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Background and Purpose: Cluster headache is a relatively rare, disabling primary headache disorder with a major impact on patients' quality of life. This work presents evidence-based recommendations for the treatment of cluster headache derived from a systematic review of the literature and consensus among a panel of experts., Methods: The databases PubMed (Medline), Science Citation Index, and Cochrane Library were screened for studies on the efficacy of interventions (last access July 2022). The findings in these studies were evaluated according to the recommendations of the European Academy of Neurology, and the level of evidence was established using GRADE (Grading of Recommendations Assessment, Development, and Evaluation)., Recommendations: For the acute treatment of cluster headache attacks, there is a strong recommendation for oxygen (100%) with a flow of at least 12 L/min over 15 min and 6 mg subcutaneous sumatriptan. Prophylaxis of cluster headache attacks with verapamil at a daily dose of at least 240 mg (maximum dose depends on efficacy and tolerability) is recommended. Corticosteroids are efficacious in cluster headache. To reach an effect, the use of at least 100 mg prednisone (or equivalent corticosteroid) given orally or at up to 500 mg iv per day over 5 days is recommended. Lithium, topiramate, and galcanezumab (only for episodic cluster headache) are recommended as alternative treatments. Noninvasive vagus nerve stimulation is efficacious in episodic but not chronic cluster headache. Greater occipital nerve block is recommended, but electrical stimulation of the greater occipital nerve is not recommended due to the side effect profile., (© 2023 The Authors. European Journal of Neurology published by John Wiley & Sons Ltd on behalf of European Academy of Neurology.)

Objectives and Background: Chronic cluster headache (CCH) is a rare but severely debilitating primary headache condition. A growing amount of evidence suggests that occipital nerve stimulation (ONS) can offer effective treatment in patients with severe CCH for whom conventional medical therapy does not have a sufficient effect. The paresthesia evoked by conventional (tonic) stimulation can be bothersome and may thus limit therapy. Burst ONS produces paresthesia-free stimulation, but the amount of evidence on the efficacy of burst ONS as a treatment for intractable CCH is scarce., Methods: In this case series, we report 15 patients with CCH treated with ONS at Aarhus University Hospital, Denmark, from 2013 to 2020. Nine of these received burst stimulation either as primary treatment or as a supplement to tonic stimulation. The results were assessed in terms of the frequency of headache attacks per week and their intensity on the Numeric Rating Scale, as well as the Patient Global Impression of Change (PGIC) with ONS treatment., Results: At a median (range) follow-up of 38 (16-96) months, 12 of the 15 patients (80%) reported a reduction in attack frequency of ≥50% (a reduction from a median of 35 to 1 attack/week, p < 0.001). Seven of these patients were treated with burst ONS. A significant reduction was also seen in maximum pain intensity. Overall, 10 patients stated a clinically important improvement in their headache condition following ONS treatment, rated on the PGIC scale. A total of 16 adverse events (nine of which were in the same patient) were registered., Conclusion: Occipital nerve stimulation significantly reduced the number of weekly headache attacks and their intensity. Burst ONS seems to function well alone or as a supplement to conventional tonic ONS as a preventive treatment for CCH; however, larger prospective studies are needed to determine whether the effect can be confirmed and whether the efficacy of the two stimulation paradigms is even., (© 2023 The Authors. Headache: The Journal of Head and Face Pain published by Wiley Periodicals LLC on behalf of American Headache Society.)

In clinical practice, patients with cluster headache often ask questions or mention information that they have seen or heard on the Internet. Because YouTube (www.youtube.com) is the second most visited Web site worldwide and offers a plethora of video content, we found it timely to ascertain the quality of information on cluster headache that is freely available on YouTube. We conducted an inquiry on YouTube on January 24, 2022, with the search term "cluster headache." Eligible YouTube videos included those with ≥10,000 views and content related to cluster headache. We assessed the quality and reliability of the videos with the Global Quality Scale and DISCERN, respectively. The search strategy identified 644 videos of which 134 were eligible for inclusion. The sources of the included videos were categorized as "healthcare professional/institution" (n = 45), "personal experience" (n = 52), and "other" (n = 37). According to the Global Quality Scale, 70 (52%) were low quality, 34 (25%) were of moderate quality, and 30 (22%) were of high quality. According to DISCERN, 104 (78%) were of low reliability, 28 (21%) were of moderate reliability, and 2 (1%) were of high reliability. The quality and reliability of cluster headache-related information on YouTube has room for improvement, even the content provided by healthcare providers. These findings should incentivize stakeholders, for example, government services, professional societies, healthcare providers, to provide accessible and better information on cluster headache., (© 2022 The Authors. Headache: The Journal of Head and Face Pain published by Wiley Periodicals LLC on behalf of American Headache Society.)

Objective: To characterize patient-reported ideas and concerns about cluster headache, treatment options, and management strategies., Background: Cluster headache patients experience severe pain and often suffer additional consequences from their disease. Patients have identified methods to cope with and combat cluster headache that are not widely known., Methods: Secondary analysis was performed using deidentified data from the online Clusterbusters Medication Use survey, wherein 10 questions allowed for freely written comments. Using mixed-methods techniques, neurologists with expertise in headache medicine identified themes from these comments. Subgroup analysis sought to identify variables associated with specific themes., Results: Among 2274 free-text responses from 493 adult participants, 23 themes were identified. Themes commonly discussed in the literature included such topics as "nothing worked" (24.7%, 122/493), "side effects" (12.8%, 63/493), and difficulties with "access/cost" (2.4%, 12/493). Less widely recognized themes included the use of "illicit substances" (35.5%, 175/493) and "vitamins/supplements" (12.2%, 60/493) in disease management. Lesser-known themes included "coffee" (5.3%, 26/493) and "exercise/physical activity" (4.7%, 23/493). Using strict significance criteria, no subgroup was associated with any theme. Several poignant quotes highlighted patient thoughts and experiences., Conclusions: This mixed-methods analysis identified challenges endured by cluster headache patients, as well as a variety of patient-directed disease management approaches. The volunteered information spotlights pharmacological, physiological, and psychological aspects of cluster headache that warrant further exploratory and interventional investigation., (© 2020 American Headache Society.)

