G Lorimer Moseley
School of Physiotherapy, The University of Sydney, Sydney, Australia
Regional anesthesia results in shrinkage of the primary sensory cortex (S1) representation of the area and the perception that the area is larger than it is. Complex regional pain syndrome type 1 (CRPS1) also involves shrinkage of S1 representation and, anecdotally, the perception of marked swelling when none is apparent. We posited that if a reduced S1 representation of the affected limb is involved in generating a perception that the limb is larger than it really is, then this effect should be present in patients with CRPS1.
Patients with CRPS1 perceived the affected limb to be larger than it really was. This distortion of body image may be an important part of the presentation of CRPS1. The mechanisms involved are not clear, but S1 changes may be involved. S1 changes have been proposed to underpin clinical phenomena (eg stimulation at one site referring sensation to body parts represented immediately adjacent to the affected area in S1) that occur in patients following amputation, tooth extraction, spinal cord injury, stroke, local anesthesia, and CRPS1. Those groups also describe distortion of body image such that the anesthetized part feels large, full, or swollen. Perhaps though neural connections indirectly linking S1 and association cortices in the ‘what’ visual pathway, shrinkage of the S1 representation of the affected limb engenders alteration of visual magnitude perception. It is notable that the perceived size of the affected limb related to the duration of CRPS1,and in other patient groups characterised by changes in S1 representation, eg amputees, cortical reorganisation correlates with the duration of symptoms.
The current sample was not homogeneous; symptoms, anatomic site, and medications varied. Although these factors did not relate to selected image, future work could elucidate the importance of such factors and verify the current results. The results corroborate other findings of distorted body image in people with CRPS1, but the mechanisms remain poorly understood.
See full article at Neurology, 65; 773