Imagine that you want to grab a cup of coffee. Successful planning and execution of this and many other everyday life tasks crucially depends on a good sense of the position and movements of your body parts (= proprioception). Such tasks would be very difficult to perform if you have no (or perhaps the wrong) idea of where your hand is, or what it is doing!
Some patients with Complex Regional Pain Syndrome (CRPS) need to closely watch their affected limb in order to control movement (Galer et al. 1995). This may indicate that they rely on vision to compensate for disturbed proprioception. After all, CRPS is characterized by (often severe) pain and various sensory impairments that may interfere with proprioception (e.g. Huge et al. 2011; van Rooijen et al. 2013), and the mental image of the affected body part is often distorted (e.g. Förderreuther et al. 2004; Lewis et al. 2007).
Against this background, it seems likely that proprioceptive deficits contribute to the disabling motor dysfunction of CRPS. We therefore examined the accuracy and precision of joint position sense of the wrist in 25 chronic CRPS patients (affected and unaffected side) and in 50 healthy controls (see Bank et al. 2013). The tested hand (which of course was not visible to the participant) was moved towards various target positions, either by means of active movements by the patient or by means of passive movements that were imposed by a motor. As soon as the target position was reached, the participant indicated the perceived joint angle by means of a pointer. The (angular) error between the orientation of the pointer and the concurrent orientation of the hand was thenanalysed.
CRPS patients were less able than controls to properly estimate the position of both their affected and unaffected hand. In particular, patients were less precise (i.e., more variable) and displayed a systematic ‘misperception’ of extension positions: the hand was perceived to be more towards extension than it actually was. Because target positions were calculated on the basis of the range of motion, and given that many CRPS patients had a restricted range of motion, a special control condition was needed in which controls were tested at wrist angles that corresponded to those of the patient’s affected side. It showed that the differences between patients and controls cannot simply be attributed to the smaller range of target positions of the patients’ affected hands. Interestingly, poorer proprioceptive performance was associated with more severe motor impairment of the affected hand, which suggests a close relationship between proprioceptive impairment and CRPS-related motor dysfunction.
We also aimed to identify at which stage of information processing these proprioceptive deficits arise. To this end, we performed additional sensory tests, compared active and passive displacements, and examined variations in proprioceptive performance over the range of wrist angles. Together, these analyses led to the conclusion that the disturbances of proprioceptive performance in CRPS most likely resulted from altered processing of afferent (rather than efferent) information and its subsequent interpretation in relation to a ‘body schema’ that does not accurately match the actual status of the limb.
In sum, the present results point at a significant role for impaired central processing of proprioceptive information in the motor dysfunction of CRPS. Although still speculative, we suggest that therapeutic strategies aimed at identification of proprioceptive impairments and their restoration may promote the recovery of motor function in CRPS patients.
About Paulina JM Bank
Linda Bank (1986) has been working on her PhD thesis at the department of Neurology in the Leiden University Medical Center under the supervision of Prof. van Hilten and dr. Marinus (LUMC, Department of Neurology), and Prof. Beek and dr. Peper (VU University, Research Institute MOVE, Faculty of Human Movement Sciences) after she graduated cum laude for the BSc and MSc Human Movement Sciences at the VU University in Amsterdam (specialization ‘learning, development, and coordination of movement’) in 2009. The aim of her PhD project was to obtain a better understanding of the motor dysfunction in patients with Complex Regional Pain Syndrome by means of evaluating changes in the motor system, changes in sensory processing and problems in motor sensory-motor integration. She hopes to defend her thesis early 2014.
At present, Linda works as a post-doctoral researcher at the LUMC, where she strives to build a bridge between clinicians and engineers in order to develop a set-up that allows to search for the weak(est) links in a patient’s motor performance. Here is a link to Linda’s published research.
References
Bank PJ, Peper CL, Marinus J, Beek PJ, & van Hilten JJ (2013). Motor dysfunction of complex regional pain syndrome is related to impaired central processing of proprioceptive information. J Pain, 14 (11), 1460-74 PMID: 24064035
Förderreuther S, Sailer U, & Straube A (2004). Impaired self-perception of the hand in complex regional pain syndrome (CRPS). Pain, 110 (3), 756-61 PMID: 15288417
Galer BS, Butler S, & Jensen MP (1995). Case reports and hypothesis: a neglect-like syndrome may be responsible for the motor disturbance in reflex sympathetic dystrophy (Complex Regional Pain Syndrome-1). J Pain Symptom Manage, 10 (5), 385-91 PMID: 7673771
Huge V, Lauchart M, Magerl W, Beyer A, Moehnle P, Kaufhold W, Schelling G, & Azad SC (2011). Complex interaction of sensory and motor signs and symptoms in chronic CRPS. PloS one, 6 (4) PMID: 21559525
Lewis JS, Kersten P, McCabe CS, McPherson KM, & Blake DR (2007). Body perception disturbance: a contribution to pain in complex regional pain syndrome (CRPS). Pain, 133 (1-3), 111-9 PMID: 17509761
van Rooijen DE, Marinus J, Schouten AC, Noldus LP, & van Hilten JJ (2013). Muscle hyperalgesia correlates with motor function in complex regional pain syndrome type 1. J Pain, 14 (5), 446-54 PMID: 23541068