Background: Cluster headache is a highly disabling neurological disorder., Purpose: The purpose of this review is to highlight recent therapeutic advances in the treatment of cluster headache such as monoclonal antibodies as well as non-invasive vagus nerve stimulation, and examine future potential therapeutic targets., Discussion: Several therapeutic agents currently in use may have underlying mechanisms important to cluster headache pathophysiology and have yet to be completely elucidated. The psychobiological aspects of cluster headache have a significant impact on patients, as well as pose limitations for treatment. Neuropeptides may play a role in underlying mechanisms in why cluster headache patients are frequent tobacco smokers. Alterations in the hypothalamic-pituitary-adrenal axis and neuroinflammation may play a role in suicidality. The circadian nature of cluster headache may generate the development of future treatment options. New understanding of mechanisms underlying post-traumatic headache may also provide insights into cluster headache pathophysiology., Conclusion: Molecular targets and neuromodulation advances have paved the way for a new generation of therapeutic agents in cluster headache. There are several other potential targets., (© 2020 American Headache Society.)

Background and Purpose: The management options for chronic cluster headache (CCH) are limited and a significant proportion of patients become refractory to pharmacological treatments. Pulsed radiofrequency (PRF) of the sphenopalatine ganglion (SPG) may present an efficacious, minimally invasive treatment modality for patients with refractory CCH. We describe the clinical outcomes of 14 patients with refractory CCH treated with PRF of the SPG., Methods: Patients with medically refractory CCH who underwent percutaneous SPG-PRF treatment between January 2016 and April 2019 were included in this report. Patients obtaining at least 30% reduction in weekly cluster attacks for at least 3 months were defined as responders. Treatment-related side effects were collected., Results: A total of 14 patients were included in this report (nine males). At a median follow-up of 6.5 (range 6-13) months post-procedure, eight patients (57.1%) were defined as responders to the treatment. Six patients were non-responders and reported either a reduction in frequency and severity of attacks for <3 months (2/6), no improvement (2/6) or temporary worsening of symptoms (1/6). The majority of patients (63.6%, n = 7/11) treated with >45 V were responders compared with responders treated with 45 V (33.3%, n = 1/3). Five patients (35.7%) experienced post-procedural side effects., Conclusion: This case series suggests that PRF targeting the SPG might offer a safe, minimally invasive and effective treatment for medically refractory CCH. Given the small number of cases and the short follow-up, larger and more robust studies will be needed to confirm our findings., (© 2020 European Academy of Neurology.)

Objective: A evaluation of the effect of verapamil and other calcium channel blockers in cluster headache (CH) treatment and an investigation of possible effect mechanisms., Background: Verapamil has been used in the prevention of CH for almost 3 decades, however, the mode of action and therapeutic target is still unknown., Methods: A Pubmed search was conducted: "Verapamil"[Mesh] and "Cluster Headache"[Mesh]. We identified 5 relevant studies for CH. Publications were included if they made a substantial contribution within 3 prespecified areas: Efficacy (randomized controlled-trials or open labels studies), safety, and mechanism of effect., Results: Clinical effect: Clinical preventive treatment of CH with verapamil is based on 2 randomized controlled studies and 3 open-label studies. In total, 183 CH patients participated. Verapamil 360 mg/day was used in both controlled studies. Half of the chronic patients experienced benefit from verapamil treatment and the attack burden of episodic patients was, on average, reduced by 1 attack/day. Open-label studies support a dose-dependent level of efficacy. Mechanism of effect: Human and animal studies indicate that verapamil may exert its effect by modulating circadian rhythms, perhaps in central pacemakers, and/or by affecting release of calcitonin gene-related peptide., Conclusion: Verapamil appears to be an effective prophylactic drug in the treatment of CH and despite the scarcity of controlled trials, it is still the drug of choice. A chronotherapeutic approach might increase the effect. More basic and pharmacokinetic research is needed before the mechanism can be fully understood., (© 2019 American Headache Society.)

Headache disorders are among the most common and disabling medical conditions worldwide. Pharmacologic acute and preventive treatments are often insufficient and poorly tolerated, and the majority of patients are unable to adhere to their migraine treatments due to these issues. With improvements in our understanding of migraine and cluster headache pathophysiology, neuromodulation devices have been developed as safe and effective acute and preventive treatment options. In this review, we focus on neuromodulation devices that have been studied for migraine and cluster headache, with special attention to those that have gained food and drug administration (FDA) clearance. We will also explore how these devices can be used in patients who might have limited pharmacologic options, including the elderly, children, and pregnant women., (© 2019 American Headache Society.)

Objective: To assess the effectiveness and adverse effects of acute cluster headache medications in a large international sample, including recommended treatments such as oxygen, commonly used medications such as opioids, and emerging medications such as intranasal ketamine. Particular focus is paid to a large subset of respondents 65 years of age or older., Background: Large international surveys of cluster headache are rare, as are examinations of treatments and side effects in older cluster headache patients. This article presents data from the Cluster Headache Questionnaire, with respondents from over 50 countries and with the vast majority from the United States, the United Kingdom, and Canada., Methods: This internet-based survey included questions on cluster headache diagnostic criteria, which were used as part of the inclusion/exclusion criteria for the study, as well as effectiveness of medications, physical and medical complications, psychological and emotional complications, mood scores, and difficulty obtaining medications. The diagnostic questions were also used to create a separate group of respondents with probable cluster headache. Limitations to the methods include the use of nonvalidated questions, the lack of a formal clinical diagnosis of cluster headache, and the grouping of some medications (eg, all triptans as opposed to sumatriptan subcutaneous alone)., Results: A total of 3251 subjects participated in the questionnaire, and 2193 respondents met criteria for this study (1604 cluster headache and 589 probable cluster headache). Of the respondents with cluster headache, 68.8% (1104/1604) were male and 78.0% (1245/1596) had episodic cluster headache. Over half of respondents reported complete or very effective treatment for triptans (54%, 639/1139) and oxygen (54%, 582/1082). Between 14 and 25% of respondents reported complete or very effective treatment for ergot derivatives (dihydroergotamine 25%, 42/170; cafergot/ergotamine 17%, 50/303), caffeine and energy drinks (17%, 7/41), and intranasal ketamine (14%, 5/37). Less than 10% reported complete or very effective treatment for opioids (6%, 30/541), intranasal capsaicin (5%, 7/151), and intranasal lidocaine (2%, 5/241). Adverse events were especially low for oxygen (no or minimal physical and medical complications 99%, 1077/1093; no or minimal psychological and emotional complications 97%, 1065/1093), intranasal lidocaine (no or minimal physical and medical complications 97%, 248/257; no or minimal psychological and emotional complications 98%, 251/257), intranasal ketamine (no or minimal physical and medical complications 95%, 38/40; no or minimal psychological and emotional complications 98%, 39/40), intranasal capsaicin (no or minimal physical and medical complications 91%, 145/159; no or minimal psychological and emotional complications 94%, 150/159), and caffeine and energy drinks (no or minimal physical and medical complications 89%, 39/44; no or minimal psychological and emotional complications 91%, 40/44). This is in comparison to ergotamine/cafergot (no or minimal physical and medical complications 83%, 273/327; no or minimal psychological and emotional complications 89%, 290/327), dihydroergotamine (no or minimal physical and medical complications 81%, 143/176; no or minimal psychological and emotional complications 91%, 160/176), opioids (no or minimal physical and medical complications 76%, 416/549; no or minimal psychological and emotional complications 77%, 423/549), or triptans (no or minimal physical and medical complications 73%, 883/1218; no or minimal psychological and emotional complications 85%, 1032/1218). A total of 139 of 1604 cluster headache respondents (8.7%) were age 65 and older and reported similar effectiveness and adverse events to the general population. The 589 respondents with probable cluster headache reported similar medication effectiveness to respondents with a full diagnosis of cluster headache., Conclusions: Oxygen is reported by survey respondents to be a highly effective treatment with few complications in cluster headache in a large international sample, including those 65 years or over. Triptans are also very effective with some side effects, and newer medications deserve additional study. Patients with probable cluster headache may respond similarly to acute medications as patients with a full diagnosis of cluster headache., (© 2019 The Authors. Headache: The Journal of Head and Face Pain published by Wiley Periodicals, Inc. on behalf of American Headache Society.)

