Amplified Musculoskeletal Pain Syndrome (AMPS)

The exact cause of AMPS is not well understood; however, the most current research suggest that this chronic non-inflammatory pain condition is the result of malfunction, or disordered response, and over intensification of the pain signal by the central nervous system and peripheral nervous system. There may be a component of genetic susceptibility which is then triggered by an environmental stimulus. This amplified pain response is easiest to understand using the analogy of an electric guitar with an amplifier. For someone who is not experiencing AMPS, a pain stimulus will cause a standard, expected amount of pain ‘signal,’ analogous is the electric guitar that is being strummed while not hooked up to an amplifier. For the individual living with AMPS, the amplifier is turned way up, and over time gets louder and louder. What this means is that even though the stimulus or ‘input’ is the same, the output is significantly ‘louder,’ resulting in a much stronger pain sensation.

The most common signs and symptoms of AMPS include:

• Chronic musculoskeletal pain without other explanation.
• Somatic symptoms including, but not limited to, headaches, abdominal pain, dizziness, arthralgias, tachycardia, etc.
• Allodynia (a painful sensation in response to non-painful touch) – in about 70%.
• Affect that is incongruous with the situation (e.g. smiling despite experiencing pain).
• Disproportional physical dysfunction relative to the anticipated amount of pain that would occur in response to the stimulus. This may include inability to bear weight, disuse of the extremity, intolerance of touch from other people or even clothing or bedding, school absences and discontinuation or reduction in participation in extra-curricular activities.
• Fatigue and disrupted or non-restorative sleep which may include an inability to fall asleep, inability to stay asleep, and waking up without any feeling of refreshment.
• Psychological co-morbidities, including anxiety and/or depression, in the affected child may be common, and should be considered in all newly diagnosed patients.
• Stress plays a role in triggering AMPS and stressors should be routinely assessed for, including bullying, marital discord among patients’ parents, loss of a loved one, or other life changes.
• Conversion symptoms (neurologic symptoms not explained by a physical disorder) may occur, including, but not limited to, extremity shaking, paralysis, blindness, non-epileptic seizures, and conversion gait.

There is not a single blood test or physical examination check that can make a definitive diagnosis. When your child’s provider is assessing his pain, an accurate and complete history (including any preceding illness or injury) will be a critical component of diagnosis. The physical exam will include joint inspections, palpation, range of motion and strength testing. The information gained on the physical exam is critical to the diagnosis and management of AMPS. A detailed assessment of any pain associated disability, such as impact of pain on daily life will also be done, which will include sleep, school, and social, emotional and physical function.

AMPS is diagnosed when it is clear that the symptoms being described are not due to an underlying injury or trauma, inflammatory or infectious causes (such as juvenile arthritis (JIA) or osteomyelitis) or tumors. In order to rule out other possible causes of the pain, further testing such as blood tests or imaging studies may be recommended; however, these tests are not required as part of diagnosis of AMPS. It is important to note that AMPS can be a complication of an underlying condition, such as JIA. It this case, both conditions need to be recognized and treated.

The goal of AMPS treatment is to return the child to normal daily function by minimizing pain, restoring normal sleep and mood and decreasing any negative impact that the pain syndrome may have on health-related quality of life (HRQL). In order to do this, diagnosis of the primary and secondary causes is important and may involve referral to other specialists, such as psychologists, physical and occupational therapists. This multidisciplinary approach to pain management is an important part of AMPS treatment.

Treatment of AMPS consists of a non-pharmacologic approach involving cognitive behavioral therapy, physical and occupational therapy, and regular aerobic exercise with a focus on stress reduction. Since AMPS can often affect the entire family, family counseling is often recommended as well. Typically, once a clear diagnosis is established and all unnecessary medications and testing modalities are stopped, the burden of the ‘unknown illness’ is lifted which can be a relief. Pain management recommendations are heavily weighted towards graded (gradually increasing) exercise programs, regular daily activity in the form of functional aerobic training, desensitization for allodynia and psychotherapy. There are in-patient and out-patient treatment centers around the country who work daily with patients who have severely debilitating AMPS; these cumulative therapy sessions can be up to six hours in duration.

The impact of AMPS on activities of daily living is what drives most patients to seek medical evaluation to begin with. Constant pain, poor sleep, resultant fatigue, decreased tolerance of physical activity, and change in mood can all significantly impact daily activities, social interactions, and school attendance. Once a diagnosis of AMPS has been made and the child is cleared to participate in normal activity, pursuit of appropriate recommended therapies and gradual (as tolerated) return to a normal schedule is recommended. For children requiring intensive treatment at a multidisciplinary center, return to normal function has been seen for 80% of patients within one month. Most patients however will not require this intensive of an intervention, in which case establishing your own multidisciplinary team of physical, occupational and mental health professionals is key. In addition to working to resume normal function, these specialists can teach your child tools and techniques to utilize when he feels pain coming on. If your child is missing large amounts of school, work with your medical provider and the administration of your school to make sure that catch up material is provided and set up a plan for return to a full day of school. Often, even if your child is not able to absorb every word that is being taught, going to school, interacting with friends and gradually building endurance is a key component of returning to school. Lastly, it is important to recognize that the pain that your child is experiencing, while not dangerous, is very real. Validation of the pain is an important part of working to eliminate it and the child must recognize that he or she is an important part of the treatment team. With the appropriate intervention and work on their part, the vast majority of patients will do very well and resume a fully functional life with no pain. In studies conducted at inpatient AMPS treatment centers, 95% of patients felt significantly better, and only 5% saw no pain improvement. Overall significant relapses were infrequent with only 15% requiring retreatment. At 5 years post study, 90% of patients were doing well.