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Trigeminal Autonomic Cephalalgias (TACs) – Cluster Headache AD Nesbitt, University of Surrey, Surrey, UK PJ Goadsby, Wellcome-NIHR Clinical Research Facility, King’s College Hospital, London, UK; and University of California San Francisco, San Francisco, CA, USA r 2014 Elsevier Inc. All rights reserved. Introduction Cluster headache defines a specific primary headache syndrome, which manifests itself as repetitive, highly stereotyped attacks of excruciating one-sided head pain. It is the most prevalent form of a group of neurological disorders termed trigeminal autonomic cephalalgias (TACs), all of which consist of consecutive attacks of similar unilateral pain, of varying duration, with the common shared feature of aberrant tone within cranial autonomic pathways on the same side as the pain, which causes both visible ocular and facial signs, and additional symptoms. Few medical disorders are more painful, and it thus places an exceptional burden on the sufferers. Historical Context Many of the features of cluster headache were first described in two separate reports detailed during the seventeenth century. In 1641, the eminent Dutch physician and anatomist Nicholaes Tulp described the suffering endured by one of his patients: In the beginning of the summer season, [he] was afflicted with a very severe headache, occurring and disappearing daily on fixed hours, with such intensity that he often assured me that he could not bear the pain anymore or he would succumb shortly. For rarely it lasted longer than two hours [y] but this recurring pain lasted until the 14th day [y] and lost a great deal of fluid from the nose. Three decades later, the Oxford physician Thomas Willis, widely regarded as the founding father of clinical neuroscience, published De Anima Brutorum, the first textbook of clinical neurology. The first two chapters comprise his treatise on headache, De Cephalalgia, in which he describes the peculiar periodicity of possible cluster headache attacks: Usually the attacks of seemingly suppressed headache recur around the solstices and equinoxes [...] but the majority, provided with subordinate periods, habitually molests at fixed hours within every cycle of 24 hours. Taken collectively, these accounts conform to many of the current diagnostic criteria for cluster headache, although neither physician commented on the unilateral, side-locked nature of the attacks. The disorder received wider attention from the midnineteenth century, when it was variously given the eponyms Sluder’s syndrome, Bing’s headache, Horton’s headache; the descriptive terms red migraine, angioparalytic hemicrania, eythroprosopalgia, vidian neuralgia; and most commonly migrainous neuralgia, ciliary neuralgia, and histaminic cephalgia. The use of the current term cluster headache is attributed to Encyclopedia of the Neurological Sciences, Volume 4 Kunkle, who described a case series from the USA in 1952, and refers to the tendency of the individual attacks to cluster together in time into bouts, during which the attacks occur daily, usually for periods of several weeks or months at a time. Medical historians have debated whether the disabling headaches suffered by the US president Thomas Jefferson were actually bouts of cluster headache rather than migraine. Classification The International Classification of Headache Disorders (third edition), published by the International Headache Society, outlines the diagnostic criteria needed to make an accurate diagnosis of cluster headache (Table 1). Of note, it further subdivides the disorder into two forms, episodic and chronic cluster headache, based on the duration of active periods (or bouts), during which the attacks cluster together, and periods of quiescence or remission. Episodic cluster headache can only be diagnosed if a patient has had at least 2 bouts, lasting between 7 and 365 days, and separated by a period of remission of Z1 month. For the diagnosis of chronic cluster headache to be fulfilled, attacks must persist for a period 41 year, without any remission period of Z1 month. Patients who only ever have one bout are simply classified as having cluster headache. Chronic cluster headache is the less common of the two subtypes, with only approximately 10% of the sufferers meeting the time criterion for this. Symptomatic (or secondary) cluster headache is the term given to a syndrome that is otherwise identical to cluster headache, but caused by an identified lesion, often in the pituitary fossa. Epidemiology and Genetics Pooled data from limited epidemiological studies conducted mainly in Europe and North America give cluster headache a lifetime prevalence of 0.12%, with data from a door-to-door study in Norway showing a 1-year prevalence of 0.3%. The condition has a heritable tendency in some