Showing posts with label Complex regional pain syndrome. Show all posts
Showing posts with label Complex regional pain syndrome. Show all posts

Saturday, October 25, 2014

Procustean Science: Re-Gifting IVIG

Part of me doesn't even want to post this, as it is recycled material from the famous or infamous -- I cannot decide, discern -- Andreas Goebel, forever presenting IVIG as a silver bullet for CRPS.  That's okay, I have seen good things come from focused scientists.

But it seems to me, the layperson with a dangerous small bit of knowledge, that repackaging a theory every few years in the pretty wrapping paper of a new context eventually makes the re-gifting exercise less one of diverse generosity and more one of desperately searching for a respectable vehicle.

In his most recent reincarnation of IVIG as cure all, Dr.Goebel blithely tosses on the rubbish heap the notion of trauma/injury/physical insult as an inciting event in CRPS.  There has always been a caveat to that observation -- that many cannot recall an inciting event, that many cases of "spread" (Dear God, please give us a better and more accurate word!) occur without trauma, large or small, and so on.

Still, I'd wager that most of "us"experience onset, instances of "spread," and, according to most reports I've read of people in remission coming out of that remission, after some sort of inciting injury/insult/trauma.  Call me crazy... (I'll give you a few moments.) -- Call me crazy, but trimming a disease profile so it better fits in the box you're wrapping this year... doesn't make me all a-dither about what's under the Christmas tree.

It makes me want to gift you with "Procrustes" as a middle name.  Andreas Procrustes Goebel.

Dr. Goebel presents himself in the following way on various websites that deal with disease and (all) encompassing theories of immunology and auto-immune scenarios

I am a senior lecturer in pain medicine at the University of Liverpool, and an honorary consultant in pain medicine at the Walton Centre NHS Trust, both in Liverpool in the United Kingdom. After receiving my medical and doctoral degrees from the University of Würzburg in Germany, I trained in anaesthesia and pain medicine first in Germany, then at the Oxford School of Anaesthesia in the United Kingdom.  This was followed by further specialized pain training at University College London Hospitals, and interventional training in Notwill, Switzerland.  I completed a 2-year fellowship in post-trauma immunology at Harvard Medical School in Boston. My main professional interest is with the role of the immune system in chronic pain, and immune modulating drug treatments for unexplained chronic pain conditions. I have a particular interest in a condition called ‘Complex Regional Pain Syndrome’ (CRPS).
I am a fellow of the Royal College of Anesthaesthetists, a member of the British and German Pain Societies and the International Association for the Study of Pain, and founding member of the CRPS network UK.

All of my bitchiness about the window dressing aside, Dr. Goebel was kind enough to answer an email inquiring about any IVIG/immunotherapy ("immune modulating drug treatments for UNEXPLAINED chronic pain conditions"/CAPS mine, all mine) research being done in the U.S., as he is centered in the UK:
This is all experimental at the moment. The only US group which I am aware of, who is trying immune treatments relatively systematically, is the Philadelphia group. You might wish to inquire with Dr. Lopez: Enrique.AradillasLopez@DrexelMed.edu and inquire. 
I have not inquired, as my experience with the staff at Drexel University's Neurology Department has been abysmal, and that's adding a dose of "sweetness and light" to the assessment.*

Well, time to rein myself in and give you the latest Dr. Andreas Procrustes Goebel's  Bento Box for a treatment that may well have tremendous merit, despite how it may be overblown in its marketing hype. This is much easier to take than past incarnations, being constrained by the format of a clinical trial.

Low-dose intravenous immunoglobulin treatment for complex regional pain syndrome (LIPS): study protocol for a randomized controlled trial

Longstanding complex regional pain syndrome (CRPS) is refractory to treatment with established analgesic drugs in most cases, and for many patients, alternative pain treatment approaches, such as with neuromodulation devices or rehabilitation methods, also do not work. The development of novel, effective treatment technologies is, therefore, important.

There are preliminary data suggesting that low-dose immunoglobulin treatment may significantly reduce pain from longstanding CRPS. 

