The muscles that control the position and movement of your jaw are all controlled by a single branch of the trigeminal nerve. The nerve fibres allow for muscle contraction and relaxation, and also the sensory feedback signals the provide information about jaw position sense. Here is the fascinating part: the group of brain cells that receive that sensory information (called the spinal trigeminal nucleus) actually descends to the level of C2 (and even as low as C4) in the upper cervical spine!
The importance of this arrangement is not to be underestimated! The vertebrae in the upper part of your neck - specifically the C1 (atlas) and C2 (axis) - contain thick ligaments that anchor onto the spinal cord. These ligaments assist with normal protection of the spinal cord. However, if you have ever suffered a whiplash-type injury where your head snapped back-and-forth, it can disrupt the normal alignment and motion of these vertebrae. If that happens, the normal protective function of these ligaments can create a physical pull on the brainstem, which can lead to neurological or other health issues.
Now, your body is not so fragile that things will break down all at once. Instead, your body will work to compensate by shifting the pressure into other parts of the body, potentially affecting head, neck and jaw position. … And in order to affect jaw position, your brain will change the activity of the muscles that allow you to move your mouth, causing one side to relax and the other side to tighten.
This change - multiplied by days, weeks or even years - can cause the TMJ to start to rub, and voila (!), you can experience a clicking jaw. As I mentioned before, a clicking jaw doesn’t always have pain associated with it. That said, if you experience clenching, tension or grinding (called bruxism), these may also be indicators of the underlying problem. If left to progress, the symptoms can evolve into nastier things including headaches on the side of your head or the back of your neck, a variety of TMJ disorders, a condition known as trigeminal neuralgia, arthritis and even fibromyalgia. And all this not even starting in your jaw, but all stemming from an issue with the alignment and movement of your upper neck.