families, and first-degree relatives of affected people have an estimated 14–48-fold increased risk of developing it. However, in familial cases, segregation analysis has not revealed a single mode of inheritance, and it is likely that penetrance can be highly variable, even within the same kindred. Two studies have reported a polymorphism of the type 2 hypocretin receptor gene in association with cluster headache, although this was not replicated in a third multinational study. Males are 2.5–3.5 times more likely to be affected than females, and patients typically start to develop the attacks in their third to fifth decade, although patients as young as 4 doi:10.1016/B978-0-12-385157-4.01094-0 499 500 Trigeminal Autonomic Cephalalgias (TACs) – Cluster Headache Table 1 International Classification of Headache Disorders, 3rd edition (ICHD-III) of the International Headache Society diagnostic criteria for cluster headache Diagnostic Criteria for Cluster Headache 1. 2. 3. 4. 5. At least five attacks fulfilling criteria 2–4 Severe or very severe unilateral orbital, supraorbital and/or temporal pain lasting 15–180 min (when untreated)a Either, or both of the following: a. At least one of the following symptoms or signs, ipsilateral to the headache: i. conjunctival injection and/or lacrimation ii. nasal congestion and/or rhinorrhea iii. eyelid edema iv. forehead and facial sweating v. forehead and facial flushing vi. sensation of fullness in the ear vii. miosis and/or ptosis b. A sense of restlessness or agitation Attacks have a frequency from one every other day to 8 per day for more than half of the time when the disorder is active Not better accounted for by another ICHD-III diagnosis a During part (but less than half) of the time course of cluster headache, attacks may be less severe and/or of shorter or longer duration. Source: Reproduced with permission from the Headache Classification Subcommittee of the International Headache Society (IHS) (2013) The International Classification of Headache Disorders, 3rd edition (beta version). Cephalalgia 33: 629–808. years and as old as 96 years have been affected. There seems to be an association with smoking, with approximately 65% of patients being active smokers or reporting a history of smoking. However, a causative link to smoking has not been proven and seems unlikely, as smoking cessation does not seem to alter the clinical course of the disorder and cannot easily account for the disorder in children. The natural course of cluster headache can be difficult to predict, with some people showing a bidirectional transition between the episodic and chronic forms of the condition. Less frequent bouts of attacks and more prolonged, and sometimes permanent, periods of remission can occur with advancing age. Clinical Features Pain Individual attacks of cluster headache are strictly unilateral in at least 97% of individuals, although very rare reports of simultaneous bilateral attacks do exist. Less than 20% of sufferers may experience attacks alternating between the right and left sides, and the side may vary between bouts or less commonly between attacks within a bout. The pain is typically focused in the distribution of the ophthalmic branch of the trigeminal nerve, behind the eye, over the temple or over the maxilla, although it may extend to other areas of the head and the neck. Patients often describe the pain as a sharp, piercing, burning, or pulsating sensation like ‘having a red hot poker forced through my eye,’ and they report that the intensity is so extreme it is unlike anything they have ever experienced (‘11 out of 10’), including childbirth, limb fractures, and acute abdominal pathology such as a ruptured viscera. Cranial Autonomic Symptoms and Other Features Each attack is accompanied by one or more cranial autonomic symptoms or signs on the same side as the pain. The most commonly experienced symptoms of exaggerated parasympathetic tone are lacrimation and watery rhinorrhea. Common mixed signs are conjunctival redness and periorbital swelling. Nasal congestion is a symptom of sympathetic interruption, of which ptosis and miosis (postganglionic Horner’s syndrome) are classic signs. All these signs and symptoms are transient and resolve with the cessation of pain, although a partial Horner’s syndrome or isolated ptosis may persist between attacks. The vast majority of patients describe a sense of restlessness and agitation during an attack and will often pace, rock back and forth, and bang their heads. Most wish to isolate themselves and seek a cold environment. Fewer than half report nausea, and fewer again may vomit during an attack. Photophobia may be reported, often limited to the same side as the pain, with fewer reporting an aversion to loud noise or strong smells during the attack. Aura phenomena, similar to those experienced during