Have you ever wondered why you get brain freeze or ice cream headaches? Why should eating something cold give you a headache? Or have you wondered why pain in your arm is a symptom of a heart attack?
These are both examples of referred pain, where pain in one part of your body is actually felt in a different part. The ice cream headache is really pain in the top of your mouth, and the arm pain actually is pain in your heart, but your brain thinks it’s coming from your arm. Referred pain may seem strange, but it’s actually very common, and if you want to find the source of your chronic pain, you have to understand the phenomenon.
Understanding the Cause of Referred Pain
In the modern age, we often compare nerves to a network of wires or fiber optic cables, which is sort of accurate because they carry information between parts of our body. But our nerves are made up of living cells in an organic network, so they don’t work like wires or cables.
A wire is connected between two specific points and will only carry signals from the one point to the other, but your nerves aren’t so specific. They’re designed to pass signals in multiple directions and sometimes nerves get so excited by the signal a neighboring nerve is sending, they will send it, too. This means that when nerves go from individual strands into a bundle, the signals the bundle carries could be from any of the nerves on the bundle.
Your brain understands how your nerves work, and it tries to account for it by making a judgment call when the signal reaches it. It looks at the message and says, “this looks like a signal from the arm.” Usually it’s accurate, but sometimes it makes a mistake.
Adjacent Nerves and Referred Pain
In most cases of referred pain, the two nerves involved are adjacent. This means that the place the pain is actually coming from and the place your brain thinks the pain is coming from are right next to each other, or on the same branch nerve. For example, pain from your forehead and the roof of your mouth both travel along the trigeminal nerve, which is why your brain thinks the pain from a cold drink is coming from your head.
Another way nerves can be adjacent is by entering the spinal column at the same point. For example, the nerves from your heart and from your left arm enter the spinal column at the same place. The same is true of nerves from your your shoulder blade and those from your stomach, gallbladder, liver, and other organs.
Learned Referred Pain
There may also be times when your brain comes to expect a certain pain so tends to interpret new pain as being the old pain it expects. For example, if you suffer an injury that causes chronic pain in a particular part of your body, your brain may think new pain is coming from that area, too. This may persist long after your injury is healed.
To some extent, all referred pain is learned. The reason your brain thinks pain from your organis is actually coming from your limbs is that it’s used to pain coming from your extremities, while organ pain is relatively rare.
Nerve Pain Becomes Referred Pain
Another cause of referred pain is when the nerve itself is in pain. If the nerve is irritated, pinched, or pressured, you may feel pain at the point where the nerve is experiencing pain, but it’s more likely that you’ll experience the pain as being from any of the tissues that it reports from. Sciatica is a common type of this pain–the nerve is being irritated at the spine or in the pelvis, but you feel the pain (as well as numbness or weakness) in your legs.
Referred Pain and TMJ
TMJ can cause many different types of pain, especially pain anywhere in your face. Your face, head, eyes, and teeth all report pain along the trigeminal nerve, the same one that reports jaw pain.
TMJ may cause referred pain in any of these places by causing jaw pain that gets referred to them, or it may be irritating the trigeminal nerve, which reports its irritation as coming from any of the tissues it reports from.
The good news is that this means TMJ treatment can take care of all these pains, as well as neck pain, back pain, and others all at the same time.