Evidence for converging pathophysiology in complex regional pain-syndrome and primary headache disorders: results from a case–control study

Background Neuroinflammation and maladaptive neuroplasticity play pivotal roles in migraine (MIG), trigeminal autonomic cephalalgias (TAC), and complex regional pain syndrome (CRPS). Notably, CRPS shares connections with calcitonin gene-related peptide (CGRP) in its pathophysiology. This study aims to assess if the documented links between CRPS and MIG/TAC in literature align with clinical phenotypes and disease progressions. This assessment may bolster the hypothesis of shared pathophysiological mechanisms. Methods Patients with CRPS ( n = 184) and an age-/gender-matched control group with trauma but without CRPS ( n = 148) participated in this case–control study. Participant answered well-established questionnaires for the definition of CRPS symptoms, any headache complaints, headache entity, and clinical management. Results Patients with CRPS were significantly more likely to suffer from migraine (OR: 3.23, 95% CI 1.82–5.85), TAC (OR: 8.07, 95% CI 1.33–154.79), or non-classified headaches (OR: 3.68, 95% CI 1.88–7.49) compared to the control group. Patients with MIG/TAC developed CRPS earlier in life (37.2 ± 11.1 vs 46.8 ± 13.5 years), had more often a central CRPS phenotype (60.6% vs. 37.0% overall) and were three times more likely to report allodynia compared to CRPS patients with other types of headaches. Additionally, these patients experienced higher pain levels and more severe CRPS, which intensified with an increasing number of headache days. Patients receiving monoclonal antibody treatment targeting the CGRP pathway for headaches reported positive effects on CRPS symptoms. Conclusion This study identified clinically relevant associations of MIG/TAC and CRPS not explained by chance. Further longitudinal investigations exploring potentially mutual pathomechanisms may improve the clinical management of both CRPS and primary headache disorders. Trial registration German Clinical Trials Register (DRKS00022961).