Fine-grained mapping of cortical somatotopies in chronic Complex Regional Pain Syndrome

Abstract

32It has long been thought that severe chronic pain conditions, such as Complex Regional 33 Pain Syndrome (CRPS), are not only associated with, but even maintained by a 34 reorganisation of the somatotopic representation of the affected limb in primary 35 somatosensory cortex (S1). This notion has driven treatments that aim to restore S1 36 representations, such as sensory discrimination training and mirror therapy. However, 37 this notion is based on both indirect and incomplete evidence obtained with imaging 38 methods with low spatial resolution. Here, we used functional MRI to characterize the S1 39 representation of the affected and unaffected hand in patients with unilateral CRPS. At 40 the group level, the cortical area, location, and geometry of the S1 representation of the 41 CRPS hand were largely comparable to those of the healthy hand and controls. 42However, the area of the map of the affected hand was modulated by disease duration 43 (the smaller the map, the more chronic the CRPS), but not by pain intensity, pain 44 sensitivity and severity of the physical disability. Thus, if any map reorganization occurs, 45it does not appear to be directly related to our pain measures. These findings compel us 46 to reconsider the cortical mechanisms underlying CRPS and the rationale for 47 interventions that aim to "restore" somatotopic representations to treat pain. 49Significance statement 50 51This study shows that the spatial map of the fingers in S1 is largely preserved in chronic 52 CRPS. Shrinkage of the area of the affected hand map can occur in the most chronic 53 stages of disease. Map shrinkage is related to CRPS duration rather than diagnosis, and 54 is unrelated to how much pain patients experience or to the severity of the physical 55 disability. These findings challenge the rationale for using sensory interventions to treat 56 pain by restoring somatotopic representations in CRPS patients. 58 59 Introduction 60Chronic pain is a highly common and debilitating disorder, that can be associated with 61 functional and morphological changes in the brain. For instance, it has long been 62 thought that some severe chronic pain conditions, such as Complex Regional Pain 63 Syndrome (CRPS), are not only associated with, but even maintained by, maladaptive 64 topographic changes in the primary somatosensory cortex (S1) (Maihofner et al., 2003, 93 quantification of the representation of the fingers (i.e. with exclusion of the thumb) in 94 patients with chronic and unilateral CRPS to the upper limb. We tested whether the S1 95 representation of the fingertips of the affected hand was different from that of the healthy 96 hand of CRPS patients and from controls in terms of its spatial extent, location relative to 97 the central sulcus, and geometry (i.e. variability of the map gradients). 98 99 Materials and Methods 100 101 4 Participants. We recruited 20 adults with unilateral CRPS to the upper limb and 20 102 healthy controls (HC) matched for age, gender and handedness. Each participant gave 103 written inf...

Attentional modulation of neural dynamics in tactile perception of complex regional pain syndrome patients

“…Nevertheless, it is encouraging to notice, for instance, how the “super‐subject” decoding time‐course did yield similar “peaks” to those often reported in in classical somatosensory ERP research: the earliest cortical components emerging between 20 and 80 ms, followed by a N1‐like wave (commonly observed around 80–120 ms) (Luck, 2005) can be appreciated in both conditions (Figure 3). These results lend further support to the thesis that CRPS does not show changes in the fine grained cortical somatotopies (Mancini et al, 2019). These two early modulations are meant to mirror the more “physiological” aspects of sensory processing, tracking afferent inputs from peripheral nerves into primary cortical areas (S1; <50 ms; Lueders et al, 1983; Wood et al, 1988), and from there to secondary processing stages (S2; >80 ms), building up to the (yet unconscious) detection of sensory stimuli (Chennu et al, 2013; Garrido et al, 2009; Schubert et al, 2006, 2008).…”

“…The initial idea, developed in analogy to other pain conditions such as phantom limb or chronic back pain (Bray & Moseley, 2011; Flor et al, 1995, 1997), was that misperception symptoms could result from CRPS‐induced maladaptive plasticity (i.e., cortical reorganization) in the contralateral primary sensory cortex (S1) (Maihöfner et al, 2004; Pleger et al, 2004). However, the few neuroimaging studies conducted so far have led to contradicting results, spanning from a similar representation of affected and unaffected sides of the body, to an enlarged (rather than shrunk) representation of the affected limb onto S1 (Di Pietro et al, 2013, 2015; Mancini et al, 2019; Pfannmöller et al, 2019; van Velzen et al, 2016). However, as recently pointed out by some authors (Brown et al, 2020; Kuttikat et al, 2018), most work on CRPS‐related body misperception (mirroring the larger branch of body perception research) has traditionally focused on early, more “physiological” components of somatosensory processing (i.e., <50 ms; e.g., Lenz et al, 2011; Pleger et al, 2004), relying on experimental architectures that are more concerned with stimulation precision rather than its ecological validity.…”

Neurocognitive consequences of hand augmentation

“…It is highly consistent within (8) and across (9) participants and is preserved even after severe loss of motor functions due to e.g. stroke (9), spinal cord injury (10), disability (11) or even hand amputation (12)(13)(14). Hand representation has been suggested to reflect daily hand use (9), with studies showing that it may be altered under constrained circumstances.…”

Attentional Modulation of Neural Dynamics in Tactile Perception of Complex Regional Pain Syndrome Patients

“…cortical reorganization) in the contralateral primary sensory cortex (S1) (Maihöfner et al ., 2004; Pleger et al ., 2004). However, the few neuroimaging studies conducted so far have led to contradicting results, spanning from a similar representation of affected and unaffected sides of the body, to an enlarged (rather than shrunk) representation of the affected limb onto S1 (Di Pietro et al ., 2013; Di Pietro et al ., 2015; van Velzen et al ., 2016; Mancini et al ., 2019; Pfannmöller et al ., 2019). However, as recently pointed out by some authors (Kuttikat et al ., 2018; Brown et al ., 2020), most work on CRPS-related body misperception (mirroring the larger branch of body perception research) has traditionally focused on early, more “physiological” components of somatosensory processing (i.e.…”