Pain amplification syndromes
Generalised and localised pain amplification syndromes
Joint and muscle pains are a not infrequent occurrence during childhood and adolescence. Most of the time, the pain is harmless and self-limiting. Occasionally, joint ailments can be symptoms of serious illnesses, such as the onset of chronic arthritis.
In the event of very pronounced joint and muscle pains that place restrictions on patients' daily activities, pain amplification syndrome must be considered as a potential differential diagnosis. This syndrome is characterised by the intensity of the pain, its chronicity and the lack of objective findings explaining the intensity of the pain. Patients experience extended suffering, with a progressive reduction in their activities being accompanied by an increase in the pain symptoms.
An increasing number of cases of pain amplification syndrome in children and adolescents is being observed in paediatric rheumatology centres. Pronounced discomfort usually begins at around the time of puberty, although a third of patients are afflicted by pain from early childhood. The syndrome predominantly affects girls – only around 10% of patients are boys.
Subgroups and therapeutic approaches
Pain amplification syndromes can be divided into a generalised form and a localised form. Generalised pain amplification syndromes in childhood are frequently referred to using the synonyms 'juvenile fibromyalgia' or 'soft tissue rheumatism'. All three terms refer to a chronic pain syndrome. The symptoms manifest as generalised (i.e. affecting several regions of the body) joint and muscle pains, accompanied by vegetative symptoms. Examination of patients can reveal pain on pressure in the areas around muscle and tendon insertions, known as tender points. These points are typically not detected empirically in child patients, however. The assumed aetiology is centred around defective pain processing with resultant amplification and chronification. Therapeutically, a multidisciplinary/multimodal therapy brings the best results. Regulated physical training, relaxation and pain processing form a major part of treatment, which initially focuses on restoring normal functionality in the affected regions of the body. The effectiveness of drug therapy remains limited. Approaches (from adult medicine) act on the central metabolism (tricyclic antidepressives, 5-HT3 receptor antagonists). In children and young people, for whom the perception and processing of pain are subject to a natural learning process, drug therapy schemes should be used only after careful consideration and, with regard to the side effects, it should be considered on a regular basis whether taking the drugs is still necessary. Occasionally, spontaneous remissions (or at least significant drops in the subjective pain levels) are seen in children and adolescents. For the remainder of the patients, the goal of therapy is to minimise the degree of impairment felt in everyday life. Localised pain amplification syndromes in children and young people, such as complex regional pain syndrome (CRPS I), also referred to as M. Sudeck or algodystrophy, typically show trophic changes to tissue. In addition, extreme pain (hyperalgesia) and sensitivity to touch (allodynia) are observed. Alongside this form of local pain amplification syndrome, however, there are also local pain points or body regions that experience extreme pain in the absence of tissue changes or primary, objectively verifiable diagnostic findings. Localised pain amplification syndromes form only a small percentage of the total number of pain amplification syndromes. They also frequently have a progression extending over a long period of time. The defective pain processing leads to the conjecture that a central sensitisation occurs. The resulting severe, localised pain is further worsened if the extremity affected is not used on a daily basis, since this is closely associated with the tumefaction of the soft tissue regions affected. Our therapeutic approach is once again a multidisciplinary therapy concept. It is based on the treatment scheme developed by Professor Sherry (USA), who has demonstrated positive results in studies involving numerous patients. In our view, methods that are conventional in adult medicine, such as drug combinations and using catheters to treat pain, are passive therapies, and we try to avoid them where possible. This is based on our experienced that the effectiveness of drug therapy remains limited for most patients. The options involved are approaches (from adult medicine) with peripheral and central analgesics, 'low dose' steroids and membrane-stabilising neuroleptics. We refrain from using these drugs wherever possible, owing to the side effects they frequently cause and also to the positive results obtained from our activating multimodal therapy. Instead, the pain management process for children and young people should centre around the possibility of active change. We have obtained good results from our activating therapy, in which the function of the affected extremity is paramount. The psychosocial effects of chronic pain, or the cumulative psychic factors, are dealt with during regular meetings with our psychologists. In localised pain amplification syndromes, particularly CRPS I, a significant drop in subjective pain, accompanied by improved functionality in the affected extremity and potential recovery, is often observed in children and adolescents.
