Background Primary headache disorders are common and burdensome conditions. They are associated to several comorbidities, such as cardiovascular or psychiatric ones, which, in turn, contribute to the global burden of headache. The aim of this study is to provide a comprehensive description of the pooled prevalence of comorbidities of primary headache disorders using a meta-analytical approach based on studies published between 2000 and 2020. Methods Scopus was searched for primary research (clinical and population studies) in which medical comorbidities were described in adults with primary headache disorders. Comorbidities were extracted using a taxonomy derived from the Global Burden of Disease (GBD) study. We compared prevalence of comorbidities among headache sufferers against general population using GBD-2019 estimates, and compared comorbidities’ proportions in clinical vs. population studies, and by age and gender. Results A total of 139 studies reporting information on 4.19 million subjects with primary headaches were included: in total 2.75 million comorbidities were reported (median per subject 0.64, interquartile range 0.32–1.07). The most frequently addressed comorbidities were: depressive disorders, addressed in 51 studies (pooled proportion 23 %, 95 % CI 20–26 %); hypertension, addressed in 48 studies (pooled proportion 24 %, 95 % CI 22–26 %); anxiety disorders addressed in 40 studies (pooled proportion 25 %, 95 % CI 22–28 %). For conditions such as anxiety, depression and back pain, prevalence among headache sufferers was higher than in GBD-2109 estimates. Associations with average age and female prevalence within studies showed that hypertension was more frequent in studies with higher age and less females, whereas fibromyalgia, restless leg syndrome, and depressive disorders were more frequent in studies with younger age and more female. Conclusions Some of the most relevant comorbidities of primary headache disorders – back pain, anxiety and depression, diabetes, ischemic heart disease and stroke – are among the most burdensome conditions, together with headache themselves, according to the GBD study. A joint treatment of headaches and of these comorbidities may positively impact on headache sufferers’ health status and contribute to reduce the impact of a group of highly burdensome diseases.

Several lines of evidence support a role of the immune system in headache pathogenesis, with particular regard to migraine. Firstly, alterations in cytokine profile and in lymphocyte subsets have been reported in headache patients. Secondly, several genetic and environmental pathogenic factors seem to be frequently shared by headache and immunological/autoimmune diseases. Accordingly, immunological alterations in primary headaches, in particular in migraine, have been suggested to predispose some patients to the development of immunological and autoimmune diseases. On the other hand, pathogenic mechanisms underlying autoimmune disorders, in some cases, seem to favour the onset of headache. Therefore, an association between headache and immunological/autoimmune disorders has been thoroughly investigated in the last years. The knowledge of this possible association may have relevant implications in the clinical practice when deciding diagnostic and therapeutic approaches. The present review summarizes findings to date regarding the plausible relationship between headache and immunological/autoimmune disorders, starting from a description of immunological alteration of primary headaches, and moving onward to the evidence supporting a potential link between headache and each specific autoimmune/immunological disease.

Experimental findings suggest an involvement of neuroinflammatory mechanisms in the pathophysiology of migraine. Specifically, preclinical models of migraine have emphasized the role of neuroinflammation following the activation of the trigeminal pathway at several peripheral and central sites including dural vessels, the trigeminal ganglion and the trigeminal nucleus caudalis. The evidence of an induction of inflammatory events in migraine pathophysiological mechanisms has prompted researchers to investigate the Human leukocyte antigen (HLA) phenotypes as well as cytokine genetic polymorphisms in order to verify their potential relationship with migraine risk and severity. Furthermore, the role of neuroinflammation in migraine seems to be supported by evidence of an increase in pro-inflammatory cytokines, both ictally and interictally, together with the prevalence of Th1 lymphocytes and a reduction in regulatory lymphocyte subsets in peripheral blood of migraineurs. Cytokine profiles of cluster headache patients and those of tension-type headache patients further suggest an immunological dysregulation in the pathophysiology of these primary headaches, although evidence is weaker than for migraine. The present review summarizes available findings to date from genetic and biomarker studies that have explored the role of inflammation in primary headaches.

Guidelines regarding long-term use with onabotulinumtoxinA (onaBT-A) in chronic migraine (CM) prophylaxis are lacking. This multicentric prospective real-life study aimed to assess the efficacy and safety of a long-term treatment. A total of 195 chronic migraine patients were treated with onaBT-A, every 3 months for 5 cycles (Phase 1). In the Phase 2 of the study, depending on response rate, patients were divided into “responders” (R), “partially responders” (PR) and “non-responders” (NR). Then, we proposed to R and PR patients to continue with an additional 12 months of treatment (additional 4 sessions). Response to treatment and adverse events were collected for the entire duration of the study. Of the 195 patients included (females 82.1%, mean age 47.4 ± 12.4), at the end of Phase 1 there were 52.3% of R patients, 17.9% of PR patients, 15.4% of NR patients and 14.4% drop-outs. During Phase 2 of treatment, R patients presented a maintenance of the improvement achieved during the first year of treatment, as well as PR patients. Except for three serious adverse events not related to treatment, all other adverse events were mild or moderate in severity and resolved without sequelae. In the literature, adherence to oral migraine-preventive medications among patients with CM was found to be less than 25%. The results of this prospective real-life multicenter study show efficacy, safety and adherence to a long-term treatment with onaBT-A.

Background A novel formulation of diclofenac, complexed with hydroxypropyl-β-cyclodextrin (HPβCD) as a solubility enhancer, in a prefilled syringe for self-administered subcutaneous injection may overcome the limitations of acute migraine treatments administered by oral, rectal, intramuscular, or intravenous routes. Methods This multicentre, phase 2, double-blind, randomized, placebo-controlled, dose-finding pilot study evaluated the efficacy, safety and tolerability of three different doses (25/50/75 mg/1 mL) of subcutaneous diclofenac sodium in the treatment of an acute migraine attack in 122 subjects. The primary efficacy endpoint was the percentage of patients pain-free at 2 hours after the study drug injection. Results A significantly higher percentage of patients in the 50 mg diclofenac group 14 (46.7%) were pain-free at 2 hours when compared with placebo: 9 (29.0%) ( p = 0.01). The 50 mg dose proved superior to placebo also in the majority of the secondary endpoints. The overall global impression favoured diclofenac vs placebo. There were no adverse events leading to study withdrawal. The majority of treatment-emergent adverse events were mild. Conclusions The 50 mg dose of this novel formulation of diclofenac represents a valuable self-administered option for the acute treatment of migraine attacks. Trial registration: EudraCT Registration No. 2017-004828-29.