The insulin tolerance test and ovine corticotrophin-releasing-hormone test in episodic cluster headache. II: Comparison with low back pain patients

Biomarkers in cluster headache: A systematic review

OBJECTIVE

To systematically investigate previously examined biomarkers in blood, urine, cerebrospinal fluid, tear fluid, and saliva of patients with cluster headache.

BACKGROUND

Cluster headache is a condition with extensive clinical challenges in terms of diagnosis and treatment. Identification of a biomarker with diagnostic implications or as a potential treatment target is highly warranted.

METHODS

We conducted a systematic review including peer reviewed full text of studies that measured biochemical compounds in either blood, urine, cerebrospinal fluid, tear fluid, or saliva of patients with cluster headache diagnosed after the implementation of the International Classification of Headache Disorders (1988) written in English, Danish, Swedish, or Norwegian. Inclusion required a minimum of five participants. The search was conducted in PubMed and EMBASE, in September 2022, and extracted data were screened by two authors. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines for reporting systematic reviews were followed. The Newcastle-Ottawa Scale was used to assess the risk of bias in case-controlled studies.

RESULTS

We included 40 studies involving 832 patients with cluster headache and 872 controls, evaluating 80 potential biomarkers. The risk of bias for case-controlled studies was a median of 6 (range: 3-8) and 20 studies out of 40 (50%) were of fair or good quality. Most studies were identified within three groups: hypothalamic-regulated hormones, inflammatory markers, and neuropeptides. Among the hypothalamic hormones, cortisol was the most frequently investigated (N = 7) and was elevated in cluster headache in most of the studies. The most frequently examined inflammatory marker was interleukin 1 (N = 3), but findings were divergent. Calcitonin gene-related peptide was the most investigated neuropeptide (N = 9) and all studies found increased levels during attacks.

CONCLUSION

Biomarker findings have been inconsistent and widely non-specific for cluster headache, which explains why none of the previous studies succeeded in identifying a unique biomarker for cluster headache, but instead contributed to substantiating the underlying pathophysiologic mechanisms. Several of the examined biomarkers could hold promise as markers for disease activity but are unfit for a clear distinction from both controls and other headaches.

The neurobiology of cluster headache

Cluster headache is a primary headache form occurring in paroxysmal excruciatingly severe unilateral head pain attacks usually grouped in periods lasting 1-2months, the cluster periods. A genetic component is suggested by the familial occurrence of the disease but a genetic linkage is yet to be identified. Contemporary activation of trigeminal and cranial parasympathetic systems-the so-called trigemino-parasympathetic reflex-during the headache attacks seem to cause the pain and accompanying oculo-facial autonomic phenomena respectively. At peripheral level, the increased calcitonin gene related peptide (CGRP) plasma levels suggests trigeminal system activation during cluster headache attacks. The temporal pattern of the disease both in terms of circadian rhythmicity and seasonal recurrence has suggested involvement of the hypothalamic biological clock in the pathophysiology of cluster headache. The posterior hypothalamus was investigate as the cluster generator leading to activation of the trigemino-parasympathetic reflex, but the accumulated experience after 20 years of hypothalamic electrical stimulation to treat the condition indicate that this brain region rather acts as pain modulator. Efficacy of monoclonal antibodies to treat episodic cluster headache points to a key role of CGRP in the pathophysiology of the condition.

Neurobiology and sleep disorders in cluster headache

Cluster headache is characterized by unilateral attacks of severe pain accompanied by cranial autonomic features. Apart from these there are also sleep-related complaints and strong chronobiological features. The interaction between sleep and headache is complex at any level and evidence suggests that it may be of critical importance in our understanding of primary headache disorders. In cluster headache several interactions between sleep and the severe pain attacks have already been proposed. Supported by endocrinological and radiological findings as well as the chronobiological features, predominant theories revolve around central pathology of the hypothalamus. We aimed to investigate the clinical presentation of chronobiological features, the presence of concurrent sleep disorders and the relationship with particular sleep phases or phenomena, the possible role of hypocretin as well as the possible involvement of cardiac autonomic control. We conducted a questionnaire survey on 275 cluster headache patients and 145 controls as well an in-patient sleep study including 40 CH-patients and 25 healthy controls. The findings include: A distinct circannual connection between cluster occurrence and the amount of daylight, substantially poorer sleep quality in patients compared to controls which was present not only inside the clusters but also outside, affected REM-sleep in patients without a particular temporal connection to nocturnal attacks, equal prevalence of sleep apnea in both patient and control groups, reduced levels of hypocretin-1 in the cerebrospinal fluid of patients and finally a blunted response to the change from supine to tilted position in the head-up tilt table test indicating a weakened sympathoexcitatory or stronger parasympathetic drive. Overall, these findings support a theory of involvement of dysregulation in hypothalamic and brainstem nuclei in cluster headache pathology. Further, it is made plausible that the headache attacks are but one aspect of a more complex syndrome of central dysregulation manifesting as sleep-related complaints, sub-clinical autonomic dysregulation and of course the severe attacks of unilateral headache. Future endeavors should focus on pathological changes which persist in the attack-free periods but also heed the possibility of long-lived, cluster-induced pathology.

