Enhanced temporal pain processing in multiple system atrophy.

Pain processing has been poorly studied in multiple system atrophy (MSA), notwithstanding these subjects complaint pain very frequently. We hypothesized that, as observed in other basal ganglia neurodegenerative disorders involving the striatonigral projections, also in MSA with predominant parkinsonian signs could be detected an abnormal pain processing. We used the temporal summation threshold (TST) of the nociceptive withdrawal reflex (NWR) and the related pain sensation to evaluate the temporal pain processing at spinal level in eleven MSA subjects and compared them with fifteen Parkinson's disease (PD) subjects, in both during "on" and "off" treatment with l-Dopa, and fifteen healthy subjects. MSA showed a significant reduction in NWR TST as well as facilitation in other pain responses when compared to healthy subjects; no differences were detected between "on" and "off" condition; no differences were detected between MSA and PD subjects in term of neurophysiological and pharmacological responses. We demonstrated a facilitated temporal processing of pain in MSA subjects paralleling findings from PD. We hypothesize that the abnormal pain processing detected in both MSA and PD, could represent a consequence of the striatonigral neurodegeneration which in turn make these subjects more prone to develop pain conditions.