Premature ossification of the skull seams (Craniosynostosis)
A baby's skull is made up of several "bony pieces" connected by flexible seams (sutures). These seams allow the skull to expand as the brain grows rapidly during the first months of life. Craniosynostosis is a condition in which one or more of these seams close too early, before the brain is fully formed.
Why does the shape of the head change?
Even if one suture closes, the brain continues to grow. Because the skull cannot expand at the closed suture, it grows more strongly in the directions where the sutures are still open. This causes the head to have an abnormal shape.
The most common types
The shape of the head depends on which seam has closed:
Sagittal (Boat Skull): The seam across the top of the head closes. The head grows long and narrow. This is the most common type.
Coronal: The seam runs from ear to ear across the head.
If only one side closes, the forehead may appear flat on one side and the eye socket may rise higher.
If both sides close, the head is short and wide.
Metopic (Triangular skull): The seam running down the middle of the forehead closes. The forehead becomes triangular and the back of the head widens.
Lambdoid ideal: The seam running along the posterior furrow closes. The posterior furrow may appear flat and one ear may be higher than the other. This is a very rare type.
Identify the symptoms
Symptoms are usually visible at birth or become more pronounced during the first months of life:
Abnormal head shape.
Asymmetry of the face or ears.
A hard, raised ridge at the closed seam.
Absence or abnormal sensation of the areola (the soft spot on the baby's head).
Is it always ossification of the seams?
Not usually. Most often, the flattening of the back of the head (this is often accompanied by asymmetrical positioning of the ears) is caused by the baby spending a lot of time on his back in the same position (so-called positional plagiocephaly). This is usually corrected with positioning treatments and when the child starts to move more. At the time of writing, helmet treatments are not recommended for use in Finland.
Why is treatment important?
If craniosynostosis is left untreated, it can cause:
Permanent changes to the shape of the face and head.
Increased pressure inside the skull (rare if only one suture is closed).
Untreated intracranial pressure can lead to even worse problems
Treatment and recovery
Craniosynostosis is usually treated with with surgery, in which the skull is reshaped. The surgery ensures sufficient space for the brain to grow.
Early treatment and diagnosis are very important. Most children develop completely normally after surgery, and the head shape becomes more normal.
Mayo Clinic article
https://www.mayoclinic.org/diseases-conditions/craniosynostosis/symptoms-causes/syc-20354513
HUSUKE information package
https://www.hus.fi/potilaalle/hoidot-ja-tutkimukset/kallon-saumojen-luutumishairiot