Methods: LIPS is a multicentre (United Kingdom), double-blind, randomised parallel group, placebo-controlled trial, designed to evaluate the efficacy, safety, and tolerability of intravenous immunoglobulin (IVIg) 0.5 g/kg plus standard treatment, versus matched placebo plus standard treatment in 108 patients with longstanding complex regional pain syndrome. Participants with moderate or severeCRPS of between 1 and 5 years duration will be randomly allocated to receive IVIg 0.5 g/kg (IntratectTM 50 g/l solution for infusion) or matching placebo administered day 1 and day 22 after randomisation, followed by two optional doses of open-label medication on day 43 after randomisation and on day 64 after randomisation.

The primary outcome is the patients'pain intensity in the IVIG group compared with the placebo group, between 6 and 42 days after randomisation. The primary trial objective is to confirm the efficacy and confidently determine the effect size of the IVIG treatment technology in this group of patients.Trial registration: ISRCTN42179756 (Registered 28 June 13).

Author: Andreas Goebel, Nicholas Shenker, Nick Padfield, Karim Shoukrey, Candida McCabe, Mick Serpell, Mark Sanders, Caroline Murphy, Amaka Ejibe, Holly Milligan, Joanna Kelly, Gareth Ambler



* LIFTED FROM A POST PUBLISHED OCT. 3, 2011:
Remember Dr. Schwartzman of Drexel University fame?  I was so excited at the thought of being Philly bound, and getting to see one of the world's best in the field of CRPS.  It did not work out, mostly because the rarefied air around experts makes them incapable of understanding the limitations of their own impossible schedules!  That's why they have experienced gate-keepers, usually older women with cigarette-ravaged voices and an attitude.  The gate-keepers get to tell all the patients to whom the expert has offered the moon that the moon is made of cheese. 







© 2013 L. Ryan

Wednesday, July 24, 2013

An Unusual Case Study of CRPS Movement Disorder: Drexel Cheerleaders!


Drexel Cheerleaders



As my struggle with CRPS evolves -- we are in our eleventh year together -- more and more, the pain that I cannot tolerate is born from dystonia / spasticity / Jerk-O-Rama sessions.  Much time and mental energy is wasted as CRPS endeavors to turn my feet and legs into some sort of fancy artisinal pretzel.  The solution is an intrathecal delivery device for a sufficient amount of baclofen to render my muscles, nerves, and connective tissues all loosey-goosey and amenable to the instructions delivered by the central nervous system.  Because of my body's decision to harbor bacteria in my bones (osteomyelitis) in the form of evil biofilm communities, I cannot have any further "implants," as they'll only become another petri dish for bacterial growth.  

Alas!

I joke, but it is hell.  

RSDSA has an excellent little library subsection on CRPS movement disorders/dystonia.  Check it out!

The latest paper I've come across comes from some of the best -- the CRPS Brethren of Drexel's Department of Neurology:


Complex regional pain syndrome with associated chest wall dystonia: a case report.

David J. Irwin and Robert J. Schwartzman
Drexel University College of Medicine, Department of Neurology, Philadelphia, PA, USA

David J Irwin MD
Robert J Schwartzman MD
Department of Neurology
Drexel University College of Medicine
New College Building
245 N 15tl1 St
Philadelphia P A USA 19102
TEL: (215) 762-7090; FAX: (215) 762-3161;
e-mail: dirwin@drexelmed.edu (corresponding author),
robert.schwartzman@drexelmed.edu


Abstract
Patients with complex regional pain syndrome (CRPS) often suffer from an array of associated movement disorders, including dystonia of an affected limb. We present a case of a patient with long standing CRPS after a brachial plexus injury, who after displaying several features of the movement disorder previously, developed painful dystonia of chest wall musculature. Detailed neurologic examination found palpable sustained contractions of the pectoral and intercostal muscles in addition to surface allodynia. Needle electromyography of the intercostal and paraspinal muscles supported the diagnosis of dystonia. In addition, pulmonary function testing showed both restrictive and obstructive features in the absence of a clear cardiopulmonary etiology. Treatment was initiated with intrathecal baclofen and the patient had symptomatic relief and improvement of dystonia. This case illustrates a novel form of the movement disorder associated with CRPS with response to intrathecal baclofen treatment.

