Craniosynostosis

Question 1

Craniosynostosis: premature closure of the cranial sutures. Skull shape then undergoes characteristic changes depending on which suture(s) close early.

3:1 male predominance; 1/2000-2500; 8% syndromic or familial

Primary form: sporadic or familial

Secondary form: endocrine disorders (hyperparathyroidism, hypophosphatemia, vitamin D deficiency, hypercalcemia); hematologic disorders causing bone marrow hyperplasia (sickle cell, thalassemia); inadequate brain growth (microcephaly, shunted hydrocephalus)

Answer 1

Ages of normal sutural/fontanelle closure:

• metopic: 3-9 months
• anterior fontanelle: 18-24 months
• sphenosquamosal: 6-10 years
• sphenofrontal: approximately 15 years
• occipitomastoid: approximately 16 years
• sagittal: approximately 22 years
• coronal: approximately 24 years
• lambdoid: approximately 26 years
• squamosal: approximately 60 years

Question 2

Most occur as isolated anomalies but syndromic associations can be seen in a small proportion of cases (~10%):

1. acrocephalosyndactyly/acrocephalopolysyndactyly types

• Apert syndrome
• Carpenter syndrome
• Crouzon syndrome

2. choanal atresia

Answer 2

Acrocephalosyndactyly syndromes (ACS) are a rare group of disorders collectively characterized by:

• calvarial anomalies, e.g. craniosynostoses
• digital anomalies, e.g. syndactyly

Choanal atresia refers to a lack of formation of the choanal openings. It can be unilateral or bilateral.

• approximately 2/3rds are unilateral

Question 3

What is the most commonly involved suture?

A. Lambdoid

B. Metopic

C. Coronal

D. Sagittal

Answer 3

D. Sagittal

The sagittal suture is most commonly involved (≈50%).

• coronal (~20%)
• lambdoid (~5%)
• metopic (~5%)

Question 4

The cephalic index (CI) is a value calculated using two fetal biometric parameters:

• the occipitofrontal diameter (OFD)
• the biparietal diameter (BPD).

Cephalic index (CI) = biparietal diameter (BPD) / occipitofrontal diameter (OFD) x 100

Often the mean value is taken ~78 (range 74-83​)

Grossly decreased cephalic index –> suggests dolichocephaly

Grossly increased –> suggest brachycephaly

Answer 4

Scaphocephaly (also known as dolichocephaly) is the most common form of craniosynostosis, where premature closure of the sagittal suture results in an impediment to the lateral growth of the skull while anteroposterior growth continues, producing a narrow and elongated skull.

Brachycephaly refers to a calvarial shape where the bi-parietal diameter to fronto-occipital diameter approaches the 95th percentile. It can result from craniosynostosis involving the coronal and lambdoid sutures.

Question 5

Answer 5

Brachycephaly

The head may appear rounder than usual on an axial scan and the cephalic index is increased.

Question 6

Brachycephaly:

A. Sagittal

B. Coronal

C. Lambdoid

D. Metopic

Question 7

Question 8

Answer 8

SCAPHOCEPHALY / DOLICOCEPHALY

Question 9

Answer 9

BRACHYCEPHALY

Question 10

Answer 10

TRIGONOCEPHALY​

Question 11

Answer 11

Anterior plagiocephaly

Unilateral coronal synostosis

Question 12

Answer 12

Posterior plagiocephaly

Unilateral lambdoid synostosis

Question 13

Answer 13

Trigonocephaly

Metopic synostosis

Question 14

Answer 14

Brachycephaly

Bilateral coronal synostosis

Question 15

Answer 15

Scaphocephaly

Sagittal synostosis