Background: The back of the head is usually a smooth convex shape. While the amount of convexity will vary amongst different people, protrusions on its outer surface are not usually seen as aesthetically desirable. Thus the discrete occipital knob deformity stands out.
The occipital knob deformity is a well known central bony protrusion just above the bottom of the occipital bone. It sticks out like the knob in its name. It is most typically composed of a large growth of bone that develops centrally at the nuchal ridge line. It is a thicker than normal protrusion of bone which when reduced solves the occipital contour concern.
The occipital knob skull deformity is also known as the occipital bun or occipital horn. It is well known to occur in Neanderthal skulls but much less commonly so in modern man. Why it occurs is not known but it is always thought of as a pure bone excess. But in its aesthetic reduction the overlying soft tissue must be considered as well.
Case Study: This 35 year-old male was bothered by the bump on the back of his heads. It was also associated with a thick overlying scalp and a horizontal skin crease both above and below the bump.
Under general anesthesia and in the prone position, the occipital knob reduction was approached through the lower skin crease in non-hair bearing neck skin. The bony bump was identified and reduced down to the surrounding skull bone with a handpiece and burr. Surprisingly the size of the occipital knob was less than its outward appearance would suggest. There was a very thick fibrofatty tissue layer between the skin and the bone which was excised and thinned out. Redundant overlying scalp was also excised. A small drain was then placed and the wound was closed in layers.
His immediate intraoperative results showed a significant flattening effect to a more normal contour. In this case such a reduction would not have been possible without concurrent soft tissue thinning as well. It appears that in some occipital knobs the overlying scalp becomes thicker than normal, much like that which has occurred with the underlying bone.
Highlights:
- The occipital knob deformity is not always a pure bony deformity.
- Some occipital knobs have a significant soft tissue component that must also be removed to optimize the flattening effect.
- The lowest horizontal skin crease should be used to reduce this type of occipital knob.
Dr. Barry Eppley
Indianapolis, Indiana