Understanding the pathophysiology of idiopathic intracranial hypertension (IIH): a review of recent developments.

Idiopathic intracranial hypertension (IIH) is a condition of significant morbidity and rising prevalence. It typically affects young people living with obesity, mostly women of reproductive age, and can present with headaches, visual abnormalities, tinnitus and cognitive dysfunction. Raised intracranial pressure without a secondary identified cause remains a key diagnostic feature of this condition, however, the underlying pathophysiological mechanisms that drive this increase are poorly understood. Previous theories have focused on cerebrospinal fluid (CSF) hypersecretion or impaired reabsorption, however, the recent characterisation of the glymphatic system in many other neurological conditions necessitates a re-evaluation of these hypotheses. Further, the impact of metabolic dysfunction and hormonal dysregulation in this population group must also be considered. Given the emerging evidence, it is likely that IIH is triggered by the interaction of multiple aetiological factors that ultimately results in the disruption of CSF dynamics. This review aims to provide a comprehensive update on the current theories regarding the pathogenesis of IIH.

Cognitive assessment during the phases of a spontaneous migraine: a prospective cohort study.

INTRODUCTION: Cognitive symptoms are reported commonly throughout all phases of a migraine; however, there is a paucity of objective cognitive profiling. Previous studies have been limited by practice effect, and variable populations. METHODS: Participants completed 1 month of daily testing with a computerised cognitive battery involving a simple reaction (SRT), choice reaction (CRT) and a working memory test (WM). Results were correlated with their diary to identify interictal scores, and scores during each phase of a migraine, and non-migraine headache days. RESULTS: A total of 16 patients with episodic migraine participated. During the headache phase of a migraine, responses to SRT, CRT and WM tasks were significantly slower and less accurate than interictally. During the postdrome, WM task performance was slower and less accurate. Non-migraine headache days were not associated with significant change. CONCLUSION: The headache and postdromal phase of a migraine day was associated with objective evidence of cognitive dysfunction in patients with episodic migraine.

Australian Headache Epidemiology Data (AHEAD): a pilot study to assess sampling and engagement methodology for a nationwide population-based survey.

BACKGROUND: There are no robust population-based Australian data on prevalence and attributed burden of migraine and medication-overuse headache (MOH) data. In this pilot cross-sectional study, we aimed to capture the participation rate, preferred response method, and acceptability of self-report questionnaires to inform the conduct of a future nationwide migraine/MOH epidemiological study. METHODS: We developed a self-report questionnaire, available in hard-copy and online, including modules from the Headache-Attributed Restriction, Disability, Social Handicap and Impaired Participation (HARDSHIP) questionnaire, the Eq. 5D (quality of life), and enquiry into treatment gaps. Study invitations were mailed to 20,000 randomly selected households across Australia's two most populous states. The household member who most recently had a birthday and was aged ≥ 18 years was invited to participate, and could do so by returning a hard-copy questionnaire via reply-paid mail, or by entering responses directly into an online platform. RESULTS: The participation rate was 5.0% (N = 1,000). Participants' median age was 60 years (IQR 44-71 years), and 64.7% (n = 647) were female. Significantly more responses were received from areas with relatively older populations and middle-level socioeconomic status. Hard copy was the more commonly chosen response method (n = 736). Females and younger respondents were significantly more likely to respond online than via hard-copy. CONCLUSIONS: This pilot study indicates that alternative methodology is needed to achieve satisfactory engagement in a future nationwide migraine/MOH epidemiological study, for example through inclusion of migraine screening questions in well-resourced, interview-based national health surveys that are conducted regularly by government agencies. Meanwhile, additional future research directions include defining and addressing treatment gaps to improve migraine awareness, and minimise under-diagnosis and under-treatment.

New daily persistent headache: A systematic review and meta-analysis.

OBJECTIVE: To perform a systematic review and meta-analysis of the epidemiology, precipitants, phenotype, comorbidities, pathophysiology, treatment, and prognosis of primary new daily persistent headache. METHODS: We searched PubMed/Medline, EMBASE, Cochrane, and clinicaltrials.gov until 31 December 2022. We included original research studies with any design with at least five participants with new daily persistent headache. We assessed risk of bias using National Institutes of Health Quality Assessment Tools. We used random-effects meta-analysis where suitable to calculate pooled estimates of proportions. The Preferred Reporting Items for Systematic Reviews and Meta-Analysis compliant study is registered with PROSPERO (registration number CRD42022383561). RESULTS: Forty-six studies met inclusion criteria, predominantly case series, including 2155 patients. In 67% (95% CI 57-77) of cases new daily persistent headache has a chronic migraine phenotype, however new daily persistent headache has been found to be less likely than chronic migraine to be associated with a family history of headache, have fewer associated migrainous symptoms, be less vulnerable to medication overuse, and respond less well to injectable and neuromodulatory treatments. CONCLUSIONS: New daily persistent headache is a well described, recognisable disorder, which requires further research into its pathophysiology and treatment. There is a lack of high-quality evidence and, until this exists, we recommend continuing to consider new daily persistent headache a distinct disorder.