Objective: To determine the efficacy of high-volume anesthetic suboccipital nerve blocks (HVSON) for chronic cluster headache (CCH) and to define consistency of response over long-term use., Background: There are studies showing efficacy of greater occipital and suboccipital nerve block injections for CCH and also their possible use as a preventive treatment modality. There are scant data about the long-term efficacy of repetitive greater occipital and suboccipital nerve injections in CCH. HVSON has not been studied for CH., Methods: This was an open label, observational, case series study. Patients with CCH seen at a dedicated headache clinic over a 7-year time period and injected on at least 2 separate occasions were used for analysis. All were deemed medicinal treatment refractory. HVSON consisted of 9 mL 1% lidocaine and 1 mL triamcinolone 40 mg/mL injected on the side of CH., Results: Ten CCH patients were retrospectively studied. Range of mean average response to HVSON (all patients had complete pain freedom) was 1.5-31 weeks (longest: 44 weeks in 2 patients). Only one patient did not respond; 2 patients had 1.5-2 weeks of response; the remainder had at least 4 weeks of response. The mean average duration of effect was 10.3 weeks in the responders. Five patients were injected serially for 2-4 years (30x, 17x, 15x, 10x and 3x, respectively) with a consistent response of 6 weeks, 4 weeks, 12 weeks, 4 weeks, and 31 weeks, respectively, after each injection. Response duration was very reliable per individual patient. All 5 patients felt HVSON was effective as a preventive treatment. Smoking history did not appear to alter treatment response (8/10 were chronic current smokers and 7/8 responded to HVSON). The one patient who received the most injections developed avascular necrosis of the hip; the remainder of the subjects had no adverse events., Conclusion: HVSON from this open label study appears to be effective in the preventive treatment of medicinal refractory CCH and shows consistent response over long-term use with high rates of pain freedom., (© 2018 American Headache Society.)

Objective: In this secondary analysis of the Clusterbusters ® Medication Use survey, the use, effectiveness, and tolerability of inhaled oxygen were investigated and compared with injectable sumatriptan. We also sought to understand the predictors of medication response., Background: Inhaled oxygen is a mainstay abortive intervention in cluster headache but is not approved by the Food and Drug Administration (FDA). Unlike injectable sumatriptan, the only FDA-approved pharmacologic intervention for cluster headache, oxygen can be used multiple times a day, which is highly relevant for a condition with numerous daily attacks. In addition to obstacles in obtaining oxygen therapy, optimal oxygen delivery (ie, mask, flow rate) is not uniformly employed in cluster headache. These factors lead to underuse and imprecise therapeutic response rates., Methods: A secondary analysis was conducted using deidentified data from the Clusterbusters ® Medication Use survey, which was modeled after previously published surveys and available online. Subjects were recruited from headache clinics and cluster headache websites. Most responses were chosen from a list; others were free-texted. The final analysis included responses from 493 adult participants with a validated diagnosis of cluster headache. This analysis of deidentified data from the Clusterbusters ® Medication Use survey received institutional approval., Results: The most commonly used delivery system used by subjects was a non-rebreather-type mask. The use of oxygen flow rates >10 L/min was a positive predictor of medication response (OR = 2.36, P = .016). Among those who used flow rates >10 L/min, both inhaled oxygen (81.5%) and injectable sumatriptan (80.5%) were efficacious and did not differ significantly from each other in any specific group examined. At flow rates >10 L/min, positive predictors of oxygen response were male gender (OR = 2.07, P = .031) and cigarette smoking (current or historical; OR = 2.25, P = .017). Among the groups examined, there were no predictors of sumatriptan response. Most comments about side effects and concerns were directed at triptans., Conclusion: Therapeutic response to inhaled oxygen at sufficiently high flow rates (>10 L/min) had comparable efficacy to that of injectable sumatriptan for the acute treatment of cluster headache. Other factors in oxygen delivery (ie, flow rate changes) should be explored for optimization of therapy. The reasons for improved oxygen response in males and those with a cigarette smoking history require further exploration. While both oxygen and sumatriptan can be effective in the management of cluster headache, patient-reported side effects and concerns were more commonly directed at triptan medications. Current restrictions on access to inhaled oxygen, which exist at many levels, limit the therapeutic options available for patients with cluster headache, thereby doing a disservice to this patient population and the providers who deliver their care., (© 2018 American Headache Society.)

Objective: To report a case series of sneezing systematically occurring in two cases with migraine and cranial autonomic symptoms and two with cluster headache., Background: Sneezing occurring systematically during cluster headache or migraine is a rare condition. Sneezing has been described as a specific trigger for migraine., Methods: Case reports., Case Series: We describe four patients with primary headaches, presenting systematic sneezing at a definite time of premonitory, postdromal, or headache phase. All of these headaches were associated with cranial autonomic symptoms., Conclusion: Sneezing is a symptom associated with primary headaches. The definite place of sneezing in these patients suggests a particular implication of hypothalamus in the pathophysiology of these cases., (© 2017 American Headache Society.)