Keywords: complex regional pain syndrome, dystonia, movement disorder, dyspnea













© 2013 L. Ryan

Saturday, October 13, 2012

Sensorimotor Problems in CRPS: Utilizing Novel Treatment Approaches


JOURNAL OF NEUROIMMUNE PHARMACOLOGY
2012, DOI: 10.1007/s11481-012-9405-9

Imaging and Clinical Evidence of Sensorimotor Problems in CRPS: Utilizing Novel Treatment Approaches

Jacqueline Bailey, Sara Nelson, Jenny Lewis and Candida S. McCabe


Abstract
Inflammation and altered autonomic function are diagnostic signs and symptoms of Complex Regional Pain Syndrome. In the acute stages these are commonly at their most florid accompanied by severe pain and reduced function. Understandably this has directed research towards potential peripheral drivers for the causal mechanisms of this condition. In particular this is now focused on the inflammatory process and the potential role of autoantibodies. More subtle changes also occur in terms of altered tactile processing within the affected limb, disturbances in body perception and motor planning problems that become more evident as the condition progresses. Through careful clinical observation and neuro-imaging techniques, these changes are now thought to be associated with altered cortical processing that includes reorganisation of both the motor and sensory maps. Furthermore, there appears to be a close relationship between the intensity of pain experienced and the extent of cortical re-organisation. This increased knowledge around the peripheral and central mechanisms that may be operating in CRPS has been used to inform novel therapeutic approaches. We discuss here the presenting signs and symptoms of CRPS, with particular focus on sensory and motor changes and consider which mechanisms may drive these changes. Finally, we consider the emerging therapeutic options designed to correct these aberrant mechanisms.




An earlier article, some of the same authors, similar topic:

Hand Therapy Vol. 16 No. 2 June 2011

‘Now you see it, now you do not’:sensory–motor re-education in complex regional pain syndrome
Jennifer S Lewis,* Karen Coales,* Jane Hall* and Candida S McCabe*

*The Royal National Hospital for Rheumatic Diseases, Bath, UK;

The Faculty of Health and Life Sciences, Universityof the West of England, Bristol, UK
Correspondence: Professor Candy McCabe, Bath Centre for Pain Services, The Royal National Hospital for Rheumatic Diseases, Upper Borough Walls, BathBA1 1RL, UK. Email: candy.mccabe@uwe.ac.uk

Abstract
The patient with complex regional pain syndrome (CRPS) commonly describes a lack of ownership of theirpainful limb, poor definition of that body part and difficulty with localization of the limb when performingdaily activities. These descriptions suggest that sensory input from the limb may be reduced leading toneglect of the limb and poor motor control. However, the cardinal symptom of CRPS is pain, commonlysevere, which demands a high level of attention. Patients are highly protective of the painful region andhypervigilant to any potential threats to their affected limb. These seemingly conflicting behaviouralresponses and sensory descriptions are confusing for the patient and health-care professional. In recent yearsour understanding has greatly advanced on how altered sensory perception of a CRPS affected limb relatesto changes in the central representation of that body part, and how this may interact with motor planningand autonomic function. Excitingly, this increased knowledge has directly informed clinical practice via anew evaluation of sensory–motor re-education techniques and the development of novel interventions toenhance sensory discrimination. We review the common sensory problems seen in CRPS, the mechanismsthat may be behind these clinical symptoms, and how sensory, motor and autonomic systems interact.Therapies designed to enhance sensory discrimination and motor planning are discussed, supported by theresults of a small case series undergoing sensory re-education for CRPS. The clinical protocol and two case studiesare available as additional online material to illustrate how all of this is applied in practice.

