Microvascular Response in Patients with Complex Regional Pain Syndrome as Measured by Laser Doppler Imaging

Bilateral deficiency of Meissner corpuscles and papillary microvessels in patients with acute complex regional pain syndrome

ABSTRACT

Complex regional pain syndrome (CRPS) presents postinjury with disproportionate pain and neuropathic, autonomic, motor symptoms, and skin texture affection. However, the origin of these multiplex changes is unclear. Skin biopsies offer a window to analyze the somatosensory and vascular system as well as skin trophicity with their protecting barriers. In previous studies, barrier-protective exosomal microRNAs were altered in CRPS. We here postulated that tissue architecture and barrier proteins are already altered at the beginning of CRPS. We analyzed ipsilateral and contralateral skin biopsies of 20 fully phenotyped early CRPS patients compared with 20 age- and sex-matched healthy controls. We established several automated unbiased methods to comprehensively analyze microvessels and somatosensory receptors as well as barrier proteins, including claudin-1, claudin-5, and claudin-19. Meissner corpuscles in the skin were bilaterally reduced in acute CRPS patients with some of them lacking these completely. The number of Merkel cells and the intraepidermal nerve fiber density were not different between the groups. Dermal papillary microvessels were bilaterally less abundant in CRPS, especially in patients with allodynia. Barrier proteins in keratinocytes, perineurium of dermal nerves, Schwann cells, and papillary microvessels were not affected in early CRPS. Bilateral changes in the tissue architecture in early CRPS might indicate a predisposition for CRPS that manifests after injury. Further studies should evaluate whether these changes might be used to identify risk patients for CRPS after trauma and as biomarkers for outcome.

Complex Regional Pain Syndrome (CRPS) and the Value of Early Detection

PURPOSE OF REVIEW

The goal of this narrative review is to describe the current understanding of the pathology of Complex Regional Pain Syndrome (CRPS), as well as diagnostic standards and therapeutic options. We will then make the case for early recognition and management.

RECENT FINDINGS

CRPS remains an enigmatic pain syndrome, comprising several subtypes. Recent recommendations clarify diagnostic ambiguities and emphasize the importance of standardized assessment and therapy. Awareness of CRPS should be raised to promote prevention, early detection, and rapid escalation of therapy in refractory cases. Comorbidities and health costs (i.e., the socioeconomic impact) must also be addressed early to prevent negative consequences for patients.

Effect of different thermal stimuli on improving microcirculation in the contralateral foot

Background

The lower extremities of the body often suffer from impaired microcirculation, particularly in the elderly or people with underlying conditions such as diabetes. Especially for people suffering from peripheral vascular diseases, skin lesions or wearing an external fixator in one side of limbs, direct contact treatments are not suitable for them to improve microcirculation. Heating the contralateral limb has been reported to improve blood flow in the impaired limb. However, its effect on plantar microvascular responses has not been previously investigated. Thus, the aim of this study was to explore how heating by warm bath and infrared radiation affects the circulations in the contralateral foot. Twelve healthy adults participated in this study and were randomly assigned to either placing the left foot in a warm bath or exposing it to infrared radiation for 10 min intervention every other day. The skin temperature (Temp) and skin blood flow (SBF) in the second metatarsal head of the contralateral foot were measured before and after the intervention.

Results

The results showed that both Temp (Bath: from 29.05 ± 3.56 °C to 31.03 ± 4.14 °C; Infrared: from 29.98 ± 3.86 °C to 31.07 ± 3.92 °C) and SBF (Bath: from 62.26 ± 48.12 PU to 97.76 ± 63.90 PU; Infrared: from 63.37 ± 39.88 PU to 85.27 ± 47.62 PU) in the contralateral foot were significantly increased after heating in both tests (p < 0.05). However, the contralateral SBF increased for 5 min after heating in warm bath test, but only for 1 min in infrared radiation test.

Conclusions

The results of this study show that both heating methods are the effective at increasing contralateral Temp and SBF, but the warm bath has a stronger residual thermal effect.

Complex regional pain syndrome: a focus on the autonomic nervous system

PURPOSE

Although autonomic features are part of the diagnostic criteria for complex regional pain syndrome (CRPS), the role of the autonomic nervous system in CRPS pathophysiology has been downplayed in recent years. The purpose of this review is to redress this imbalance.

METHODS

We focus in this review on the contribution of the autonomic nervous system to CRPS pathophysiology. In particular, we discuss regional sympathetic and systemic autonomic disturbances in CRPS and the mechanisms which may underlie them, and consider links between these mechanisms, immune disturbances and pain.

RESULTS

The focused literature research revealed that immune reactions, alterations in receptor populations (e.g., upregulation of adrenoceptors and reduced cutaneous nerve fiber density) and central changes in autonomic drive seem to contribute to regional and systemic disturbances in sympathetic activity and to sympathetically maintained pain in CRPS.

CONCLUSIONS

We conclude that alterations in the sympathetic nervous system contribute to CRPS pathology. Understanding these alterations may be an important step towards providing appropriate treatments for CRPS.

Microvascular Response in Patients with Complex Regional Pain Syndrome as Measured by Laser Doppler Imaging

Objectives

Our aim was to investigate the hypothesis that microvascular dysfunction occurs in patients with CRPS. Specifically, whether there were functional differences in either deeper cutaneous blood vessels or more superficial nutritive vessels between the affected and unaffected limb in patients with CRPS, and between CRPS patients and healthy control subjects.

Methods

Twenty‐two patients with CRPS (five male; mean age 45 years; eight upper limb involvement, 14 lower limb) and 23 healthy control subjects (one male; 43 years) were recruited. Microvascular flow at affected and unaffected contralateral sites was measured, following local heating, using laser Doppler imaging (red/green wavelengths). Corresponding sites were imaged in healthy controls. Maximum flux level and area under the curve (first 20 scans, AUC20) were measured.

Results

Vasodilator responses to heat were similar in affected and unaffected limbs, and in healthy controls. For example, median (IQR) “red” AUC20 in CRPS was 138.6 (120.0–152.9)% change from baseline in affected limb and 135.0 (120.7–166.8)% in unaffected limb, and (in healthy controls) 133.1 (117.2–145.9)% and 139.1% (126.0–162.1) in limb 1 and 2.

Conclusions

We found no impairment of vasodilation in cutaneous microvessels in CRPS. The vasomotor changes in CRPS may relate to larger vessel dysfunction.