migraine, including visual phenomena and paresthesia, preceding the attacks by up to 60 min, have been described in a small minority of patients. Patients commonly have tenderness and cutaneous allodynia at and around the site of pain between attacks, including over the ipsilateral greater occipital nerve. Attack Duration and Frequency Attacks typically last between 15 and 180 min, although on rare occasions they can last longer. In a case series of British patients, a mean untreated minimum duration of 72 min and maximum duration of 159 min was reported. The onset of pain is rapid, and the sensation increases from serious discomfort to excruciating pain over the course of a few minutes. The pain usually stays at maximal intensity for the duration of the attack, although it may wax and wane slightly, or be punctuated by superintense stabs of pain. The attack will often end as abruptly as it started. Trigeminal Autonomic Cephalalgias (TACs) – Cluster Headache The frequency of attacks varies from one attack every 48 h to eight separate attacks in 24 h, although less frequent attacks may occur at the beginning and end of bouts. Typically 1–2 attacks will occur each day, and case series have reported a mean maximum number of attacks as 4.6 per 24 h. Just over a third of patients report an often highly predictable time of onset during the day, with three quarters reporting attacks occurring at predictable times during the night, awakening them from sleep. Bout Duration and Frequency Most people with episodic cluster headache experience one bout a year, with a mean duration of approximately 8–9 weeks. However, patients may go for several years without a bout (up to 20 years in some cases), and others may have more frequent bouts each year. The onset of bouts can be very regular in some individuals, with spring and autumn months being particularly noted for bout onsets, which is potentially related to the changes in day length. Precipitants Small quantities of alcohol will precipitate an attack in the majority of sufferers, usually within an hour of ingestion. However, this only occurs during a bout, rather than when in remission. In three quarters of patients, attacks are related to nocturnal sleep, with daytime naps also being triggers in some. Small case series have reported a raised apnea–hypopnea index in some patients, suggesting a higher frequency of obstructive sleep apnea, although no convincing mechanistic or therapeutic insights currently exist to explain this. Odors from volatile organic compounds, such as perfumes and paints, can also trigger attacks, as can nitrates and the phosphodiesterase inhibitor sildenafil. Pathophysiology The pathophysiology of cluster headache, as with the other TACs, is complex, and no single unifying mechanism has been identified to explain the syndrome as a whole. The classic reflex arc, which underpins much of the acute symptomatology of the TACs, is the trigeminovascular reflex. This mechanism involves reflex activation of parasympathetic outflow via the facial nerve and sphenopalatine ganglion caused by incoming nociceptive signals carried to the brainstem by the trigeminal nerve, which provides afferent pain innervation from the sensate structures of the face, orbit, cranial vault, and vasculature. The postganglionic parasympathetic efferent neurons colocalize with the trigeminal sensory afferent fibers throughout this region, and release of proinflammatory neurotransmitters by the activated parasympathetic fibers (namely vasoactive intestinal peptide (VIP)) further stimulate the trigeminal nerve endings, causing local release of the potent vasodilator calcitonin gene-related peptide (CGRP) by the trigeminal neurons, all of which further potentiates the reflex. Increased parasympathetic tone in the sphenopalatine 501 ganglion causes the lacrimation and rhinorrhea seen during cluster headache attacks. It is thought that vasodilation and neurogenic inflammation in and around the wall of the internal carotid artery and cavernous sinus may compress oculosympathetic fibers that travel with these structures from the superior cervical ganglion, resulting in partial ptosis, miosis, and partial Horner’s syndrome often seen during the attacks. It is widely accepted that a permissive state must exist within the central nervous system to facilitate central disinhibition of this neurovascular reflex, and that the origin of the pain does not lie solely within the periphery or indeed is not entirely mediated by the trigeminal nerve, as sectioning of this nerve does not provide universal relief from attacks. The simultaneous integration of both trigeminal pain and cranial autonomic signs afforded by this reflex may not always be a mutual relationship, as painless attacks of autonomic disturbance have been observed, both in trigeminally intact patients and those