Objective: To characterize demographics, clinical characteristics, and treatment patterns of patients with cluster headache (CH)., Background: CH is an uncommon trigeminal autonomic cephalalgia with limited evidence-based treatment options. Patients suffer from extremely painful unilateral headache attacks and autonomic symptoms with episodic and chronic cycles., Design/methods: This retrospective analysis used insurance claims from Truven Health Analytics MarketScan ® research databases from 2009 to 2014. Two cohorts were compared: CH patients (with ≥2 CH claims) were propensity score matched with 4 non-headache controls, all with continuous enrollment for 12 months before and after the date of first CH claim or matched period among controls., Results: CH patients (N = 7589) were mainly male (57.4%) and 35-64 years old (73.2%), with significantly more claims for comorbid conditions vs controls (N = 30,341), including depressive disorders (19.8% vs 10.0%), sleep disturbances (19.7% vs 9.1%), anxiety disorders (19.2% vs 8.7%), and tobacco use disorders (12.8% vs 5.3%), with 2.5 times greater odds of suicidal ideation (all P < .0001). Odds of drug dependence were 3-fold greater among CH patients (OR = 2.8 [95% CI 2.3-3.4, P < .0001]). CH patients reported significantly greater use of prescription medications compared with controls; 25% of CH patients had >12 unique prescription drug claims. Most commonly prescribed drug classes for CH patients included: opiate agonists (41%), corticosteroids (34%), 5HT-1 agonists (32%), antidepressants (31%), NSAIDs (29%), anticonvulsants (28%), calcium antagonists (27%), and benzodiazepines (22%). Only 30.4% of CH patients received recognized CH treatments without opioids during the 12-month post-index period. These patients were less likely to visit emergency departments or need hospitalizations (26.8%) as compared to CH patients with no pharmacy claims for recognized CH treatments or opioids (33.6%; P < .0001)., Conclusions: The burden of CH is associated with significant co-morbidity, including substance use disorders and suicidal ideation, and treatment patterns indicating low use of recognized CH treatments., (© 2017 Eli Lilly and Company Headache published by Wiley Periodicals, Inc. on behalf of American Headache Society.)

Background: Oxygen is the standard of care for acute treatment of cluster headache. CMS, the US Centers for Medicaid and Medicare Services, has made the indefensible decision to not cover oxygen for cluster headache for patients with Medicaid and Medicare insurance, despite the evidence and professional guidelines. Commercial insurance generally covers oxygen for cluster headache., Objective: This is a "how-to" guide for successfully prescribing oxygen in the US., Summary: Prescription information is provided that can be incorporated as dot phrases, smart sets, or other standard templates for prescribing oxygen for cluster patients. In many states, oxygen is affordable and can be prescribed for Medicaid and Medicare patients who wish to pay cash. Welding or nonmedical grade industrial oxygen is almost the same cost as medical oxygen. However, it is less pure, lacks the same inspection of tanks, and is delivered without regulators to provide appropriate flow rates. Patients who pay cash should be strongly encouraged to buy medical oxygen., (© 2017 American Headache Society.)

Background: Cluster headache (CH) is a primary headache disorder associated with low levels of diagnosis and high unmet medical need. The pain attacks, associated anxiety, and fear in anticipation of the attacks are extremely debilitating to a patient with CH. For acute therapy, treatment guidelines recommend inhalation of high flow oxygen during the period of an attack. However, the use of oxygen for treatment of CH remains largely underutilized., Objectives: The objectives of the study, which covered each of the US states, were to map the current market landscape of medical grade oxygen for use in CH and to develop a cost simulator based on a patient's needs and geography., Methods: Desk research was undertaken to obtain price lists and product catalogs from wholesale and retail suppliers of medical grade oxygen across all US states. Base case scenarios for chronic and episodic forms of CH were assumed. A cost simulator was used to calculate the cost of oxygen use using inputs including the state in USA, tank size and price, exacerbations per year, duration of exacerbation, attacks per day, flow rate and duration of flow. Information was also collected to determine if healthcare insurers covered the costs of home oxygen use for CH., Results: Out of the 42 US states where pricing information of medical grade oxygen was available from suppliers, in 38 states the annual cost of high-flow oxygen for a patient with episodic CH was estimated to be <$1000. In 39 states, the annual cost of high-flow oxygen for a patient with chronic CH was estimated to be <$5000. Most of the home oxygen suppliers were familiar with CH and stocked the special non-rebreather masks and regulators necessary for this condition. It was found that many of the private commercial healthcare insurance providers reimbursed the cost of oxygen use for CH. However, the US Centers for Medicare and Medicaid Services (CMS) maintains there is insufficient evidence for coverage and continues to deny coverage for US Medicare and Medicaid patients., Conclusions: Results from our study showed that the current costs for oxygen use as an acute therapy in CH are not prohibitively expensive for patients and healthcare insurance providers. Apart from CMS, many insurers do reimburse the cost of oxygen use for CH. Our study suggests that further research is needed to determine if a lack of physician awareness about treatments and ways to prescribe are barriers for patients to access the high-flow oxygen treatment., (© 2017 American Headache Society.)

Objective: To describe the history of and available data on sphenopalatine ganglion (SPG) neuromodulation in the treatment of headache up to the present., Background: The SPG has been a therapeutic target to treat primary headache disorders for over 100 years. Multiple destructive lesions have also been tried with variable rate and duration of success. Neurostimulation of the SPG for cluster headache was first described in 2007., Methods: This is not a systematic review. The authors review the anatomy and pathophysiology of the SPG and cluster headache and the important clinical trials, relating a history of how SPG neuromodulation reached the current state of approval in the European Union (EU) and pivotal registration study for cluster headache in the US., Results: The EU approved SPG stimulation for cluster headache with a CE Mark in February of 2012. Since then, several EU countries have elected to reimburse implantation for cluster headache, and over 300 patients have been implanted worldwide., Conclusions: Success rates for implanted SPG neuromodulation in the experimental phase of the European randomized controlled trial, in the open label extension trial, and in the registry of patients implanted outside of the trial remain at about two-thirds of patients implanted being responders, defined as being able to terminate at least 50% of attacks or having at least a 50% decrease in attack frequency or both. A US pivotal registration study is underway to confirm these results and obtain FDA approval for this treatment for cluster headache patients. Further studies in migraine are also underway., (© 2017 American Headache Society.)

