In this video, I would like to review the anatomy of the corrugator muscle with regards to botulinum toxin treatment. If we look at the origin of the corrugator muscle, it is deep on the medial aspect of the superciliary arch of the orbit. From this region, it will go up and oblique laterally and become more superficial. We can see here that the fibres will actually pass through the frontalis and that the corrugator itself has a dermal insertion. Accordingly, when we target this muscle with botulinum toxin, we need to inject the origin deep onto the bone. However, we must inject the tail superficially using a subdermal injection. If for any reason we inject too deep here at the tail, the product will track behind the muscle and potentially affect the levator palpebrae muscle, the muscle responsible for elevating the eyelid. Accordingly, we could end up with a lid ptosis.
In this video, we are going to review some of the forehead. If we start from the skin layer and reflect this back, we will notice that there is a scant amount of subcutaneous fat just below the skin. Below this fat layer, we have the muscle layer, the main muscle being the frontalis. The frontalis is a paired muscle, which often has a gap in the middle, and it originates from a posterior aponeurosis. The fibres then interdigitate with fibres of the orbicularis oculi, corrugator, and procerus. Laterally, we have the temporal fusion line, and we almost never find fibres of the frontalis lateral to this area. If we reflect the frontalis back, we will notice that it sits on a firm layer called the galea. Below the galea is the periosteum, and if we look on the other side we can see that there is a close connection between the periosteum and the galea, and that there is a sliding space between the two. This allows the movement when the frontalis contracts and we raise or drop our eyebrows. As we move the frontalis back into position, we can also notice the presence of some superficial blood vessels, and these are branches of the supraorbital and supratrochlear arteries. These arteries have a deep origin, emerging from the skull through foramina, and after a variable distance become more superficial. On the other side, we will see the supratrochlear artery, emerging from the skull, as it is just visible on the underside of the soft tissue. We can see therefore in the lower pole of the frontalis that there are very few blood vessels visible. However, after approximately a centimetre and a half, the blood vessels cross through the muscle fibres and become more superficial. Therefore, if we inject in the upper part of the forehead, we are safe as long as we inject deep. Closer to the glabella, however, we must inject superficially in the subdermal plane or extremely deep with a cannula.
In this video, we will explore the use of dermal filler in forehead filling. We’re going to use a needle technique and avoiding the vessels that are found more inferiorly, we adopt a mid-forehead approach, and we inject the filler deep, aiming for the periosteum. We will use boluses of product, deep. Having injected the filler, we will apply a bit of manual pressure just to smooth it out. We will now dissect the various tissues to indicate the location of the injected product. As we just start dissecting the skin back, you will immediately notice the presence of large vessels just under the skin. This is the reason why, when we inject the product, we must be in the deep plane, to avoid these vessels. After further dissection, we are aware of some vessels in the glabella region. As I pull the skin back, you can see how superficial these vessels are. Many experts advocate the use of filler superficially to fill glabella lines, however, it would take a lot of skill to ensure that you are not going to hit one of these vessels. Accordingly, I suspect that possibly the best technique in this region is maybe to use a cannula and be deep to avoid these vessels on the bone. As we continue to dissect the muscle away, we will start noticing the presence of the filler. This filler is trapped between the galea and the periosteum, which we are now dissecting away. This is the ideal placement for filler in the forehead as it avoids all of the vascular structures.