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• About this document
• Executive Summary

I · History & Nature

• The History and Nature of Cluster Headaches
• 1 History
  • The priority question: who described it first?
  • The 19th century: fragments before synthesis
  • Wilfred Harris and the 1926 turning point
  • Horton, histamine, and the “suicide headache”
  • Naming evolution: a syndrome hunting for its name
  • From migraine subtype to independent diagnosis: the classification story
  • Sjaastad, the “Cluster Club,” and the birth of oxygen therapy
  • History in languages other than English
• 2 What a Cluster Headache Is
  • The current formal definition (ICHD-3)
  • How much does it hurt? The best available quantitative answer
  • Attack anatomy: onset, peak, duration, and the restlessness that defines the disease
  • Differential diagnosis: cluster headache vs. its look-alikes
  • What patients actually say it feels like
  • The psychological weight of the disease

II · Mechanism

• Mechanism and Pathophysiology
  • Mechanism and Pathophysiology

III · Epidemiology

• Epidemiology and Demographics
  • Epidemiology and Demographics

IV · Diagnosis & Differentials

• Types, Diagnosis and What Else It Might Be
• 1 Classification
  • Episodic vs chronic cluster headache
  • Conversion between forms — the numbers, precisely
  • Where CH sits within the TACs
• 2 The TAC Family & Differentials
• 3 Diagnosis in Practice
  • How diagnosis is made
  • Why misdiagnosis is so common, and how long it takes — a global picture
  • Patient experiences of the diagnostic journey community report
• 4 Triggers & Patterns
  • Established triggers
  • Sleep architecture: REM association and obstructive sleep apnoea
  • Community-reported triggers and protective factors
• 5 Comorbidities & Impact
  • Psychiatric comorbidities
  • Sleep and physical comorbidities
  • Quality of life and employment impact
• References (Part IV)

V · Treatment

• Treatment
  • Acute / Abortive Treatment
• 1.1 High-Flow Oxygen
  • Evidence base
  • Mechanism of action
  • Delivery technique — what the numbers actually mean
  • Community-optimised technique — where the community diverges from the guidelines
  • Citizen-science efficacy data
  • Access barriers by country
  • Oxygen — bottom line for a chronic daily sufferer
• 1.2 Triptans
  • Subcutaneous sumatriptan — the strongest acute drug
  • Intranasal sumatriptan
  • Zolmitriptan
  • Comparison table — acute drug efficacy
  • Dose limits and cardiovascular contraindications
  • The chronic/daily problem — the central tension of this chapter
• 1.3 Other Acute Options
  • Intranasal lidocaine
  • Ergotamine and dihydroergotamine (DHE)
  • Octreotide
• 2 Transitional / Bridge Therapy
  • Why bridging exists at all
  • Corticosteroids
  • Greater occipital nerve (GON) / suboccipital steroid injections
  • Bridge therapy — practical summary
• 3 Preventive Treatment
• 3.1 Verapamil
  • Status and why it is first-line
  • Efficacy — the actual numbers
  • Dosing and titration — four national protocols compared
  • ECG monitoring: rationale and protocol
  • Side effects
  • What the patient community says — verapamil
  • 2024–2026 updates
  • Australia specifically
• 3.2 Lithium
  • Status
  • Efficacy — the open-label record vs the one RCT
  • Dosing, serum levels and monitoring
  • Side effects and contraindications
  • Odd findings and minority observations
  • Community view
• 3.3 Topiramate
  • Status
  • Efficacy — and a big internal inconsistency in the literature
  • Dosing and side effects
  • Community view
• 3.4 Melatonin
  • Why melatonin at all: the circadian rationale
  • Efficacy — the positive trial
  • Efficacy — the negative trial
  • The contradictory case reports
  • Dosing and safety
  • Community view — the sharpest divergence in the chapter
• 3.5 Other Weaker-Evidence Preventives
  • Warfarin / anticoagulation — the surprising one
  • Civamide / capsaicin (intranasal, TRPV1 desensitisation)
  • Sodium valproate / divalproex — negative RCT, positive open studies
  • Gabapentin
  • Baclofen
  • Clonidine (transdermal)
  • Pizotifen
  • Botulinum toxin
  • Briefly: agents evaluated and found negative
• 3.6 CGRP Monoclonal Antibodies
  • CGAL: galcanezumab in episodic CH — the one positive trial
  • The chronic CH galcanezumab trial — the failure
  • Fremanezumab — both trials terminated
  • Eptinezumab: ALLEVIATE and CHRONICLE
  • The 2026 meta-analyses: do they genuinely conflict?
  • The real-world data — where the community and the trials diverge hardest
  • What the community says about Emgality — in detail
  • Summary judgement on CGRP mAbs
• 4.0 Framing note: what “refractory chronic CH” means, and why it matters here
• 4.1 Non-invasive vagus nerve stimulation (nVNS / gammaCore)
  • What it is
  • ACT1 — the first sham-controlled acute trial
  • ACT2 — the trial that made the episodic/chronic split undeniable
  • Pooled analysis of ACT1 + ACT2
  • PREVA — nVNS as a preventive in chronic CH (the one positive chronic trial)
  • Real-world open-label data in refractory chronic CH
  • Guideline positions
  • Regulatory status
  • Cost and access — Australia specifically
  • Patient community experience and sentiment
• 4.2 Sphenopalatine ganglion (SPG) stimulation — Pulsante / Pathway CH-1 and CH-2
  • What it is
  • Pathway CH-1 — the pivotal European trial
  • Pathway CH-2 — the US confirmatory trial
  • Pathway R-1 — the European registry (non-Anglophone-led)
  • Guideline position
  • The commercial collapse — and why this section matters more than the efficacy numbers
  • Current status, 2025–2026
  • Community sentiment
• 4.3 Occipital nerve stimulation (ONS)
  • What it is
  • Early evidence base — open-label case series
  • ICON — the phase 3 dose-controlled trial
  • L-ICON — long-term extension (2–8 years)
  • Fogh-Andersen 2026 — the placebo-controlled Danish trial (newest evidence)
  • Complication rates across the wider literature
  • Guideline position — the most negative in this chapter
  • Community experience
• 4.4 Deep brain stimulation (DBS) of the posterior hypothalamus
  • History and rationale
  • Leone’s pooled series — 79 patients
  • Series-by-series results and adverse events
  • The death — Schoenen 2005
  • Systematic review and meta-analysis — 108 cases
  • The negative randomised trial
  • Acute use — doesn’t work
  • Current status and guideline position
  • Community experience
• 4.5 Surgical history — what was tried, and why most of it was abandoned
  • Timeline
  • Trigeminal nerve section / rhizotomy
  • Percutaneous radiofrequency trigeminal gangliorhizolysis
  • Gamma knife radiosurgery
  • Microvascular decompression (MVD)
  • Greater occipital nerve blockade (still used, and standing apart from the rest)
  • The EAN’s summary judgement on surgery
  • The pattern worth naming
• 4.6 Cross-Cutting Summary Table
• 4.7 Honest Overall Assessment for a Person With Chronic Daily CH
• 5 Access & Practical Realities
  • Australia
  • United States
  • United Kingdom (the best-organised system of the four)
  • European Union / Germany
  • Cross-Cutting Community Knowledge community report
  • Side-by-Side Summary
• 7 Cross-Cutting Observations, Oddities and Divergences
  • The episodic/chronic split is the dominant axis of this entire chapter
  • The citizen-science ranking largely validates clinical evidence — with one major exception
  • Cardiac monitoring failure on verapamil is real and documented from two independent directions, and the danger window is wider than commonly advised
  • Access, not efficacy, is frequently the binding constraint — and this cuts across every treatment category, not just oxygen
  • Language bias in the literature is measurable, not hypothetical, and non-English sourcing changed several conclusions in this chapter
  • Community practice on hardware/technique frequently outruns formal guidance; community explanations of mechanism frequently lag behind or diverge from it
  • The field has been strikingly static for 20–25 years, with a partial exception in neuromodulation
  • The disease’s severity is independently documented, not a matter of patient self-report alone
• References (Part V)