who have undergone trigeminal nerve section. The characteristic timing of the attacks, their seasonal preponderance, and the striking autonomic features of the attacks have led to decades of speculation that the hypothalamus might house the generator of cluster attacks. This hypothesis gained further support from seminal neuroimaging studies, which showed both strong activation of an area of the posterior hypothalamus ipsilateral to the side of pain specific to the attacks of cluster headache using positron emission tomography, as well as anatomical derangement within this same area during voxel-based morphometric magnetic resonance imaging (MRI) studies of patients. However, therapeutic deep brain stimulation of this area is only effective in approximately 60% of patients, and stimulation cannot acutely terminate an attack, which suggests that this area may be activated as part of a pain matrix response specific to a cluster headache attack, but that is not responsible for triggering the attack. Indeed, it may be that it is intensely activated as a breaking mechanism to terminate the attack, rather than trigger it. A small population of neurons containing the neurotransmitter orexin (or hypocretin) localize specifically to this area of the hypothalamus. They have widespread connections throughout the brainstem and are implicated in stabilizing sleep–wake transitions, as well as a host of other functions relating to appetite and autonomic control. It has been demonstrated in animals that infusion of orexin-A into the posterior hypothalamus attenuates neuronal firing within the trigeminal nucleus caudalis, whereas orexin-B has the opposite effect and potentiates firing, hence providing an attractive possible mechanism by which these neurotransmitters might also facilitate periodic pain processing at the level of the trigeminal nucleus caudalis, and thus be implicated in stabilizing the interface between the cranial autonomic system and the central pain mechanisms. Treatment Treatment of cluster headache falls into four main categories: abortive, transitional, preventive, and neuromodulatory, each of which is considered separately below. 502 Trigeminal Autonomic Cephalalgias (TACs) – Cluster Headache Abortive Treatment Abortive treatment is aimed at abolishing, or significantly reducing, the intensity of individual attacks. The current mainstay of this approach is the use of high-flow inhaled oxygen and parenteral triptan preparations. All other conventional analgesia, particularly the common oral preparations used to treat acute pain, are believed to be ineffective in cluster headache and not supported by any evidence base. In support of the use of high-flow inhaled oxygen, a recent double-blind randomized placebo controlled crossover trial found that 78% of subjects were pain free after inhalation of 100% oxygen at 12 l/min for 15 min. Preclinical studies in rats have identified that oxygen appears to reduce the firing of specific populations of neurons in the trigeminocervical complex, namely those giving rise to the facial nerve parasympathetic outflow, which not only reduces parasympathetic tone but also reduces subsequent trigeminovascular-evoked neuronal activation within the trigeminocervical complex, which effectively dampens the trigeminovascular reflex during an attack. The triptans are a family of tryptamine-based analgesic drugs with agonist action at 5-hydroxytriptamine (5-HT or serotonin) 1B/1D receptor subtypes distributed throughout the craniofacial vasculature. This class of drugs was specifically developed as migraine-abortive analgesia, and two subtypes, sumatriptan and zolmitriptan, also demonstrate efficacy in randomized controlled trials of use in cluster headache. However, the tablet forms of these agents show little effect, possibly due to the speed of onset and short duration of cluster headache attacks making the oral route of administration, and enteric absorption, less efficient within the time frame of an attack. However, sumatriptan given subcutaneously by injection works rapidly and can be extremely effective, as are preparations of sumatriptan and zolmitriptan delivered via the nasal route. Transitional Treatment Patients with episodic cluster headache often need a therapeutic bridge between the beginning of a bout and establishing definitive preventive treatment, which often has a longer latency to be effective and requires dose escalation over a longer time period. This approach can often be useful at minimizing the side effects from too rapid an escalation of preventive therapy, particularly with untried treatments. Two approaches are widely used in this regard. A short pulse of high-dose oral corticosteroids, which is then incrementally reduced every few days, may temporarily reduce the frequency and intensity of headaches. Another approach, which is