What is the role of autonomic function testing (AFT) in the workup of complex regional pain syndrome (CRPS)?

Updated: Jun 20, 2018
  • Author: Gaurav Gupta, MD; Chief Editor: Stephen A Berman, MD, PhD, MBA  more...
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Answer

AFT includes infrared thermometry, infrared thermography, quantitative sudomotor axon reflex test (QSART), thermoregulatory sweat test (TST), and laser Doppler flowmetry. Skin temperature differences can be easily assessed by infrared thermometry or thermography. [67] Currently, a characteristic sensory pattern has not been identified. Such a pattern would allow clinicians to determine the presence of CRPS and quantify the individual signs of each patient so that responses to successful treatments can be measured and documented. Caution is necessary with AFT since autonomic differences are dependent on environmental conditions that can alter pertinent test dynamics within minutes. Therefore, measurements should be repeated at the beginning, middle, and end of a patient visit.

In a study of 21 patients with CRPS, enhanced sudomotor output was demonstrated with QSART and TST in the affected limb compared with the contralateral limb within the mean disease duration of 5 weeks. [68] At a mean duration of 94 weeks, TST findings remained abnormal, whereas QSART showed no differences from healthy subjects.

In a study using laser Doppler flowmetry to assess vascular reflex responses, 3 different vascular regulation patterns were demonstrated in CRPS type I. With short-term CRPS (ie, with a mean duration of 4 mo), the affected limb showed higher perfusion than the contralateral limb. In patients with a mean CRPS duration of 15 months, the affected limb showed either higher or lower skin perfusion than the contralateral limb. Finally, in patients with a mean CRPS duration of greater than 20 months, the affected limb showed lower perfusion of the skin. Skin temperature changed correspondingly for each pattern. [27]


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