Cluster headache is often described by patients and clinicians alike as one of the most severe pains the human body can experience. Yet despite its brutality, the disorder remains underrecognized, underfunded, and frequently misdiagnosed. This article summarizes major scientific advances published through 2025, including new insights into the genetic architecture of cluster headache, emerging biomarkers of neuroinflammation, and high resolution neuroimaging studies revealing dysfunction within hypothalamic and limbic brain networks.
Introduction
Cluster Headache (CH) is one of the most agonizing and debilitating primary headache disorders known to medicine. Characterized by excruciating unilateral pain typically localized to the orbital or temporal regions, CH attacks are accompanied by striking cranial autonomic symptoms and a profound sense of physical restlessness.
Research throughout 2025 provided a meaningful expansion of our knowledge regarding this condition. The scientific community published an array of studies on its genetic architecture, structural and functional neuroanatomy, profound psychosocial burden, and rapidly evolving therapeutic landscape. This review synthesizes these recent findings to provide an update on the pathophysiology, clinical phenotyping, psychosocial impact, and management of cluster headache.
Epidemiology, Diagnostic Delays and Public Health Burden
Despite being infamous for its severity, CH research and public health recognition remain disproportionately low. The global prevalence of CH is approximately 0.1%, or roughly 124 per 100,000 individuals (Yuan et al., 2025). Chronic Cluster Headache (CCH) meets the regulatory thresholds for a rare disease set by both the FDA and the EMA, yet it lacks formal rare disease designation, creating substantial barriers to research funding and drug development (Yuan et al., 2025). A 2025 analysis of research investment in the UK revealed that CH receives orders of magnitude less funding than multiple sclerosis, a condition with similar prevalence, reflecting systemic health inequalities in pain research (Parra-Hinojosa et al., 2025).
A major clinical failure continues to be the substantial diagnostic delay. A 2025 diagnostic-delay systematic review and meta-analysis found that patients still wait years for diagnosis, with average delays varying widely across cohorts and countries (Van Obberghen et al., 2025). Educational gaps also persist among family and emergency medicine physicians, where recognition does not always translate into adequate referral or specialist management (Hasirci Bayir et al., 2025). In a recent tertiary headache center cohort, patients with CH arrived after a median disease duration of 5.5 years, and more than a third had not received guideline-recommended acute treatment before referral (Lange et al., 2025).
Clinical Phenotyping and Prolonged Remission
Our understanding of the natural course and clinical phenotypes of CH has been refined. What were formerly called cluster tics have been proposed to be renamed "cluster stabs" (Carney et al., 2025). These brief, sharp, neuralgic pain paroxysms in the trigeminal distribution affect up to 47% of certain CH cohorts and present with pain intensity comparable to trigeminal neuralgia, but importantly lack the typical triggerability seen in classic neuralgias (Carney et al., 2025).
Prospective longitudinal data reveals that CH is a dynamic disease over the lifespan. About 12% of patients presenting with their first-ever cluster bout were reclassified as chronic at early reassessment (2-4 weeks), while the rate of newly-developing chronic CH over five-year follow-up was low (roughly 1-4%); relapse risk was highest early in the disease course and declined with advancing age and longer disease duration (Lee et al., 2025). Spontaneous prolonged remission is possible, and physicians must carefully distinguish true remission from medication suppressed states (Naber et al., prolonged-remission cohort, 2025).
A novel multicenter cross sectional study reported an inverse association between body mass index (BMI) and bout periodicity in ECH, raising questions about metabolic influences on cyclic rhythmicity without proving a protective effect of obesity (Kim et al., 2025). A 2025 case report also described chronic CH affected by gender affirmation treatment, a signal that supports further study of sex hormones in CH but should not be overgeneralized from a single patient (Granata and Gantenbein, 2025).
The Psychosocial and Psychiatric Impact
The psychological trauma of enduring CH is severe. Qualitative explorations highlight the desperation of patients, with one study participant noting that if they had blood pouring out of their eyeballs, people would finally notice their invisible pain (Whitley et al., 2025). Pain related disability in CH is profoundly influenced by the Fear Avoidance Model. The persistent fear of attacks drives social withdrawal, anxiety, and depression even during attack free remission periods (Fox et al., 2025).