supported by randomized controlled trial data, is the injection of a mixture of local anesthetic and corticosteroid solution over the greater occipital nerve on the side of the pain. This approach would normally be limited to use once in every 8–12 weeks. Preventive Treatment Preventive treatment aims to suppress the attacks for the duration of the bout, or over longer periods in those with chronic cluster headache. High doses of preventative medications are often required, so this approach aims to balance a good or satisfactory response in terms of reducing the frequency, severity, and duration of attacks against minimal drug-related side effects. Verapamil, an L-type calcium channel blocker of the phenylalkylamine class, is the preventive drug of choice, and this largely consensus agreement is supported by a small double-blinded multicenter placebo controlled study. Baseline electrocardiography must be performed before initiating verapamil, with monitoring electrocardiograms performed fortnightly before each incremental dose increase. High doses are often needed, and electrocardiogram monitoring is essential as conduction delays and cardiac arrhythmias are a common side effect. Lithium salts can also be a useful preventive treatment, even though it is generally less effective than verapamil and it is associated with greater side effects and the need for regular plasma monitoring. Observational studies have also suggested that methysergide (no longer available in the US), a headache specific ergot derivative with mixed 5-HT receptor effects, can be efficacious, particularly for short bouts, but its use is restricted owing to its serious fibrotic side effects, and it should therefore be given for short periods only under specialist supervision. Temporary relief, and sometimes termination of bouts, can also occasionally be provided by controlled, repetitive intravenous infusions of dihydroergotamine, another of the ergot derivatives. Other agents such as melatonin, the anticonvulsants topiramate, gabapentin, and sodium valproate, in addition to the benzocycloheptine-based drug pizotifen, are occasionally used with some success, although data from clinical trials are limited. Neuromodulation Several neuromodulatory approaches of varying degrees of invasiveness and risk exist, which can be effective in providing relief to patients, especially those who are refractory to pharmacological interventions. Newer approaches, which are less invasive, include sphenopalatine ganglion stimulation and the noninvasive delivery of vagus nerve stimulation using a custom-made external device. Occipital nerve stimulation involves the extracranial implantation of stimulating electrodes around the greater occipital nerve, situated below the scalp and overlying the occipital bones, and is generally considered to be a safe approach providing relief to approximately 70% of chronic sufferers who do not respond to medication. Deep brain stimulation in the area of the posterior hypothalamus is also being used to treat refractory cases. This technique offers good efficacy in approximately 60% of patients, although a small controlled trial was negative, and death has been reported as a complication of this approach. Thus, its use should be restricted to patients who have failed peripheral stimulation techniques. See also: Autonomic Nervous System; Overview. Headache and Craniofacial Neuralgias. Headache, Hypnic. Horner’s Syndrome. Horton, Bayard Taylor. Migraine; Clinical Aspects. Migraine; Genetics. Migraine, Pathophysiology of. Neuroimaging, Headache Disorders and. Neuromodulation Techniques, Pain and. Pain; Basic Trigeminal Autonomic Cephalalgias (TACs) – Cluster Headache Mechanisms. Parasympathetic System; Overview. Pituitary Tumors. Ptosis. Pupillary Disorders, Afferent. Trigeminal Autonomic Cephalalgias (TACs) – Hemicrania Continua. Trigeminal Autonomic Cephalalgias (TACs) – Paroxysmal Hemicrania. Trigeminal Autonomic Cephalalgias (TACs) – SUNCT/SUNA. Willis, Thomas Further Reading Akerman S, Holland PR, and Goadsby PJ (2011) Diencephalic and brainstem mechanisms in migraine. Nature Reviews in Neuroscience 12: 570–584. Leone M and Bussone G (2009) Pathophysiology of trigeminal autonomic cephalalgias. Lancet Neurology 8: 755–764. May A (2005) Cluster headache: Pathogenesis, diagnosis, and management. Lancet 366: 843–855. 503 May A, Bahra A, Büchel C, Frackowiak RS, and Goadsby PJ (1998) Hypothalamic activation in cluster headache attacks. Lancet 352: 275–278. Nesbitt AD and Goadsby PJ (2012) Cluster headache. British Medical Journal 344: 37–42. Relevant Websites http://learning.bmj.com/learning/module-intro/cluster-headache-diagnosismanagement.htmlmoduleId=5004479 BMJ Learning. http://ihs-classification.org/en/ IHS Classification. http://www.ouchuk.org/ Organisation for the Understanding of Cluster Headache.