The short-term effects of CGRP monoclonal antibodies on bone turnover: A prospective cohort study.

BACKGROUND: Calcitonin gene-related peptide monoclonal antibodies (CGRP mAb) are an effective treatment of migraine however may have possible off-target effects. Pre-clinical studies implicate CGRP in several aspects of bone turnover and homeostasis. The clinical effect of CGRP mAb on bone turnover is not known, however. METHODS: Between June 2021 and July 2022, a multi-centre prospective cohort study was undertaken with eligible patients undergoing paired testing of the validated bone turnover markers procollagen type I N-terminal propeptide (P1NP) and serum C-terminal telopeptide of type I collagen (CTX) prior to and at least three months following administration of a CGRP mAb. RESULTS: A total of 45 patients with a mean age of 41.8 (SD 11.9) were included in the final analysis, all of whom received a ligand-targeting CGRP mAb. Administration of a CGRP mAb was associated with a statistically significant increase in P1NP from 44.5 microg/L to 51.5 microg/L (p = 0.004), but no significant change in CTX. CONCLUSION: In otherwise homeostatic conditions, short-term administration of a CGRP mAb is associated with increased P1NP, a bone formation marker but not with increased CTX, a bone resorption marker. Further study is required to validate these findings over longer time periods, in a larger cohort, and in pre-existing states of increased calcium stress and bone-turnover.

Cytokines in primary headache disorders: a systematic review and meta-analysis.

BACKGROUND: The role of inflammation and cytokines in the pathophysiology of primary headache disorders is uncertain. We performed a systematic review and meta-analysis to synthesise the results of studies comparing peripheral blood cytokine levels between patients with migraine, tension-type headache, cluster headache, or new daily persistent headache (NDPH), and healthy controls; and in migraine between the ictal and interictal stages. METHODS: We searched PubMed/Medline and Embase from inception until July 2022. We included original research studies which measured unstimulated levels of any cytokines in peripheral blood using enzyme-linked immunosorbent assay or similar assay. We assessed risk of bias using the Newcastle-Ottawa Quality Assessment Scale. We used random effects meta-analysis with inverse variance weighted average to calculate standardised mean difference (SMD), 95% confidence intervals, and heterogeneity for each comparison. This study is registered with PROSPERO (registration number CRD42023393363). No funding was received for this study. RESULTS: Thirty-eight studies, including 1335 patients with migraine (32 studies), 302 with tension-type headache (nine studies), 42 with cluster headache (two studies), and 1225 healthy controls met inclusion criteria. Meta-analysis showed significantly higher interleukin (IL)-6 (SMD 1.07, 95% CI 0.40-1.73, p = 0.002), tumour necrosis factor (TNF)-α (SMD 0.61, 95% CI 0.14-1.09, p = 0.01), and IL-8 (SMD 1.56, 95% CI 0.03-3.09, p = 0.04), in patients with migraine compared to healthy controls, and significantly higher interleukin-1ß (IL-1ß) (SMD 0.34, 95% CI 0.06-0.62, p = 0.02) during the ictal phase of migraine compared to the interictal phase. Transforming growth factor (TGF)-ß (SMD 0.52, 95% CI 0.18-0.86, p = 0.003) and TNF-α (SMD 0.64, 95% CI 0.33-0.96, p = 0.0001) were both higher in patients with tension-type headache than controls. CONCLUSIONS: The higher levels of the proinflammatory cytokines IL-6, IL-8 and TNF-α in migraine compared to controls, and IL-1ß during the ictal stage, suggest a role for inflammation in the pathophysiology of migraine, however prospective studies are required to confirm causality and investigate the mechanisms for the increase in cytokine levels identified. Cytokines may also have a role in tension-type headache. Due a lack of data, no conclusions can be made regarding cluster headache or NDPH.

IVIg-exposure and thromboembolic event risk: findings from the UK Biobank.

