Table 4 Results summary of the eligible articles

Terkelsen et al. [18]

  CRPS type 1 (n = 18) + CRPS type 2 (n = 2)

20 (11 women) with unilateral upper limb CRPS with mean age 45 (ranged from18-72 years) and pain duration of 37 months

  Healthy Control group: (n = 20) matched for age, sex, and BMI

Mean age: 44 (ranged from 19 to 68 years)

The diagnosis was based on IASP criteria

PPT, CDT, WDT, HPT, CPT, capsaicin induced pain, flare area, and perfusion area

  PPT measured at proximal inter-phalangeal joint of middle finger and skin fold between thumb and index fingers

  CDT, CPT, WDT, and HPT measured at dorsum of the hand between first and second metacarpal and at thenar eminence using thermal tester (Somedic AB)

  Capsaicin 5% was applied for 30 min to the dorsum of the hand at fixed skin temperature of 35 °C while laser Doppler perfusion was used to assess the flare area. Also, pain intensity was measured after the application of capsaicin. This variable measured only in 16 patients and 15 healthy subjects

Maximum pain after capsaicin application:

  In affected and non-affected limbs of CRPS, it was 63 (27/100) and 54 (18)

  In the control group, it was 37 (27/100) and 36 (22) in the hands matched to the affected and non-affected limbs to CRPS

Flare area

  In affected and non-affected limbs, it was 24.7 (8.3 cm²) and 23.5 (11.0 cm²) in CRPS

  In control group was 30.6 (11.5 cm²) and 31.1 (10.4 cm²) in the matched hands to affected and non-affected limbs to CRPS

Area under curve of pain (AUC)

  In affected and non-affected limbs of CRPS, it was 64.079 (37.99 cm²) and 54.354 (27.755 cm²)

  In the control group, it was 33.605 (24.888 cm²) and 35.434 (34.108 cm²) in the hands matched to the affected and non-affected limbs to CRPS

PPT at skin fold:

  In CRPS group, it was 190 (132 kPa) and 362 (126 kPa) in affected and non-affected hands, respectively

  In the control group, it was 591 (275 kPa) and 600 (270 kPa) in matched hands to CRPS

PPT at inter-phalangeal joint:

  In CRPS group, it was 172 (98 kPa) and 315 (106 kPa) in affected and non-affected hands, respectively

  In control group, it was 569 (154 kPa) and 597 (156 kPa) in the matched hand of affected and non-affected hands of CRPS

CPT at thenar area:

  In CRPS group was 23.2 (5.7 °C), 16.6 (6.3 °C) in affected and non-affected hand, respectively

  In control group was 12.1 (3.0 °C), 12.3 (3.6 °C) in the matched hand to affected and non-affected hands of CRPS group

CPT at dorsum of the hand between first and second metacarpal:

  In CRPS group was 23.4 (5.5 °C), 17.7 (6.7 °C) in affected and non-affected hand, respectively

  In the control group, it was 11.3 (2.5 °C), 12.3 (4.7 °C) in the matched hand to affected and non-affected hands of CRPS group

HPT at thenar area:

  In CRPS group was 38.1 (4.5 °C), 41.2 (4.2 °C) in affected and non-affected hand, respectively

  In control group was 45.1 (3.1 °C), 45.2 (3.3 °C) in the matched hand to affected and non-affected hands of CRPS group

HPT at dorsum of the hand between first and second metacarpal:

  In CRPS group was 38.4 (4.1 °C), 41.3 (4.1 °C) in affected and non-affected hand, respectively

  In control group was 44.3 (3.3 °C), 44.0 (3.6 °C) in the matched hand to affected and non-affected hands of CRPS group

Vartiainen et al. [42]

  Chronic upper limb CRPS type 1 (n = 8)

(All right-handed females; ages 26–57, mean 45.5 years)

Mean duration of 5.5 years

  Healthy age-matched female (n = 9)

(8 right-handed; ages ranged from 28 to 57, mean 46.0 years)

The diagnosis of CRPS type 1 was based on the criteria of IASP

  Presence of allodynia using brush

  The needed laser intensity to elicit pain and max Pain intensity after laser application. Thulium-laser stimulator (BLM 1000 Tm:YAG; Baasel Lasertech, Starnberg, Germany)

  Allodynia was investigated on the affected hand

  Laser noxious stimulus was applied on the dorsum of the hand

  Brush mechanical allodynia was present in all CRPS patients with no identified allodynia in the control group

  Laser intensity needed to elicit pain in CRPS was 520 mJ while in control group, it was 740 mJ

Maximum pain after laser noxious stimulation:

  In CRPS, it was 7.5 ± 0.7 and 5.4 ± 1.0 in affected and non-affected hands, respectively, while

  In the control group, it was 4.1 ± 0.5 and 4.1 ± 0.3 in the matched hands

Rasmussen et al. [43]

  CRPS type 1 (n = 8) (Seven females, one male, mean age 45.5(SD 5.19 years), six upper limbs, two lower limbs)

  Eight healthy controls (n = 8) matched to the Patients by gender and age (seven females, one male, mean age 46.9 (SD 4.83 years) and by handedness

Diagnosis of CRPS type 1 based on Budapest criteria

  CDT, CPT, WDT, and HPT were assessed using Medoc TSA-II thermode (Ramat Yishai, Israel)

  Pain rating after noxious heat or cold was assessed using VAS

  Presence of allodynia in the affected and contralateral regions was assessed using brush

All variables were measured at the affected limbs and unaffected limbs in CRPS while in the control group the region matched to affected limb was assessed

HPT:

  In the affected limb of CRPS, it was 35.6 (3.8 °C) while in the unaffected limb, it was 37.58 (1.64 °C)

  In the control group, it was 38.4 (2.8 °C)

NB. There is significant reduction in HPT in CRPS-affected limb than in control (p < 0.05)

WDT:

  In the affected limb of CRPS, it was 36 (1.7 °C), while in unaffected limb it was 34.95 (1.61 °C)

  In the control group, it was 37 (3.4 °C)

Data were transformed using Wan’s method from median (maximum, minimum values)

CDT:

  In the affected limb of CRPS, it was -2.43 (2.06 °C), while in unaffected limb it was –3.45 (3.8 °C)

  In the matched limb of control group, it was − 1.95 (1.05 °C)

Data were transformed using Wan’s method from median (maximum, minimum values)

CPT:

  In the affected limb of CRPS, it was − 5.03 (2.75 °C), while in unaffected limb, it was -8.3 (5.5 °C) and

  In the matched limb of control group was -18(9.8 °C)

Data were transformed using Wan’s method from median (maximum, minimum values)

Pain rating after noxious cold application (cold pain rating):

  In affected limb of CRPS, it was 7.0 (7.1), while in unaffected limb it was 1.5 (2.1)

  In the matched limb of control group, it was 0.0 (0.8)

Pain rating after cold application (cold rating):

  In the affected limb of CRPS was 7.0 (4.0) while in the unaffected limb was 5.04 (2.13) and

  In the matched limb of control group, it was 2.5 (2.8)

Pain rating after noxious heat application (heat pain rating):

  In affected limb of CRPS, it was 4.25 (3.5), while in unaffected limb it was 1 (1.4)

  In the matched limb of control group, it was 0.25 (0.35)

Pain rating after heat application (heat rating):

  In the affected limb of CRPS, it was 7.0 (4.3) and in the unaffected limb, it was 5.5 (1.8)

  In the matched limb of control group, it was 2.8 (2)

Data were transformed using Wan’s method from median (maximum, minimum values)

Intraepidermal nerve fiber density (IENFD):

  In the affected limb of CRPS, it was 3.55 (2.39 /mm), while in unaffected limb, it was 2.80 (4.02/mm) and

  In the control group, it was 14.50 (4.06/mm)

  Mechanical allodynia was present in all eight subjects with CRPS

Kemler et al. [44]

  CRPS type 1 (n = 53) (37 women and 16 men), with a mean age of 38.6 years (33 CRPS in the arm, 20 CRPS in the leg).

