Russell Mackenzie has written this blog to explain one of the most important ideas about headaches/migraines that has been discovered recently – the trigeminocervical nucleus. Understand this idea and you are on the way to understanding how something like a food or a smell or even a normal hormonal cycle can provoke headaches and migraines.
Back in the mid nineties, a group of Australian scientists (Bogduk and team) discovered a structure called the trigeminocervical nucleus. This was a big deal. It was now possible to give an anatomical explanation for what so many people experience with their neck and headaches.
So what is the trigeminocervical nucleus?
The trigeminocervical nucleus is an area in the lower brainstem (in the skull not far above the top of the neck), that receives information from areas that the trigeminal nerve supplies (see diagram) and also receives information from the top three spinal nerves of the neck (spinal nerves of C1, C2 and C3).
There is what is called ‘convergence’ of these inputs. This gives the neuroanatomical basis for how ‘danger messages’ (nociception) from upper cervical structures can be felt as pain anywhere in the head, This includes areas like the forehead, behind the eyes, nose, jaw, and anywhere on the scalp or back of the skull.
Have a look at this diagram. You can easily see that between the trigeminal nerve and the cervical nerve, the entire head is accounted for. This diagram shows you the breakdown of which nerves supply which area.
So how does your neck refer pain to the head?
I’m sure you have all experienced referred pain whether you know it or not. This is when one part of the body has a nociceptive signal (danger message) that creates pain in another area, sometimes at a distance. One example is the shoulder pain you can get after abdominal surgery that irritates your diaphragm (in this case the phrenic nerve is involved, which is supplied by C3-5, and your shoulder is also supplied by C3-5).This occurs because the danger is ‘assigned’ an area to be felt on a virtual map of your body when the danger message is being assessed by your brain. And sometimes the area that is assigned is incorrect ie abdomen-shoulder or neck-head in the case of headache/migraine.
But this is just part of the story. Next time, I will explain another way that has been proposed to explain headaches and migraines involving the trigeminocervical nucleus.