Impaired Performance in Mental Rotation of Hands and Feet and Its Association with Social Cognition in Patients with Complex Regional Pain Syndrome.

OBJECTIVES: So far, dysfunction in mental rotation has been assessed in relation to the left- or right-sided CRPS. Here we examined mental rotation in patients with upper or lower limb CRPS. Considering the potential role of socio-emotional functioning on the perception of body image, we further investigated the association between performance on mental rotation and socio-emotional characteristics. METHODS: We examined the performance of 36 patients with upper or lower limb CRPS on the limb laterality recognition. Accuracy and response times for pictures of hands and feet at 4 rotation angles were evaluated. Socio-emotional functioning was measured by the Interpersonal Reactivity Scale and the Toronto Alexithymia Scale. RESULTS: Patients with upper limb pain showed longer RTs to recognize the laterality of hands than feet (P = 0.002), whereas patients with lower limb pain showed longer RTs for feet than hands (P = 0.039). Exploratory correlation analyses revealed that RTs for feet were negatively correlated with the levels of empathic ability to take another's perspective (P = 0.006) and positively correlated with the level of emotional difficulty in identifying feelings (P = 0.006). CONCLUSIONS: This study is the first to report selectively impaired mental rotation of hands vs feet in patients with upper or lower limb CRPS. The findings suggest that impaired mental rotation derives from relative deficits in the representation of the affected limb. Correlations between impaired mental rotation and socio-emotional inability indicate that an altered body schema may be closely associated with impaired social cognitive aspects in CRPS patients.

Different patterns in mental rotation of facial expressions in complex regional pain syndrome patients.

Although facial pain expressions are considered to be the most visible pain behaviors, it is known that the association between pain intensity and facial pain expression is weak for chronic pain. The authors hypothesized that the facial pain expressiveness was altered in chronic pain and investigated it with a mental rotation task using various facial expression, which seems to be associated with actual facial movements. As a task stimulus, 4 types of facial expression stimuli consisted of upper (tightening of eye and furrowed brows) and lower (raising upper lip) pain-specific facial expressions, and upper (eyeball deviation) and lower (tongue protrusion) facial movements not using facial muscles were used. Participants were asked to judge whether a stimulus presented at various rotation angles was left- or right-sided. The authors tested 40 patients with complex regional pain syndrome (CRPS) (12 women, age range 21-60) and 35 healthy controls (15 women, age range 26-64). In an analysis of reaction time (RT) using a linear mixed model, patients were slower to react to all types of stimuli (P = .001) and a significant interaction between group (patient or control) and type of facial expression was observed (P = .01). In the post hoc analysis only patients showed longer RTs to raising upper lip than other types of facial expressions. This reflects a deficit in mental rotation tasks especially for lower facial region pain expressions in CRPS, which may be related to the psychosocial aspects of pain. However, comprehensive intra- and interpersonal influences should be further investigated.