Intact 2D-form recognition despite impaired tactile spatial acuity in complex regional pain syndrome type I

Abstract

Tactile acuity measured by 2-point discrimination performance is impaired in patients with complex regional pain syndrome type I (CRPS-I). This is mirrored by pain-associated shrinkage of the cortical representation of the affected limb. We investigated whether, also, more complex tactile performance assessed by a dynamic 2D-form perception task is disturbed in CRPS-I patients. Therefore, we developed a Braille-like recognition task (BT) for geometrical dot pattern identification by dynamic touch. We studied 47 healthy volunteers (Study I) and compared them to 16 CRPS-I patients (Study II). Besides recognition time and error quote of the BT, we assessed static 2-point discrimination thresholds (TPDT). In healthy subjects, the performance in the BT correlated significantly with age and TPDT. In CRPS patients, TPDT was significantly increased on the affected side compared to sex- and age-matched controls from study I (2.98 ± 0.84 mm vs 2.05 ± 0.82 mm, P<0.01). The performance in the BT was not impaired in CRPS-I patients (compared to sex- and age-matched controls from study I) and was not correlated to the TPDT. The intact 2D-form recognition ability in CRPS-I patients might be explained by intact dynamic tactile and proprioceptive functions, which appear to be uncompromised by the impaired static tactile perception, provided that the spacing of the dot pattern is above the individual tactile acuity. These intact 2D-form perception capacities may also be related to higher sensory integration functions like the visual system and intact semantic understanding, which may be spared by the cortical reorganization phenomena in CRPS-I.

The rubber hand illusion in complex regional pain syndrome: Preserved ability to integrate a rubber hand indicates intact multisensory integration ☆

“…Although our data have yet to be supported by imaging results and interpretation should hence be made tentatively, it may be hypothesized that the integration of multimodal percepts in association areas such as the ventral premotor cortex or posterior parietal region is unaffected in CRPS, the retained illusion strength suggesting similar functionality to that of healthy subjects and patients with upper limb pain of other origin. In line with this notion, Reiswich et al [51] reported preserved 2-dimensional form recognition abilities in CRPS patients, indicating intact higher order sensory integration, despite impaired tactile acuity (corresponding to S1 and SII function). Moreover, Moseley and Wiech [40] also observed intact visuotactile integration despite impaired tactile discrimination in CRPS patients.…”

“…At the same time, recent findings indicate that despite dysfunctional sensory processing, integration of body-related multisensory perceptions is intact in CRPS [40,51,64]. For example, despite decreased tactile spatial acuity, CRPS patients present intact 2-dimensional form-recognition abilities, provided that the form is above the spatial resolution performance [51]. Moreover, visuotactile integration was shown to be unaffected when CRPS patients underwent tactile training while simultaneously watching their healthy hand [40].…”

“…Several studies linked decreased tactile acuity with the reduced size of cortical hand representation and altered excitability in the somatosensory cortex of CRPS patients [27,34,46,47]. At the same time, recent findings indicate that despite dysfunctional sensory processing, integration of body-related multisensory perceptions is intact in CRPS [40,51,64]. For example, despite decreased tactile spatial acuity, CRPS patients present intact 2-dimensional form-recognition abilities, provided that the form is above the spatial resolution performance [51].…”

Reduction of head and face pain by challenging lateralization and basic emotions: a proposal for future assessment and rehabilitation strategies

“…42,[47][48][49] This is clinically seen by an increase in the two-point discrimination threshold in the affected region. 50 In addition, correlations between tactile discrimination and cortical representation on the somatosensory cortex have been identified, 43 showing changes in representation in the sensory homunculus in persistent pain.…”

Neues aus der Forschung zum Komplexen Regionalen Schmerzsyndrom (CRPS)

“…Interessanterweise fand sich eine bilaterale kortikale Disinhibition nach Doppelpuls-SEP-Reizung[ 15 ] . In einer neuen Studie wurde auch der Befund der erhöhten Zweipunktdiskriminationsschwelle reproduziert[ 16 ] . Zudem zeigte sich, dass diese Störung bei Patienten mit dystonen Symptomen stärker ausgeprägt war als bei sonstigen CRPS-Patienten[ 10 ] .…”