Ultrasound and Somatosensory Median Nerve Evaluation in CRPS I

Complex regional pain syndrome (CRPS) is a disorder falling within the sphere of neuropathic pain, characterised by a plethora of symptoms. Regional pain out of proportion to the triggering event is the main presentation, accompanied by allodynia, dysesthesia, thermal asymmetry, trophic changes, oedema and stiffness. Recently, preliminary observational studies have found that the management of patients with CRPS, refractory to pharmacological treatment, by carpal tunnel release may be resolving; This suggests that an irritative carpal tunnel syndrome may be masked as CRPS due to non-specific symptoms and negative electrodiagnostic studies (electromyography-EMG). Classical carpal tunnel syndrome (CTS) is a well-defined clinical condition that can be ascertained by EMG. In contrast, irritative carpal tunnel syndrome has symptoms attributable to CRPS with negative EMG that arises after trauma that required surgery or immobilisation. It is unclear how to define the presence of irritative carpal tunnel syndrome in patients diagnosed as CRPS, and thus how to make a correct diagnosis. Nor is the management of these patients defined. The aim of the research is to analyse all patients with typical symptoms for CRPS to investigate the morphological appearance of the median nerve at the level of the carpal tunnel by means of dynamic ultrasound in comparison with the healthy limb. In addition, in order to quantify the function of the median nerve, investigators will analyse patients by means of a sensory conduction velocity study (SNVC), as common EMG examinations are negative in these patients, while it is possible that the quantification of the sensory part of the nerve may be impaired. In addition, the autonomic component will be investigated by studying the Skin Sudomotor Response (SSR).The hypothesis is that some patients, after an injury that required surgery or immobilisation, develop fibrous soft tissue scarring that creates a kind of space-occupying lesion that compresses the median nerve at the level of the carpal tunnel and reduces its sliding under the transverse ligament of the carpus, a structure that is not elastic and therefore unable to adapt to the volumetric increases within it. The other hypothesis is that the fibrosis and post-traumatic oedema, which is structured, directly involves the median nerve sheath, resulting in irritation. Classical CTS develops due to mechanical trauma, high pressure and ischaemic damage affecting the median nerve and develops as a clinical condition of pure nerve suffering, with symptoms referable to a sensory and motor deficit. In CRPS, on the other hand, allodynia, hyperalgesia, sudomotor and vasomotor abnormalities and trophic changes are all symptoms that may be related, but are not specific, to nerve suffering.