Amplified musculoskeletal pain syndrome (AMPS) is a very painful medical condition. It frequently affects a limb (a foot or leg more commonly than a hand or arm), but can cause pain anywhere in the body. In fact, children with AMPS can experience pain throughout most or all of their bodies.
Most children with AMPS have constant pain, although some children experience intermittent attacks of pain followed by pain-free periods. Whenever it occurs, the degree of pain children with AMPS experience is more intense than one would normally expect because the pain signal is amplified.
First, look at the illustration to see how people normally feel pain. Usually pain is triggered in response to tissue damage, such as stepping on a tack. When that happens, the following chain reaction takes place:
In AMPS, there is an abnormal short circuit in the spinal cord (4). Therefore, the pain signal not only travels up to the brain, but also goes to the neurovascular (or autonomic – i.e. "fight or flight") nerves (5) that control blood flow through the blood vessels (6).
These nerves cause the blood vessels to constrict, decreasing blood flow. The decreased blood flow deprives the skin, muscles and bones of oxygen and leads to a build-up of acid waste products such as lactic acid. This lack of oxygen and acid build-up cause pain.
This new pain signal also goes across the abnormal reflex and causes a further decrease in blood flow, leading to more pain. Thus, the pain is greatly amplified through this continuous cycle.
There are various patterns or kinds of AMPS that are called a variety of names. We prefer the term amplified musculoskeletal pain syndrome since it refers to the fact that the body takes a mild pain signal and makes it very painful, similar to when a guitar amplifier takes a soft sound and makes it very loud.
Most of the names given to this condition are related to where the pain is or to changes in the skin temperature and color (autonomic changes). Some of the many names used include:
Information in medical literature and on the Internet can be quite confusing; most of it applies to adults with specific syndromes, especially the terms fibromyalgia and reflex sympathetic dystrophy (RSD). The term "sympathetic" can be mistakenly construed to suggest children with AMPS are just looking for sympathy and are not truly in pain.
Children with AMPS are different from adults with AMPS. The way the disease presents in children – its signs and symptoms, the way it responds to treatment and the long-term prognosis – varies. Long-term outcomes for children with AMPS are generally better than those for a similarly affected adult. We avoid using the terms RSD or fibromyalgia in describing pain in children, except for research purposes.
More than one form of AMPS can coexist in the same child or, if there is a recurrence, the second form may be different from the first form.
The forms of AMPS include:
Autonomic changes include coldness, blueness, swelling or perspiration.
AMPS has multiple manifestations, and each form can be named separately as shown above. We use the term amplified musculoskeletal pain syndrome to encompass the spectrum of these pain syndromes.
We will discuss your child’s specific AMPS diagnosis with you and your child after the evaluation. We want to emphasize that all amplified pain is severe and we are not sure one type hurts any more or less than another.