VI · Citizen Science

• What Sufferers Have Worked Out: Citizen Science and Community Knowledge
• 1 The Organised Community
  • Clusterbusters: origin and structure
  • National and language-specific equivalents
  • Community survey research
• 2 The Vitamin D3 Regimen (“Batch Protocol”)
  • History and originator
  • Loading protocols
  • The published survey evidence
  • Formal trial activity
  • Proposed mechanism and evidence quality assessment
• 3 Psychedelics — The Community Origin of a Research Agenda
  • From bulletin board to Harvard: Sewell, Halpern & Pope (2006)
  • The 2015 Clusterbusters Medication Use Survey (Schindler et al.)
  • Yale/VA controlled trials (Schindler et al.)
  • BOL-148: turning a psychedelic into a non-hallucinogenic drug candidate
  • Legal status by jurisdiction, including Australia
• 4 Other Community-Identified Threads
  • Energy drinks / caffeine aborts
  • Physical exertion / exercise
  • Cold, heat, and breathing manoeuvres
  • Kudzu
  • Capsaicin
  • Community observations on remission
  • Wearables and self-tracking
• 5 Where Community and Clinic Disagree
• References (Part VI)

VII · The Frontier

• The Frontier: Current Research and Where This Is Heading
• 5.1 Active Research: The Global Trial Landscape
  • The CGRP story: one win, four losses
  • What’s genuinely new since the last pass (2024–2026 registrations)
  • The psychedelics pipeline, in detail
  • PACAP: the strongest un-trialled target in headache medicine
  • Orexin antagonists and circadian-targeted drugs — the direct answer to a specific question
  • Regional registry coverage — a note relevant to an Australian patient
  • Diagram: selected trial timeline
• 5.2 Emerging Science: Genetics, Chronobiology, Imaging, Biomarkers (2023–2026)
  • Genetics — the field’s most solid ground, with corrections
  • Chronobiology — real phenotype, unsupported genotype
  • Imaging — an open, unresolved contradiction
  • Biomarkers and inflammation — a corrected and genuinely contested picture
  • Competing hypotheses — the field’s live arguments
  • Diagram: competing pathophysiology models
• 5.3 The Chronic-CH Problem
• 5.4 Structural Future: Funding, Advocacy, and Realistic Timelines
  • The funding numbers, quantified
  • Patient advocacy: doing the work public funders are not
  • Realistic timelines — informed projection, explicitly labelled as such

Unresolved Conflicts

• Unresolved Conflicts

Open Questions & Loose Threads (Consolidated)

• Open Questions & Loose Threads (Consolidated)
  • From Parts I–III (history, nature, mechanism, epidemiology)
  • From Part IV (types, diagnosis and differentials)
  • From Part V (treatment)
  • From Part VI (citizen science and community knowledge)
  • From Part VII (the frontier)

Editor’s Queries

• Editor’s Queries

Watchlist

• Watchlist

Changelog

• Changelog