From
StayCurrentMD
Understanding craniosynostosis: skull sutures, growth patterns, and diagnosis in infants
With Dr. Jesse Skoch
Chapter 1 of 5
Skull anatomy basics
Definition, epidemiology, and normal infant skull anatomy
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Educational content from recorded physician discussions — not medical advice. Talk to your (or your child's) care team about your situation.
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What the experts said
Dr. Jesse Skoch states that skull volume essentially doubles during the first year, representing an impressive change.
According to Virchow's law, when a suture is fused, skull growth perpendicular to that suture will be arrested and growth will happen in the parallel direction.
Dr. Skoch prefers a three-dimensional concept of Virchow's law, thinking of it as squeezing a balloon, which better predicts the resulting skull shape.
Trigonocephaly is the triangular head shape seen in metopic craniosynostosis.
The metopic suture is by far the earliest closing suture, typically closing between 3 to 9 months, while other sutures don't typically close until late adulthood.
Dr. Skoch states that if a suture closes in the first year or two of life but isn't closed right at birth, patients can often do perfectly fine with very minimal deformity; prenatal closure is what truly warrants concern.
Minor suture fusion usually does not cause significant deformity or risks to brain development.
Head shape is more important than palpation findings (ridge, fontanelle size, prominent suture) in diagnosing craniosynostosis.
Dr. Skoch states that with true lambdoid synostosis there is almost always a height differential of the ears with a lower-set ear on the affected side, whereas ear height is typically normal with positional plagiocephaly.
Dr. Skoch states that CT is the gold standard but most of the time it's not necessary for diagnosis, and CTs should not be obtained on patients who don't really need them.
Dr. Skoch states that partially fused sutures are the real deal and deserve all the attention of a fully fused suture, comparing them to a partially locked door—if it's stuck, it's stuck, regardless of how much.
Dr. Skoch states that multi-suture, typically syndromic deformities are important to treat much earlier because of the significant risk of elevated intracranial pressure.
Craniosynostosis occurs in roughly 1 in 2500 births.
Most craniosynostosis cases involve a single suture with no underlying syndrome, and the sagittal suture is most often affected.
A minority of craniosynostosis cases are syndromic (Apert, Crouzon, Muenke, and others) and tend to involve more than one suture.
Infant skull bone does not expand from the middle but gets laid down at the edges, at the sutures, as the brain pushes outward.
The dura mater signals the bone-forming edges of each suture, and the brain's growth is the trigger for skull expansion.
The posterior fontanelle closes by around 2 to 3 months of age.
The anterior fontanelle stays open until somewhere between 9 and 18 months.
The fastest skull growth is over by 12 months of age.
The metopic suture runs down the midline of the forehead from the anterior fontanelle to the root of the nose and allows the forehead to widen.
The coronal sutures run transversely, one on each side, separating the frontal bone from the parietal bones and allow the forehead and orbital rim to advance.
The sagittal suture runs front to back down the midline between the two parietal bones and allows the skull to widen.
The lambdoid sutures angle back from the midline, separating the parietals from the occipital bone, and allow the posterior skull to grow.
Virchow published his law in the 1850s and it remains the current framework for understanding craniosynostosis.
Positional plagiocephaly is far more common than any fused suture and is caused by a baby lying the same way for long stretches, with all sutures remaining open.
Positional molding produces a parallelogram shape from above, while lambdoid synostosis produces a trapezoid shape.
In positional molding, the ear shifts forward but the two ears stay level.
CT with three-dimensional reconstruction is the confirmatory study for craniosynostosis, showing the sutures directly.
Ionizing radiation from CT in infants is associated with increased cancer risk in the future with large doses.
In practice, the specialist orders CT once the exam has raised the question, usually to plan an operation rather than to make the diagnosis.
If the skull genuinely cannot keep up with the brain, intracranial pressure rises, which is what surgery exists to prevent.
With a single fused suture, elevated intracranial pressure happens to a minority of children.
When more than one suture is involved, the restriction is greater and the risk of elevated intracranial pressure is real.
Every operation for craniosynostosis is built around a specific suture, where it sits, what it was holding back, and how much growth is left to harness.