Cognitive Multisensory Rehabilitation, a Novel Sensorimotor Intervention for Pain Reduction in Complex Regional Pain Syndrome: a Feasibility Study

Introduction This protocol describes a study aimed to investigate the feasibility and appropriateness of a novel sensorimotor treatment approach called Cognitive Multisensory Rehabilitation (CMR) for symptom reduction in people living with Complex Regional Pain Syndrome (CRPS). This study has been informed by the findings of a CRPS-patient focus group as well as clinical observations at the Royal United Hospital in Bath. The findings from this feasibility study will inform the design of larger studies to investigate the effectiveness of CMR in CRPS, offering a novel, non-drug related treatment to CRPS treatment.

Background CRPS is a chronic pain condition of unknown aetiology that commonly occurs following trauma to a limb, although it may occur spontaneously. It is defined as type 1 or type 2, depending on whether known major nerve damage is absent or present, respectively. Patients with Complex Regional Pain Syndrome commonly describe a diverse range of sensory and motor abnormalities. Sensory problems include pain to touch or the threat of touch, evoked pain, pain hypersensitivity (allodynia or/and hyperalgesia; pain due to a stimulus that does not normally provoke pain and an increased sensitivity to feeling pain and an extreme response to pain, respectively), but at the same time non-noxious sensory loss (hypoesthesia). Motor problems include troubles in initiating movement, weakness and reduced function amongst others.

Clinical features often present in people living with CRPS commonly resulting in patients having difficulty to engage with their affected limb and therefore having a detrimental effect on rehabilitation outcomes are:

• Body perception disturbances: the reported individual's perceived alteration of their CRPS affected body part while regarding the remainder of their body as normal.
• Loss of self-ownership and amputation desire: patients' perception that the painful limb(s) do not belong to them and the desire to amputate these body parts.
• Allodynia: painful response to a stimulus that does not normally produce pain.
• Motor impairments: including tremor, decreased range of movement, muscle weakness, and/or having the affected limb set in a sustained, fixed posture (i.e. dystonia).

Sensorimotor interventions (i.e. interventions aiming to improve sensory and motor feedback of the affected limb) have shown promising outcomes on increasing perception associated with the affected limb (i.e. tactile acuity; precision with which we can sense touch) and decreasing pain intensity. Although its mechanisms are largely unknown, it is thought that the 'normalized' sensory and motor feedback may compete with pain stimulus resulting in pain reduction in people with CRPS. The evidence for the effectiveness of these treatment modalities in CRPS is weak, and often focus only on pain reduction. Thus further research is required on novel sensorimotor interventions that target also other abnormalities present in CRPS (i.e. body perception disturbances, loss of self-ownership and amputation desire and motor impairments).