BACKGROUND: Arterial and venous thromboembolic events (TEEs) have been associated with intravenous Ig use, but the risk has been poorly quantified. We aimed to calculate the risk of TEEs associated with exposure to intravenous Ig. METHODS: We included participants from UK Biobank recruited over 3 years, data extracted September 2020.The study endpoints were incidence of myocardial infarction, other acute ischaemic heart disease, stroke, pulmonary embolism and other venous embolism and thrombosis.Predictors included known TEE risk factors: age, sex, hypertension, smoking status, type 2 diabetes mellitus, hypercholesterolaemia, cancer and past history of TEE. Intravenous Ig and six other predictors were added in the sensitivity analysis.Information from participants was collected prospectively, while data from linked resources, including death, cancer, hospital admissions and primary care records were collected retrospectively and prospectively.  FINDINGS: 14 794 of 502 492 individuals had an incident TEE during the study period. The rate of incident events was threefold higher in those with prior history of TEE (8 .7%) than those without previous history of TEE (3.0%).In the prior TEE category, intravenous Ig exposure was independently associated with increased risk of incident TEE (OR=3.69 (95% CI 1.15 to 11.92), p=0.03) on multivariate analysis. The number needed to harm by exposure to intravenous Ig in those with a history of TEE was 5.8 (95% CI 2.3 to 88.3).Intravenous Ig exposure did not increase risk of TEE in those with no previous history of TEE. INTERPRETATION: Intravenous Ig is associated with increased risk of further TEE in individuals with prior history of an event with one further TEE for every six people exposed. In practice, this will influence how clinicians consent for and manage overall TEE risk on intravenous Ig exposure.

The prevalence of headache disorders in Postural Tachycardia Syndrome: A systematic review and meta-analysis of the literature.

BACKGROUND: Headache is a common presentation of postural tachycardia syndrome, yet robust prevalence data is lacking. OBJECTIVES: To undertake a systematic review and meta-analysis to estimate the prevalence of headache disorders in postural tachycardia syndrome, and to explore the potential shared pathophysiological mechanisms that underpin these conditions as well as treatment options. METHODS: Three databases were searched for publications evaluating prevalence of migraine (primary outcome) and general and orthostatic headache (secondary outcomes) in patients with postural tachycardia syndrome. Two independent reviewers selected studies and extracted data. A random-effects meta-analysis calculated the pooled prevalence of migraine in postural tachycardia syndrome. A narrative literature review explored the pathophysiology and treatment options for concurrent headache disorders and postural tachycardia syndrome. RESULTS: Twenty-three articles met inclusion criteria. Estimated pooled prevalence of migraine in postural tachycardia syndrome was 36.8% (95% CI 2.9-70.7%). Various shared pathophysiological pathways for these conditions, as well as proposed treatment strategies, were identified.Limitations: Heterogeneity of study design, populations, and methodology for identifying headache disorders and postural tachycardia syndrome limited the generalisability of results. CONCLUSIONS: Migraine is a commonly reported comorbidity in POTS, however the true prevalence cannot be determined from the current literature. Further studies are required to assess this comorbidity and investigate the underlying mechanisms, as well as identify effective treatment strategies.

Association of plasma neurofilament light chain with disease activity in chronic inflammatory demyelinating polyradiculoneuropathy.

BACKGROUND AND PURPOSE: This study was undertaken to explore associations between plasma neurofilament light chain (pNfL) concentration (pg/ml) and disease activity in patients with chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and examine the usefulness of pNfL concentrations in determining disease remission. METHODS: We examined pNfL concentrations in treatment-naïve CIDP patients (n = 10) before and after intravenous immunoglobulin (IVIg) induction treatment, in pNfL concentrations in patients on maintenance IVIg treatment who had stable (n = 15) versus unstable disease (n = 9), and in clinically stable IVIg-treated patients (n = 10) in whom we suspended IVIg to determine disease activity and ongoing need for maintenance IVIg. pNfL concentrations in an age-matched healthy control group were measured for comparison. RESULTS: Among treatment-naïve patients, pNfL concentration was higher in patients before IVIg treatment than healthy controls and subsequently reduced to be comparable to control group values after IVIg induction. Among CIDP patients on IVIg treatment, pNfL concentration was significantly higher in unstable patients than stable patients. A pNFL concentration > 16.6 pg/ml distinguished unstable treated CIDP from stable treated CIDP (sensitivity = 86.7%, specificity = 66.7%, area under receiver operating characteristic curve = 0.73). Among the treatment withdrawal group, there was a statistically significant correlation between pNfL concentration at time of IVIg withdrawal and the likelihood of relapse (r = 0.72, p < 0.05), suggesting an association of higher pNfL concentration with active disease. CONCLUSIONS: pNfL concentrations may be a sensitive, clinically useful biomarker in assessing subclinical disease activity.