Keywords:
Complex regional pain syndrome, cortical reorganization, pain, sensory re-education, sensory discrimination

FULL TEXT AVAILABLE HERE




Sunday, October 7, 2012

Tele-Health Improves Clinical Care in CRPS


JOURNAL OF NEUROIMMUNE PHARMACOLOGY  
2012, DOI: 10.1007/s11481-012-9408-6


Making Connections: Using TeleHealth to Improve the Diagnosis and Treatment of Complex Regional Pain Syndrome, an Underrecognized Neuroinflammatory Disorder
Joanna G. Katzman
jkatzman@salud.unm.edu
Department of Neurosurgery, University of New Mexico School of Medicine, Albuquerque, New Mexico 87131-0001, USA


ABSTRACT:
Complex Regional Pain Syndrome (CRPS) is a common and complex, but often underrecognized neuroinflammatory disorder. This syndrome can cause significant intractable pain, worsening motor changes, negative sensory symptoms as well as autonomic, vasomotor and trophic changes. Primary care providers and specialists are frequently challenged with patients who present with unusual symptoms and are unsure of the differential diagnosis and best practices treatment options for CRPS. The Project ECHO Pain Team leverages tele-health technologies to connect clinician specialists and primary care providers in order to increase awareness and create knowledge networks regarding improvement in clinical care for patients with CRPS.

REFERENCES:

Arora S, Thornton K, Murata G, Deming P, Kalishman S, Dion D, Parish B, Burke T, Pak W, Dunkelberg J, Kistin M, Brown J, Jenkusky S, Komaromy M, Qualls C (2011a) Outcomes of treatment of hepatitis C virus infection by primary care providers. N Engl J Med 364:2199–2207 CrossRef

Arora S, Kalishman S, Don D, Som D, Thornton K, Bankhurst A, Boyle J, Harkins M, Moseley K, Murata G, Komaramy M, Katzman J, Colleran K, Deming P, Yutsy S (2011b) Quality profile: partnering urban academic medical centers and rural primary care clinicians to provide complex chronic disease care. Heal Aff 30(6):1176–1184 CrossRef

Berwick DM, Nolan TW, Whittington J (2008) The triple aim: care, health, cost. Heal Aff 27(3):759–769 CrossRef

Binkley KE (2012) Improving the diagnosis and treatment of CRPS: insights from a clinical immunologist's personal experience with an underrecognized neuroinflammatory disorder. J Neuroimmune Pharmacol [Epub ahead of print]

Burton R, Boedeker B (2000) Application of telemedicine in a pain clinic: the changing face of medical practice. Pain Medicine 1(4):351–357 CrossRef

Cook NL, Hicks LS, O’Malley AJ, Keegan T, Guadagnoli E, Landon BE (2007) Access to specialty care and medical services in community health centers. Health Affair 26(5):1459–1468

Cooper MS, and Clark VP (2012) Neuroinflammation, neuroautoimmunity, and the co-morbidities of complex regional pain syndrome. J Neurimmune Pharmacol [Epub ahead of print]

de Mos M, de Bruijn AGJ, Huygen FJPM, Dieleman JP, Stricker BH, Sturkenboom MCJM (2006) The incidence of complex regional pain syndrome: a population-based study. Pain 129(1–2):12–20

Goebel A (2011) Complex regional pain syndrome in adults. Rheumatology 50(10):1739–1750 CrossRef

Ingelfinger JR, Drazam JM (2011) Patient organizations and research on rare diseases. N Engl J Med 364(17):1670–1691 CrossRef

Marinus J, Moseley GL, Birklein F, Baron R, Maihofner C, Kingery WS, Van Hilten JJ (2011) Clinical features and pathophysiology of complex regional pain syndrome. Lancet 10(7):637–648 CrossRef

Meyer BC, Clarke CA, Troke TM, Friedman LS (2012) Essential telemedicine elements (Tele-Ments) for connecting the academic health center and remote community providers to enhance patient care. Academic Medicine 87(8):1032–1040 CrossRef

Singh G, Willen SN, Boswell MV, Janata JW, Chelimsky TC (2004) The value of interdisciplinary pain management in complex regional pain syndrome type I: a prospective outcome study. Pain Physician 7:203–209

Sood S, Mbarika V, Jugoo S, Dookhy R, Doarn CR, Prakash N, Merrell RC (2007) What is telemedicine? A collection of 104 peer-reviewed perspectives and theoretical underpinnings. Telemedicine and e-Health 13:573–590 CrossRef



Wednesday, April 25, 2012

Space Perception and Neglect in CRPS

[I've no idea why, but Blogger has decided to go rogue in formatting this post... Please excuse the excessive variety in spacing and fonts!]

