Someone recently asked this question on one of the forums and I thought it was a very good question the answers for which may not be immediately clear. First of all, I think it is important to define exactly what is meant by ‘neuralgia’. The prefix ‘neur’ simply refers to a nerve and the term ‘algia’ means pain. Therefore, simply put, neuralgia means pain cause by a nerve or nerves. The question always becomes which ‘neur’’ is causing the ‘algia’ and if you can answer that question, can you then do something about it?
Occipital neuralgia (ON) is a neurological condition in which the occipital nerves are irritated or compressed (i.e. pinched) and hence cause pain. The typical symptoms are episodic (i.e. paroxysmal) bouts of “lightning-like” pain in the back of the head although as many of you know and as I have blogged about many times, the symptoms can vary widely. Because each person is unique, they will each experience pain differently. Similarly, trigeminal neuralgia (TN) is a neurological condition in which the main trigeminal nerve trunk is compressed. Not surprisingly, the classic symptoms are episodic bouts of “lightning-like” pain in the face which are the areas innervated by the various branches of the trigeminal nerve. These sets of nerves are not physically connected so why is it that ON often co-exists with TN? The answer lies in the anatomy. I will have a picture of a peripheral nerve included in this post to help illustrate the points I make below.
Many people don’t realize that the upper-most, neural elements in the neck (e.g. the occipital nerves) have a common connection zone in the medulla which is a part of the brain stem, with the cell bodies forming the trigeminal nerve before continuing into the upper cervical spinal cord. This zone is known as the cervico-trigeminal complex and can potentially explain why discomfort from lesser occipital neuralgia may sometimes also be referred to the trigeminal nerve territories anteriorly. Referring to the image of a neuron (i.e. nerve cell) below, you can see that when the long part (axon) of the nerve is injured (e.g. in a whiplash accident), the whole nerve becomes inflamed including the cell body. This injury is depicted in #1 in the attached image. When the cell body of a cervical nerve (e.g. one that begets the greater occipital nerve) is chronically inflamed, the adjacent cell bodies (e.g. those of a trigeminal nerve branch – for example, the supraorbital nerve) also become inflamed. This injury is depicted in #2 & #3 in the attached image. Then the axons of those latter nerves cause pain in their respective nerve distributions (e.g. in the forehead in the case of the supraorbital nerve). This injury is depicted in #4 in the attached image. In this way, an injury to the GON can ultimately result in forehead discomfort. To use an analogy close to home here in California, think of it as a forest fire that has burned too long and the embers from one part of the forest jump the clearing to the adjacent wooded area and cause a fire there.
Hopefully, it now becomes clear why ON and TN often co-exist. It is usually the case that one begets the other and I have seen countless patients in my office whose pain started in the neck area and eventually spread elsewhere. Fortunately, the process can also reverse itself. I hope everyone finds relief this holiday season. Happy Thanksgiving.