Validation of disease specific patient reported outcome measures, such as the Cluster Headache Quality of Life scale, confirms that mental health deterioration is a major driver of quality of life impairment, beyond attack frequency alone (Naber et al., CHQ validation study, 2025). In a pre-hospitalization cohort, 92.7% of patients had severe limitations in health and functionality on WHODAS 2.0 assessment (Gobel et al., 2025).
Tragically, suicidality remains high. Pooled rates across all studies were lower (8.0% ideation, 1.2% attempts) and overall suicidal risk was not clearly elevated above the general population, but among patients seen in specialized headache settings rates were far higher (44.6% ideation, 5.1% attempts), underscoring the need for psychiatric screening in headache clinics (Van Obberghen et al., 2025).
Neuroimaging, Pathophysiology and Biomarkers
Advances in ultra high field 7T MRI and functional connectivity have provided unprecedented clarity on the CH brain (Wang et al., 2025).
- Restlessness and Agitation: A core diagnostic feature of CH, physical restlessness has been associated with functional connectivity patterns involving the Locus Coeruleus (LC) and Substantia Nigra pars compacta (SNpc) (Chen et al., 2025). Rather than clearly originating from traditional aggression circuits, weakened connectivity from the dopaminergic SNpc to the superior frontal cortex may represent a downstream pathway contributing to restlessness (Chen et al., 2025).
- Limbic and Hypothalamic Networks: Multimodal 7T MRI analyses reported significant volumetric and functional abnormalities within the limbic system, particularly in the right anterior inferior hypothalamus, amygdala, and hippocampus (Wang et al., 2025). Additionally, patients with CCH present with dysfunctional mesocorticolimbic circuitry, showing blunted Ventral Tegmental Area (VTA) activity during reward anticipation, which correlates with anhedonia and pain chronification (Ferraro et al., 2025).
Biomarker research has further clarified the neurochemical milieu of the disorder. Pituitary Adenylate Cyclase Activating Polypeptide 38 (PACAP-38) was elevated in CCH, ECH during bouts, and ECH during remission compared to healthy controls, positioning it as a potential therapeutic target (Soborg et al., 2025).
Conversely, the exact role of Calcitonin Gene Related Peptide (CGRP) as a stable biomarker is debated, with some recent studies finding reduced levels in CH patients, pointing to assay variability or complex disease dynamics (Petersen et al., 2024).
Biomarker data support a neuroinflammatory component. Elevated cytokines like Oncostatin M (OSM) are found across all CH states, while high Interleukin 1 beta is specifically correlated with CCH, marking it as a potential indicator of chronification (Lund et al., 2025).
Genetics and Proteomics
Recent CH genetics work has continued to shape the 2025 discussion. A large international meta-GWAS analyzed more than 4,700 cases and identified risk loci near genes including WNT2, PLCE1, and LRP1, while replicating established hits including MERTK, DUSP10, and FHL5 (Winsvold et al., 2023; Jennysdotter Olofsgaard, 2025). MERTK, a macrophage related receptor kinase, has also been investigated in the trigeminal system, with elevated expression reported in blood samples from CH patients and MERTK/Galectin-3 expression mapped in rat trigeminal ganglia. These findings support, but do not prove, a link between genetic susceptibility, neuroinflammation and trigeminal biology (Edvinsson et al., 2024).
Proteome Wide Mendelian Randomization (PWMR) studies identified plasma proteins with evidence of causal association with CH. Proteins including PXDNL, CCN4, PKD1, LGALS9, and MRC1 emerged as potential drug-target candidates with no significant disease-related adverse effects detected in phenome-wide MR screening, but these remain hypothesis-generating targets until experimentally and clinically validated (Xiong et al., 2025). PXDNL interacts with both acute and preventive CH drug target networks, presenting a possible dual purpose target. Additionally, Mendelian Randomization suggested that CD39+ CD4+ T cells may exert a protective causal effect against CH risk through ADP, N-acetylneuraminate, and choline metabolic pathways (Zeng et al., 2025).