Nocturnal secretion of growth hormone, noradrenaline, cortisol and insulin in cluster headache remission

We have previously shown decreased, nocturnal lipolysis in both phases of cluster headache (CH). Lipolysis is stimulated by noradrenaline (NA), growth hormone (GH) and cortisol, and inhibited by insulin, hormones which are directly or indirectly regulated by the hypothalamus. Our aim was to investigate the nocturnal secretion of NA, GH, cortisol and insulin in nine CH patients in remission and 10 healthy controls. Nocturnal venous blood samples were collected in hourly intervals for analysis of NA, cortisol and insulin and in 30-min intervals for GH. We found a reduced increase in GH between 24.00 h and 01.00 h (anova, P < 0.05) in CH patients. Nocturnal secretion of NA, cortisol and insulin did not differ significantly between the groups. The altered nocturnal GH pattern that was seen in CH patients in remission might in part explain the altered nocturnal lipolysis previously found and further indicate a permanent hypothalamic disturbance in CH.

Steroid hormones in cluster headaches

For decades, glucocorticoid therapy has been a well-recognized abortive treatment for cluster headaches. However, the role of steroid hormones, including both glucocorticoids and sex steroids, in the pathophysiology and therapy of cluster headaches has been a topic of much debate and speculation. Current research now points to the importance of cortisol and testosterone in the pathogenesis of cluster headaches, and they appear to be linked mechanistically to another hormone, melatonin. Melatonin, unlike cortisol or testosterone, is not a product of the hypothalamic pituitary axis but of the retinohypothalamic pineal axis, and is the major biomarker of circadian rhythms. The regulation of steroids and melatonin in the pathogenesis of cluster headaches in turn depends on the sympathetic nervous system. Accumulated evidence suggests sympathetic dysfunction--embodied in the Horner sign so commonly seen in the cluster headache--as a necessary ingredient in the inception of the cluster headache. Sympathetic dysfunction now is thought to be associated with the hypercortisolism, hypotestosteronism, and lower-than-normal melatonin levels in the active cluster patient. Future research may hold the key to a fuller explanation of the complex interaction of hormonal systems in the cluster headache.

Corticosteroid treatment in cluster headache: Evidence, rationale, and practice

The use of corticosteroids in the treatment of cluster headache (CH) is commonplace and has been a mainstay of clinical practice for this indication for 50 years. The published evidence supporting this practice is weak, with no methodologically rigorous or large-scale controlled trials executed. Nonetheless, the clinical experiences of practitioners and the conclusion of investigators provide a clear signal of benefit from corticosteroid use in CH. The pathophysiologic explanation for this beneficial effect is unknown, but corticosteroid influences on inflammatory, hypothalamic-pituitary-adrenal, histaminergic, and opioid systems have been proposed. Best-practice parameters are unclear, but the professional consensus is that corticosteroids generally are effective for arresting CH attacks, only if administered in relatively high doses, and that safety concerns warrant courses of 4 weeks or less. Concomitant use of other prophylactic agents for CH in addition to corticosteroids usually is advisable because attacks often recur when the corticosteroid dose is tapered.

