Background & Aims
Complex regional pain syndrome (CRPS) is a disorder characterised among others by continuous, disproportionate pain. In the chronic phase, the affected extremity may become cold due to vasomotor disturbances decreasing blood flow [1,2].
Spinal cord stimulation (SCS) is an invasive treatment targeting the dorsal column. SCS has proven effective in targeting several CRPS-specific mechanisms, including pain and vasomotor disturbances [3,4]. Quantifying changes in vasomotor activity is challenging. Thermal imaging has been used to measure the skin temperature and determine temperature differences in CRPS patients [5], but with new technology a much larger set of medical image features has become available [6].
The aim of this case study is to assess medical image features from thermographic images to quantify changes in vasomotor activity in a CRPS patient who receives SCS therapy. Furthermore, the correlation with changes in pain scores is assessed.
Methods
The patient (47 yo woman) was a candidate for SCS. She had CRPS of the right foot for 2 years, with cold CRPS before implantation. Thermographic images and pain scores were collected at baseline, trial period, 1 and 3 months follow-up. The two-week trial was used to assess the effects of SCS therapy before permanent implantation.
Thermographic images show the skin temperature per pixel. For this study, we analysed temperature distribution features based on these pixels. Due to vasomotor disturbances in the affected foot, the temperature distribution is expected to differ from the unaffected foot. A smaller difference indicates more symmetry and should correlate with improved vasomotor activity in the affected foot.
The differences between the unaffected and affected foot were determined for distribution features: median, maximum, minimum and peak temperature. The differences were also compared with the reported Numeric Rating Scale (NRS) pain scores.
Results
At baseline, there was a difference of 2.5 – 3.5 degrees between the unaffected and affected foot for the median, maximum and peak features.
Already during the two-week trial, there was a decrease in these feature differences, indicating that the affected foot was becoming more similar to the unaffected foot.
At 1 and 3 months, the difference between the unaffected and affected foot was eventually reduced to 0.5 – 2.0 degrees for the median, maximum and peak features. Indicating more symmetry between the two feet.
This reduction in temperature difference was not seen for the minimum temperature feature.
Pain scores at the same measurement moments showed a similar reduction. From an NRS score of 8 at baseline to 6 at the trial period and 2 at 3 months follow-up.
Conclusions
Visually assessing the thermographic images, differences in temperature between measurement moments were difficult to detect to the human eye. Several distribution features, however, revealed reduction in temperature differences after SCS therapy.
Only the minimum temperature feature showed a different trend. This patient’s CRPS area extends from the toes to the outer ankle, however her toes on the unaffected side are also cold. It is important to investigate which features are most informative for monitoring vasomotor changes. The distribution features are only a subset of all medical image features. Incorporating more features would increase insight in skin temperature changes and therefore in the effects of CRPS treatment.
Changes in skin temperature after SCS implantation were quantified using medical image features from thermographic images. These changes indicated an improvement in CRPS vasomotor disturbances, which also corresponded to improved pain scores.
References
1.KD Bharwani, M Dirckx, FJPM Huygen. Complex regional pain syndrome: diagnosis and treatment, BJA Education 2017;17:262–268.
2.Wasner G, Schattschneider J, Heckmann K, Maier C, Baron R. Vascular abnormalities in reflex sympathetic dystrophy (CRPS I): mechanisms and diagnostic value. Brain. 2001;124(Pt 3):587-99.
3.Kumar K, Rizvi S, Bnurs SB. Spinal cord stimulation is effective in management of complex regional pain syndrome I: fact or fiction. Neurosurgery. 2011;69(3):566-78; discussion 5578-80.
4.Kriek N, Groeneweg JG, Stronks DL, de Ridder D, Huygen FJPM. Preferred frequencies and waveforms for spinal cord stimulation in patients with complex regional pain syndrome: A multicentre, double-blind, randomized and placebo-controlled crossover trial. Eur J Pain (United Kingdom). 2017 Mar 1
5.Huygen FJ, Niehof S, Klein J, Zijlstra FJ. Computer-assisted skin videothermography is a highly sensitive quality tool in the diagnosis and monitoring of complex regional pain syndrome type I. Eur J Appl Physiol. 2004;91(5-6):516-24
Presenting Author
Elinevan Lange
Poster Authors
Topics
- Specific Pain Conditions/Pain in Specific Populations: Complex Regional Pain Syndrome (CRPS)