Table 4 Studies on the role of CGRP in neuropathic pain
From: Calcitonin gene-related peptide and pain: a systematic review
Study | Objectives | Reported pain as part of phenotype | Method and sample size | Source of CGRP | Results | Duration of the investigated condition | Correlation between CGRP level and pain |
|---|---|---|---|---|---|---|---|
Albrecht, 2006 [1] | Investigate CGRP expression in skin from amputated extremity affected by CRPS | CRPS after amputation in upper and lower limbs | Skin tissue from 2 patients and 5 controls | Tissue biopsies (skin) | Loss of CGRP expression in CRPS patients | NR | NR |
Attal, 2016 [2] | Determine CGRP levels in peripheral neuropathic pain patients after treatment with botulinum toxin A | Peripheral neuropathic pain, mixed group | ELISA of biopsy from 23 patients with active treatment and 17 patients with placebo treatment at week 1 and 4 after study start | Skin | No change in CGRP levels at week 4 compared to week 1. Average pain score was not changed either | NR | None |
Awawdeh, 2002 [3] | Investigate presence of CGRP in the gingival crevicular fluid of teeth diagnosed with pain of pulpal origin | Tooth pain | Gingival crevicular fluid from a painful and non-painful site from 54 patients undergoing pulpectomy. 1Â week after fluid was collected from 21 patients | Gingival crevicular fluid | No difference in CGRP-levels between painful tooth compared to the contralateral control tooth | NR | No clear association between CGRP-levels and dental pain |
Boras, 2010 [4] | Determine saliva and serum CGRP levels in patients with BMS | Burning mouth syndrome | Saliva and serum from 26 patients and 22 controls | Saliva and serum | No difference between patients and controls | NR | NR |
Birklein, 2001 [5] | Test contribution of neuropeptide release to pathophysiology of CRPS | CRPS in upper or lower limbs | Serum CGRP concentrations were measured in 19 patients on the affected (n = 19) side and non-affected side (n = 13) before and 9 months after therapy (n = 9). Comparison with controls (n = 16) | Blood (serum) | Increased CGRP levels in CRPS patients. No difference in CGRP levels in blood taken from affected versus non-affected side. After therapy – normalization of CGRP levels compared to healthy controls | Mean 29 weeks (range: 2 to 188 weeks) | No correlation between CGRP-levels and pain |
ChavarrÃa-Bolanos, 2014 [6] | Determine CGRP-levels in dental pulp tissue samples from 8 patients subjected to undergo controlled orthodontic intrusive forces | Tooth pain | Human premolar dental pulp tissue was extracted from 8 patients, and 8 controls | Tissue biopsies (dental pulp) | No differences in CGRP levels between the two groups | 24Â h | NR |
Hou, 2011 [7] | Determine whether CGRP-IL is increased among epidermal keratinocytes in PHN and diabetes | PHN and small fiber neuropathy | Punch biopsies from 5 patients with PHN from painful areas, 5 patients with diabetes (biopsies from feet) and 11 controls | Tissue biopsies (skin) | Increased CGRP-levels in keratinocytes from PHN patients compared to controls | NR | CGRP levels were higher in painful skin areas compared to non-painful locations |
Kalliomäki, 2011 [8] | Investigate structural and functional differences between patients with and without chronic pain following nerve injury | Hand pain due to nerve injury | Skin biopsies from 21 patients with pain and 9 controls without pain. All participants required hand surgery | Tissue biopsies (skin) | No difference in CGRP-staining between patients and controls | >1 year | No significant difference between pain and non-pain patients |
Lindqvist. 2000 [9] | Examine CGRP expression in painful Morton’s neuroma patients | Forefoot Morton’s neuroma | 11 nerve biopsies from 8 patients and 4 controls | Nerve biopsies | Increased levels of CGRP-IR nerve fibers compared to controls | NR | NR |
Schinkel, 2009 [10] | Compare systemic inflammatory mediators in patients with CRPS I with controls | CRPS in the upper limb | Blood samples were obtained from 22 patients. 12 patients had chronic CRPS and 10 patients had acute CRPS. Patients were compared to 8 controls | Blood (plasma) | CGRP-levels were lower in chronic CRPS patients, compared to controls | Acute: < 6Â months Chronic: > 6Â months | NR |
Zidverc-Trajkovic, 2009 [11] | Determine saliva CGRP levels in patients with BMS | Burning mouth syndrome | Saliva from 78 patients and 16 healthy controls | Saliva | Inconclusive, CGRP levels were non-significantly decreased in comparison to controls | At least 6Â months | NR |