The mean duration of CRPS type 1 was 38.2 months

  Healthy subjects (n=50).

(25 females, 25 males) in the control group with age range (20–70 years).

Diagnosis of CRPS type 1 based on IASP criteria

  CDT, WDT, CPT, HPT, PPT, and PDT

  Thresholds for warmth, cold, heat-induced pain, and cold-induced pain were measured using a 5 3 2.5-cm water-cooled Peltier probe (TSA-2001; Medoc Ltd., Ramat Yishai, Israel)

  PPT was assessed by Semmes–Weinstein monofilaments

  Thresholds for the foot was assessed at the dorsal aspects of both feet, immediately proximal to the basis of the second and third toe

  Thresholds for the hand were assessed at the volar aspects of both wrists, immediately proximal to the base of the hand

In RT side wrist of healthy subjects:

  CDT was 31.3 (1.4 °C), WDT was 32.5 (2.89 °C), CPT was 5.4 (27.78 °C), HPT was 46.5 (13.7 °C), PDT was 0.07 (0.27 gm) and PPT was not detected through monofilaments used

In RT side foot of healthy subjects:

  CDT was 30.9 (5.1 °C), WDT was 35.4 (20.2 °C), CPT was 3.4 (27.24 °C), HPT was 46.7 (12.45 °C), PDT was 0.34 (1.56 gm) and PPT was not detected through the monofilaments used

In affected wrist of CRPS subjects:

  CDT was 30.9 (4.1 °C), WDT was 33.1 (5.7 °C), CPT was 21 (46.5 °C), HPT was 40.3 (24.18 °C), PDT was 7.9 (255 gm) and PPT 113 (1008gm)

In unaffected wrist of CRPS subjects:

  CDT was 31.3 (1.7 °C), WDT was 32.7 (2.9 °C), CPT was 10.6 (38.24 °C), HPT was 44.6 (16.85 °C), PDT was 0.14 (0.53 gm) and PPT was not detected

In affected foot of CRPS subjects:

  CDT was 28.8 (21.8 °C), WDT was 36.5 (19.00 °C), CPT was 20.1 (49.2 °C), HPT was 41.6 (19.39 °C), PDT was 4.5 (33.8 gm) and PPT 137 (732.4 gm)

In unaffected foot of CRPS subjects:

  CDT was 30 (12.2 °C), WDT was 35.7 (17.3 °C), CPT was 10.5 (39.13 °C), HPT was 44.1 (12.21 °C), PDT was 0.98 (3.87 gm) and PPT could not be detected

  Mechanical allodynia was present in 27/33 subjects with CRPS in arm while in CRPS of foot, it was 18/20

Seifert et al. [45]

  Upper limb CRPS type 1 (n = 24) + upper limb CRPS type 2 (n = 3) (9 males, 18 females, mean age 57.6 years (2.56)

The mean CRPS-duration was 22.12 (SD 4.3 months)

  Healthy age-matched controls (n = 14) (3 males, 11 females, mean age 52.8 years (SD 3.43 years)

The patients had to meet Budapest criteria

  Electric detection threshold (EDT), electric pain threshold (EPT), MDT, and MPT

  Flare area after current stimulation was assessed using laser Doppler perfusion

  Pinprick hyperalgesic area induced by electric stimulation

  Normalized electric current needed to induce pain intensity of 6/10 on numerical rating scale

  Pain rating during adaptation phase to induced electric current

All variables measured in the dorsum of affected hand, contralateral hand, and control group hand of CRPS

  In the affected hand of CRPS group, EDT was 1.62 (0.67), EPT was 4.31(2.44), MDT was 28.04 (30.97mN), and MPT was 213.60 (223.1 mN)

  In the unaffected hand of CRPS group, EDT was 1.32 (0.21), EPT was 4.16(1.92), MDT was 15.58 (16.06 mN), and MPT was 278.11 (247.7 mN)

  In the control group, EDT was 1.48 (0.3), EPT was 3.80 (1.05), MDT was 8.14 (5.95mN), and MPT was 310.82 (167.25 mN)

Data of EDT, EPT, MDT, and MPT was represented as mean (SEM) while SEM was transformed into SD using Cochrane handbook

Flare area:

  In CRPS affected hand, it was 2.2 (0.4 cm²), while in unaffected hand it was 2.6 (0.5 cm²) and

  In the control group it was 2.1 (0.4 cm²)

Area of electrically induced pinprick hyperalgesia:

  In the affected hand of CRPS, was 12.72 (1.36 cm²), while in the unaffected hand was 7.80 (1.44 cm²)

  In the control group, it was 8.03 (1.18 cm²)

NB. There was a significant increase in hyperalgesic area in affected hands of CRPS subjects compared to control and unaffected hands

Normalized electric current needed to induce pain of 6/10 intensity:

  In the affected hand of CRPS, it was 1.044(0.31au), while in unaffected hand, it was 1.022 (0.26au)

  In the control group the normalized current was 1.16 (0.42au)

The pain rating during electric current adaptation:

  In affected hand of CRPS, it was 4.15 (2.03), while in unaffected hand, it was 3.92 (1.92) and

  In the control group was 2.84 (1.39)

NB. Enhanced pain facilitation was evident by significant reduction of pain adaptation to electric stimuli in CRPS compared with control. Also, this was confirmed by increased hyperalgesic area after electric stimulation

  DMA was present in 21 of the patients

Sethna et al. [46] (children and adolescents)

  Children and adolescents with CRPS (n = 42) (40 females) with mean age of 13.2 (2.6 years)

  Age and sex matched healthy control (n = 101) (53 females) with mean age of 11.5 (3 years)

Both types of CRPS were included based on IASP criteria

  WDT, CDT, HPT, CPT, and VDT were assessed through Medoc Ltd., Ramat Yishai, Israel)

  Static and dynamic allodynia, and allodynia to punctate temporal summation were assessed through brush and pinprick

Assessment of all variables occurred in the most painful area of the affected foot

WDT:

  In the affected foot of CRPS, it was 35.4 (1.6 °C), while in unaffected foot it was 35 (1.3 °C)

  In the control group, WDT was 35.3(1.2 °C)

CDT:

  In the affected foot of CRPS group, it was 29.3 (2 °C) while in the unaffected foot, it was 30.3 (1.1 °C)

  In the control group, CDT was 30 (1.2 °C)

HPT

  In the affected foot of CRPS, it was 39.4(3.15 °C) while in the unaffected foot, it was 40.87 (3.3 °C)

  In the control group, HPT was 42.6 (3.15 °C)

CPT

  In the affected foot of CRPS, it was 25.53 (6.22 °C), while in unaffected foot it was 18.16 (9.2 °C)

  In the control group, CPT was 19.4 (9.32 °C)

VDT

  In the affected foot of CRPS group, it was 0.65(0.84 µm) while in the unaffected foot, it was 0.68 (0.48 µm)

  In the control group, VDT was 0.52(0.21 µm)

NB. Data reported as median (1st, 3rd quartiles) and transformed based on Wan’s method

  Mechanical static allodynia was observed in 29 patients

  Mechanical dynamic allodynia was observed in 28 patients

  Allodynia to punctate temporal summation was observed in 30 patients

  All types of allodynia were observed in 26 patients

Huge et al. [47]

  Upper extremity CRPS type 1 (n = 61) (54 females) with mean age of 59.1 (12.9 years)