Imaging in headache disorders.

Patients with a suspected change in intracranial pressure or a trigeminal autonomic cephalgia require MRI. The need for investigation for other headache disorders is guided by the clinical evaluation of the patient. Particular care should be taken to identify any 'red flags'. Incidental findings on MRI occur in approximately 2% of patients. Patients with migraine have an increased rate of white matter lesions, but these are of uncertain clinical significance.

Cluster headache in adults.

Cluster headache is characterised by attacks of very severe, unilateral headache lasting 15-180 minutes, up to eight times per day. The attacks are associated with cranial autonomic symptoms on the same side and a sense of agitation or restlessness First-line acute abortive treatments include intranasal or subcutaneous sumatriptan or high-flow oxygen. Neuromodulation may benefit some patients First-line preventive therapy is high-dose verapamil. Close monitoring is required for the adverse effect of arrhythmia There are several emerging therapies that have either proven efficacy, or possible benefit for cluster headache. They include drugs aimed at the calcitonin gene-related peptide.

Calcitonin gene related peptide in migraine: current therapeutics, future implications and potential off-target effects.

Migraine is the second largest cause of years lost to disability globally among all diseases, with a worldwide prevalence over 1 billion. Despite the global burden of migraine, few classes of therapeutics have been specifically developed to combat migraine. After 30 years of translational research, calcitonin gene-related peptide (CGRP) inhibitors have emerged as a promising new tool in the prevention of migraine. Like all new therapeutics; however, we have limited real-world experience and CGRP has several known systemic actions that warrant consideration. This article provides a narrative review of the evidence for CGRP antagonists and summarises the known and potential side effects that should be considered.

Inflammatory complications of CGRP monoclonal antibodies: a case series.

BACKGROUND: Calcitonin gene-related peptide (CGRP) is expressed throughout the body and is a known mediator of migraine, exerting this biological effect through activation of trigeminovascular, meningeal and associated neuronal pathways located in close proximity to the central nervous system. Monoclonal antibodies (mAb) targeting the CGRP pathway are an effective new preventive treatment for migraine, with a generally favourable adverse event profile. Pre-clinical evidence supports an anti-inflammatory/immunoregulatory role for CGRP in other organ systems, and therefore inhibition of the normal action of this peptide may promote a pro-inflammatory response. CASES: We present a case series of eight patients with new or significantly worsened inflammatory pathology in close temporal association with the commencement of CGRP mAb therapy. CONCLUSION: This case series provides novel insights on the potential molecular mechanisms and side-effects of CGRP antagonism in migraine and supports clinical vigilance in patient care going forward.

Erenumab in Chronic Migraine: An Australian Experience.

OBJECTIVE: To determine the effectiveness and safety of erenumab in patients with chronic migraine in the real-world setting of 3 headache centers in Australia. METHODS: Patients with migraine were prescribed erenumab (70 or 140 mg) in the setting of either a product familiarization program or paid access to the medication in 3 headache centers in Australia. We obtained baseline and monthly prospective data on monthly headache days, monthly migraine days, monthly triptan use days, monthly codeine use days, Headache Impact Test-6 scores, and adverse reactions. In this paper, we present our data at 3 and 6 months in our subgroup of patients with chronic migraine with and without medication overuse. RESULTS: A total of 170 patients with chronic migraine were prescribed erenumab in the 3 headache centers. At 3 months, 100/170 (58.8%) had 50% or greater reduction in monthly migraine days. At 6 months, 79/170 (46.5%) had 50% or greater reduction in monthly migraine days. At 6 months, there was a mean reduction in monthly headache days of 9.2 days, a mean reduction in monthly migraine days of 10.2 days. There were few adverse events reported. CONCLUSION: This is the first report from 3 Australian headache centers about erenumab in the real world. Our analysis has supported erenumab as an effective and well-tolerated migraine preventative therapy for patients with chronic migraine who have failed many preventative therapies.

Pain and small fiber function in Charcot-Marie-Tooth disease type 1A.