Background: The trigeminal autonomic cephalalgias (TACs) are highly disabling primary headache disorders. There are several issues that remain unresolved in the understanding of the pathophysiology of the TACs, although activation of the trigeminal-autonomic reflex and ipsilateral hypothalamic activation both play a central role. The discovery of the central role of the hypothalamus led to its use as a therapeutic target. After the good results obtained with hypothalamic stimulation, other peripheral neuromodulation targets were tried in the management of refractory cluster headache (CH) and other TACs., Methods: This review is a summary both of CH pathophysiology and of efficacy of the different neuromodulation techniques., Results: In chronic cluster headache (CCH) patients, hypothalamic deep brain stimulation (DBS) produced a decrease in attack frequency of more than 50% in 60% of patients. Occipital nerve stimulation (ONS) also elicited favorable outcomes with a reduction of more than 50% of attacks in around 70% of patients with medically intractable CCH. Stimulation of the sphenopalatine ganglion (SPG) with a miniaturized implanted stimulator produced a clinically significant improvement in 68% of patients (acute, preventive, or both). Vagus nerve stimulation (VNS) with a portable device used in conjunction with standard of care in CH patients resulted in a reduction in the number of attacks. DBS and ONS have been used successfully in some cases of other TACs, including hemicrania continua (HC) and short-lasting unilateral headache attacks (SUNHA)., Conclusions: DBS has good results, but it is a more invasive technique and can generate serious adverse events. ONS has good results, but frequent and not serious adverse events. SPG stimulation (SPGS) is also efficacious in the acute and prophylactic treatment of refractory cluster headache. At this moment, ONS and SPG stimulation techniques are recommended as first line therapy in refractory cluster patients. New recent non-invasive approaches such as the non-invasive vagal nerve stimulator (nVNS) have shown efficacy in a few trials and could be an interesting alternative in the management of CH, but require more testing and positive randomized controlled trials., (© 2016 American Headache Society.)

Background and Purpose: Chronic cluster headache is a rare, highly disabling primary headache condition. When medically intractable, occipital nerve stimulation can offer effective treatment. Open-label series have provided data on small cohorts only., Methods: We analyzed 51 subjects to evaluate the long-term outcomes of highly intractable chronic cluster headache with occipital nerve stimulation. Patients with intractable chronic cluster headache were implanted with occipital nerve stimulators during the period 2007-2014. The primary endpoint was improvement in daily attack frequency. Secondary endpoints included attack severity, attack duration, quality-of-life measures, headache disability scores and adverse events., Results: We studied 51 patients [35 males; mean age at implant 47.78 (range 31-70) years; mean follow-up 39.17 (range 2-81) months]. Nineteen patients had other chronic headache types in addition in chronic cluster headache. At final follow-up, there was a 46.1% improvement in attack frequency (P < 0001) across all patients, 49.5% (P < 0.001) in those with cluster headache alone and 40.3% (P = 0.036) in those with multiple phenotypes. There were no significant differences in response in those with or without multiple headache types. The overall response rate (defined as at least a 50% improvement in attack frequency) was 52.9%. Significant reductions were also seen in attack duration and severity. Improvements were noted in headache disability scores and quality-of-life measures. Triptan use of responders dropped by 62.56%, resulting in significant cost savings. Adverse event rates were highly favorable., Conclusion: Occipital nerve stimulation appears to be a safe and efficacious treatment for highly intractable chronic cluster headache even after a mean follow-up of over 3 years., (© 2016 EAN.)

Objective: To evaluate non-invasive vagus nerve stimulation (nVNS) as an acute cluster headache (CH) treatment., Background: Many patients with CH experience excruciating attacks at a frequency that is not sufficiently addressed by current symptomatic treatments., Methods: One hundred fifty subjects were enrolled and randomized (1:1) to receive nVNS or sham treatment for ≤1 month during a double-blind phase; completers could enter a 3-month nVNS open-label phase. The primary end point was response rate, defined as the proportion of subjects who achieved pain relief (pain intensity of 0 or 1) at 15 minutes after treatment initiation for the first CH attack without rescue medication use through 60 minutes. Secondary end points included the sustained response rate (15-60 minutes). Subanalyses of episodic cluster headache (eCH) and chronic cluster headache (cCH) cohorts were prespecified., Results: The intent-to-treat population comprised 133 subjects: 60 nVNS-treated (eCH, n = 38; cCH, n = 22) and 73 sham-treated (eCH, n = 47; cCH, n = 26). A response was achieved in 26.7% of nVNS-treated subjects and 15.1% of sham-treated subjects (P = .1). Response rates were significantly higher with nVNS than with sham for the eCH cohort (nVNS, 34.2%; sham, 10.6%; P = .008) but not the cCH cohort (nVNS, 13.6%; sham, 23.1%; P = .48). Sustained response rates were significantly higher with nVNS for the eCH cohort (P = .008) and total population (P = .04). Adverse device effects (ADEs) were reported by 35/150 (nVNS, 11; sham, 24) subjects in the double-blind phase and 18/128 subjects in the open-label phase. No serious ADEs occurred., Conclusions: In one of the largest randomized sham-controlled studies for acute CH treatment, the response rate was not significantly different (vs sham) for the total population; nVNS provided significant, clinically meaningful, rapid, and sustained benefits for eCH but not for cCH, which affected results in the total population. This safe and well-tolerated treatment represents a novel and promising option for eCH. ClinicalTrials.gov identifier: NCT01792817., (© 2016 The Authors Headache published by Wiley Periodicals, Inc. on behalf of American Headache Society.)