Abnormal 5-HT1D receptor function in cluster headache: a neuroendocrine study with sumatriptan

The purpose of this study was to assess the sensitivity of 5-HT(1D) receptors in patients with episodic cluster headache using sumatriptan as a pharmacological probe. The drug, a selective 5-HT(1B/1D) agonist, stimulates the secretion of growth hormone and inhibits the release of prolactin, adrenocorticotropic hormone (ACTH) and cortisol. These effects may be used to explore the function of serotonergic systems in vivo. We administered subcutaneous sumatriptan and placebo to 20 patients with cluster headache (10 in the active phase and 10 in the remission period) and to 12 controls. The sumatriptan-induced increase of growth hormone concentrations was significantly (P < 0.05) blunted in patients with active cluster headache. Prolactin and ACTH responses to the drug were significantly (P < 0.05) reduced in patients with cluster headache, both in the active and in the remission period. Our results suggest that cerebral serotonergic functions mediated by 5-HT(1D) receptors are altered in patients with episodic cluster headache.

Cluster headache: evidence for a disorder of circadian rhythm and hypothalamic function

This article reviews the literature for evidence of a disorder of circadian rhythm and hypothalamic function in cluster headache. Cluster headache exhibits diurnal and seasonal rhythmicity. While cluster headache has traditionally been thought of as a vascular headache disorder, its periodicity suggests involvement of the suprachiasmatic nucleus of the hypothalamus, the biological clock. Normal circadian function and seasonal changes occurring in the suprachiasmatic nucleus and pineal gland are correlated to the clinical features and abnormalities of circadian rhythm seen in cluster headache. Abnormalities in the secretion of melatonin and cortisol in patients with cluster headache, neuroimaging of cluster headache attacks, and the use of melatonin as preventative therapy in cluster headache are discussed in this review. While the majority of studies exploring the relationship between circadian rhythms and cluster headache are not new, we have entered a new diagnostic and therapeutic era in primary headache disorders. The time has come to use the evidence for a disorder of circadian rhythm in cluster headache to further development of chronobiotics in the treatment of this disorder.

The m-chlorophenylpiperazine test in cluster headache: a study on central serotoninergic activity

The central serotoninergic agonist m-chlorophenylpiperazine (m-CPP) stimulates several 5HT receptor subtypes. It induces the release of both cortisol and prolactin (PRL). In this study we investigated central serotoninergic responsiveness in cluster headache by monitoring cortisol and PRL responses to m-CPP administration. Twenty-three patients with episodic cluster headache and 17 sex-matched and age-matched healthy subjects were studied. The cluster headache patients were tested during a cluster period, and none were receiving prophylaxis. A single oral dose of m-CPP, 0.5 mg/kg, was given at time 0. Blood samples were drawn at -30, 0, 30, 60, 90, 120, 150 and 180 min. PRL and cortisol levels were assayed in the samples. PRL and cortisol delta maxima (delta maximum = maximum response - baseline level at time 0/baseline level at time 0) were evaluated in each patient and mean values compared. Serum levels of m-CPP were detected by HPLC and correlated to hormonal responses. Reduced cortisol (p < 0.02) and increased PRL (p < 0.05) delta maxima were observed in cluster headache patients. Increased basal cortisol plasma levels (p < 0.05) and reduced basal PRL plasma levels (p = 0.06) also characterized cluster headache patients. This is the first study evaluating central serotoninergic responsiveness to m-CPP in cluster headache and these data suggest impaired central serotoninergic function in this pathology.

Twenty-four-hour melatonin and cortisol plasma levels in relation to timing of cluster headache

The cyclic recurrence of cluster periods and the regular timing of headache occurrence in cluster headache (CH) induced us to study the circadian secretion of melatonin and cortisol in 12 patients with episodic CH, during a cluster period, and compare them with 7 age- and sex-matched healthy controls. Blood was sampled every 2 h for 24 h. All subjects were confined to a dark room from 22.00 to 08.00. Plasma melatonin levels were significantly reduced in CH patients (repeated measures ANOVA p < 0.03; mesor p < 0.02), and the cortisol mesor was significantly increased (p < 0.03). Amplitudes and acrophases did not differ between the groups. Individual cosinor analysis showed that 4/12 (33.3%) CH patients had no significant melatonin rhythm, and that 5/11 (45.5%) had no cortisol rhythm. Group analysis of cosinor revealed significantly rhythmicity of melatonin and cortisol secretion in both groups. In controls, the timing of melatonin and cortisol acrophase significantly correlated with each other, indicating that the biorhythm controllers for the secretion of these hormones were synchronized. Such correlation was not found in the CH patients; mesor, amplitude and acrophase of melatonin and cortisol did not correlate with duration of illness, duration of headache in course, or time since last headache attack.