Examination of the Pathophysiologic Mechanisms of CRPS by Using QST, CPM, RIC, and Heart Rate Variability QST

This study aims for a better understanding of the pathophysiological mechanisms of the complex regional pain syndrome (CRPS). This will be done by testing the quantitative sensory testing, the remote ischemic conditioning, the conditioned pain modulation (CPM) and the analysis of the heart-rate variability in patients with CRPS and a control-group. We hypothesize decreased conditioned pain modulation, less effects of remote ischemic conditioning and an affection of the heart-rate variability in patients with CPRS.

CRPS is an illness which (seriously) affects patients in their daily life activity. The fact that the pathophysiological mechanisms are not well understood yet makes it hard to treat these patients in the right manner.

Possible patho-mechanisms might be microvascular changes and dysfunctions of the inhibitory descending pain system. Furthermore, recent studies showed that CRPS patients have macrovascular changes and a lower blood level of NO on the affected side. This indicates a NO mediated perfusion dysfunction.

Aim of this study is to examine the pathophysiological mechanism of CRPS in relation to healthy subjects and patients with a different type of pain syndrome (carpal tunnel syndrome) on the upper limb.

The investigators try to get a better understanding of the changes in the pain inhibitory system and micro- and macrocirculating blood-systems, as well as of the autonomic system of CRPS-patients.

Eligibility Criteria:
CRPS-patients

Inclusion Criteria:

* Unilateral pain on the upper limbs, based on a scintigraphic ensured CRPS (average pain in the last 4 weeks ≥ 3 in pain Detect)
* Pain history \< 1 year

Exclusion criteria:

* Bilateral pain on the upper limbs
* Inadequate knowledge of the german language in speaking and writing
* Acute psychiatric sickness
* Polyneuropathy
* Any added neuropathic sickness on the not affected upper limb sight
* Intolerable pain during the testing
* Injuries within the tested areal
* Acute injuries on the hand
* Pregnancy
* Missing informed consent

CTS-patients

Inclusion Criteria:

* Unilateral pain on the upper limbs, based on a scintigraphic ensured CRPS (average pain in the last 4 weeks ≥ 3 in pain Detect)
* Pain history \< 1 year

Exclusion criteria:

* Bilateral pain on the upper limbs
* Inadequate knowledge of the german language in speaking and writing
* Acute psychiatric sickness
* Polyneuropathy
* Any added neuropathic sickness on the not affected upper limb sight
* Intolerable pain during the testing
* Injuries within the tested areal
* Acute injuries on the hand
* Pregnancy
* Missing informed consent

Healthy subjects

Inclusion Criteria:

* Age \> 18 years
* Written consent

Exclusion criteria:

* Inadequate knowledge of the german language in speaking and writing
* Current pain
* Pain within in the last 14 days
* Any serious internistic medicin
* Any chronic skin disease
* Any central neural sickness
* Polyneuropathy
* Peripheral nerve lesion within the testing areal
* Any radiculopathy with permanent pain (in the last 3 months)
* Any psychiatric sickness
* Migraine ( at least one attack in the last 24 h)
* Repeating headache (in the last 3 month on \>5 days/month)
* Taking any analgesics in the last 14 days
* Taking triptans in the last 24 months
* Taking any psychotropic's in the last 3 months
* Any repeated taking of medication, including amber or different psychostimulants (excluding contraceptives)
* Taking of any prescription and non-prescription drugs (except contraceptives) in the last 7 days or 5 half-life periods(which is always longer) before including into the study
* Achilles reflex absent or within in the side-difference pathologic hypoactive or hyperactive
* pallaesthesia \<5/8 (\<4/8 at \>60 years) on the internal malleolus on both sides
* abuse of alcohol or medications/drugs (corresponding to the DSM IV criteria)
* joining a medical study \<30 days before inclusion into the current study
* jet lag, irregular work schedule, sleep deprivation within the last 3 days
* change of intestity during physical activity, e.g. beginning an activity in the last weeks before inclusion into the current study