I was excited to see the reference to this topical review in PAIN, as the subject is currently near and dear to my heart, and legs! CRPS is best known for its disabling sensory symptoms, including pain, allodynia, and abnormal skin temperature. Yet, motor dysfunction is common in CRPS and can result in major disability. In  addition to weakness of the involved 

limb, CRPS patients may develop symptoms akin to a neurological neglect-like syndrome, whereby the limb may feel 

foreign ('cognitive neglect') and directed mental and visual attention is needed to move the limb ('motor neglect').

Published in PAIN: Journal of IASP;  Also available on author's NOCION page.

Topical review 

Pain, body, and space: what do patients with complex regional pain syndrome really neglect?

Valéry Legrain a,b, Janet H. Bultitude c,d, Annick L. De Paepe a, Yves Rossetti d,e


a  Department of Experimental Clinical and Health Psychology, Ghent University, Ghent, Belgiumb  Institute of Neuroscience, Université catholique de Louvain, Louvain-la-Neuve and Brussels, Belgiumc  Centre for Functional Magnetic Resonance Imaging of the Brain, University of Oxford, Oxford, UKd  ImpAct, Centre de Recherche en Neurosciences de Lyon, Inserm U1028, CNRS UMR 5092, Université Claude Bernard Lyon 1, Bron, Francee  Mouvement et Handicap, Hôpital Henry Gabrielle, Hospices Civils de Lyon, Lyon, France

1. Introduction

Space is an important dimension in perception. It helps to perceive the relative position between objects including one’s own body in order to guide interaction with the outer world. The brain is able to process spatial information according to different frames of reference. A first dissociation can be made between egocentric and allocentric representations [28]. The egocentric, subject-centered frame of reference enables spatial representations of objects depending on their position relative to the perceiver’s body. In this case, left and right are defined according to the midline of the body or of specific body parts. In representations that depend on an allocentric frame of reference, the perception of position in space is independent of the observer. Space is then perceived in terms of positions between objects or between parts of the same objects. Another important distinction is the dissociation between personal, peripersonal and extrapersonal spaces [30]. Personal space corresponds to the space of the body, peripersonal space to the immediate space surrounding the body allowing direct manipulation of proximal objects, and extrapersonal space to the far space in which objects are reached by limb movements.

In humans, these dissociations have been documented by the neuropsychological investigations of patients affected by hemispatial neglect or hemineglect syndromes [1,9,10,23]. Hemineglect is an attentional deficit after damage to one hemisphere characterized by an inability to explore and report stimuli on the side of space contralateral to the damaged hemisphere, in the absence of sensory and motor deficits [40]. The term hemi denotes the main feature of the disorder, stressing that hemineglect is not a global deficit of space perception. It can affect different sensory systems and motor functions, in isolation or together [40].


2. An impaired body representation in complex regional pain syndromes
It has been proposed that nociceptive stimuli can also be perceived according to different spatial frames of reference [15]. Indeed, the fact that nociceptive processing is greatly influenced by selective spatial attention [14] and by proprioceptive and proximal visual inputs [8,18,20] supports the idea that nociceptive information is integrated in multimodal and peripersonal representations of the body [15]. Evidence is also proposed by the clinical observation of neglect-like behaviors in patients with complex regional pain syndromes (CRPS) [21]. In addition to the major characteristics of CRPS—i.e., pain, swelling, and skin changes in the affected limb—some of these patients tend to ignore or have an altered mental representation of the affected limb (somatoparaphrenia); movementsare smaller and less frequent (hypokinesia), and they take conscious effort [5–7,16]. They have difficulties recognizing their own limb [24] and estimating its position [17], its size [25], and its orientation [34]. Stimulation of the affected limb is difficult to be perceived when the unaffected limb is concurrently stimulated [26] (Table 1). These clinical observations and self-administered surveys have led to the hypothesis that sensory-motor symptoms observed in CRPS could be due to more than pain.


