Treatment of cluster headache consists of acute remedies for attacks (mainly 100% O2, sumatriptan), transitional treatment for temporary frequency reduction (subcutaneous steroid injection at the greater occipital nerve (GON block), oral steroids or frovatriptan) and prolonged prophylaxis (e.g. verapamil, lithium, topiramate). Although the latter compounds have shown some efficacy in reducing the attack frequency, the evidence for their effect is weak. All current prophylactics are prescribed off-label and are limited in their utility due to associated side effects. Despite treatment, many (notably chronic) cluster headache patients continue suffering headache attacks. Invasive, expensive treatments like hypothalamic deep brain stimulation, occipital nerve stimulation and sphenopalatine ganglion stimulation are last resort options. Recently, a monoclonal antibody targeting calcitonin gene related peptide (CGRP) received FDA approval for episodic cluster headache, but was shown to be ineffective in cCH. Thus, there is a considerable unmet need for effective treatments that are better tolerated, safe and affordable.~In this study, the investigators will assess the efficacy of prophylactic treatment with LSD in cCH. The evidence for the efficacy of LSD is limited, with the majority of data originating from case reports or uncontrolled and retrospective (internet) surveys. Nevertheless, these studies do provide indications that LSD may hold potential as a cluster headache prophylaxis.~The primary objective of this randomized double-blind placebo-controlled trial is to compare the efficacy of LSD 25μg every 3 days for 3 weeks versus placebo in cCH. The investigators aim to show that, at the end of treatment, verum is more efficacious than placebo with comparable tolerability in an ambulatory setting. To explore the sustainability of benefit the investigators will also assess the (sustained) response at 5 weeks post-treatment (8 weeks postrandomization).~If the study findings are positive, LSD should be further studied before use in routine clinical practice. Non-hallucinogenic low-dosed LSD may provide an alternative or adjunctive option for patients who do not respond to or cannot tolerate currently available treatments.~The functional connectivity between the hypothalamus and other brain regions that are relevant in the psychophysiology of cluster headache has yet to be investigated in a placebo-controlled study. The implementation of pre- and post-treatment resting state functional MRI (rsMRI) in the placebo-controlled LICIT study presents a unique opportunity to verify the selectivity of previous fMRI findings pertaining to cluster headache, to further elucidate the potential involvement of the trigeminal cervical complex (TCC) in cluster headache pathophysiology, and to acquire a more profound comprehension of the neural regions and networks that are significant to the effector mechanism(s) of LSD in the context of cluster headache. This study can examine whether a change in the presumed cluster headache-specific brain regions and networks is related to the individual pharmacokinetics of LSD. Moreover, by correlating changes in functional connectivity with clinical outcome measures, the clinical relevance of these changes can be explored. By distinguishing between responders and non-responders, this study could be the first step in identifying an imaging biomarker as a predictor of treatment effect.
This study aims to investigate the efficacy and safety of LSD 25μg every 3 days for 3 weeks versus placebo in the treatment of chronic cluster headache (cCH).~It is a 3-week double-blind placebo-controlled intervention study, preceded by a 4-week baseline observation period and followed by a 5-week post-treatment observation period.~Primary objective: to evaluate the efficacy of LSD 25μg every 3 days for 3 weeks in cCH.~Additional objectives:~To evaluate the safety of LSD 25μg every 3 days for 3 weeks in cCH.~To explore the exposure-response relationship of 25μg LSD in cCH.~To assess the effect of treatment with 25μg LSD on hypothalamic functional connectivity in patients with cCH, using resting state functional magnetic resonance imaging (rsMRI).~To explore cost-effectiveness of treatment with LSD in cCH.~To evaluate the efficacy of LSD on health-related quality of life.