Background: The most recognizable skull deformity on the back of the head is the occipital knob or the overgrown inion which is seen most commonly in men. It appears as a solitary midline projection sticking out of the lower end of the occipital bone. It presents in variable sizes from a small bump to a large protrusion. Why the inion develops a larger size to make it more visible is not known.
The occipital knob can always be completely removed due to the thickness of the skull in this area. Due to the attachments of the neck muscles on the lower end of the visible occiput the bone naturally gets thicker. And most inions have a thickening on the inside of the occipital bone opposite the knob, further increasing the bone thickness over other skull areas. As a result occipital knob removal is both effective and safe.
Many patients that present for occipital knob removal are males with shaved heads. This is not surprise since any lump or bump on such a head is very visible. While the inion is the most common hard tissue solitary bump on the head, the most common soft tissue isolated bump is that of a lipoma. Can a bony knob and a lipoma occur in the same shaved head patient….statistically possible but I have never seen it until now.
Case Study: This shaved head male presented with two bumps on the back of his head. A large midline bony mass on the bottom of the occipital bone and a softer squishy round mass over the left mastoid area.
Under general anesthesia and in the prone position an incision was made in a horizontal skin crease below the occipital knob for its exposure. The depth of occipital knob removal was initially made with a deep bone cut down its midline. A similar deep bone cut was then made in the transverse direction creating four separate bony mounds. Each individual bony mound was then burred flat. The bottom end of the reduced knob was further burred down so that it curved inward.
After closing the occipital knob excision site the left mastoid lipoma was excised through a horizontal skin crease above it.
Both back of the head bumps were reduced in one procedure.
The result of the large bony knob removal was a dramatic change in the profile of the back of the head.
Key Points:
1) Large occipital knob can be completely reduced through a nearby scalp skin crease.
2) Complete occipital knob reduction may enter the diploic space of the prominence.
3) The most common soft tissue mass of the scalp is a lipoma which in this case produced a circular soft tissue mass over the mastoid bone behind the ears.
Dr. Barry Eppley
World-Renowned Plastic Surgeon