 months of age, the following options are available:
- Midline strip craniectomy⁸
  - A 4–8 cm wide craniectomy is performed, from the coronal to just posterior to the lambdoid sutures.
  - Bilateral barrel stave osteotomies are then done (Fig. 68.2).
  - Blood transfusion is common.
  - There is up to a 10% chance of having a residual bone defects.
  - Good cosmetic results can be obtained (Fig. 68.3).
- Pi procedure^9,10
  - This procedure immediately provides anteroposterior shortening of the skull.
  - It may also give a better cosmetic result.
- Endoscopic strip with molding helmet therapy
  - This method significantly lowers the rate of transfusion.¹¹
- In cases where treatment is contemplated late (after 6 months of age), the following options are available.
  - Variations of the Pi procedure⁹
  - Total cranial vault reconstruction¹²
What is the accepted hypothesis for the pathogenesis of deformities caused by craniosynostosis?
- An older hypothesis described by Virchow (in 1851) states, “Craniosynostosis is caused by a lack of growth perpendicular to the fused suture and compensatory growth parallel to the suture in the calvarial vault.”¹³
- The currently accepted hypothesis devised by Delashaw et al. states, “The calvarial bones directly adjacent to a fused suture act as a single bone plate with decreased growth potential.”¹³
- Asymmetrical bone deposition occurs at the sutures along the perimeter of the bone plate with increased bone deposition at the outer margin.¹³
- Nonperimeter sutures in line with the fused suture deposit bone symmetrically at their sutural edges.¹³
- Perimeter sutures adjacent to the fused suture compensate to a greater degree than other distant sutures.¹³
What is more clinically important, timing of head and brain growth or timing of normal sutural closure, and why?
- Timing of head and brain growth is more clinically significant than normal suture closure.¹
  - The brain doubles in size by 6 months of age and doubles again by 2 years of age.
  - The skull is 35% of its adult size at birth, and 90% of the adult size is reached by age 7 years.