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Headache is the most common neurologic symptom and affects nearly half the world's population at any given time. Although the prevalence declines with age, headache remains a common neurologic complaint among elderly populations. Headaches can be divided into primary and secondary causes. Primary headaches comprise about two-thirds of headaches among the elderly. They are defined by clinical criteria and are diagnosed based on symptom pattern and exclusion of secondary causes. Primary headaches include migraine, tension-type, trigeminal autonomic cephalalgias, and hypnic headache. Secondary headaches are defined by their suspected etiology. A higher index of suspicion for a secondary headache disorder is warranted in older patients with new-onset headache. They are roughly 12 times more likely to have serious underlying causes and, frequently, have different symptomatic presentations compared to younger adults. Various imaging and laboratory evaluations are indicated in the presence of any "red flag" signs or symptoms. Head CT is the procedure of choice for acute headache presentations, and brain MRI for those with chronic headache complaints. Management of headache in elderly populations can be challenging due to the presence of multiple medical comorbidities, polypharmacy, and differences in drug metabolism and clearance.

Migraines are among the most common headache disorders. They are now considered to be of neuronal, rather than vascular, origin. Because they can vary widely in their presentation, intensity, and associated symptoms, they tend to be underdiagnosed and thus untreated or undertreated. With some frequency, migraines are confused with symptoms of infectious or allergic sinusitis and treated as such. The number of drugs available for treatment and prevention, including routes of administration, continues to expand at a rapid pace and provides ever increasing options for treatment. Nonetheless, effectiveness of these drugs still proves unsatisfactory for many patients and prompts them to try unproven treatments. Increasingly, patients opt for treatment that may be limited to, or include, complementary and alternative modalities; several over-the-counter supplements with possible activity, and one with a warning, are listed. The trigeminal autonomic cephalagias (TAC) are a group of headaches that are related to each other and to migraines. Trigeminal neuralgia is differentiated from the TAC by the absence of autonomic symptoms in the neuralgia. Although TAC frequently respond to the same drugs as migraines, each also responds to specific treatments.

The sphenopalatine ganglion (SPG), also called the pterygopalatine ganglion, is the switching station for the final common pathway for cluster headache, may serve as the final synapse in the other trigeminal autonomic cephalalgias, and may also be pivotal in the efferent pathway to the dura and meninges in migraine. Inhibiting SPG outflow offers a specific and targeted approach for primary headache termination or prevention, and this chapter reviews the current state of this approach. Blocking or inhibiting outflow from the SPG terminates cluster. A long history of SPG blocks led to proof of concept that inhibitory neuromodulation is useful in cluster headache therapy. A small remote-controlled SPG neuromodulation stimulator, without external wires and powered externally, can be implanted with a minimally invasive approach. This device has both acute and preventive benefit for cluster headache patients, and is approved and available in the European Union and the United Kingdom. Efficacy is high, tolerability is excellent, and adverse events are consistent with an oral surgical procedure. A registration study for this device is under way at the time of writing (September 2017).

Primary headache disorders, including migraine and the trigeminal autonomic cephalalgias, are characterized by normal clinical examination and structural brain imaging. While a central nervous system origin for these disorders has been postulated since the nineteenth century, only recently with the development of functional brain imaging has this been directly studied. Brain imaging methods have enabled the identification of structures underlying headache and hallmark symptoms, such as photophobia, premonitory symptoms, and typical migraine aura. This article gives an integrated view of the clinical presentation and associated functional changes in the brains of patients with primary headache disorders.

Cluster headache and the cluster headache variants are grouped as one of the primary headache disorders. These headaches are rarely compared to migraine or tension-type headache, although the associated pain and disability are substantial. All of the disorders are characterized by relatively short-duration headaches that are strictly unilateral and are associated with autonomic symptoms typically in the distribution of the trigeminal nerve. Treatment tends to be similar to migraine in many aspects but with a greater reliance on preventive therapy. With these headaches, procedural options may be more important than in migraine because of the historically poor response to preventive medications over the life of the disorder.

Cluster headache is among the most painful of all neurological disorders. Unilateral attacks, lasting up to 180 min, of excruciating first-division trigeminal pain, together with features of amplified cranial parasympathetic and interrupted sympathetic outflow, may afflict the patient up to 8 times in 24 h.

Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) and short-lasting unilateral neuralgiform headache attacks with cranial autonomic symptoms (SUNA) are rare trigeminal autonomic cephalalgias (TACs), with multiple brief attacks of severe unilateral facial pain with prominent cranial autonomic symptoms. They are distinguished from other TACs by a history of short, frequent attacks, and the differential response to treatment. SUNCT/SUNA may be the primary syndromes, or secondary to an underlying structural cause. Abnormal activation in the region of the posterior hypothalamus is suggested as a pathophysiological cause for SUNCT/SUNA, as in the other TACs. Their clinical phenotype, diagnosis, workup, and treatment are summarized.

Hemicrania continua (HC) is a relatively rare primary headache disorder characterized by unilateral pain and an exquisite response to indomethacin. Since the term was introduced in 1984, more than 100 cases have been reported in the literature. Useful information regarding the pathophysiology comes from functional imaging that suggests a role for subcortical neural structures. A positron emission tomography (PET) study in HC patients showed activation of the contralateral posterior hypothalamus, the ipsilateral dorsal pons, and ipsilateral ventral midbrain. Taken together with the unique effect of indomethacin to block the pain, the data point to the classification of HC as a unique syndrome that belongs to trigeminal autonomic cephalalgias (TACs).

Clinical neurophysiology and neuroimaging are two non-invasive approaches used to investigate the pathophysiological basis of primary headaches, including cluster headache (CH) and other trigeminal autonomic cephalalgias (TACs). Modern neuroimaging has revolutionized our understanding of the pathophysiology of primary headaches, and of TACs in particular, focusing on a cerebrovascular dysfunction hypothesis toward a central triggering cause. The introduction of single-photon emission computed tomography (SPECT), positron emission tomography (PET), and voxel-based morphometry has allowed us new insights into mechanisms underlying TACs and occurring during peripheral and/or central neuromodulation. The specific activation of neural structures that is observed exclusively in migraine and in TACs supports the hypothesis that primary headaches are driven predominantly by central nervous system dysfunction, and this has important implications from a therapeutic perspective. Neurophysiological examinations are of little value in the clinical setting; however, most of these tools offer vast potential for exploring further the pathophysiology of primary headaches and the effects of pharmacological treatments Trigeminofacial reflexes, the nociceptive flexion reflex, and evoked potentials have been used in TACs to explore the functional state of brainstem and spinal structures involved in pain processing, contributing to our understanding of the pathophysiology of these primary headaches.

Publisher Summary This chapter discusses pathophysiological mechanisms in cluster headache (CH). CH has been recognized for many years, whereas short-lasting unilateral neuralgiform pain with conjunctival injection and tearing (SUNCT) and the paroxysmal hemicranias (PH) are rare headache syndromes that is described in the chapter. Consequently, there are far more studies regarding CH than SUNCT and PH. Typically CH attacks are strictly unilateral, with the maximal pain localized deep behind one eye or the temple, and associated with ipsilateral facial autonomic symptoms. Mapping of the trigeminovascular system and the trigeminoautonomic reflex has provided a new basis for the understanding of the trigeminal autonomic cephalalgias (TACs). The ipsilateral facial autonomic symptoms associated with the cluster attack suggest both sympathetic deficit and parasympathetic hyperactivity. Several sources of the autonomic symptoms are presently under consideration at central as well as peripheral levels. The episodic nature of CH, in particular the timing of single attacks and periods, circadian neurendocrine disturbances and systemic effects such as altered lipolysis, is likely to be related to hypothalamic dysfunction. Recurrent activation of the trigeminovascular system with parasympathetic recruitment and vasodilation explains many of the clinical features of CH but the trigger of this activation is unknown. Possibly attacks may be initiated by hypothalamic discharge. The local sympathoplegia, overt or subclinical, most probably is of peripheral origin and not a cause of the pain, but once the attack begins these autonomic disturbances may contribute to the rapid escalation of pain.

Publisher Summary This chapter discusses the diagnostic criteria of cluster headache and other trigeminal autonomic cephalalgias. The diagnosis of cluster headache that is primarily clinical is based on the history of the attacks, a careful description of the pain, the temporal profile, the trigger factors, and the associated autonomic manifestations. The rapid escalation of the pain, the predominance of nocturnal attacks, and the limited duration of each headache are important details of the history. Despite the rarity of associated structural abnormalities, it is appropriate to obtain an MRI scan of the brain or a contrast-enhanced CT scan. PET and voxel-based morphomatic analysis of T 1 -weighted MRI scans are only possible in specialized centers. Cluster headache is distinguished from migraine by the male predominance, strict unilaterality of pain, short-lived attacks (45 min to 1 h), multiple attacks per day, associated autonomic features, restlessness and inability to lie down during the attack, and the periodicity (clustering) of attacks. Migraines tend to occur primarily in females. Attacks may be associated with prodrome or aura and last a number of hours to days. Nausea, vomiting, and photophobia are prominent features in migraine; they may occur, but less frequently, in cluster headache.