Differential diagnoses
Most of our patients have a long history of doctor's visits and stays at clinics behind them owing to the unbearable pain they feel. The lack of any clear cause for the symptoms means that laborious diagnostic procedures are carried out again and again. These differential diagnoses look for inflammatory rheumatic illnesses, benign tumors such as osteoid osteoma or even malignant conditions such as leukaemia. Rarely, the underlying illness will be erythromelalgia with massive pain in the hands and feet (patients attempt to alleviate this pain by the permanent application of intense cold), or metabolic illnesses such as Fabry's disease, with episodic burning pain experienced in the hands and feet. We are also increasingly observing that inflammatory rheumatic illnesses such as HLA B 27-positive enthesitis, sarcoidosis or periodic fever syndrome can lead to a secondary amplification of pain. CRMO (chronic recurrent multifocal osteomyelitis) is yet another possibility to explain localised pain that changes location. Clinical tests, laboratory examinations or imaging techniques usually reveal the existence of these illnesses.
Diagnostic criteria for pain amplification syndrome
For the general form, diagnosis is based on the patient's case history and clinical findings. Laboratory values and imaging techniques give no pathological findings. Various diagnostic criteria have been developed for fibromyalgia in adults. The classification criteria of the ACR (American College of Rheumatology) are internationally recognised (Wolfe et al. 1990). The diagnosis here is primarily based on a case history illustrating joint and muscle pain coupled with evidence of at least 11-18 pressure-sensitive points typically in the area of muscle and tendon insertions. In children and adolescents, the pressure points are often not clearly pronounced or not pronounced at all, and therefore the criteria are not met. We therefore prefer the term 'generalised pain amplification syndrome'. The localised form is characterised not only by massive pain symptoms (hyperalgesia and allodynia) but also by an oedematous trophic change in tissue. Mostly the affected foot or hand is no longer used and wearing shoes or socks is no longer tolerated, which leads to a massive restriction in everyday activities. Local pain amplification syndromes without swelling and allodynia show, in the same way as general pain amplification syndromes, no objectively verifiable diagnostic findings and often tend towards a generalisation as they progress.
Clinical signs of pain amplification syndrome
Very severe joint and muscle pain, partially accompanied by pressure-sensitive points, are leading symptoms of the illness. A vegetative condition can complete the picture. A typical factor is a changeable progression, influenced by external stresses, and we frequently see a seasonal worsening of the condition in the winter months.
Generalised joint and muscle pain
These are depicted very clearly in the patient's case history. During acute phases children report constant pain that is sometimes felt to be unbearable. The regions of the body affected can change. Pain is most frequently localised in the hand, knee and ankle joints, but the back and the musculature in the extremities are often painful as well. During examination the joints appear to be freely mobile and often even hypermobile, but movement triggers intense pain.
Tender points
These are localised spots around muscle and tendon insertions that are very painful when pressed. The areas predominantly affected are the pes anserinus of the knee, the epicondyle of the humerus, the shoulder-neck area, the crests of the hips and the entire spinal column including the paravertebral musculature. Firm pressure applied to the sensitive points causes a prompt reaction from the patient, referred to in English as a 'jumping sign'. Palpitation apart from these sites is, however, tolerated.
Further symptoms in the musculoskeletal system
A good two-thirds of children and adolescents report stiffness in their joints, particularly first thing in the morning. This affliction often results in it being mistaken for morning stiffness in chronic arthritis. Almost all young patients report that the particularly painful joints swell up on a repeated basis. Here, a discrepancy exists between the strong sensation of swelling experienced subjectively and the actual swelling, which is barely discernable objectively. The feeling of tension is triggered by swellings in the periarticular soft tissue. Intra-articular swellings do not form part of the clinical picture for pain amplification syndrome. In the event of doubt, sonography can be used to exclude the possibility of effusion in the joint.