INTRODUCTION: Charcot-Marie-Tooth (CMT) disease type 1A is the most common form of CMT. The main clinical features are distal weakness, sensory loss, and skeletal deformities. Although pain is a frequent complaint, small fiber involvement in CMT1A has not been studied extensively. METHODS: We assessed pain and small fiber involvement in 49 CMT1A patients using a variety of pain scales, pain questionnaires, and thermal thresholds. RESULTS: Forty-three of 49 patients (88%) complained of pain. The pain was localized to the feet in 61% of patients. Only 18% of patients had neuropathic pain. Cold and warm detection thresholds were elevated in 53% and 12% of patients, respectively. CONCLUSIONS: Our findings confirm that CMT1A patients have significant pain, which is more likely to be multifactorial in origin and suggests that a proportion of patients have small fiber dysfunction affecting mainly thinly myelinated Aδ fibers.

A pilot study of proximal strength training in Charcot-Marie-Tooth disease.

Gait analysis of people with Charcot-Marie-Tooth (CMT) disease revealed proximal adaptive gait strategies to compensate for foot drop. We previously demonstrated that hip flexor muscle fatigue can limit walking endurance. This pilot study used a single-blinded cross over design to investigate the effect of a 16-week home-based programme of resistance training on hip flexor muscle strength. Measures of walking endurance, gait speed, exertion, fatigue, and general activity were also recorded. The exercise protocol was based on American College of Sports Medicine recommendations. A mixed effects model was used for analysis. Twenty-six people finished the study, with average reported exercise participation of 93%. No negative effects of exercise were observed. Significant increase in hip flexor muscle strength was observed on the left, but not the right. No changes were observed in walking speed and endurance measures. This pilot study of home-based resistance training showed a modest improvement in hip strength but only on one side. The lack of a more significant improvement and no improvement in walking measures suggests that this training protocol may not be optimal for people with CMT and that patients may need to stratified differently for training studies in CMT.

Interventional treatments.

In migraine, when patients have failed medication management or are unable to be treated with systemic medications, minimally invasive interventions can be options used to provide pain relief. The type of intervention depends on the pain location, associated clinical features, clinical context, medical comorbidities, and response to prior injections. Interventions can vary from bedside peripheral nerve blocks to fluoroscopically guided interventions. Growing evidence is supporting the use of interventions in migraine, and judicious use can improve clinical outcomes.

Relationship of migraine and other forms of chronic pain.

The disability of migraine, a highly prevalent condition, is worsened by a second comorbid chronic pain condition. There is evidence of a relationship between migraine and several visceral pain conditions including irritable bowel syndrome, endometriosis, and dysmenorrhoea, as well as nonvisceral conditions including temporomandibular dysfunction, fibromyalgia, and lower back pain. While the mechanisms linking these conditions are inadequately surmised, a two-way relationship between migraine and these comorbidities likely exists. The progression and chronification of migraine is associated with peripheral and central sensitization, which may predispose to other conditions. Conversely, aspects of the mechanism of each comorbid condition may promote further migraine attacks. This chapter introduces each comorbidity, briefly summarizes the existing evidence, and discusses implications for treatment.

Twelve-month efficacy of CGRP monoclonal antibodies and predictive value of short-term response: results of an Australian multicentre study.

Introduction: Clinical trials show that calcitonin gene-related peptide monoclonal antibodies (CGRP mAbs) are effective preventative treatments for chronic migraine. Their efficacy over longer time periods and in cohorts originally excluded from trials remains uncertain. This study aims to explore the impact of CGRP mAbs in an Australian real-life setting. Methods: A multicentre cohort study was performed in the tertiary headache clinics of the Alfred and Austin Hospitals, Melbourne, Australia. Patients were commenced on a CGRP mAb for chronic migraine and asked to keep a headache diary, recorded at 3 monthly appointments for 12 months. Primary outcome was a ≥50% reduction in monthly headache days (MHD). Results: From a population of 105 patients, 90 patients commenced galcanezumab and 15 commenced fremanezumab. The ≥50% responder rate of the cohort was 52.4% after 3 months. Over 12 months follow-up, 25.7% of the cohort ceased due to a lack of efficacy and 16.2% ceased due to an adverse event. There was no difference in response or cessation between medications. There was poor agreement in 3-month and 12-month response rates (Cohen's κ=0.130; p=0.171). On subgroup analysis, continuous headache at baseline and number of trialled preventative treatments were the only factors associated with efficacy. Conclusion: CGRP mAbs were associated with sustained reductions in MHD over 12-month follow-up in patients with resistant migraine in Australia. Further studies are required to determine treatment options for patients with continuous headache. Poor agreement between outcomes at 3 and 12 months highlights the need to assess some patients at later timepoints.