Publisher Summary This chapter presents the diagnosis and treatment guidelines for migraine developed by the American Academy of Neurology (AAN). These guidelines are discussed and additional evidence is included based on the new studies that have become available since their initial publication. In addition, the European Consensus Conference recently established evidence-based treatment guidelines for the treatment of trigeminal autonomic cephalalgias. These guidelines are also discussed as they are the only evidence-based guidelines available for the treatment of these primary headache disorders. The therapeutic and diagnostic guidelines presented in this chapter represent the most exhaustive, rigorous, and recent in the field of headache. They represent a systematic evaluation of the evidence base for the acute and prophylactic treatment of migraine and trigeminal autonomic cephalalgias generated by international experts in the field of headache medicine. The variability in diagnosis and appropriate treatment of primary headache disorders is wide and it is the intention that these specific guidelines, if systematically and appropriately implemented in clinical practice, will improve the quality, appropriateness, and cost-effectiveness of the care of patients with headache.

Patients with cluster headache or any of the trigeminal autonomic cephalalgias (TACs) are often good candidates for preventive treatment as their headaches are frequent and severe. While acute and symptomatic therapies must be used often, they do not alter the course of the cluster period or the duration of the TACs, and they do not usually decrease the frequency of attacks. In this chapter we discuss the aim and the choice of prevention. Verapamil is considered the first choice for prevention of cluster headache, but as with all of the medications to be mentioned, it has various adverse effects to be aware of. Other frequently used preventives for cluster include lithium carbonate, methysergide where available, methylergonovine, clonidine, melatonin, valproate, gabapentin, topiramate, and others. Several other medications can be used as bridge therapy, to decrease the frequency of cluster temporarily, giving time for the preventives to begin to work. The most commonly used bridge therapies are 7-21 days of prednisone at high and then tapering doses and ergots such as ergotamine tartrate and dihydroergotamine. Patients with chronic cluster headache who are unresponsive to all medical therapies can be considered for occipital nerve stimulation and various surgical procedures such as ganglyogliolysis of all three branches of the ipsilateral trigeminal nerve at the root entry zone. A somewhat controversial but highly successful procedure, at least as done by the neurosurgeons in Professor Bussone's group at the Institute of Neurology in Milan, has been deep-brain stimulation of the posterior hypothalamus. Other TACs, such as short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), can be hard to treat effectively with medications, but the paroxysmal hemicranias and cluster tic respond somewhat better to traditional therapies.

Publisher Summary The term “trigeminal autonomic cephalalgias” (TACs) was introduced to delineate a group of primary headache syndromes characterized by short-lasting pain with unilateral trigeminal distribution, associated with ipsilateral cranial autonomic symptoms. These forms include cluster headache (CH), paroxysmal hemicrania, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), and probable TAC. The etiology of these syndromes is largely unknown, notwithstanding the quite high number of investigations performed, at least in the case of CH. The lack of specific animal models for TACs and their rarity have probably contributed to hampering the process of understanding their underlying mechanisms. If pathophysiological knowledge of TACs is far from satisfactory, the treatment of these conditions emerges as even more challenging. In the case of CH, only a few options are available for prophylactic treatment, with a rate of success that varies between and within subjects. With regard to symptomatic treatment, subcutaneous sumatriptan is very effective, but it has limitations in the daily frequency of intake and it is contraindicated when hypertension or other cardiovascular disorders are present.

Chronic paroxysmal hemicrania (CPH) is a rare primary headache syndrome, which is classified along with cluster headache and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing as a trigeminal autonomic cephalalgia (TACs). Hemicrania continua (HC) was previously classified as one of the TACs, but in the recent second classification of the International Headache Society this disorder was moved to the group of other primary headaches. Both CPH and HC are characterised by moderate to excruciating pain requiring pharmacological treatment; furthermore, both conditions are characterised by an absolute response to indomethacin, which represents one of the current diagnostic criteria for these two syndromes. Unfortunately, in about one-fourth of cases treatment with indomethacin may cause adverse events, mostly gastrointestinal. We report one subject with CPH and another with HC intolerant to indomethacin, who responded remarkably well to topiramate.