Vegetative disorders
When asked, most children also report vegetative disorders. They most often complain of chronic stomach- and/or headaches. Constant tiredness is also often reported, sometimes in combination with sleep disturbances. Therapy can bring about a change in the leading pain symptoms. In this case, we sometimes observe a movement 'away' from joint pain and 'towards' vegetative symptoms
Influence from external factors
The changing character of the disorders is typical for generalised pain amplification syndromes. Often, external influences can be discerned that lead to a change in symptoms. Most patients report that they experience more severe pain during changes in the weather or when the weather is cold and damp. They feel better in warm, dry climates. Physical stress exacerbates the disorders, whereas at the beginning gentle sporting activities can often have positive effects. As the troubles progress, even short bicycle rides or swims lead to exhaustion and increased joint pain for many patients. Intensive physical activities become impossible. Paradoxically, patients report an increase in chronic pain despite their level of physical activity decreasing as a result of the illness. Together with physical stress, emotional stress, primarily from increasing demands in school or vocational training and situations of family conflict, leads to a worsening of the symptoms. Conversely, chronic pain is itself also a stress factor that can lead to emotional stress. Additionally, more severe pain is frequently experienced, when the children have an infection.. Localised pain amplification syndromes are characterised by being unaffected by seasonal factors. Nevertheless, the pain is intensified by physical influences. Movement and touch initially make the symptoms worse, but are essential for the recovery process.
Hypotheses on aetiology and pathogenesis
There is unanimous agreement as to the multifactorial genesis of pain amplification syndromes. Our own observations and examinations from literature both reveal that the syndromes tend to run in families. Genetic disposition could play a role in this regard, as could experiences of pain and methods of pain management passed on through the family. Occasionally, acute trigger events such as infections or trauma (particularly the latter in the case of CRPS I) are observed. Of probably far greater significance are chronic overloads of psychosocial or physical stress. Acute or even chronic arthritis that has since gone into remission are found with a greater than average frequency in the child's case history. Previous experience of pain or pain processing obviously plays a role. Distinctive features in the patient's molecular biology are becoming an ever-increasingly frequent occurrence. These features can be detected only with the patient's consent and are therefore of no use in diagnosing individual cases. A decline in the levels of serum serotonin (S-5-HT) is often put forward as a cause. Serotonin plays an important role in nociception. Modern therapy trials have focused on this aspect, using 5-HT3 receptor antagonists on adults. Neurocrine dysregulation is manifested inter alia in a rise in CRH and ACTH and a drop in STH and somatomedin C. Overall, pain amplification syndromes can be described as a fundamental regulatory dysfunction of the nociception process accompanied by a pronounced peripheral and central sensitisation. The general lowering of the pain threshold explains the considerable pain in the musculoskeletal system. The vegetative nervous system and the neuroendocrine system are also affected by the regulatory dysfunction by virtue of their close communication with the CNS. The obvious suspicion is that these molecular biological changes are more likely to be the result of pain amplification syndromes than the cause. They can still provide approaches for a symptomatic drug therapy, however.
Effects on everyday life
Children and young people are significantly restricted in their daily activities as a result of their disorders. Sporting activities are almost always cut back on or given up altogether. In a survey carried out on 115 patients on their arrival at our clinic, 54 children said that they were exempted from sport at school and 42 practised considerably less sport than before. Poor resilience in the patients leads to increasing social isolation. Participation in joint activities with friends is refused, and family outings become less and less frequent. Patients become withdrawn. Sometimes, the only contact persons left are the parents, particularly the mothers. This pathological relationship, in an age in which chilren are supposed to be becoming independent, makes solving the problem more difficult for both sides. The situation becomes particularly serious if children start to be absent from school for extended periods of time because of their pain. Just under half of the 115 patients we asked said that they had missed school several times in a week or had been absent for weeks or even months at a stretch. These absences often cannot be made up for later. Failing in their schoolwork makes children depressed and leads to a vicious circle of increasing pain. Completing school and going on to further education are jeopardised.
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