Objective: Our aim was to explore the views and experiences of a group of Spanish men suffering from cluster headache (CH)., Background: CH has considerable effects on patients' quality of life, impairs everyday activities, and can modify lifestyle. This is the first time the experience of patients with CH is examined in a clinical study using a qualitative, phenomenological approach., Methods: We conducted a qualitative phenomenological study exploring how 20 male patients with CH, followed at the Headache Unit of a Spanish hospital, perceived their disease. Data were collected through in-depth interviews, researchers' field notes and patients' personal letters. A systematic text condensation analysis was performed following appropriate guidelines for qualitative research., Results: Mean age was 41.15 years (standard deviation, 11.25). Seventeen patients had episodic CH and three patients had chronic CH. Five main themes describing the significance of suffering CH emerged: (a) meaning of disease, (b) experience of attacks, (c) meaning of treatment, (d) healthcare, and (e) social and family interaction. Patients with CH often live in fear and uncertainty because of their condition. Intensity and frequency of attacks, the use of ineffective treatments, skepticism perceived from social and workplace environments and physician unawareness play a significant role., Conclusions: Qualitative research offers insight into the way CH patients experience their disease, and may be helpful in establishing a fruitful relationship with these patients., (© 2016 American Headache Society.)

Background: Migraine and cluster headaches are severe and disabling. Migraine affects up to 18% of women, while cluster headaches are much less common (0.2% of the population). A number of acute and prophylactic therapies are available. Hyperbaric oxygen therapy (HBOT) is the therapeutic administration of 100% oxygen at environmental pressures greater than one atmosphere, while normobaric oxygen therapy (NBOT) is oxygen administered at one atmosphere. This is an updated version of the original Cochrane review published in Issue 3, 2008 under the title 'Normobaric and hyperbaric oxygen for migraine and cluster headache'., Objectives: To examine the efficacy and safety of normobaric oxygen therapy (NBOT) and hyperbaric oxygen therapy (HBOT) in the treatment and prevention of migraine and cluster headache., Search Methods: We updated searches of the following databases up to 15 June 2015: CENTRAL (the Cochrane Library), MEDLINE, EMBASE, and CINAHL. For the original review we searched the following databases up to May 2008: CENTRAL, MEDLINE, EMBASE, CINAHL, DORCTIHM, and reference lists from relevant articles. We handsearched relevant journals and contacted researchers to identify trials., Selection Criteria: Randomised controlled trials comparing HBOT or NBOT with one another, other active therapies, placebo (sham) interventions, or no treatment in participants with migraine or cluster headache., Data Collection and Analysis: Three review authors independently extracted data and assessed the quality of the evidence using the GRADE approach., Main Results: In this update, we included 11 trials with 209 participants. Five trials (103 participants) compared HBOT versus sham therapy for acute migraine, three trials compared NBOT to sham therapy or ergotamine tartrate for cluster headache (145 participants), two trials evaluated HBOT for cluster headache (29 participants), and one trial (56 participants) compared NBOT to sham for a mixed group of headache. The risk of bias varied considerably across these trials but in general trial quality was poor to moderate. One trial may not have been truly randomised and two included studies were reported as abstracts only. Seven trials did not indicate allocation concealment or randomisation method. Notably, 10 of the 11 trials used a sham comparator therapy and masked the outcome assessor to allocation.We pooled data from three trials, which suggested that HBOT was effective in relieving migraine headaches compared to sham therapy (risk ratio (RR) 6.21, 95% CI 2.41 to 16.00; 58 participants, three trials). The quality of evidence was low, having been downgraded for small crossover studies with incomplete reporting. There was no evidence that HBOT could prevent migraine episodes, reduce the incidence of nausea and vomiting, or reduce the requirement for rescue medication. There was no evidence that HBOT was effective for the termination of cluster headache (RR 11.38, 95% CI 0.77 to 167.85; P = 0.08) (one trial), but this trial had low power.NBOT was effective in terminating cluster headache compared to sham in a single small study (RR 7.88, 95% CI 1.13 to 54.66), but not superior to ergotamine administration in another small trial (RR 1.17, 95% CI 0.94 to 1.46; P = 0.16). A third trial reported a statistically significant difference in the proportion of attacks successfully treated with oxygen (117 of 150 attacks were successfully treated with NBOT (78%) versus 30 of 148 attacks treated with NBOT (20%)). The proportion of responders was consistent across these three trials, and suggested more than 75% of headaches were likely to respond to NBOT.No serious adverse events during HBOT or NBOT were reported., Authors' Conclusions: Since the last version of this review, two new included studies have provided additional information to change the conclusions. There was some evidence that HBOT was effective for the termination of acute migraine in an unselected population, and some evidence that NBOT was similarly effective in cluster headache. Given the cost and poor availability of HBOT, more research should be done on patients unresponsive to standard therapy. NBOT is cheap, safe, and easy to apply, so will probably continue to be used despite the limited evidence in this review.

The most evidence exists for mixed anesthetic/steroid occipital nerve blocks (which are also useful in non-refractory patients), deep brain stimulation, sphenopalatine ganglion (SPG) blocks, SPG radiofrequency ablation, and SPG stimulation with the Autonomic Technologies, Inc (ATI) SPG Neurostimulator, the latter approved in the European Union and reimbursed in several countries., (© 2013 American Headache Society.)

Background: Drug-resistant chronic cluster headache (drCCH) is a devastating condition for which various invasive therapeutic procedures have been tempted without any satisfactory effect. Recent studies suggest that occipital nerve stimulation (ONS) could be an efficient preventive treatment of drCCH., Objective: We conducted a prospective pilot trial of ONS in 8 subjects suffering from drCCH with encouraging results at 15 months. However, studies on a larger population with a longest follow-up were warranted., Methods: We recruited 15 patients with drCCH according to the previously published criteria of intractability. They were implanted with suboccipital stimulators on the side of their headache. Long-term follow-up was achieved by questionnaires administered during a headache consultation and/or by phone interviews., Results: Mean follow-up time post surgery is 36.82 months (range 11-64 months). One patient had an immediate post-operative infection of the material. Among the 14 remaining patients, 11 (i.e., ∼80%) have at least a 90% improvement with 60% becoming pain-free for prolonged periods. Two patients did not respond or described mild improvement. Intensity of residual attacks is not modified by ONS. Four patients (29%) were able to reduce their prophylaxis. The major technical problems were battery depletion due to the use of high current intensities (N = 9/14, 64%) and immediate or delayed material infection (N = 3/15, 20%). Significant electrode migration was only seen in 1 patient. Clinical peculiarities during the ONS follow-up period were side shift with infrequent contralateral attacks (N = 5/14, 36%), and/or isolated ipsilateral autonomic attacks without pain (N = 5/14, 36%). Two patients found ONS-related paresthesias unbearable: one had his stimulator removed, and the other switched it off although he was objectively ameliorated. Subjectively, 9 patients are very satisfied by ONS and 3 patients moderately satisfied. Effective stimulation parameters varied between patients., Conclusions: Our long-term follow-up confirms the efficacy of ONS in drCCH, which remains a safe and well-tolerated technique. The occurrence of contralateral attacks and isolated autonomic attacks in nearly 50% of ONS responders may have therapeutic and pathophysiological implications., (© 2011 American Headache Society.)