The cohort of CRPS was divided into two groups, the first group was acute CRPS (27 patients) with mean disease duration of 3.5 (SD 2.1 months) while the second group was chronic CRPS (34 patients) with mean disease duration of 37.4 (SD 15.1 months)

We included the data of chronic cases only

  Healthy control (n = 56) (40 females), with mean age of 56.8 (12.3 years)

CRPS type 1 diagnosed based on the research diagnosis criteria proposed by Bruehl et al. 1999 and IASP diagnostic criteria 1994

CDT, WDT, CPT, HPT, TSL, and paradoxical heat sensation (PHS) were assessed via Medoc Thermal Stimulus Analyser TSA-2001 device (Medoc, Ramat Yishai, Israel)

All parameters were measured at painful area of the affected hand and the matched area of control group (both dominant and non-dominant hands were reported in the study, while we mentioned only the results of dominant hands)

WDT:

  In the affected hand of CRPS, it was 37.2 (4.1 °C) while in the unaffected hand, it was 36.2(3.00 °C)

  In the dominant hand of the control group, it was 34.3 (1.5 °C)

CDT:

  In the affected hand of CRPS, it was 28.4 (2.4 °C) while in the unaffected hand, it was 29.2(1.6 °C)

  In the dominant hand of control group, it was 30.5 (1.00 °C)

TSL:

  In the affected hand of CRPS, it was 0.9 (0.3 °C) while in the unaffected hand, it was 0.8(0.2 °C)

  In the dominant hand of control group, it was 0.52 (0.3 °C)

HPT:

  In the affected hand of chronic CRPS was 44.21 (4.3 °C) while in the unaffected hand of CRPS, it was 44.6 (4.3 °C)

  In the dominant hand of control group, it was 45.24 (3 °C)

CPT:

  In the affected hand of CRPS, it was 15.8 (9.9 °C) while in the unaffected hand, it was 13.8 (9.3 °C)

  In the dominant hand of control group, it was 9.8 (7.6 °C)

PHS:

  In CRPS, it was present in 2/31 patients

  In the control group, it was almost absent (occurred in 1/336 TSL trials in both hands of healthy controls (0.3%)

Results of huge et al. reported as mean (SE) in the article, while we mentioned in the table mean (SD) after using Cochrane guidelines to transform SE into SD

Vatine et al. [48]

  CRPS type 1 (n = 17)

(6 women with mean age of 56.7 (SD 14.5 years) and 11 men with mean age of 37.3 (SD 14.5 years)

Symptom duration was 21.1(SD 39.2 months). Only 2 patients have a duration of one month that is not considered chronic

  13 patients with other chronic pain conditions (6 women with mean age of 46.2 (26.6 years) and 7 men with mean age of 40 (SD 17.8 years)

  Pain-free volunteers (n = 24)

(10 women with mean age of 36.9 (SD 12.7 years) and 14 men with mean age of 40 (SD 11.2 years)

Diagnosis based on the diagnostic criteria of the IASP

PPT

Pressure pain tolerance (the pressure that induces intolerable pain)

Sternum

Mean threshold and tolerance values were significantly lower in patients with CRPS (2.7 ± 1.0 kg and 5.4 ± 2.0 kg, respectively) and in patients suffering from other chronic pain syndromes (2.6 ± 1.1 and 4.6 ± 1.7 kg) than in healthy subjects (5.4 ± 2.3 and 8.4 ± 2.6 kg)

Mainka et al. [49]

  Upper limb CRPS type 1 (n = 18)

(7 females) and mean age of 51.7 (10.1 years)

The duration of symptoms was 3.3 (SD 2.6 months)

  16 subjects with upper limb pain but not diagnosed as CRPS (non-CRPS) with mean age of 45.5 (SD 15.3 years)

  Healthy control group (n = 18)

(9 females) with mean age of 41.2 (SD 11.3 years)

Patients with CRPS type 1, diagnosed in accordance with the revised Budapest criteria

PPT was measured using Somedic Production AB, Sweden, algometer type II

Thenar area, metacarpophalangeal (MCP) and proximal inter-phalangeal (PIP) joints. The average PPT of all five MCP and PIP joints was reported

PPT of affected thenar area:

  In CRPS, it was 243.1 ± 150 kPa while in the unaffected thenar area, it was 522.5 ± 121.9 kPa

  In the control group, it was 477.9 ± 105.9 kPa

PPT of affected MCP joints:

  In CRPS, it was 79.8 ± 66.6 kPa while in the unaffected thenar area, it was 279.4 ± 148.8 kPa

  In the control group, it was 254.0 ± 50.4 kPa

PPT of affected PIP joints:

  In CRPS. it was 79.7 ± 55.7 kPa while in the unaffected thenar area, it was 300.2 ± 140.5 kPa

  In the control group, it was 274.7 ± 75.9 kPa

NB. There was a significant reduction of all PPT thresholds in affected hands of CRPS compared to control group

The study reported the finding of right and left hands of the control group. Thus, we used the dominant right-hand findings for comparison

Rooijen et al. [50]

  Upper limb CRPS type 1 (n = 48)

(With dystonia, n = 31 and mean age of 45.5 (SD 12.4 years); without dystonia, n = 17 and mean age of 47.9 (SD 11.7 years)

  Age and sex matched healthy controls (n = 42)

(16 women) with mean age of 46.7 (12.0 years)

Diagnosis of CRPS type 1 was based on IASP criteria

  CDT, WDT, CPT, HPT, PPT, WUR, and VDT

  CDT, WDT, CPT, And HPT Measured By TSA-II Neurosensory Analyzer (Medoc Ltd, Ramat Yishai, Israel)

  VDT was measured via Vibrameter (Type II; Somedic, Stockholm, Sweden)

  PPT was measured via electronic algometer (FPX50; Wagner Instruments, Greenwich, CT)

-WUR was measured via a custom-made pinprick of 256 mN was used

  CDT, WDT, CPT, HPT, and WUR Measured at dorsum of the hand

  PPT was measured over the M. abductor pollicis brevis

  VDT was measured over the first metacarpal bone

In affected hand of CRPS group with dystonia:

  CDT was 29.4 (28.0–30.9 °C), WDT was 36.4 (34.7–43.5 °C), CPT was 26.5 (4.8–30.0 °C), HPT was 41.7 (35.6–48.0 °C), WUR was 1.4 (1–2), PPT was 2.0 (1.0–3.8 kg/cm), and VDT was .45 (.40–5.5 µm)

In affected hand of CRPS group without dystonia:

  CDT was 30.0 (28.4–30.6 °C), WDT was 36.4 (35.3–43.2 °C), CPT was 24.5 (12–26.7 °C), HPT was 44.7 (38.9–48.1 °C), WUR was 1.4 (1–3.4), PPT was 3.4 (2.2–5.6 kg/cm), and VDT was .35 (.20–1.05 µm)

In matched hand of control group without dystonia:

  CDT was 30.9 (30.1–31.3 °C), WDT was 35.2 (33.4–36.1 °C), CPT was 13.8 (4.9–22.5 °C), HPT was 43.7 (40.8–47.6 °C), WUR was 2.0 (1–3), PPT was 6.1 (4.9–6.9 kg/cm), and VDT was .22 (.17–.41 µm)

All data reported as median and IQR while transformed into mean and SD using Wan’s method

In both types of CRPS, there was significant loss of warm, cold, vibration detection thresholds as well as significant gain of pressure pain and cold pain thresholds compared to control group

NB. compared to healthy controls, pain levels after the first pinprick were significantly higher in CRPS patients with dystonia (p = .001)

Rooijen et al. [51]

  Upper limb CRPS type 1 (n = 48)

(With dystonia, n = 31 and mean age of 45.5 (12.4 years); without dystonia, n = 17 and mean age of 47.9 (11.7 years)

