Non-syndromic (single suture) craniosynostosis
Most non-syndromic craniosynostosis can be subdivided into four different types, according to which suture (gap) is affected. The underlying suture involved will also generally determine the type of treatment and surgery required.
This is the most common form of non-syndromic craniosynostosis. It occurs when the sagittal suture – the growth line running along the top of the skull from front to back - fuses too early. The result is a characteristic head shape where the length of the skull is increased and the width reduced (said to be like the shape of a boat). It is traditionally referred to as ‘scaphocephaly’.
Metopic craniosynostosis is also known as ‘trigonocephaly’, from the Greek for ‘triangleshaped head’. It occurs when the metopic suture - which runs from the front fontanelle (soft spot) through the forehead to the top of the nose - fuses too early. The head viewed from above is sometimes pointed in a triangular shape to the front and top of the skull. In some cases, the eyes may appear slightly misaligned.
Coronal – and especially bicoronal – craniosynostosis is much more frequently associated with syndromic than non-syndromic craniosynostosis.
Bicoronal synostosis is when both coronal sutures are involved. , The skull becomes excessively wide and short from front to back. There may be excessive growth at the upper part of the forehead and both eyebrows are pulled up and are flattened. This short front to back appearance of the skull has given rise to the name ‘brachycephaly’ or ‘short skull’.
Unicoronal synostosis is where one coronal suture is involved and there isn’t enough growth on the side of the fused suture, making the forehead and eye socket on one side flatter, whilst the opposite side of the forehead grows forward to compensate. In some cases, the eyes may be slightly misaligned.
This is a very rare type of craniosynostosis , affecting less than around 1 in 100,000 births. It occurs when one of the lambdoid sutures at the back of the head fuses prematurely, leading to an asymmetric skull shape flattened at the back.
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