Background: The shape of the skull is influenced by a variety of structural elements within it as well as external forces. The internal elements are mainly the suture lines around which the skull bones form and are shaped. The sutures lines have a major influence particularly where they join other suture lines. These junctional areas are well known in newborns and babies as the fontanelles.
The fontanelles are the soft spots of the newborn skull which occur most prominently at the junction of the sagittal suture line and the paired coronal sutures lines (anterior fontanelle) and the sagittal suture line and the paired lambdoidal suture. (posterior fontanelle) They are other fontanelles (sphenoidal and mastoid) but they are at the base of the skull and thus not visible. The fontanelles are open at birth to allow the brain to rapidly grow and close secondarily over time with bone ingrowth. The posterior fontanelle closes soon after birth (2 to 3 months) while the anterior fontanelle does so much later.
One of the unrecognized types of aesthetic skull depression/indentations is at the location of the original fontanelles. While these originally open areas fill in with bone they may not always do so completely to match that of the surrounding skull areas. This is particularly seen at the posterior fontanelle area at the upper back of the head. There can be a contour depression which may have various surface irregularities to it. In some cases it is associated with a high posterior sagittal crest in which each one magnifies the appearance of the other.
Case Study: This male had a prior history of a successful posterior sagittal crest skull reduction surgery to take down a high midline peak. The scar was well healed and barely detectable. He now desired to have the contour depression behind the reduced sagittal crest augmented. A 3D CT scan showed the contour depression at the upper back of the head which was associated with paired holes which represent perforating vessels through the bone.
A custom skull implant was designed to fill in the depressed areas and blend out smoothly with the surrounding skull. In other words, the footprint of the implant always needs to be greater than one would think to create a natural contour shape.
Under general anesthesia and in the prone position his existing fine line scar from his proper sagittal crest reduction surgery was opened. Wide subperiosteal undermining was done beyond the marked outline of the implant on the scalp. Once the pocket was developed the custom skull implant was prepared by placing perfusion holes through it as well as checking to make sure all the edges were as smooth as possible.
The implant was then rolled, inserted and unrolled once inside the pocket. The implant was positioned as designed and secured with double screw fixation.
His immediate intraop results showed the improved contour over the original posterior fontanelle site of the upper back of the head.
Case Highlights:
1) An underdeveloped posterior fontanelle region of the skull is frequently associated with a posterior sagittal crest deformity.
2) The posterior fontanelle skull deficiency is at the upper back of the head just above the junction with the lambdoidal suture lines.
3) A custom skull implant design provides the best contour restoration is this area of the back of the head and can be placed through a previous sagittal crest skull reduction incision.
Dr. Barry Eppley
Indianapolis, Indiana