  Age and sex matched healthy controls (n = 42)

(16 women) with mean age of 46.7 (12.0 years)

Diagnosis was based on IASP criteria

CDT, WDT, CPT, HPT, PPT, WUR, and VDT

CDT, WDT, CPT, HPT, and WUR Measured at matched site in contralateral arm (21 measurements), contralateral leg (30 measurements), cheek (48 measurements), and ipsilateral site away from the affected area (24 measurements)

  WDT measured at contralateral arm of CRPS was 34.9 (34–38.2) while in controls, WDT was 34.5 (33.6–36.1)

   In the ipsilateral leg of CRPS, WDT was 37.6 (35.5–42.4) while in healthy group, WDT was 37.3 (35.6–40)

  In the contralateral leg, WDT in CRPS was 38.3 (35.7–41.7) while in control group, it was 37 (34.9–39)

  In cheek, WDT in CRPS was 35.1 (34.3–36.5), while in the control group, it was 34.3 (33.4–35.3)

  CDT of the contralateral arm of CRPS was 30.3 (29.6–31.3), while in control group, it was 30.6 (30.2–31.1)

  CDT of the ipsilateral leg of CRPS was 27.5 (24.5–29.4), while in control group, it was 29.4 (27–30.3)

  CDT of the contralateral leg of CRPS was 29.1 (27.2–30.3), while in the control group, it was 28.2 (26.6–29.7)

  CDT of the cheek of CRPS was 30.7 (30.3–31.0), while in the control group, it was 31 (30.4–31.4)

  HPT of the contralateral arm of CRPS was 42.7 (4.7), while in the control group, it was 44.3 (3.9)

  HPT of the ipsilateral leg of CRPS was 44.5 (4.1), while in the control group, it was 45.4 (3)

  HPT of the contralateral leg of CRPS was 43.6 (4), while in the control group, it was 45.5 (2.8)

  HPT of the contralateral arm of CRPS was 39.3 (37.3–46.4), while in the control group, it was 45.1 (41–47.6)

  CPT of the contralateral arm of CRPS was 22.9 (6.1–26.4), while in the control group, it was 9.3 (3.1–20.8)

  CPT of the ipsilateral leg of CRPS was 16.8 (0–24.9), while in the control group, it was 10.2 (0–19.9)

  CPT of the contralateral leg of CRPS was 20.2 (8.1–24.6), while in the control group, it was 6.5 (0–20.9)

  CPT of the cheek of CRPS was 26.2 (4.4–28.4), while in the control group, it was 16.7 (0.6–23.5)

  PPT of the contralateral arm of CRPS was 3.6 (2.7–5.4), while in the control group, it was 6.2 (4.9–7.5)

  PPT of the ipsilateral leg of CRPS was 4.6 (3.4–7.1), while in the control group, it was 6.9 (5.7–8.6)

  PPT of the contralateral leg of CRPS was 4.6 (3.6–6), while in the control group, it was 6.6 (5.6–8)

  PPT of the cheek of CRPS was 1.4 (1–2), while in the control group, it was 2 (1.7–2.5)

  VDT of the contralateral arm of CRPS was 0.32 (0.23–1.13), while in the control group, it was 0.31 (0.22–0.38)

  VDT of the ipsilateral leg of CRPS was 2.8 (1.4–11.5), while in the control group, it was 2.0 (0.68–7.6)

  VDT of the contralateral leg of CRPS was 2.2 (1.0–11.2), while in the control group, it was 1.9 (0.64–6.8)

  VDT of the cheek of CRPS was 1.6 (0.84–2.39), while in the control group, it was 0.8 (0.41–1.89)

All data reported as median and IQR while transformed into mean and SD using Wan’s method

Palmer et al. [52]

  Unilateral upper or lower CRPS type 1 (n = 36) (29 female)

Mean age was 48.94 ± 13.70 years)

  Healthy controls (n = 37) (29 women) with mean age of 50.27 (15.28 years)

Based on Budapest criteria for unilateral CRPS for upper and lower limb affection

Cold and heat sensitivity based on numerical rating from 0 to 10 using Hot and cold metal rollers (Therroll; Somedic Production AB, Sweden)

PPT was assessed on distal phalanges of index fingers bilaterally using digital algometer (Somedic Production AB)

Light touch threshold (LTT) was measured using Von Frey monofilaments on hands and sternum

Cold and hot sensitivity was measured using a scale from 0 to 10, at the nearest location to the most painful area at which patients can tolerate heat and cold sensations

PPT was measured at distal phalanges of index fingers

LTT was measured at both hands and sternum

  In the affected region of CRPS, cold sensitivity was 3.00 (1.00) while heat sensitivity was 6.00 (1.00), LTT of the affected hand was 0.14 (0.69gm), LTT of sternum was 0.09 (0.70gm), and PPT of the affected index finger was 182 (102 kPa)

  In the unaffected region of CRPS, cold sensitivity was 3.00 (0.13) while heat sensitivity was 6.00 (1.00), LTT of the unaffected hand 0.12 (0.31gm), and PPT of the unaffected index finger was 225 (169 kPa)

  In the dominant right side of control group, cold sensitivity was 3.00 (1.00) while heat sensitivity was 6.00 (0.00), LTT of the right hand was 0.06 (0.09 gm), LTT of the sternum was 0.05 (0.11gm), and PPT of right index finger was 280 (144 kPa)

Data were represented as median and IQR, while we used these values as a mean and SD during meta-analysis as we could not transform these values

Both results of right and left sides of control group were reported, while we mentioned only the right dominant side

Kumowski et al. [53]

  CRPS type 1 (n = 21) + CRPS type 2 (n = 3)

Mean age was 51.6 (SD 9.8 years) and the disease duration was 24.2 (SD 11.7 weeks)

  Age and gender matched healthy controls (n = 23)

Based on the Budapest research criteria for CRPS

CPM

A heat pain stimulus served as test stimulus (TS) and was applied to a pain-free area on the volar forearm of the affected side with a 30 by 30 mm2 contact stimulation device (TSA-II, Medoc, Ramat Yishai, Israel)

Conditioned stimulus of cold-water immersion applied on contralateral hand

All QST parameters were measured at the thenar area bilaterally

  In CRPS, heat pain (TS) before conditioning was 46.2 (13.2), during conditioning was 31.4 (15.7), five minutes after conditioning was 40 (14.6)

Regarding conditioned pain modulation (CPM) effect:

  Early CPM (TS during—before) was − 14.7 (15.7), while late CPM (TS after 5 min—before) was − 6.2 (9.4)

  In the control group, heat pain (TS) before conditioning was 50.2 (12.3), during conditioning was 37.7 (15.8), five minutes after conditioning was 44.6 (15.9)

Regarding conditioned pain modulation (CPM) effect,

  Early CPM (TS during—before) was − 12.5 (12.4), while late CPM (TS after 5 min—before) was − 5.6 (13)

Data of heat pain and CPM effect represented as mean and (SE)

  Based on QST, somatosensory abnormalities in the CRPS group were loss of thermal detections (CDT: 25%, WDT: 21%; TSL: 33%), thermal hyperalgesia (CPT: 17%, HPT: 22%), and mechanical hyperalgesia (MPT: 33%)

QST values were represented as z-score. A value outside the 95%-confidence interval of published data from healthy subjects (corresponding to z-values higher than + 1.96 or lower than -1.96) were considered as abnormal value (Rolke et al. 2006; Magerl et al. 2010)

Gierthmühlen et al. [15] (frequencies of sensory abnormalities)

  CRPS type 1 (n = 298) (233 females)

Mean age was 53.0 (SD 13.4 years) and symptoms duration was 21.2 (SD 35.5 months)