Cluster headache (CH) pain is the most severe of the primary headache syndromes. It is characterized by periodic attacks of strictly unilateral pain associated with ipsilateral cranial autonomic symptoms. The majority of patients have episodic CH, with cluster periods that typically occur in a circannual rhythm, while 10% suffer from the chronic form, with no significant remissions between cluster periods. Sumatriptan injection or oxygen inhalation is the first-line therapy for acute CH attacks, with the majority of patients responding to either treatment. The calcium channel blocker verapamil is the drug of choice for CH prevention. Other drugs that may be used for this purpose include lithium carbonate, topiramate, valproic acid, gabapentin, and baclofen. Transitional prophylaxis, most commonly using corticosteroids, helps to control the attacks at the beginning of a cluster period. Peripheral neural blockade is effective for short-term pain control. Recently, the therapeutic options for refractory CH patients have expanded with the emergence of both peripheral (mostly occipital nerve) and central (hypothalamic) neurostimulation. With the emergence of these novel treatments, the role of ablative surgery in CH has declined., (© 2011 American Headache Society.)

Introduction: Cluster headaches (CH) are primary headaches marked by repeated short-lasting attacks of severe, unilateral head pain and associated autonomic symptoms. Despite aggressive management with medications, oxygen therapy, nerve blocks, as well as various lesioning and neurostimulation therapies, a number of patients are incapacitated and suffering. The sphenopalatine ganglion (SPG) has been implicated in the pathophysiology of CH and has been a target for blocks, lesioning, and other surgical approaches. For this reason, it was selected as a target for an acute neurostimulation study., Methods: Six patients with refractory chronic CH were treated with short-term (up to 1 hour) electrical stimulation of the SPG during an acute CH. Headaches were spontaneously present at the time of stimulation or were triggered with agents known to trigger clusters headache in each patient. A standard percutaneous infrazygomatic approach was used to place a needle at the ipsilateral SPG in the pterygopalatine fossa under fluoroscopic guidance. Electrical stimulation was performed using a temporary stimulating electrode. Stimulation was performed at various settings during maximal headache intensity., Results: Five patients had CH during the initial evaluation. Three returned 3 months later for a second evaluation. There were 18 acute and distinct CH attacks with clinically maximal visual analog scale (VAS) intensity of 8 (out of 10) and above. SPG stimulation resulted in complete resolution of the headache in 11 attacks, partial resolution (>50% VAS reduction) in 3, and minimal to no relief in 4 attacks. Associated autonomic features of CH were resolved in each responder. Pain relief was noted within several minutes of stimulation., Conclusion: Sphenopalatine ganglion stimulation can be effective in relieving acute severe CH pain and associated autonomic features. Chronic long-term outcome studies are needed to determine the utility of SPG stimulation for management and prevention of CH.

Cluster headache (CH) is characterized by a series of sudden attacks of short-lasting severe headache pain with ipsilateral autonomic features, including lacrimation, rhinorrhea, localized sweating, eyelid edema, and partial or complete Horner's syndrome. Just like in migraine, brush allodynia has been described for CH and for short lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) syndrome. Administration of normobaric oxygen is part of the standard therapy for CH attacks. Here, we describe a young male with a first CH attack and the influence of oxygen on pain and concomitant cutaneous allodynia.

Background: Migraine and cluster headaches are severe and disabling. Migraine affects up to 18% of women, while cluster headaches are much less common (0.2% of the population). A number of acute and prophylactic therapies are available. Hyperbaric oxygen therapy (HBOT) is the therapeutic administration of 100% oxygen at environmental pressures greater than one atmosphere, while normobaric oxygen therapy (NBOT) is oxygen administered at one atmosphere., Objectives: To assess the safety and effectiveness of HBOT and NBOT for treating and preventing migraine and cluster headaches., Search Strategy: We searched the following in May 2008: CENTRAL, MEDLINE, EMBASE, CINAHL, DORCTIHM and reference lists from relevant articles. Relevant journals were hand searched and researchers contacted., Selection Criteria: Randomised trials comparing HBOT or NBOT with one another, other active therapies, placebo (sham) interventions or no treatment in patients with migraine or cluster headache., Data Collection and Analysis: Three reviewers independently evaluated study quality and extracted data., Main Results: Nine small trials involving 201 participants were included. Five trials compared HBOT versus sham therapy for acute migraine, two compared HBOT to sham therapy for cluster headache and two evaluated NBOT for cluster headache. Pooling of data from three trials suggested that HBOT was effective in relieving migraine headaches compared to sham therapy (relative risk (RR) 5.97, 95% confidence interval (CI) 1.46 to 24.38, P = 0.01). There was no evidence that HBOT could prevent migraine episodes, reduce the incidence of nausea and vomiting or reduce the requirement for rescue medication. There was a trend to better outcome in a single trial evaluating HBOT for the termination of cluster headache (RR 11.38, 95% CI 0.77 to 167.85, P = 0.08), but this trial had low power.NBOT was effective in terminating cluster headache compared to sham in a single small study (RR 7.88, 95% CI 1.13 to 54.66, P = 0.04), but not superior to ergotamine administration in another small trial (RR 1.17, 95% CI 0.94 to 1.46, P = 0.16). Seventy-six per cent of patients responded to NBOT in these two trials. No serious adverse effects of HBOT or NBOT were reported., Authors' Conclusions: There was some evidence that HBOT was effective for the termination of acute migraine in an unselected population, and weak evidence that NBOT was similarly effective in cluster headache. Given the cost and poor availability of HBOT, more research should be done on patients unresponsive to standard therapy. NBOT is cheap, safe and easy to apply, so will probably continue to be used despite the limited evidence in this review.

