What is amplified musculoskeletal pain syndrome (AMPS)?

Amplified musculoskeletal pain syndrome (AMPS) is a very painful medical condition that can cause pain anywhere in the body. These episodes of pain can be intermittent or constant, can affect the whole body or be localized to one area of the body or affect just a limb. Whenever it occurs, the degree of pain children with AMPS experience is more intense than one would normally expect.

To understand what amplified pain is, first look at the illustration to see how pain is normally felt. Normally, pain is triggered in response to tissue damage such as would occur when a child steps on a tack. When that happens, the following events occur:

• The damage sends a signal through the pain nerve to the spinal cord.
• The signal is transferred up to the brain.
• The brain recognizes the signal as being painful.

In AMPS, there is an abnormal short circuit in the spinal cord. The normal pain signal not only travels up to the brain, but also goes to the neurovascular nerves (also known as autonomic or “flight or fight” nerves) that control blood flow through the blood vessels.

These nerves cause the blood vessels to become smaller (constrict). This constriction restricts blood flow and oxygen to muscles and bone and leads to an increase in waste products such as lactic acid. It is this lack of oxygen and acid build-up that causes pain.

This new pain signal also goes across the abnormal short circuit in the spinal cord and causes a further decrease in blood flow leading to more pain. The pain then becomes greatly “amplified” through this continuous cycle.

Forms of amplified pain

• Diffuse amplified pain – also called total body pain or pediatric fibromyalgia
• Intermittent amplified pain
• Complex regional pain syndrome (CRPS) with autonomic changes
• Localized amplified pain without autonomic changes (autonomic changes include color and temperature changes - for example, cold and blue - as well as swelling and sweating.)

Causes of amplified musculoskeletal pain syndrome (AMPS)

There are three major causes for amplified pain: injury, illness and psychological stress. There may be other factors such as age, genetics or hormones that can also affect amplified pain. It is often a combination of these factors that lead to amplified pain.

Injuries

These children have suffered a significant specific injury such as a broken bone, moderate to severe musculoskeletal injury or have developed pain after surgery. The symptoms of AMPS can occur suddenly or take weeks to develop.

Illnesses

Illness is an infrequent cause of AMPS, but can be more commonly seen in conjunction with inflammatory conditions such as arthritis, tendonitis, myositis or enthesitis. Other illnesses that may be the initial cause are infections such as mononucleosis, gastroenteritis or influenza.

Psychological stress

Stress can be both a complicating factor and trigger for amplified pain. Stressors can be positive or negative, big or small, and can include not just events, but feelings and personality styles.

Many children with AMPS and their families have been negatively affected by peers, school officials and even health care professional who have dismissed the child’s symptoms.

Chronic pain can also significantly affect individual and family dynamics. Exploring individual and family dynamics does not imply that the pain is not real or is entirely due to psychological cause.

Children with AMPS and their families can benefit from various forms of psychotherapy such as cognitive-behavior therapy (CBT) which can help the child with more immediate coping strategies to deal with the pain and dysfunction as well as identify stressors, such as school, family, and friendship, and to practice expression of feelings and emotions.

Testing and diagnosis of amplified musculoskeletal pain syndrome (AMPS)

Amplified pain is diagnosed by listening carefully to the child’s history, both physical and emotional.

Some children have autonomic changes at the time of examination or can be extremely sensitive to touch.

Blood tests are generally normal unless there are other conditions present.

In some children, a bone scan or MRI can show abnormalities that are very suggestive of AMPS, but the results may be normal.

Early diagnosis may be difficult for several reasons:

• Not all AMPS symptoms may be present at first but may evolve over time.
• Urgent problems such as infections or musculoskeletal injuries may need to be ruled out before starting a treatment plan for AMPS.
• There is a wide spectrum of AMPS, so unless a clinician has seen a variety of children with AMPS they may not recognize it.