Sagittal Synostosis (Scaphocephaly)
What is Sagittal Synostosis?
Sagittal synostosis (scaphocephaly) is the most common form of isolated (non-syndromic) craniosynostosis, representing about half of all cases of craniosynostosis. Boys tend to have this type of craniosynostosis more than girls with a ratio of 4 boys to each girl with sagittal synostosis. The sagittal suture is located on the top of the head running between the parietal bones from the anterior fontanelle (soft spot) and coronal sutures to the lambdoid sutures. Normal growth at the sagittal suture adds bone to the parietal bones that adds width to the middle and back parts of the skull. As seen in the figure below, the sagittal suture runs lengthwise along the top of the skull. The direction of growth at the cranial sutures (RED ARROWS) is away from the suture (perpendicular to the suture).
In sagittal synostosis the sagittal suture is closed, meaning the suture permanently changes to bone and the parietal bones are fused together as one big skull bone. The normal transverse growth that the sagittal suture provides is lost causing the skull to be abnormally narrow at the middle and back regions. The brain continues to grow at the same pace even though the sagittal suture is closed. The skull is forced to grow at the remaining open cranial sutures to make space for the growing brain. This compensatory growth at the open sutures causes the skull to grow longer than normal from front to back and also causes increased width and projection (bossing) of the forehead.
Scaphocephaly describes the general head shape in sagittal synostosis, but there is a fair amount of variability in the head shape depending upon how the compensatory growth is distributed. In some children, there is more fullness (bossing) and increased height of the forehead as the dominant feature. In others, the back of the head may be more significantly affected with a longer, narrow and coned shape. In most patients, the changes in head shape resulting from sagittal synostosis are evenly distributed throughout the head. The figures below show a two month old child with the characteristic changes of sagittal synostosis including increased width and forward projection of the forehead (bossing), increased length of the skull and narrowing of the middle and back portions of the skull.
Sagittal Synostosis Surgery
There are two main types of surgical options for treating sagittal synostosis. Strip craniectomy procedures remove a strip of bone from the skull, including the closed sagittal suture, in order to allow the brain to remodel the skull as it grows. These techniques are usually combined with a molding helmet that is worn after surgery in order to direct the growth of the brain and skull more efficiently. Strip craniectomy procedures are usually performed before age 4 months of age. Open cranial vault remodeling procedures normalize the head shape by removing large segments of the skull bones that are reshaped by hand and then reattached to the skull using sutures or plates that the body will dissolve in time. Open cranial vault remodeling is usually performed between 6-12 months of age.
sagittal Strip Craniectomy
For patients less than 4 months of age, I prefer to perform minimally invasive (endoscopic) extended sagittal strip craniectomy. This procedure uses very small incisions - only about 1.5 inches long - placed at the ends of the sagittal suture. Through these small incisions a 2 inch wide strip of bone, including the closed sagittal suture, is removed. Additional wedges of bone are removed behind the coronal sutures and in front of the lambdoid sutures. These additional cuts allow the parietal bones of the skull to move outward passively by hinging on the squamosal suture at the bottom of the parietal bones. The brain immediately starts to push the parietal bones out after the bone cuts are made in surgery because the brain does not want to be in the abnormal scaphocephalic shape. A normal head shape is a normal brain shape and the brain will rapidly normalize its shape after the bone cuts are made. Removing these wedges of bone also makes it easier for the brain to grow normally and further reshape the skull with minimal resistance from the bone. The bone cuts are essentially creating a temporary skull defect that allows the brain to return to a normal shape and grow normally and reshape the skull until the bone heals in.
After the procedure a helmet is worn to allow the baby to lie on the back of the head and relieve the pressure from the weight of the head from the parietal bones. Allowing the baby to lie on the back of the head improves the efficiency of reshaping the skull because it makes it easier for the brain to push the parietal bones outward and expand back into a normal shape. It also allows normal growth of the brain once the initial rapid expansion back to a normal shape has occurred. Infants are able to heal large bone defects of the skull with new bone up until about 1 year of age. The areas where bone is removed in this strip craniectomy procedure typically heal in by 3-4 months after surgery. The figures below show the location of the bone excision in red and expected movement of the skull bones in blue and green. Read more about my approach minimally invasive extended sagittal strip craniectomy.
Open Cranial Vault Remodeling
Children with sagittal synostosis who present at an age of older than 4 months are treated with open cranial vault remodeling. Excellent results can be achieved with open cranial vault remodeling, so parents should not despair if their child is diagnosed with sagittal synostosis after age 4 months of age. After the age 4 months the skull bones and scalp are typically too stiff to achieve the desired changes in head shape using strip craniectomy procedures. Surgery is usually performed between ages 6-12 months old for open cranial vault remodeling. There are many, many techniques used for open cranial vault remodeling for sagittal synostosis. Common strategies of open cranial vault remodeling procedures include the following elements. An incision is made from ear to ear. The skull bones are removed from the most abnormal areas of restricted and compensatory growth. The bones are then reshaped by hand and reattached to one another and the skull with dissolvable sutures or dissolvable plates to correct the head shape. In general, cranial vault remodeling procedures for sagittal suture craniosynostosis are aimed at restoring the normal proportions of the skull by increasing the width and decreasing the length of the skull. The figures below show patients before and after open cranial vault remodeling for sagittal synostosis. Note that these patients differ in the location of the most severe compensatory growth. The first patient has greater compensatory growth in the front of the skull and the second patient has more compensatory growth in the back portion of the skull.
Comparing Open Cranial Vault Remodling and Sagittal Strip Craniectomy
The minimally invasive extended strip craniectomy procedure for sagittal synostosis has several advantages when compared to traditional open procedures. The procedure and anesthesia time are shorter for the minimally invasive extended strip procedure (2-3 hours anesthesia time) than open procedures (4-6 hours anesthesia time). The hospital stay is shorter - 2 days for the minimally invasive strip procedure - compared to a 4-7 day hospital stay for open cranial vault remodeling procedures. The blood transfusion rates are lower for the minimally invasive procedure - 50% or less - compared to almost 100% for open cranial vault remodeling procedures (CVR). There is significantly less scarring in the scalp with the minimally invasive strip procedure and these incisions tend to heal better and are much less visible than the ear-to-ear scars required for open CVR procedures. Some surgeons will downplay the importance of the scarring on the side of the head from a coronal (ear-to-ear) incision, but the scarring is stigmatizing and is frequently what patients are most unhappy with when they get older.
Downsides of sagittal strip craniectomy is that the treatment time is longer due requirement for a molding helmet to be worn for about 1 year. No helmet is needed after open CVR making the treatment time with this approach faster. Both strip craniectomy and open CVR procedures are safe and have equivalent complication and revision rates. Read more about my approach minimally invasive extended sagittal strip craniectomy. The minimally invasive sagittal strip gallery images show many representative cases demonstrating typical results.
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