  CRPS type 2 (n = 48) (38 females)

The mean age was 52.3 (SD 12.0 years) and symptoms duration was 25.1 (SD 33.3 months)

  Healthy controls (n = 180) (110 females)

Mean age of 38.4 (SD 12.9 years)

Based on IASP and Budapest criteria

CDT, WDT, TSL, CPT, HPT, MDT, MPT, MPS, WUR, VDT, PHS, MDA (mechanical dynamic allodynia), and PPT

Thermal thresholds measured by using a TSA-2001-II (MEDOC, Ramat Yishai, Israel)

MDT was assessed using a standardized set of modified von Frey hairs (Optihair2-Set, Marstock Nervtest, Schreisheim, Germany) exerting forces between 0.25 and 512 mN

MPT, WUR, and MPS were assessed using custom-made weighted pinprick stimuli (the PinPrick; MRC Systems GmbH, Heidelberg, Germany)

Gentle/light stroking with a cotton wisp (around 3 mN), a cotton wool tip fixed to an elastic strip (around 100 mN), and a brush (around 200–400 mN) used to assess DMA

VDT was measured via Rydel–Seifert et al. tuning fork (64 Hz, 8/8 scale)

Pressure gauge device (FDN200, Wagner Instruments, Greenwich, CT, USA) used to assess PPT

The most painful area of the hand in CRPS was assessed while dorsum of the hand in the control group was assessed

  In the affected limb of CRPS group, the sensory gain of CDT was 3.8%, WDT was 2.2%, TSL was 2.65%, CPT was 30%, HPT was 39.7%, MDT was 7.85%, MPT was 32.9%, MPS was 42.1%, WUR was 12%, VDT was 1.7%, PPT was 70%, and DMA was 26.1%

  In the healthy controls, the sensory gain of CDT was 2.3%, WDT was 6.1%, TSL was 5.00%, CPT was 4.5%, HPT was 3.9%, MDT was 6.2%, MPT was 3.3%, MPS was 5%, WUR was 7.2%, VDT was 6.7%, PPT was 5.6%, and DMA was 1.1%

  In the affected limb of CRPS group, the sensory loss of CDT was 36.3%, WDT was 28%, TSL was 26.15%, CPT was 6.2%, HPT was 8.8%, MDT was 42.7%, MPT was 11%, MPS was 8.9%, WUR was 2.3%, VDT was 36.9%, and PPT was 4%

  In the healthy controls, the sensory loss of CDT was 6.7%, WDT was 7.2%, TSL was 5.5%, CPT was 4.4%, HPT was 2.8%, MDT was 6.1%, MPT was 5%, MPS was 2.2%, WUR was 2.8%, VDT was 1.1%and PPT was 3.4%

Knudsen et al. [54]

  Upper limb CRPS type 1 (n = 17) + lower limb CRPS type 1 (n = 17)

  Healthy controls (n = 45) (14 male). Age ranged from 17 to 51 years

Based on IASP research diagnostic criteria

PPT at forehead bilaterally. Pressure was applied using a spring loaded algometer with a rounded tip (1 cm in diameter)

Sharpness to mechanical stimulus was assessed based on a scale from 0 (not sharp) to 10 (stabbing) in response to a single application with a firm nylon bristle (Filament 17, Senselab von Frey Aesthesiometer, Somedic Sales AB, Sweden)

22 patients underwent cold pressor pain modulation by immersion of affected and contralateral sides in cold water 2 °C if patients cannot withstand because of allodynia, cold water of 10 °C was used

Bilateral forehead ipsilateral to affected side and contralateral to it

  In CRPS patients, PPT at ipsilateral and contralateral forehead was 497 (48 g) versus 648 (43 g), respectively

  In CRPS, sharpness to punctate stimulation on the ipsilateral than contralateral side of the forehead in both groups of patients (mean rating 3.6 (.3) versus 2.6 (.2)), respectively

  In the control group, PPT of right-side forehead = 675.71 (30 g) while for left forehead, it was 652.00 (33 g)

  Sharpness of the control group at right-side forehead was 3.2 (0.2) while at left side, it was 3.3 (0.3)

For conditioned pain modulation:

  Forehead asymmetry increased after immersion of the CRPS-affected limb (from 556.5 (61 gm) to 418.5(53.7gm) in ipsilateral side and from 606.12 (72.5 gm) to 509.8 (53.5 gm) in contralateral side; significant reduction after the affected limb immersion, p < .05), but not after immersion of the healthy limb, from 500 (55 gm) to 439 (55 gm) in ipsilateral side and from 575.5 (49 gm) to 550 (57 gm) in contralateral limb after 2 min immersion

  Sharpness was symmetrical in the forehead during each limb immersion and did not change after the immersions

  In the control group, sharpness also did not change while the PPT diminished significantly after cold pressor (from 675 (30 gm) to 564 (22gm) in ipsilateral side and from 652 (33 gm) to 572 (28 gm) in contralateral side

  Sharpness did not significantly change after cold pressor application

NB. This indicates disturbances of inhibitory control in CRPS

Data represented as mean and SE, while we used Cochrane guidelines to transform data into mean (SD)

NB. Results of CRPS and healthy controls were published separately while the same research group introduced both studies. Also, the study of CRPS compared PPT with the control values published before CRPS study

Edinger et al. [55]

  CRPS (n = 20) accompanied with total body pain

The average duration was 109.6 (SD 63.4 months). In CRPS, there were 18 women (age 21–59 years; average age, 39.9 years) and 2 men (ages 24 and 46; average age, 35 years)

  Age and gender matched healthy controls (n = 10)

Based on the Budapest clinical criteria

static and mechanical allodynia, thermal allodynia, mechanical hyperalgesia, and after sensations

Static non hyperalgesia allodynia was measured using a Wagner Force Dial TM algometer (Wagner Instruments, Greenwich, CT)

DMA measurements were obtained using a standard one-inch foam brush

A metal tuning fork chilled in an ice water bath to 2 °C was utilized to evaluate cold thermal allodynia

The threshold for algesic mechanical hyperalgesia was measured using a Neuropen (Owen Mumford, Oxford, UK)

After sensation, pain perception lasting longer than 30 s after the stimulus withdrawal was recorded following the 4 sensory tests on each limb

Most painful areas of eight selected body regions of (face, chest, abdomen, right arm, left arm, right leg, left leg, and back

  All patients with CRPS showed a significantly lower pain threshold for static allodynia in all body regions tested compared to the control participants (face, p = 0.045; chest, p = 0.004; abdomen, p = 0.012; right arm, p = 0.001; left arm, p < 0.0001; right leg, p < 0.0001; left leg, p < 0.0001; back, p < 0.0001)

  More than half of the patients with CPRS showed a significantly lower pain threshold for dynamic allodynia in all body regions tested compared to control participants (face, n = 12, P = 0.0225; chest, n = 15, P < 0.0001; abdomen, n = 13, P < 0.0001; right arm, n = 15, P < 0.0001; left arm, n = 16, p = 0.001; right leg, n = 18, p = 0.0001; left leg, n = 17, p = 0.00064; back, n = 13, p < 0.0001)

  At least 85% of the patients with CRPS had a significantly lower pain threshold for mechanical hyperalgesia in all body areas compared to control participants (face, n = 17, p = 0.001; chest, n = 19, p = 0.0001; abdomen, n = 18, p = 0.0001; right arm, n = 20, p < 0.0001; left arm, n = 18, p < 0.0001; right leg, n = 20, p < 0.0001; left leg, n = 19, p < 0.0001; back, n = 19, p < 0.0001)