Pharmacological Treatments
The excruciating severity of CH demands aggressive treatment. However, recent clinical trials evaluating CGRP monoclonal antibodies have yielded mixed results. The highly anticipated CHERUB01 phase 2 trial evaluating erenumab for CCH did not meet its primary endpoint for reducing attack frequency compared to placebo (Mecklenburg et al., 2025).
Similarly, the ALLEVIATE trial evaluating intravenous eptinezumab for ECH failed its primary endpoint for attack reduction, although numerically higher responder rates and improvements in average daily pain and patient-reported outcomes were noted (Jensen et al., 2025). Conversely, the oral gepant medication atogepant showed promise in a small refractory CH case series, but that signal remains preliminary and requires controlled testing (Serrao et al., 2025).
For transitional therapy, greater occipital nerve (GON) injection with methylprednisolone has randomized trial support in episodic CH (Brandt et al., 2025). High flow oxygen remains a core acute therapy. A 2025 OUCH-UK patient experience survey reported better patient-rated outcomes with ultra-high-flow demand valve oxygen than with standard continuous-flow systems, but this was survey evidence rather than a randomized efficacy trial (Goadsby et al., 2025).
Alternative Medicine and Psychedelics
For treatment refractory patients, indoleamine psychedelics and dissociative anesthetics continue to attract clinical and research interest. A 2025 clinical case series reported remission or marked improvement after supervised compassionate use of psilocybin, LSD, or intravenous ketamine in patients with difficult-to-treat CH, but case-series evidence cannot establish efficacy (Leighton et al., 2025). The non-hallucinogenic LSD analog BOL-148 remains an intriguing preventive candidate based on preliminary open-label data summarized in recent reviews, not a proven treatment (Coppola et al., 2025).
Neuromodulation
Neuromodulation remains critical for medically intractable CCH.
- Non-Invasive Vagus Nerve Stimulation (tcVNS): FDA cleared tcVNS has guideline support for acute treatment and prevention in ECH, with a favorable safety profile and a high degree of patient autonomy (Goadsby et al., 2025).
- Occipital Nerve Stimulation (ONS): Invasive ONS provides sustained relief for refractory CCH. Data from the ICON trial revealed that an early positive clinical response at 24 weeks is the sole reliable predictor of long term (5 year) treatment success (Brandt et al., 2025).
- Deep Brain Stimulation (DBS): Targeting the posterior hypothalamus or related deep structures remains a last-resort option for the most refractory patients, with systematic review evidence suggesting meaningful reductions in attack frequency, severity, or duration in selected cases (Uwishema et al., 2025). Novel approaches, such as third ventricle DBS, offer alternative surgical targets with early long term feasibility data (Chabardes et al., 2025).
- Combined Stimulation: A small 2025 series combining unilateral Sphenopalatine Ganglion (SPG) stimulation with ONS reported long lasting benefit in refractory chronic CH, but the evidence base remains limited by sample size and uncontrolled design (Andreani et al., 2025).
- Repetitive Transcranial Magnetic Stimulation (rTMS): A randomized crossover pilot trial reported potential benefit from rTMS over the motor cortex in refractory CCH, supporting further study rather than immediate routine adoption (Portocarrero Sanchez et al., 2025).
Conclusion
Research in 2025 expanded the horizon of Cluster Headache science. CH should not be understood only as a peripheral trigeminal pain disorder, but as a complex neuro-immune, genetic, and chronobiological disease.
Dysfunctions within mesocorticolimbic networks, combined with specific genetic loci like MERTK and neuroinflammatory signals, paint a more detailed picture of the disease state. While CGRP monoclonal antibodies have shown unexpected limits in chronic CH, the evolution of neurostimulation, transitional therapies, new biomarker targets, and carefully studied psychedelic or serotonergic approaches offers cautious hope.
Moving forward, health systems should consider formal rare disease recognition for CCH to improve research and treatment incentives, and clinicians should integrate rigorous psychiatric screening and targeted multimodal therapies to alleviate the profound burden of this devastating condition.