There are four major types of craniosynostosis (synostosis for short):
- Sagittal synostosis
- Coronal synostosis
- Metopic synostosis
- Lambdoidal synostosis
Most cases are diagnosed clinically, so when confronted with a child with a misshapen head, don’t automatically feel you have to order imaging.
If the child’s head is abnormally elongated with bulging of the frontal bone and occiput alongside a palpable and heaped-up midline ridge, they most likely have sagittal synostosis. This is the most common form of synostosis.
While there are usually no associated neurological or developmental deficiencies associated with sagittal synostosis, the cosmetic effect can be quite severe. The child’s biparietal diameter (e.g., the diameter of the child’s skull at the parietal eminences) may be significantly narrowed. As well, frontal bossing (e.g., enlarged and protruding forehead or enlarged eyebrow ridge) may be noticeable from across the room.
Sagittal synostosis responds nicely to surgery, which involves the removal of the sagittal suture and skull reshaping. Surgery can often be done with minimally invasive techniques in young babies by performing the procedure with endoscopic assistance through several small incisions.
If the procedure is performed before 6 months, the cosmesis is generally superb. If performed after 9 to 12 months, the synostosis is much more evolved and the cosmesis may not be as satisfying.
Coronal synostosis can involve one or both coronal sutures.
Unilateral coronal synostosis
A baby likely has unilateral coronal synostosis if their forehead and eye socket are recessed on one side and bulging on the other, with a palpable ridge across the recessed forehead. The occiput generally remains rounded.
Unilateral coronal synostosis responds nicely to surgery, but the surgery can be quite complex and involves cranial and facial reconstruction. Often, the orbital rim needs to be repositioned and reconfigured. Ideally, the surgery is performed at an early age. However, due to the orbital work, the surgery is sometimes performed a little later than a sagittal synostosis procedure to give the surgeon hardier bone to work with.
Bilateral coronal synostosis
Bilateral coronal synostosis can result in shortening of the skull in the anterior-posterior plane and widening in the biparietal plane. The forehead can be flattened and elevated, and the midface can be hypoplastic. The orbits may be elliptical, and the orbital rims poorly formed.
Bilateral coronal synostosis is often associated with various syndromes such as Apert syndrome and Crouzon syndrome. It can also be associated with multisuture synostosis.
Surgery for bilateral coronal synostosis can be quite involved—particularly if midface corrections are required. As well, these procedures need to be performed at craniofacial centers.
If the child has a palpable (and often visible) keel down the middle of their forehead and a laterally recessed forehead and orbits (e.g., the head is wedge-shaped), they have metopic synostosis.
The earlier metopic synostosis is addressed, the better the cosmetic effects of surgery. Metopic synostosis can be associated with genetic disorders and is often accompanied by significant developmental delay.
Lambdoidal synostosis is quite rare. It can appear as a severe case of positional molding except that the ipsilateral ear is pulled backward, and the contralateral forehead is bulging. This is generally treated with surgical resection of the affected suture.
Rule out the differential diagnosis of positional plagiocephaly
Unilateral coronal synostosis (and lambdoidal synostosis) can appear somewhat similar to positional plagiocephaly. In positional plagiocephaly, a child’s preference for lying on one side of the head can result in a severe flattening of that parietal-occipital region. The skull compensates and takes on a parallelogram shape.
The flattening of the occiput and the contralateral forehead occurs with bulging of the contralateral occipital bone and the ipsilateral frontal bone. As well, the ipsilateral ear is displaced anteriorly. The orbits remain relatively normal, and there is no palpable ridging anywhere. Opposingly, in coronal synostosis, a coronal suture is heaped up and palpable, and the occiput remains relatively normal in contour.
Positional molding starts to improve the moment babies start to spend more time off their backs. In mild to moderate cases, the flattening will generally correct itself (although not necessarily perfectly).
Improvement can be encouraged by positioning the baby on the opposite side of the head. Place items of interest on the opposite side so that the baby is more likely to turn their head away from the affected side.
Occasionally, the deformity can be severe enough that molding helmets are used to encourage a rounding of the cranium. These helmets apply gentle pressure against bulging areas and are remarkably well tolerated by the babies. Surgery is not indicated for positional molding. When in doubt, refer to a craniofacial expert.
Multisuture craniosynostosis is also possible
Multisuture synostosis (as the name implies) occurs when multiple sutures are involved and is generally obvious on inspection. The head and face will be markedly distorted with multiple palpable sutures. Head circumference will be small, and the child may show developmental delays. Surgery for multisuture synostosis is oriented to not only improve cosmesis but to allow the brain room to grow, and thus can be lifesaving.
When should you consider surgery for craniosynostosis?
Remember that single-suture synostosis rarely causes functional deficiencies. Therefore, the single greatest concern in most cases of craniosynostosis is cosmesis. The ramifications of cosmetic deformity should not be taken lightly; craniofacial deformities from synostosis can be quite striking and have significant implications for a child’s psychosocial development.
Corrective surgery for synostosis is best performed at an early age for optimal cosmetic results. This is because the brain is growing rapidly during this period, the skull is adjusting to the expanding brain, and bone is being produced at a high rate. Often, babies will undergo surgery at just a few months to nine months of age.
Since time is of the essence, you should get the patient to a craniofacial surgeon as soon as possible if you suspect synostosis. After nine months, surgery becomes much more involved and cosmesis is not as rewarding.
Surgery for synostosis is relatively safe and often quite effective. For this reason, it should be strongly considered in children with a severe cosmetic deformity or inadequate expansion of the cranial vault.
Complications of corrective surgery for synostosis
The most common serious complication of synostosis surgery is blood loss, and blood should always be immediately on hand during surgery. Inadequate cosmetic improvement may also occur, but this is subjective. Take pictures of the baby from all angles before and after surgery to help the parents recognize the improvements.
Neurological injury from the surgery is (thankfully) unusual. The procedure is performed completely outside of the protective dura.
Surgery for single-suture synostosis is generally quite satisfying; recovery is rapid, cosmesis is usually good, and development is normal. Children with syndrome-associated synostosis will face more of a challenge. The surgery may be more involved (including facial reconstruction) and the child may face neurological problems related to the primary syndrome.
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- Kabbani, H, and Raghuveer, TS. 2004. Craniosynosotosis. Am Fam Physician. 69: 2863-2870. PMID: 15222651
- Podda, S, Wolfe, SA, Kordestani, R, et al. 2020. Cranaiosynostosis Management. Medscape.https://emedicine.medscape.com
- Sheth, RDS, Ranalli, NJ, Aldana, P, et al. Pediatric Craniosynostosis. Medscape. https://emedicine.medscape.com