Shoulder-hand syndrome after stroke. A complex regional pain syndrome.
Complex regional pain syndrome (CRPS) types I and II are neuropathic pain disorders that develop as an exaggerated response to a traumatic lesion or nerve damage, that generally affects the extremities, or as the consequence of a distant process such as a stroke, spinal lesion or myocardial infarction. It rarely appears without an apparent cause. CRPS of upper limbs after stroke is frequently today called shoulder-hand syndrome (SHS). The onset and severity of SHS appears to be related with the aetiology of the stroke, the severity and recovery of motor deficit, spasticity and sensory disturbances. Another important aetiological factor is glenohumeral subluxation. The physiopathology of the disease is still not known. In CRPS, there is an exaggerated inflammatory response and some chemical mediators have been identified and are present in the inflammatory soup around the primary afferent fibres that, through different processes, can induce hyper-excitability of the afferent fibres (peripheral sensitization). It is hypothesized that a localized neurogenic inflammation is at the basis of oedema, vasodilation and hyperhidrosis that are present in the initial phases of CRPS. The repeated discharge of the C fibres causes an increased medullary excitability (central sensitization). Another important factor is the reorganisation of the central nervous system, and in particular this appears to affect the primary somatosensory cortex. The central role of the sympathetic nerve is presently in doubt. However, it is thought that a sub-group of CRPS patients exists in whom a predominant factor is the hyper-activity of the sympathetic nervous system, and that it responds positively to sympathetic block. Diagnosis is clinical and there are no specific tests, nor pathognomic symptoms to identify this disease with certainty. Diagnosis of CRPS after stroke appears more complex than in other pathological situations: the paretic upper arm frequently appears painful, oedematose, with altered heat and tactile sensations and slightly dystrophic skin within a non-use syndrome. Some investigations can aid differential diagnosis with other diseases. Treatment may be non-pharmacological, pharmacological, with psychotherapy, regional anaesthesia, neuromodulation and sympathectomy. In any case there is little evidence that supports the efficacy of the interventions normally used to treat or prevent CRPS-SHS. The key to effective treatment undoubtedly lies in a an expert multidisciplinary team that is co-ordinated and motivated and that treats the disorder with individualised therapy.