Embryology · Skeleton, muscles, limbs and skin

Craniosynostosis !

Malformation

One or more seams of a baby's skull close too early, and the head grows into an abnormal shape.

Updated 2026-11-01

See it in 3D: Frontal bone · Parietal bones · Base of the skull

What it is

Craniosynostosis is the early closure of one or more cranial sutures; it occurs in about 1 in 2500 births. Where the suture closes the skull stops growing, and it overgrows in the direction parallel to it, giving typical shapes. It is usually isolated, but it is part of more than a hundred syndromes, many due to mutations in FGF receptors.

Embryological cause

Sutures are zones of unossified mesenchyme where new bone is added; their closure is regulated by signals between neural crest and mesoderm.
Activating mutations of FGFR1, FGFR2 or FGFR3 speed up bone differentiation in the suture.
TWIST1 and MSX2 control proliferation of suture cells; loss of TWIST1 causes Saethre–Chotzen.
The shape results from the skull failing to grow perpendicular to the fused suture and compensating parallel to it.
Some drugs early in pregnancy (for example valproate) are linked to metopic synostosis.

Markers

FGFR2
FGFR3
FGFR1
TWIST1
MSX2
EFNB1

How it presents

Sagittal (the most common, more in boys): long, narrow head (scaphocephaly).
Unilateral coronal: forehead flattened on one side and a raised orbit (anterior plagiocephaly).
Bilateral coronal: short, wide head (brachycephaly); typical of Apert and Crouzon.
Metopic: keel-shaped, triangular forehead (trigonocephaly).
Lambdoid: rare; flattens the back of the head and is confused with positional plagiocephaly.
If several sutures close, intracranial pressure can rise; Apert adds syndactyly of hands and feet.

Diagnosis

Exam: skull shape, a palpable bony ridge over the suture and an absent or small fontanelle.
CT with three-dimensional reconstruction confirms which suture is closed.
Genetic testing if several sutures, hand or foot anomalies, or a family history are present.

Test yourself

Think of the answer, then tap the question to see it.

What is the most common craniosynostosis and which head shape does it cause?

Sagittal: it gives a long, narrow head, called scaphocephaly.

Which gene family is mutated in Apert, Crouzon and Pfeiffer syndromes?

The fibroblast growth factor receptors, mainly FGFR2.

Which skull shape results from early closure of the metopic suture?

Trigonocephaly: a narrow, keel-shaped, triangular forehead.

Which test confirms the affected suture?

Head CT with three-dimensional reconstruction.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

← All of embryology

Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.

Sources: Craniosynostosis | Birth Defects | CDC (Centers for Disease Control and Prevention, 2026); Craniosynostosis: MedlinePlus Medical Encyclopedia (MedlinePlus, US National Library of Medicine, 2026); Langman's Medical Embryology, 13th ed., ch. 10: The Axial Skeleton (Wolters Kluwer, 2015).

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Representative model, for educational purposes only.