  For cold allodynia, the median pain rating in all areas for the control participants was 0. For the patients with CRPS, the median pain rating for the face, chest, right upper extremity, and back was 5. For the left upper extremity and right lower extremity the median pain rating was 6. For the abdomen the median pain rating was 3 and for the left lower extremity it was 7 (face, p < 0.01; chest, p < 0.15; abdomen, p = 0.40; right arm, p < 0.0001; left arm, p < 0.0001; right leg, p = 0.013; left leg, p = .001; back, p = 0.14)

  There were significantly more reports of after sensation in all 4 limbs of the patients with CRPS compared to control participants following static touch (right arm, p = 0.004; left arm, p = 0.079; right leg, p = 0.0004; left leg, p = 0.003). There were also significantly more reports of after sensation following pin prick (right arm, n = 20, p = 0.001; left arm, n = 18, p < 0.0001; right leg, n = 20, p < 0.0001; left leg, n = 19, p < 0.0001)

Wolanin et al. [56]

  CRPS (n = 32) (23 women)

Mean age was 45.4 years) and duration of symptoms was 9.67 years

  Age and sex matched healthy controls (n = 35) (19 women)

The mean age was 42 years

Diagnosis was based on  IASP  criteria

Static and mechanical allodynia, thermal allodynia, mechanical hyperalgesia, and after sensations

The testing of thermal allodynia to cold utilized the metal handle of a standard reflex hammer at room temperature

An algometer with a 1 cm² rubber tip FDK 20 (Wagner Insling, Greenwich, CT) was utilized to measure static mechano-allodynia

Wind-up pain was elicited by 6 depressions of a von Frey hair at half second intervals: the duration of the elicited pain was measured for 30 s

A foam brush (3 inches in diameter) was lightly brushed over the skin at 6 cm/sec

Pinprick was utilized to measure a sharp mechanical (algesic) stimulus. One pinprick stimulus (a 2-inch pin steel safety pin with nickel plating) was applied

In the affected limb of CRPS and both at the dominant and non-dominant side of control group

  The spread of thermal allodynia in CRPS was 5.47 ± 0.78 cm while in the control group, it was 0 cm. Duration of cold sensation in CRPS was 24.38 ± 2.10 s while in the control group, it was 1.46 ± 0.92 s

  DMA rated by using NRS in CRPS was 6 (0–10) (median and range) while in the control group, it was 0

  Static mechanical allodynia in CRPS was 3.21 ± 0.31 Ibs while in the control group, it was 10.48 ± 0.13 Ibs

  Hyperalgesia measured through Von Frey Hair in CRPS was 6 (0–10) (median and range) while in the control group, it was 0 (0–2)

  Wind-up pain in CRPS was 8 (0–10) while in the control group, it was 0 (0–4)

  Pinprick pain in CRPS was 8 (0–10) (median and range) while in the control group, it was 0 (0–2). Also, Pinprick spread in CRPS was 5.75 ± 0.73 cm while in the control group, it was 0.01 ± 0.01. Finally, Pinprick after sensation in CRPS was 24.22 ± 2.02 s while in the control group, it was 0 s

Results were reported as median (range) or mean (SE) and we used Cochrane guidelines to transform data into mean (SD)

Truffyn et al. [64] (children)

  Children with lower limb CRPS type 1 (n = 34)

The mean age was 12.03 (SD 2.4 years) and mean duration was 8.8(SD 11.5 months)

  Age and sex matched healthy controls (n = 56) (28 females)

Mean age was 15.7 (SD 1.1 years)

Not mentioned

CDT, WDT, CPT, and HPT

Thermal stimulation was accomplished using Medoc Neuro Sensory Analyzer, Model TSA-II (Medoc Ltd, Ramat Yishai, Israel)

Pain site and contralateral site in CRPS, and matched site in the healthy control group

  In CRPS-pain site, CDT was 28.5 (2.9 °C), WDT was 37.5 (3.6 °C), CPT was 18.9 (10.3 °C), and HPT was 41.3 (4.1 °C)

  In CRPS-contralateral site, CDT was 29.1 (2.12 °C), WDT was 36.5 (2.8 °C), CPT was 18.2 (10.2 °C), and HPT was 41.3 (3.7 °C)

  In the control group, CDT was 30.9 (0.82 °C), WDT was 33.67 (1.02 °C), CPT was 17.89 (10.3 °C), and HPT was 39.95 (4.05 °C)

Raj et al. [59]

  CRPS type 1 and 2 (n = 36) with age greater than 18 years)

  Healthy control group: (n = 57)

CRPS Type 1 or 2 subject inclusion criteria were adapted from those outlined by Stanton-Hicks et al. (IASP criteria)

Current perception threshold (CPT) and pain tolerance threshold (PTT) to an electric stimulus

DMA was assessed also

Affected finger or great toe in CRPS group and matched site in the control group

  The difference between the PTT values for the CRPS subjects from the symptomatic site and the asymptomatic control site and the healthy controls was statistically significant (P < .05)

NB. No data available for the control group

  DMA was present in 29/36 of CRPS subjects

Weber et al. [58]

  CRPS (n = 10)

The mean age was 44.6 (range 35–56) years. The mean duration of CRPS symptoms was 32 weeks (range 4–190)

  Age and gender matched healthy controls (n = 10)

The mean age was 44.8 (range 24–78) years

All patients fulfilled the following IASP diagnostic criteria (Stanton-Hicks et al. [110]):

Axon reflex vasodilation (flare area) after electrical stimulation using laser Doppler imaging

Forearm in upper limb CRPS and leg in lower limb CRPS

  In CRPS, axon reflex vasodilation was 438 (68%) after the stimulation

  In the control group, axon reflex vasodilation was 306 (52%) after the stimulation

Sieweke et al. [62]

  CRPS (n = 40). This cohort further divided into a group of 23 patients and another group of 17 patients

The mean age was 48.6 years

  Age and sex matched healthy control (n = 15)

Mean age of 46 years

Based on the current IASP criteria (Stanton-Hicks et al. [110])

HPT, MPT, MPS, and WUR

Affected foot and hand in CRPS while in the control group the sites matched to that of CRPS were assessed

  In the group of 23 patients: in the affected site, HPT was 44.2 (4.12 °C). In contralateral site, HPT was 44.2 (2.6 °C)

  In the group of 17 patients: in the affected site, MPS was 48.5 (40) and WUR was 2.1 (5.8). In contralateral site, MPS was 42.4 (22.9) and WUR was 1.8 (5.2)

  In the control group: in the dominant site, HPT was 44 (2 °C) while MPS was 46.6 (19) and WUR was 1.9 (4.8)

Reimer et al. [14] (frequencies of sensory abnormalities)

  Upper limb CRPS type 1 (n = 19)

Mean age was 60.2 (SD 12.9 years) and duration of symptoms was 5.7(SD 8.3 months)

  The reference value of Rolke et al. 2006 was used as a healthy reference (180 subjects)

Diagnosis of CRPS type 1 was based on Budapest criteria for clinical diagnosis

CDT, WDT, TSL, CPT, HPT, MDT, MPT, MPS, WUR, VDT, PPT, PHS, and DMA

QST measurements were taken according to German network guidelines

  In the affected limb of CRPS group, the sensory gain of CDT was 0.00%, WDT was 0.00%, TSL was 5.3%, CPT was 36.8%, HPT was 36.8%, MDT was 5.3%), MPT was 5.3%, MPS was 42.1%, WUR was 6.7%, VDT was 5.3%, PPT was 100%, and DMA was 26.3%

  In the unaffected limb of CRPS group, the sensory gain of CDT was 5.3%, WDT was 0.00%, TSL was 0.00%, CPT was 10.5%, HPT was 0.00%, MDT was 0.00%, MPT was 0.00%, MPS was 10.5%, WUR was 0.00%, VDT was 0.00%, PPT was 15.8%, and DMA was 0.00%

