Abstract
Objective: Complex regional pain syndrome (CRPS) is a common pain condition characterized by the changes in the brain that are not yet addressed by conventional treatment regimens. Repetitive peripheral magnetic stimulation (rPMS) of muscles is painless and non-invasive and can influence these changes (the induction of brain plasticity) to reduce pain and improve motricity. In patients with CRPS, this open-label pilot study tested rPMS after-effects on the pain intensity and sensorimotor control of the upper limb along with the excitability changes of the primary motor cortex (M1).Methods: Eight patients with CRPS were enrolled in a single-session program. Patients were tested at pre- and post-rPMS over the flexor digitorum superficialis (FDS) muscle. The clinical outcomes were pain intensity, proprioception, active range of motion (ROM), and grip strength. M1 excitability was tested using the single- and paired-pulse transcranial magnetic stimulation (TMS) of M1.Results: In our small sample study, rPMS reduced instant and week pain, improved proprioception and ROM, and reduced the hemispheric imbalance of several TMS outcomes. The more M1 contralateral to the CRPS side was hyperactivated at baseline, the more pain was reduced.Discussion: This open-label pilot study provided promising findings for the use of rPMS in CRPS with a focus on M1 plastic changes. Future randomized, placebo-controlled clinical trials should confirm the existence of a causal relationship between the TMS outcomes and post-rPMS decrease of pain. This will favor the development of personalized treatments of peripheral non-invasive neurostimulation in CRPS.
Highlights
Complex regional pain syndrome (CRPS) is formerly known, among others, as reflex sympathetic dystrophy or algoneurodystrophy and is a neuropathic pain characterized by pain arising in one or more limbs, which is disproportionate to an inciting event, in combination with trophic changes and sensory, motor, and repetitive peripheral magnetic stimulation (rPMS) in CRPS autonomic disorders [1, 2]
The seven clinical outcomes at pre- and post-rPMS are reported in Table 2, and Figure 1 shows the significant changes detected after rPMS
Proprioception Interestingly, our original results on the improved performance in the blurred proprioception paradigm [49] support that rPMS enhanced the perception of the CRPS upper limb in space and its motor control after a postural perturbation
Summary
Complex regional pain syndrome (CRPS) is formerly known, among others, as reflex sympathetic dystrophy or algoneurodystrophy and is a neuropathic pain characterized by pain arising in one or more limbs, which is disproportionate to an inciting event (fracture, sprain, surgery, or no identification of traumatism), in combination with trophic changes and sensory, motor, and rPMS in CRPS autonomic disorders [1, 2]. The causes leading to CRPS remain unclear, but evidence proposes that three mechanisms could explain the symptoms: peripheral changes and sensitization, the dysregulation of the sympathetic nervous system, and maladaptive neuroplasticity [1, 3]. The interindividual variability of the contribution of each mechanism over time makes it difficult to administer an efficient treatment for all people with CRPS. Despite clinical guidelines and a medical follow-up of the response to treatment, there is almost no evidence to support the therapies currently used in CRPS [4, 5]. 15–20% of people with CRPS have pain and severe related disorders, and 31% are not back to work 2 years after the onset of symptoms [6,7,8,9]
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