Advanced Dissection 2 - Mental Nerve
philosophised at 5:32 AM
Today we started doing our electives dissecting the lower jaw. Other groups got different parts of the body ranging from the arms to the brain (which is quite interesting I think) to the neck. It is nothing like our routine dissection that we are having in our core programme now, which is quite crude, with severed nerves and vessels everywhere, to be honest. In this elective we have to be really meticulous and take our time to dissect the structures in a presentable manner.
Having been told that if we produce a really good specimen, we'll stand a chance of getting it published somewhere, we decided to go about doing everything really gingerly.
We (Edward, Sarah and I) were given a head (yes, a real head) that is literally split vertically into half in the centre. It belongs to an old man. You can see all the wrinkles and hair on the face, and if you turn it over, you can see half the brain, half the tongue and half the nose inside half the head. I actually felt really grateful and touched that he decided to donate his body for us. I don't know who he was, but I know that he used to be a living human with a story behind him.
We spent quite some time discussing how to go about doing it. Unlike our routine dissection, we were not given a dissection guide so we have to plan our incisions from first principles. We talked about things like if we should flap the skin forward or backward to best present the structures (and that depends a lot on the location of the nerve of interest and which direction it runs). We discussed on how deep the incision should be, the boundaries. In the end we settled on cutting a rather small, probably 5cm x 5cm flap of skin on the chin area (circled below). That's where this nerve called the mental nerve emerges from the jawbone. It provides sensory innervation to the lower chin, lip and a bit of the gum at the front of the mouth. During facial surgery local anaesthesia can be administered to numb this area by blocking this nerve.
However the most important point of finding this nerve is such that we can trace it all the way back, through the jawbone, where it branched off from another nerve called the inferior alveolar nerve. The inferior alveolar nerve is the whole point of our group doing this elective, because we are investigating how the inferior alveolar nerve can be damaged during wisdom tooth extraction, as it passes right through the root of the tooth. Dentists got sued a lot if this nerve is damaged, because it can be a bit of a problem if you can't feel anything at the front of your mouth, and it can affect speech and chewing as well. Very unpleasant, considering how wisdom tooth extraction is one of the most common procedures performed.
We started by cutting vertically down from the corner of the mouth, stopping just about 1cm above the lower border of the jaw. At the same time, we cut the lower lip transversely across into half, and then cut the gum in front the teeth (or where they should be, since the old man had lost all his) and peeled it away from the jawbone (it is actually very easy to peel the gum off the bone, I can do it by just sticking a finger in, waggle a bit and the gum is detached). We then spent pretty much most of our time sticking scissors in and opening the scissors up (not actually cutting through anything, but rather displacing the nerves and vessels away using the outer edges of the scissors, while tearing connective tissues at the same time to avoid damaging anything). I'd say it's some really delicate work, and I must say it almost definitely helps to improve our surgical skill should we choose to be surgeons next time.
At the end of the three hours I think we will never ever forget the function of the mental nerve and its course along the lower jaw — we just spent 3 damn hours looking for it and then nursing over it like a baby.