  In the healthy controls, the sensory gain of CDT was 2.3%, WDT was 6.1%, TSL was 5.00%, CPT was 4.5%, HPT was 3.9%, MDT was 6.2%, MPT was 3.3%, MPS was 5%, WUR was 7.2%, VDT was 6.7%, PPT was 5.6%, and DMA was 1.1%

  In the affected limb of CRPS group, the sensory loss of CDT was − 31.6%, WDT was 26.3%, TSL was 26.3%, CPT was 10.5%, HPT was 5.3%, MDT was 31.6%, MPT was 5.3%, MPS was 5.3%, WUR was 6.7%, VDT was 42.1%, and PPT was 00%

  In the unaffected limb of CRPS group, the sensory loss of CDT was 0.00%, WDT was 15.8%, TSL was 0.00%, CPT was 0.00%, HPT was 0.00%, MDT was 5.3%, MPT was 0.00%, MPS was 15.8%, WUR was 6.7%, VDT was 0.00%, and PPT was 15.8%

  In the healthy controls, the sensory loss of CDT was 6.7%, WDT was 7.2%, TSL was 5.5%, CPT was 4.4%, HPT was 2.8%, MDT was 6.1%, MPT was 5%, MPS was 2.2%, WUR was 2.8%, VDT was 1.1%, and PPT was 3.4%

Thimineur et al. [57]

  CRPS (n = 140)

  Healthy controls (n = 26)

Patients identified as having CRPS met all six of our clinical criteria:

1. pain of an extremity disproportionate to physical injury

2. hyperalgesia and hyperpathia that were inconsistent with a peripheral nerve or spinal root pattern

3. absence of underlying peripheral pathology that would otherwise explain pain and sensory abnormalities

4. evidence of autonomic dysfunction such as color, temperature, or edematous Changes

5. history of precipitant trauma (including surgery), stroke, or spinal cord injury

6. symptoms present for at least 3 months; there was no upper limit on symptom duration

TSL, PPT, MDT, and pain ratings after suprathreshold ethanol application

NB. PPT was measured at hand in case of affected feet and in feet in case of affected hand

  TSL was measured at the affected side (foot, hand, ophthalmic area, maxilla) and the contralateral side. Corresponding sites in the control group were also assessed

  PPT was measured at the dorsum of the hand and the feet

  MDT was measured at the palmar surface of the hand

  Oral pain perception to suprathreshold stimulus was assessed at tongue

  In CRPS, TSL in the foot of affected side was 18(10.7) while in the control group was 9.5(7.5)

  In CRPS, TSL in the foot contralateral to the affected side was 13 (9.2) while in the control group was 7 (3)

  In CRPS, TSL in the hand of affected side was 12.2 (10.1) while in the control group, it was 3.9 (2)

  In CRPS, TSL in the hand contralateral to the affected side was 8.2 (8) while in the control group, it was 3.7 (2.6)

  In CRPS, TSL in the maxilla of affected side was 6.5 (7.2) while in the control group, it was 1.8 (1.4)

  In CRPS, TSL in the maxilla contralateral to the affected side was 4 (5.5) while in the control group, it was 1.7 (1.3)

  In CRPS, TSL in the ophthalmic area of affected side was 11.8 (9.5) while in the control group, it was 3.2 (2.7)

  In CRPS, TSL in the ophthalmic area contralateral to the affected side was 5.5 (6.5) while in the control group, it was 3.8 (5.6)

  In CRPS, pain rating to suprathreshold stimulus in the tongue of the affected side was 163.5 (87) while in the control group, it was 236 (115)

  In CRPS, pain rating to suprathreshold stimulus in the tongue contralateral to the affected side was 203 (116.5) while in the control group, it was 240 (118)

  In CRPS, MDT of the affected side was 3.9 (0.9) while in the control group, it was 2.9 (0.3)

In CRPS, MDT in the hand contralateral to the affected side was 3.3 (0.75) while in the control group, it was 2.8 (0.3)

  In CRPS, MDT of the affected side was 3.9 (0.9) while in the control group, it was 2.9 (0.3)

  In CRPS, MDT in the hand contralateral to the affected side was 3.3 (0.75) while in the control group, it was 2.8 (0.3)

  In CRPS, PPT of the hand ipsilateral to the affected foot was 11.2 (5.1 pound) while in the control group, it was 8.0 (3.5 pound)

  In CRPS, PPT of the hand contralateral to affected foot was 8.5 (5 pound) while in the control group, it was 8 (3.3 pound)

  In CRPS, PPT of the foot ipsilateral to affected hand was 13.4 (5.65 pound) while in the control group, it was 11.2 (5.2 pound)

  In CRPS, PPT of the foot contralateral to affected hand was 11.6 (5.3 pound) while in the control group, it was 10.5 (3.5 pound)

Drummond et al. [63]

  CRPS type 1 (n = 24) + CRPS type 2 (n = 6) (22 females and 8 males) (18 upper limb and 12 lower limb CRPS)

The mean age was 49 (11 years)

  Healthy controls (n = 20) (15 females)

The mean age was 46.5 (13.5 years)

Based on Budapest criteria for diagnosis of CRPS

MPS, electric pain sensitivity, and PPT

Monofilament (× 5) used to assess MPS, an algometer (FDX, Wagner Instruments, Greenwich, CT) used to assess PPT

Affected extremity, contralateral extremity, forehead

  In CRPS, MPS of the affected limbs was 4.1 (0.8) while in the contralateral limbs, it was 2.7 (0.5)

  In the control group, MPS in the area matched to affected area was 0.6 (0.2)

  In CRPS, MPS was 2.4 (0.6) in area away from the affected part in ipsilateral limb while in matched area in the contralateral limb, it was 4 (0.4)

  In the control group, MPS at area matched to remote area of affected region was 0.6 (0.16)

  In CRPS (forehead area), MPS in the ipsilateral forehead was 2.9 (0.5) and in the contralateral forehead, it was 2.6 (0.4)

  In the control group (forehead area), MPS was 0.66 (0.1)

  In CRPS, PPT of the affected limbs was 0.825 (0.275 kg) while in the contralateral limbs, it was 1.5 (0.25 kg)

  In the control group, PPT in the area matched to the affected area was 2.1 (0.24 kg)

  In CRPS, PPT was 1.3 (0.25 kg) in area away from the affected part in ipsilateral limb while in matched area in the contralateral limb, it was 1.7 (0.25 kg)

  In the control group, MPS at area matched to the remote area of affected region was 2 (0.2)

  In CRPS (forehead area), PPT in ipsilateral forehead was 0.8 (0.1 kg) and in the contralateral forehead, it was 0.9 (0.1 kg)

  In the control group (forehead area), PPT was 1.2 (0.2 kg)

Measurements were reported as mean (SE)

Maier et al. [69] (frequencies of sensory abnormalities)

  CRPS (n = 403) (312 females)

Mean age was 52 (13 years)

  The reference value of Rolke et al. 2006 was used as a healthy reference (180 subjects)

Based on the revised criteria of Bruehl et al. 1999 and Budapest criteria

CDT, WDT, TSL, PHS, CPT, HPT, MDT, MPT, MPS, WUR, VDT, PPT, and CPM

CDT, WDT, TSL, CPT, HPT, MPT, MDT, MPS and VDT were measured from the middle finger. PPT was measured by pressure algometer at thenar eminence

Vibration detection threshold (VDT) was tested with a Rydel–Seifert et al. graded tuning fork (64 Hz, 8/8 scale)

