What causes my frontal eminences to be so prominent? (photos)

Some people just have more prominent frontal eminences than others.  They often become increasingly obvious with time as hairline recession exposes them to more direct light (creating the shadows you've noticed) and loss of volume from the the temporal fat pad on either side of them makes them appear relatively larger.  They can be reduced with surgery using a burr to smooth them to some degree.  Unfortunately, even if the reduction is done with a small camera called an endoscope, it will leave several scars.  The scars can be hidden under your hair, but any recession would make them visible.   Explaining to people that you have a prominent bone is probably easier than explaining the procedure you had to remove prominent bone.  Consider using a filler to fill the temporal fossa to the sides and maybe even the area between the prominences.  

Bryan Rolfes, MD

Not uncommon for males to have this issue. If it bothers you, it can be smoothed out. Foreheads cannot be perfectly smooth but if there is a specific area that bothers you then it can be improved. It does require an incision in the scalp. Good luck

This would depend on whether you've had a procedure previously.   If this is the case, then it could be seroma, scarring, or post operative changes. If you have not had a procedure, a follow up question would be if you've had the prominences previously or this is new development.  Each would require a different work up.