There are 5 main differences between male and female foreheads:
1. The main difference between male and female foreheads is that males tend to have a ridge of bone running right across the forehead at about eyebrow level called the “brow ridge” or “brow bossing” while female foreheads tend to be smoother and flatter and have little or no bossing.
2. Male foreheads often have a slightly backwards slope to them while female foreheads tend to be more vertical.
3. Masculine foreheads also often have an indented area above the bossing. Sometimes this indented area is only in the centre of the forehead but sometimes it runs right across from one side to the other. This indented area can make the bossing below it look much stronger than it actually is.
4. Male foreheads are more likely to have pronounced vertical ridges (temporal lines) running up either side.
5. Male foreheads may have stronger and more prominent muscles which combined with less fat under the skin can emphasise frown lines.
Here is a cross section through the skull so you can see the hollow frontal sinus clearly:
Surgical Options for Brow Bossing:
The outer third or so of the bossing that the eyebrows sit on is called the “supraorbital rim”. This is usually solid bone and can simply be ground down by the surgeon. The middle third or so of the bossing is called the “glabella”. The glabella is usually hollow and the hollow area is called the “frontal sinus”. The fact that the bossing is hollow here can make it much more difficult to remove. If the glabella has a thick wall of bone at the front, the bossing can be removed by simply grinding down the bone, however if the wall of bone is thin it may not be possible to grind the bossing away completely without breaking through it into the frontal sinus. FFS surgeons have taken 3 main approaches to solving this problem:
Option 1: Shave and Fill
Some surgeons grind down the wall of bone as far as possible without breaking through into the frontal sinus and they then build up the area around the remaining bossing with bone cement. The bone cement smoothes out any visible step between the remaining bossing and the rest of the forehead to give a smooth and feminine appearance. In these cases some additional reduction in the bossing can also be made by thinning the soft tissues that sit over it.
Option 2: Forehead Reconstruction
Most FFS surgeons can perform a procedure called a forehead reconstruction where the wall of bone is removed, taken apart, thinned, re-shaped and put back together in the new feminine position with titanium wires or titanium screws and microplates. Forehead reconstruction is the most complex technique but also the most powerful.
Option 3: Compression
Some FFS surgeons now offer a compression technique in appropriate cases where the wall of bone is first weakened and then compressed into place. It then heals in the new position.
To access the bones of the forehead in all 3 options an incision can be made across the top of the scalp from ear to ear (this is called a “coronal” incision). This means that unless you are suffering from baldness, any scar will be well hidden by your hair. If you are having a scalp advance to adjust your hairline as well as forehead work then the incision will be made along the hairline instead of over the top of the head. In both cases the skin of the forehead is then pulled down to reveal the forehead bones. Some surgeons access the bones endoscopically using smaller incisions but with this technique it is only possible to shave down the bones - it cannot be used to perform a forehead reconstruction. There is less scarring and nerve damage from an endoscopic procedure but the bruising and swelling seems to be somewhat worse.
Bone filler paste can be used to fill in various indented areas like the one that males often have in the centre of the forehead.
Surgical Options for Frown Lines:
Frown lines can be removed or reduced by working on the muscles underneath. This is often done during a brow lift or forehead surgery. If this is not an option you can often fill the lines with an injectable filler or relax the muscles with botulinum toxin ("Botox") for a temporary improvement.
The Great Forehead Debate!
There is a great deal of heated debate in FFS circles from both patients and surgeons over whether option 1 or option 2 is better in cases where the bossing is prominent but the frontal bone is thin. Some feel that a reconstruction is too invasive and that disguising the bossing with the shave and fill technique is just as good as removing it; others feel that disguising the bossing is an unacceptable compromise that can sometimes leave the forehead with an unnatural bulge. The following pictures might help to explain the debate. Please bear in mind that the pictures are for illustration purposes only and do not show all the details of forehead anatomy. Let's start by looking at a forehead with strong bossing:
We can’t tell from looking at this picture whether the bone over the frontal sinus is thick or thin. To know that, we have to look inside the forehead and that would require an x-ray. Lets look at 2 potential interiors for this forehead:
As you can see, the first one shows a very thick bone over the frontal sinus, the second shows a very thin bone. I have added a red line to show an ideal female bone structure. With the thick bone, the surgeon only has to grind down the bone to the desired level and there will still be plenty of bone left to cover the frontal sinus as you can see.
With the thin bone you can’t grind it down to the ideal line or very much at all without breaking through into the sinus. In this case, most FFS surgeons will perform a forehead reconstruction so after grinding down what they can, they actually take the wall of bone apart, re-shape it and move it backwards to the desired position so that it ends up something like this:
So, grinding down thick bones or doing a forehead reconstruction on thin bones both have the same result - the bossing is removed.
The controversy usually begins when a surgeon who does not do forehead reconstructions tackles the thin boned type of forehead. As I mentioned above under "Shave and Fill", they approach it by grinding down what they can and then building up the areas around the bossing with bone cement to disguise the bossing. They might also thin the soft tissues that sit over the bossing. Here's a picture to illustrate this approach (the bone cement is in yellow):
As you can see, the new forehead bulges forwards of the red line but it is smoothly rounded without a clear ridge.
Now, let us compare the end results for these 2 different approaches to thin frontal bone problem. The picture on the left shows the result of the reconstruction and picture on the right shows the result of the shave and fill technique:
As you can see, the difference from the outside is the degree to which the forehead bulges with the shave and fill forehead bulging forwards more than the reconstructed one. I would argue that the flatter, reconstructed forehead is closer to the forehead the patient would have had if she had been born female. However, the more bulging forehead is still feminine and the technique used to feminise it is potentially less invasive. On the other hand, I only rarely hear of significant complications associated with forehead reconstructions - certainly not as many as are associated with chin or nose surgery. Then again, if the shave-and-fill forehead also looks feminine why bother with the more invasive reconstruction?... and so the debate goes on but basically, if you want to remove the bossing rather than disguise it, then you may need to consider a forehead reconstruction depending on how thick your frontal bones are.
The two end results I have shown you are more extreme cases (although both quite common). In the case of the medium-thickness bone it is not always so clear and the difference in the end result between the reconstructed forehead and the non-reconstructed forehead is not as extreme as you can see in the next pictures - the picture on the left shows the reconstructed forehead and the picture on the right shows the shave and fill technique on medium thickness frontal bones:
All the same arguments still apply about which looks more natural or is more desirable but the debate is less fierce because there is less to choose between the two. If you are not at all bothered by the bulge in the non-reconstructed foreheads, that is fine, and you needn't worry too much about the particular technique your surgeon uses. If you are bothered by the bulge then you need to get an x-ray of your forehead to see which technique you will need for the forehead you desire. Not all surgeons offer an x-ray at consultations so be prepared to visit more than one surgeon to get all the information you need.
Here's my own x-ray as an example and you can clearly see in it that I had very thin bones over the frontal sinus: