Body Perception Disturbance (BPD) in CRPS
Complex Regional Pain Syndrome (CRPS) is a chronic pain condition of unknown etiology 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.1,2
Patients with CRPS commonly describe a diverse range of sensory and motor problems. These include pain to touch or the threat of touch, temperature, color and sweating abnormalities, problems in initiating movement and reduced function.
Changes in body perception are perhaps less easily identified since patients are commonly reluctant to discuss these phenomena unless directly questioned. They often express altered perceptions, thoughts, and feelings about their affected limb.
They may describe their limb with negative emotional feelings such as hate and anger, disgust, and repulsion. Recent research has identified a strong desire for amputation of the affected limb, perceived changes in limb size and structure and dissociation from the limb. These perceptions may influence patients’ engagement with therapy and inform the development of new interventions.
Recent evidence suggests that body perception disturbance (BPD) is becoming an increasingly recognized feature of CRPS with a reported prevalence ranging from 54.4% to 84%.3-5 Although not always immediately apparent to the clinical practitioner, these symptoms can be easily identified with an appropriate approach. The presence of BPD commonly results in patients having difficulty in engaging with their affected limb and so can be detrimental to rehabilitation outcomes. All members of the multi-disciplinary team should have an appreciation of the impact and presentation of BPD in this condition. From our clinical experience of seeing approximately 100 new CRPS patients each year, greater understanding of these seemingly bizarre phenomena can improve communication between the patient and their practitioner, build trust and confidence in the patient of their clinical team, and allay unnecessary fears of impending “madness” that patients commonly report in association with these symptoms.
The purpose of this article is to help the practitioner understand BPD in CRPS by providing a theoretical understanding of body perception processes—both normal and aberrant—and how these may relate to body schema. We provide a definition of body perception disturbances and introduce a new clinical tool, The Bath CRPS Body Perception Disturbance Scale (See Appendix 1) to aid the practitioner in the identification and assessment of BPD in CRPS. Finally, we will discuss current and emerging therapeutic approaches that target central mechanisms for the resolution of BPD.
Presentation of Disturbances in Body Perception in CRPS Patients
The symptoms of CRPS include pain, usually in a single limb, together with associated unilateral color, temperature and sweating abnormalities. There may be trophic changes such as altered hair and or nail growth and impairments in motor control. All of these symptoms are well described and a routine clinical investigation would encompass appropriate questions to determine their presence or absence. What a clinician may not cover is an assessment for the more subtle symptoms seen in CRPS that relate to body perception disturbance. With careful, targeted questions these symptoms are frequently found to be present.
Patients with CRPS commonly report that the affected limb is psychologically ‘detached’ from the remainder of their unaffected body (a sense of disowning) such that it feels alien and outside of their control.3 An extreme form of detachment is expressed by some as a desperate desire to amputate their limb.3,6,7 Despite understanding clinical opinion, advising against amputation, some patients continue to express this intense urge to amputate the limb and can commonly describe, in some detail, how they plan to get rid of it.3 In addition, when asked where they would wish this hypothetical incision to occur, they can unhesitatingly identify the exact part of their limb where they would like this to be. Commonly this “hypothetical amputation line” forms the boundary between ownership and alienation.
Many patients report that what they see when looking at their affected limb is often at odds with how the limb feels. Subjectively, the limb may be perceived as being much larger, heavier or different in temperature or pressure from objective assessment.3,8 For example, the limb feels burning hot, yet is cool to the touch. Rather than a general distortion of the whole limb, discrete parts of the affected limb may also be perceived as grossly enlarged or missing. These sensory misrepresentations of the limb are commonly accompanied by, or perhaps contribute to, a mis-localization of the limb. Patients typically report a difficulty in knowing how their affected limb is positioned despite a heightened awareness due to pain. They describe holding their limb in what feels to be a normal and more comfortable position but are unaware that it is actually abnormal until others draw their attention to it.
Typically, patients are reluctant to look at their affected limb—choosing to position it outside of their view or covering it up in some way. The lack of visualization of the affected limb may in itself have implications on altered body perception. Commonly, patients do not wish to touch the allodynic limb and clearly avoid thinking about it. A lack of conscious attention to the limb may well contribute to the perpetuation of alterations in perception about the limb. Furthermore, patients may express a dislike of looking at the anatomically-matched limb of another and feel pain or a sense of discomfort when they do. How this BPD impacts on and informs therapeutic approaches will be discussed later.
Definition of Body Perception
In order to create a cohesive representation of our bodies, we require the integration and processing of multimodal sensory perceptions that involve both the peripheral and central nervous systems.9 The awareness of one’s own body and its constituent parts is something that we generally take for granted. Yet, this typically unconscious knowledge of our body is an essential component for daily functioning. For example, in order to undertake a simple action such as picking up a pen, one must first have knowledge of the size and shape of relevant limb segments and their relationship with one another and, in particular, the position of one’s hand relative to the pen.