To test wind up ratio (WUR), a single stimulus was applied with a 256 mN pinprick stimulator probe. Then, at intervals of ten seconds a series of ten identical pinprick stimuli were applied in the same skin area. Participants were asked to rate the intensity using a numeric rating scale from 0 to 100 immediately after the single stimulation and again after the series of 10 stimuli

MPT was tested using blunt probes with increasing pressure intensities

MPS was calculated as the geometric mean of the pain ratings for pinprick stimuli

MDT was tested using glass von Frey hairs

DMA using a cotton wisp, a Q-Tip and a standardized brush (Somedic, Sweden)

CPM was measured through investigating the effect of heat noxious stimulus on PPT measured at dorsal forearm before and after the noxious stimulus

A calibrated MSA thermal sensory analyzer (Somedic, Sweden) with baseline temperature was 32 °C

Affected limb of CRPS group, the sensory gain of CDT was 2.7%, WDT was 2.5%, TSL was 2.7%, CPT was 30.5%, HPT was 40.1%, MDT was 9.5%, MPT was 28.7%, MPS was 46.6%, WUR was 13.1%, VDT was 1.5%, PPT was 66.3%, and DMA was 24.1%

The healthy controls, the sensory gain of CDT was 2.3%, WDT was 6.1%, TSL was 5.00%, CPT was 4.5%, HPT was 3.9%, MDT was 6.2%, MPT was 3.3%, MPS was 5%, WUR was 7.2%, VDT was 6.7%, PPT was 5.6%, and DMA was 1.1%

Affected limb of CRPS group, the sensory loss of CDT was 32.5%, WDT was 26.6%, TSL was 26.9%, CPT was 5.2%, HPT was 7.7%, MDT was 35.2%, MPT was 10%, MPS was 6.2%, WUR was 2.7%, VDT was 35.4%, and PPT was 3.3%

The healthy controls, the sensory loss of CDT was 6.7%, WDT was 7.2%, TSL was 5.5%, CPT was 4.4%, HPT was 2.8%, MDT was 6.1%, MPT was 5%, MPS was 2.2%, WUR was 2.8%, VDT was 1.1% and PPT was 3.4%

Bank et al. [38]

  Upper extremity CRPS type 1 (n = 25)

Mean age was 50.6 (SD 13.7 years)

  Age and gender matched healthy controls (n = 50)

Mean age was 50.1(SD 13.4 years)

Diagnosis based on IASP criteria

PPT and VDT

Affected and unaffected extremities in CRPS group and dominant and non-dominant extremities in healthy group

  In the affected extremity of CRPS, PPT was 1.77 (1.07 kg) and VDT was 0.5 (0.36 µm)

  In the unaffected extremity of CRPS, PPT was 3.6 (1.26 kg) and VDT was 0.43 (0.39 µm)

  In the dominant side of healthy controls, PPT was 4.3 (1.6 kg) and VDT was 0.49 (0.34 µm)

Kolb et.al [67]

  CRPS type 1 (n = 17) + CRPS type 2 (n = 3)

Mean age was 54.2(SD 12.5 years)

  Age and gender matched healthy controls (n = 20)

The mean age was 54.6 (SD 13.5 years)

Diagnosis based on Budapest criteria

CDT, WDT, TSL, CPT, HPT, TDT, VDT, WUR, PPT, MPT, and PHS

Allodynia was also assessed

Affected and un-affected extremity of CRPS and dominant extremity of control group

  In the affected limb of CRPS group, CDT was 26.7 (1.6), WDT was 35.7 (0.9), TSL was 6.8 (2.33), CPT was 15.6 (2.7), HPT was 41.4 (1.6), TDT was 26.6 (22.4), MPT was 138.8 (36.5), MPS was 2.14 (0.52), WUR was 4 (1.06), VDT was 7.59 (1.83), PPT was 291.2 (73.4), and DMA was 5 (1.35)

  In the healthy controls, CDT was 29.5 (0.32), WDT was 35.5 (0.57), TSL was 3.94 (0.55), CPT was 11.9 (2.1), HPT was 43.8 (0.86), TDT was 4.16 (2.72), MPT was 148.5 (41.3), MPS was 1.3 (0.4), WUR was 2 (0.21), VDT was 7.6 (0.12), PPT was 814.65(83.68), and DMA was 0.01 (0.01)

  In the unaffected limb of CRPS group, CDT was 29.5 (0.39), WDT was 34.8 (0.77), TSL was 3.9 (0.84), CPT was 9.67 (1.67), HPT was 42.9 (1.3), TDT was 2.59 (1.38), MPT was 199.5 (39.88), MPS was 0.53 (0.14), WUR was 5.5 (1.44), VDT was 7.59 (1.9 Hz), PPT was 702 (178.27) and DMA was 0.00 (0.00)

Data were represented as mean (SEM)

Munts et al. [70]

  Consecutive patients with CRPS type 1 (n = 44)

The mean age was 36 (SD 13 years) and mean disease duration of 10 (6 years)

  Healthy control women (n = 35)

Mean age was 40 (SD 13 years)

Diagnosis based on IASP criteria

CDT, WDT, and HPT

Affected and unaffected extremities of CRPS group compared to non-dominant side of healthy controls

  In the affected extremity of 44 cases with CRPS, CDT was 30.7 (1.5) in the hand while in the foot, it was 26.7 (5.3). WDT of the hand was 34.7 (3.7) while in the foot, it was 41 (7) and HPT of the hand was 42.3 (10.5) while in the foot, it was 43.2 (9.6)

  In the unaffected extremity of 7 cases with CRPS, CDT of the hand was 31.6(0.5) while in the foot, it was 30.6(1.5). WDT of the hand was 32.8(1.1) while in the foot, it was 38(8.7) and HPT of the hand was 45.7(4) while in the foot, it was 45.8(4)

  In the dominant side of 35 healthy controls, CDT of the hand was 31.7 (0.3) while in the foot, it was 31.2 (0.9). WDT of the hand was 32.5 (0.3) while in the foot, it was 35.3 (3) and HPT was 44.6 (3) in the hand while in the foot, it was 45.2 (3.2)

Data were represented as median (IQR), while we used Wan’s method to transform data into mean (SD)

Becerra et al. [41] (children)

  Lower limb CRPS (n = 26)

The Age ranged from 10 to 18 years

  Age and gender matched healthy controls (n = 12)

Diagnosis bases on neurological examination and comprehensive record review

HPT, CPT, and allodynia

The affected area of CRPS group and the matched area in the control group

  In the affected area of CRPS, HPT was 41.7 (1.2), CPT was 21.2 (3.2), and allodynia was 7 (0.8)

  In the control group, HPT was 40.5 (3.2), CPT was 11.2 (2.6), and allodynia was 0.2 (0.18)

Habig et al. [71]

  CRPS (n = 10)

Mean age was 33 years, SEM 3.3)

  Healthy control group: (n = 11)

Mean age was 43.2 years, SEM 3.9)

The revised Budapest diagnostic criteria

Pleasantness levels after C-tactile perception

The affected area and the matched contralateral area

  In the affected area of CRPS, pleasantness levels were 1.85 (2.2) and in the contralateral matched area was 3.4 (0.13)

  In the control group, pleasantness levels were 3.4 (0.37)

Gossrau et al. [72]

  CRPS type 1 (n = 19)

Mean age was 56.5 (SD 13.4 years)

  Healthy controls (n = 22)

Mean age was 60.8 (SD 11.4 years)

Budapest diagnostic criteria

Pleasantness levels after C-tactile perception

The affected area and the matched contralateral area

  In the affected area of CRPS, pleasantness levels were 1.94 (1.45) and in the contralateral matched area was 1.96 (1.53)

  In the control group, pleasantness levels were 3.7 (2)

In this study, the data were represented in figure two as mean (95% CI), while we used Cochrane guideline to transform data into mean (SD)