How can you differentiate between scaphocephaly and normal elongation of the head in infants and young children?

Differentiating Scaphocephaly from Normal Head Elongation

The key distinction is whether the sagittal suture is fused (true scaphocephaly/craniosynostosis) or patent (normal elongation/dolichocephaly), which requires imaging confirmation—ultrasound of skull sutures is the preferred initial diagnostic modality for this differentiation. 1

Clinical Assessment

Head Shape Characteristics

True scaphocephaly presents with:

• Marked elongation in the anteroposterior dimension with compensatory narrowing of the biparietal width 2
• Prominent frontal and occipital bossing (ridging) 1
• Palpable ridge along the sagittal suture line 1
• Cranial index (CI) typically <75% (width/length × 100) 2

Normal elongation/dolichocephaly presents with:

• Mild to moderate elongation without severe narrowing 1
• Smooth skull contour without ridging 1
• No palpable abnormality along the sagittal suture 1
• CI may overlap with scaphocephaly range, making clinical assessment alone insufficient 2

Historical Clues

• Positional dolichocephaly: History of prolonged supine positioning, prematurity, or intrauterine constraint 3, 1
• Constitutional dolichocephaly: Family history of similar head shape, no identifiable compressive factors 1
• True scaphocephaly: Often apparent at birth or early infancy, progressive deformity 4

Diagnostic Imaging

Preferred Approach

Ultrasound of skull sutures is the first-line imaging modality for differential diagnosis:

• Directly visualizes suture patency versus fusion 1
• Avoids radiation exposure in infants 1
• Can be performed in clinic setting 1

CT Imaging

CT with volumetric reconstruction should be obtained when:

• Ultrasound is inconclusive 1
• Surgical planning is needed 4
• Multiple suture involvement is suspected 5

Important caveat: The traditional cranial index has poor specificity (68%) despite high sensitivity (98%) for scaphocephaly, meaning many normal elongated heads will have abnormal CI values 2. Scaphocephaly severity indices (SSI) based on internal landmarks provide superior specificity (95%) at 98% sensitivity 2.

Diagnostic Algorithm

1. Measure head circumference using proper technique (above supraorbital ridges to occiput) and plot on growth charts 6

   • Assess for microcephaly (<-2 SD) or macrocephaly (>+2 SD) which may indicate underlying pathology 7, 8

2. Calculate cranial index: biparietal width/anteroposterior length × 100

   • CI <75% suggests scaphocephaly but requires confirmation 2

3. Palpate sagittal suture for ridging or fusion 1

4. Obtain skull ultrasound to assess suture patency 1

   • Patent suture = dolichocephaly (positional or constitutional)
   • Fused suture = true scaphocephaly requiring intervention

5. If ultrasound confirms fusion or is inconclusive, obtain CT for definitive diagnosis and surgical planning 4, 1

Management Implications

For Confirmed Scaphocephaly (Fused Suture)

• Age <12 months: Molding helmet therapy may be attempted for "sticky sagittal suture" (nonsynostotic scaphocephaly), though true synostosis typically requires surgery 4
• Age >12 months or failed conservative therapy: Surgical correction (linear craniectomy or cranial vault remodeling) 4, 5
• Developmental monitoring: While most cases are benign, approximately 10-12% may have developmental delays unrelated to mechanical brain constriction 5

For Dolichocephaly (Patent Suture)

• Positional dolichocephaly diagnosed <12 months: Repositioning strategies, physical therapy, and custom cranial orthoses if severe 3, 1
• Constitutional dolichocephaly: Reassurance; correction only for aesthetic indications using cranial orthoses 1
• No surgical intervention indicated 1

Critical Pitfalls

• Do not rely on cranial index alone—it has poor specificity and will misclassify many normal elongated heads as pathologic 2
• "Sticky sagittal suture" (nonsynostotic scaphocephaly) can mimic true synostosis clinically but may respond to helmet therapy; serial imaging is essential to detect progression to true fusion 4
• Untreated positional deformities may be associated with delayed motor and intellectual development, justifying early intervention even without synostosis 3