The Role of Your Central Nervous System in Chronic Pain

Central amplification of chronic back pain

The brain and spinal cord receive signals from your nerves and also send out massive patterns of signals to our muscles that control our arm, leg, and spine movements. These signal patterns develop over years and explain how we learned to walk, run, ride a bicycle, dribble a basketball, and even play a musical instrument. The signal patterns constantly update the spinal cord to include the status of sensors that detect our muscle flexibility, strength, and endurance.

We think chronic pain starts when these sensors in your muscles (peripheral signals), misfire or malfunction, and your brain and spinal cord adapt improperly to those malfunctioning sensors and become “short-circuited.” In a way, what happens is the spinal cord amplifies a normally harmless pain signal, which creates a loud chronic pain signal.

When your pain signals become amplified, your central nervous system latches onto these signals or recognizes them as intensely painful. This makes it so that even harmless stimuli appear to be intense pain signals.

Doctors commonly hear that chronic pain patients have a high pain tolerance. This central sensitization process explains exactly what patients like you have been telling us. We understand that you have been doing your best to ignore these extremely loud pain signals. The best explanation for this is that your typical achy or sore muscle pain, that others would rate only as a one or two out of ten pain intensity, has become amplified. Now your pain is at an intolerable eight, nine, or ten out of ten pain during common activities such as standing, doing dishes, or walking.

Based on that, the best medical understanding for chronic pain is the entire system of microscopic pain sensors and the central nervous system has become “short-circuited,” making normal achy muscle pain signals seem unbearable.

Your pain may feel like a pinched nerve

It can be useful to think of these peripheral nerves from your spine as if they are wires transmitting electricity to a light bulb. If an electrical wire were cut or compressed, you could expect that the light bulb it’s attached to would not shine as brightly. The same concept works for pinched nerves.

When pinched nerves occur, people complain of a shooting pain down the leg or abnormal sensations below the knees and into the foot and ankle. By checking ankle strength, toe strength, reflexes, and nerve-tension signs, your doctor can determine whether you have a pinched nerve or not. A pinched nerve will usually result in weakness in the ankle and foot muscles that gets much worse with standing or sitting with your knee extended.

If a particular nerve root does get pinched, spinal injections and even surgery may be possible to give that nerve root more space. This explains why back surgery is helpful for patients who have radiating leg pain, but is not helpful for patients with only back pain.

Understanding how central amplification affects your back pain is important

Central sensitization, or amplification, of chronic pain is a real phenomenon. As peripheral pain signals are sent to the spinal cord, tiny cells determine whether the spinal cord nerve cells should respond or not. For example, an itchy sensation, or even a sensation of having one’s sock fall down is typically filtered away from the spinal cord as not important and this signal would normally be filtered.

A weak, stiff, or poorly contracting muscle’s signals can be amplified and then interpreted as pain. When your spinal cord has become exceptionally irritable, instead of filtering normal pain signals, it incorrectly amplifies them. Some patients have intense pain with even the weight of a bed sheet over their feet or while engaging in physical activities that are followed by increased pain. When this occurs, we call it central amplification of the peripheral pain signal.

It is important to understand that this central amplification process is not voluntary. You are not doing this yourself. Your spinal cord has amplified a particular peripheral pain signal so that it is interpreted as unbearable.

Last reviewed: 
April 2018

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