3. An impaired perception of space in CRPS
But do the neglect-like symptoms observed in CRPS parallel those observed in patients with brain damage and hemineglect [4]? Which spatial coordinates are able to explain the neglect-like symptoms in CRPS, and more importantly, what can we learn about the spatial perception of pain from these patients? The neglect symptoms of CRPS patients are modified by vision of the limb [17,27]. Patients show mislocalization of the affected and sometimes also of the unaffected limbs [17]. Moseley et al. [26] have shown that during concurrent stimulations of the two limbs in the absence of vision, the attentional bias away from stimulations of the affected limb observed in normal posture is surprisingly reversed when the limbs are crossed: patients tend to neglect stimulations of the unaffected limb. These data strongly suggest that cortical impairment of CRPS does not constitute a simple modification of the sensory-motor pathways [33] and involves alterations of more complex and multimodal representations of the bodily space. These data [26] also imply that CRPS 
patients do not especially neglect the affected limb, but more exactly the side of space where the affected limb normally 
resides, suggesting an impairment of a reference frame that is not dependent of the somatotopic representation of the body (i.e., personal frame) [13]. It is therefore proposed that neglect-like symptoms in CRPS, and the underlying cortical changes, result from an implicit maladaptive reorganization of the sensory-motor system to avoid provocation of the affected limb, leading to an impaired representation of that limb [21].


Table 1

Deficits in body representation and spatial perception observed in CRPS patients.

[I'm still working on formatting this table so that I can copy and paste it.  Failing that, I'll manually insert it.]

4. An impaired perception of space not limited to the side of the affected limb
Puzzling data have revealed that CRPS patients can have an impaired spatial perception of visual stimuli presented far from the body and that the direction of neglect symptoms could be the reverse of that previously observed—i.e., CRPS patients can bias the perception of space toward, and not away from, their affected limb [35,36,38]. Sumitani et al. [36] have used a visual subjective body midline judgment task known to produce errors toward the ipsilesional hemispace in brain-damaged neglect patients [11]. During this task, a light dot was projected on a screen 2 m away from the patients’ body, and they were asked, facing the screen, to move the dot to the position they estimated to cross the trunk-centered sagittal midline of their body. To manipulate the spatial frame of reference used to perform the tasks, straight-ahead estimations were performed either in the dark or in the light. While performance in the light relied on both egocentric and allocentric frames, performance in the dark could only rely on an egocentric spatial frame of reference because of the absence of any external visual clues. Subjective judgments closely matched the real objective body midline in the light condition, but conversely, in the dark, judgments were dramatically shifted toward the side of the affected limbs. This pattern of response was not observed in patients with other kind of unilateral pain syndromes [38].

The neglect of CRPS patients observed in the visual subjective body midline judgments might result from an attentional imbalance between the sensory inputs arising from the two hemibodies as a result of ‘‘exaggerated information’’ on the affected side—i.e.,unilateral pain [36]. Neglect symptoms reduced after the application of nerve blocks, and a similar trend was noted in healthy participants [36]. In addition, the shift toward the hemispace of the affected limb during visual straight-ahead estimations can be efficiently reduced by prism adaptation [35]. This technique, previously used with brain-damaged neglect patients, consists of modifying visuospatial perception by distorting it through prismatic glasses. Looking through these glasses shifts the visual field ipsilesionally in hemineglect patients. The resulting errors in visually guided reaching force the recalibration of visual and proprioceptive spatial coordinates toward the impaired hemispace, and improve neglect symptoms [32]. As compared to hemineglect consecutive to brain damage, a different strategy was proposed in CRPS: the prism intervention is aimed at shifting spatial frames away from the affected side [35,36]. After prism adaptation, visual body midline judgments erred in the opposite direction, toward the side of the unaffected side [35]. In contrast to previous studies [5–7,16,24,25,34], these latter experiments [35,36,38] demonstrated that the side for which there is a diminished representation of space does not always correspond to that of the affected limb.