Objective: To evaluate the structure and quality of sleep and the circadian rhythm of body core temperature (BcT degrees ) in patients with drug-resistant chronic cluster headache (CH) before and during deep brain stimulation (DBS) of the posterior hypothalamus., Background: Chronic CH is a severe primary headache and frequently associated with disturbances in sleep. Posterior hypothalamus DBS is performed as an effective treatment of drug-resistant chronic CH. The effects of posterior hypothalamus DBS on sleep and the circadian rhythm of BcT degrees are unknown., Methods: Three male patients with chronic drug-resistant CH underwent 48-hour consecutive polysomnography (PSG) by means of the VITAPORT system with determination of BcT degrees by means of a rectal probe. Recordings were done before electrode implantation in the posterior hypothalamus and after optimized DBS of posterior hypothalamus., Results: Before electrode implantation PSG showed nocturnal CH attacks, reduced sleep efficiency, fragmented sleep and increased periodic limb movements in sleep (PLMS). During DBS nocturnal CH attacks were abolished and sleep efficiency and PLMS improved. BcT degrees circadian rhythm was normal both before and during DBS., Conclusions: Our data show that DBS of posterior hypothalamus in drug-resistant chronic CH is effective in curtailing nocturnal CH attacks, and is associated with improved sleep structure and quality. Chronic CH displays a normal circadian rhythm of BcT degrees, unchanged during hypothalamic DBS.

Background: Cluster headache (CH) is a rare but severe headache form with a distinct clinical presentation. Misdiagnoses and mismanagement among these patients are high., Objective: To characterize clinical features and medical treatment in patients with CH., Methods: We established a cohort of 246 clinic-based and non-clinic-based CH patients. The diagnosis of CH was verified according to International Headache Society (IHS) criteria. We used standardized questionnaires to assess associated factors as well as success or failure of treatments., Results: The majority (75.6%) was not treated before at our clinic-77.6% were males; 74.8% had episodic CH, 16.7% had chronic CH, in the remaining patients, the periodicity was undetermined because they were newly diagnosed. Cranial autonomic features were present in 98.8%, nausea and vomiting in 27.8%, and photophobia or phonophobia in 61.2% of CH patients. Most (67.9%) reported restlessness during attacks and 23% a typical migrainous aura preceding the attacks. The rate of current smoking was high (65.9%). Half of the patients reported that alcohol (red wine in 70%) triggered CH attacks. Eighty-seven percent reported the use of drugs of first choice (triptans 77.6%, oxygen 71.1%) with sumatriptan subcutaneous injection being the most effective drug for acute therapy (81.2%). The most frequently used preventive medications were verapamil (70.3%) and glucocorticoids (57.7%) with equally high effectiveness., Conclusions: Apart from the IHS criteria additional features like nausea/vomiting and migrainous aura may guide the diagnosis of CH. A large number of CH patients do not receive adequate treatments.

Some migraineurs have the additional misfortune of suffering from cluster headaches; this situation can be challenging.

Exposure to hyperbaric oxygen has been shown to be effective in cluster headache, but the mechanism of the action is still not clear. Primary nociceptive neurons, containing neuropeptides such as substance P and particularly those innervating the nasal mucosa, could be involved in the pathogenesis of cluster headache. The present study evaluated the effect of an exposure to hyperbaric oxygen on the content of substance P in the nasal mucosa of patients affected by cluster headache. The results were compared with those observed in another group of cluster headache patients who underwent a placebo procedure. The samples of nasal mucosa were analyzed by immunocytochemical methods. A qualitative analysis of the slides was carried out by an operator under "blinded conditions". A marked decrease in the content of immunoreactivity for substance P was found in the patients exposed to hyperbaric oxygen. The decrease was statistically significant when compared with the findings of the placebo procedure. The results of the present study indicate that an influence on the content of peripheral neuropeptides could be involved in the mechanism of action of the beneficial effect of hyperbaric oxygen in cluster headache.

Cluster headache is a brutal affliction characterized by excruciating pain with relatively brief, but frequent attacks. Because of the short duration of the attacks and the tremendous intensity of pain, symptomatic analgesics are often not effective. However, inhalation oxygen, while being cumbersome, is reported to be effective in the majority of sufferers. To assess the practical effectiveness and use of analgesics and/or oxygen, a review of 60 cluster patients was conducted. At initial evaluation, 48 patients had accepted oral analgesics and 51 patients accepted inhalation oxygen for breakthrough headaches. After acceptable prophylactic treatment was established, 65% of patients who accepted analgesics continued their use, although most reported only minimal relief. Only 31% of patients who accepted oxygen continued its use, in spite of the fact that most sufferers reported significant relief. From this brief study, it appears that cluster headache patients prefer to use analgesics for reasons that are not solely for relief of pain, and that patients decline the use of oxygen for reasons other than lack of effectiveness.

Six patients with episodic cluster headache were investigated as to blood pressure, heart rate, cerebrospinal fluid pressure (Pcsf) and frontal vein pressure (Pvf) during five nitroglycerin (NG) provoked attacks and one spontaneous attack. In a seventh studied patient the NG failed to provoke an attack. The earlier reported decrease of systolic blood pressure and increase of diastolic blood pressure and heart rate after NG administration were also found in these patients. The "dynamite headache" was related to the start and duration of an increase of the cerebrospinal fluid pressure. There was no relationship between the start or the maximum pain of the cluster headache attack and changes in Pcsf or Pvf. On breathing oxygen during a cluster headache attack, there was a decrease of Pcsf but in some patients a temporary increase of Pvf was observed, which possibly indicates that oxygen simultaneously attains constriction of arteries and veins.

Nuchal symptoms were found in the majority of 100 consecutive patients with cluster headache. In 10%, pain was experienced in the neck with the initial typical orbitotemporal pain; in 37%, pain radiated from the orbit or temple to the ipsilateral side of the neck. Sometimes, neck pain heralded the onset of the attack by a few minutes. During an attack, neck stiffness was reported in 40% and tenderness in 29%. Movement of the neck, especially flexion, precipitated cluster headache in 9% of patients. This was particularly true of patients with chronic cluster headache. Neck movement aggravated the headache in 16 of 100 patients and an equal number reported amelioration of pain by neck movement, especially extension. The nuchal features did not necessarily accompany every attack and were usually overshadowed by the severity of the typical headache. Nevertheless, symptoms referable to the neck occur more commonly than is generally appreciated.

A patient with severe cluster headaches was treated in a hyperbaric chamber on two occasions. Her symptoms had been refractory to other treatment modalities including conventional oxygen therapy. On both occasions her pain was promptly relieved while breathing 100% oxygen at two atmospheres of pressure. This is the first known reported case of a cluster headache treated with hyperbaric oxygen. A prospective study is needed to substantiate the efficacy of this treatment modality for cluster headaches.