Background: The skull is a collection of differing curved bone shapes that create an ovoid shape that is somewhat similar to that of an egg. (wider in the back than in the front) But because of its complex shape and the large number of developmental factors that come into play in its formation skull asymmetries are not rare. They can occur in a wide variety of geometric manifestations from flat spots, indents,to bulges. There are a few distinct types of skull asymmetries that are deformationally syndromic such as plagiocephaly. But many skull asymmetries defy a specific reason as to their occurrence.
One unique type of skull asymmetry is a linear depression running from front to back. When that occurs in a bilateral presentation it can be associated with a scaphocephalic head shape of which the most severe would be sagittal craniosynostosis. But when it occurs on just one side and is moderate by comparison there is no good explanation as to why. This is appears a unilateral depression from the forehead back along the parasagittal area to the back of the head.
In treating such a linear skull depression they are often large in surface area but not necessarily as thick (deep) as one might think. This is where the custom implant design process has a huge advantage. Using a mirroring technique from the opposite normal side the exact dimensions of what is missing can be determined from which the implant is designed. This becomes particularly relenant when the scalp incision needed to place it is going to be small. (blinded implant placement)
Case Study: This male had become bothered by his forehead/amterior skull asymmetry once his hairline started to regress. His right forehead had an indentation that ran the whole way to the back of his head. His 3D CT scan showed the linear depression/asymmetry on the right side of his skull.
While the asymmetry extended into the parietal and occipital areas on the back of his head, his interest in correction was only the forehead and the top of his head. His right-sided custom skull implant was only 3.5mm thick at its greatest with a total volume of 21ccs.
Under general anesthesia and through a 3.5cms scalp incision just behind his right frontal hairline the subperiosteal pockets were dissected out down into the forehead anteriorly and back onto the parietal bone posteriorly. The implant was inserted and secured with two micro screws through the incision. The incision was then closed over a drain in multiple layers with small resorbable sutures.
Intraoperatively the improvement in the skull asymmetry could be immediately seen after placement of the custom skull implant.
When the head dressing and drain was removed the next day the improvement in the anterior half of the skull asymmetry in the non-hair bearing scalp could be seen.
Correcting skull asymmetries is often a matter of just a few nmilliemeters. This is particularly true in forehead asymmetries. The asymmetry is as much about the extent of surface area involvement as it is about the amount of thickness of the asymmetric/missing bone. It would be impossible with any method of skull augmentation to get an accurate skull Asymmetry merry correction
Key Points:
1) Skull asymmetries come in a wide variety of shapes of which the linear skull depression is one type.
2) A custom skull implant design is the most effective method to get the correct surface area coverage and thicknesses of the linear depression.
3) A linear custom skull implant is optimally placed through a small incision centered off the mid portion of its length.
Dr. Barry Eppley
World-Renowned Plastic Surgeon