5. An impaired perception of space not limited to egocentric frames of reference

These data show that CRPS patients can neglect sensory information that is neither in direct nor proximal (i.e., peripersonal) contact with the body, assuming, however, that only an egocentric frame of reference is used to perceive the outer world. In other words, neglect symptoms in CRPS patients seem to be determined by a spatial mapping system that uses the body as the coordinate of reference. Very recent data are further complicating the interpretation of the pattern of neglect symptoms of CRPS patients.



Robinson et al. [31] have reported a single case of CRPS with impaired knowledge of spatial orientation for external objects. The patient was able to recognize and to name objects, but was unable to judge whether their orientation was canonical or not and was unable to reorient objects from noncanonical to canonical orientation. Surprisingly, this was especially marked along the horizontal axis (i.e., up vs down). The patient could correctly copy objects, but his copies were most of the time mirror reversed, as if, as outlined by the authors, the internal structure of visual objects was maintained but the main orientation axis was absent. This case ispuzzling because the deficits of the patients cannot be explained by the opposition between affected vs. unaffected sides, nor by an impaired egocentric representation of space in which the viewer’s body is the main coordinate frame.



6. Physiological and clinical implications
The data reviewed here lead us to carefully address the role of the posterior parietal cortex, not only in the pathogenesis of CRPS [19], but more largely in the cortical integration of nociceptive information in the perspective of programming the most efficientaction in response to external sensory events [15], especially those threatening the physical integration of the body. Damage to the posterior parietal cortex is involved in hemineglect [39], and this area plays an important role in the integration of sensorimotor and multimodal inputs in order to form multiple representations of space and to guide appropriate actions [3,12]. This suggests that the parietal areas are of primordial importance in nociceptive processing. On the other hand, stressing the role of space perception in nociceptive processing and pain generation outlines the fact that
pain is more than just an unpleasant sensory and emotional experience, but a signal warning the presence of a potential threat mobilizing the cognitive system in order to localize, identify and respond to this threat. The acknowledgment of distorted spatial processes is also highly relevant for the clinical management of pain. Indeed, Sumitani et al. [35] have shown that prism adaptation can additionally decrease pain and other CRPS symptoms after 2 weeks of treatment. These data were replicated by Bultitude and Rafal [2], who confirmed in one patient that daily prism adaptation could alleviate CRPS symptoms such as pain, swelling, and hand motricity after 10 days. Other techniques based on similar conceptions are also potentially relevant. Moseley et al. [27] have demonstrated modification of the perception of pain in CRPS by
distorting the visual size of the affected hand. Other teams [2,22,37] have tried to cure CRPS patients with mirror rehabilitation [29]. With this technique, synchronous movements of the two limbs are made while the affected limb is hidden behind a mirror that gives to the subject the image of the unaffected limb as if it was the affected one. The subject sees the reflected image of the unaffected limb in the space occupied by the affected one, giving the illusion of a healthy moving limb, and this change in visual input is helpful in alleviating CRPS symptoms after several days of treatment [2,22,37].



7. Conclusion
The studies presented in this review do not allow us to conclude that the neglect-like symptoms of CRPS patients simply result from an implicit defensive mechanism to avoid confronting the affected body part to increased pain, but instead suggest a deficit of spatial perception, which is not always restricted to the space of the affected limb. It also seems evident that CRPS does not affect a simple somatotopic mental schema of the body represented in primary somatosensory cortex, but instead multiple representations of space that are multimodal and not specifically limited to direct sensory inputs of the body. Dissociated impairments to distinct space representations in CRPS are yet to be demonstrated. This stresses the need to pursue neuropsychological testing of spatial perception in CRPS patients to illuminate how various reference frames are affected by CRPS. The study of nociceptive processing and pain perception in relationship to spatial perception is highly relevant, not only for understanding the role of pain in the cortical processes that underlie the coordination between detection of threat and defensive action, but also for developing new neuropsychological techniques to treat chronic pain.

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