DEFINITION AND CLASSIFICATION OF DAILY HEADACHE

Chronic daily headache implies headache on a daily, or near daily, basis—that is, 15 days or more a month. Daily headache, like many medical conditions, can be considered as primary or secondary (table 2). For consistency with clinical practice we shall deal with the secondary headaches first.

SECONDARY CHRONIC DAILY HEADACHE

Daily headache may be due to a number of causes (table 2). These are important to recognise since they are either completely treatable or life threatening. Some warning signs for secondary headache are set out in table 3. Fever, neck stiffness, personality change or abnormal neurological signs deserve prompt attention.

As a cause of CDH, giant cell (temporal) arteritis must be considered in the over 50s, and many erythrocyte sedimentation rate (ESR) assessments will be done quite correctly before the rewarding abnormal result will save a patient’s vision. In general, no elderly patient with daily headache of recent onset should be treated without having a normal ESR documented, and the clinical possibility of giant cell arteritis at least considered. Cases of giant cell arteritis occur in patients with normal ESRs,⁷ so a good clinical suspicion is always worth following. Perhaps the most pernicious form of secondary daily headache is substance overuse, and we shall return to it after discussing primary daily headache since the problems are often intertwined.

PRIMARY CHRONIC DAILY HEADACHE

The vast majority of patients with headache that persists have a primary headache syndrome. Given that most secondary headache is transient and associated with self limiting infections, it can be seen from table 1 that primary headache is the largest part of the clinical problem. There is considerable argument over the classification of daily headache; one possibility is presented in table 2. This issue is not trivial since the differentiation of migraine and tension type headache is the single, most substantial, clinical diagnostic challenge in this group of patients.

The International Headache Society (IHS) provides a phenomenologically based classification system of primary headache,⁸ dispersing daily headache with its episodic variants, although it does not provide for a frequent form of migraine. From a research viewpoint this organisation is perfectly sensible; however, in clinical practice we find utility in grouping frequent headache as CDH, and having a distinct clinical approach to this problem. The terminology itself can be confusing. The term “transformed migraine” was coined for the frequent form of migraine.⁹ For reasons of symmetry transformed migraine will be referred to as “chronic migraine” in the revised IHS classification,¹⁰ although again not everyone who uses these terms means exactly the same thing. We have adopted the term chronic migraine and use that nomenclature throughout. We would advise readers to use the term chronic migraine when referring to patients who have a frequent headache on a migrainous basis. The term reflects a view about the biology of the condition under management and is very clear to patients.

The division in table 2, which collects daily headaches together, is operational from a clinical viewpoint, since it can apply to all patients with daily headache as a first step. It is not pathophysiological since there is no clear evidence for splitting the infrequent and frequent forms of primary headache. The common types of primary daily headache in clinics are chronic tension type headache (15%) and chronic migraine (78%).¹¹ In general practice these figures are reversed with chronic tension type headache (55%) being more common than chronic migraine (33%). The patients with chronic migraine seem to have greater disability and this may result in their over representation in clinic based populations. The short lasting daily headaches are dealt with mainly as the trigeminal autonomic cephalgias (TACs), and are addressed elsewhere in this supplement (see page ii19). Hypnic headache is a rare form of short lasting daily headache seen in the elderly.¹²

Tension type headache or migraine?

It is useful to think of migraine as an inherited condition manifesting as sensitivity to afferent stimulation.¹³ During attacks patients are sensitive to some combination of light, sound, smells, and movement of the head. One might consider the entire syndrome in this way, and the pain may then be a form of sensitivity; perhaps throbbing headache reflects sensitivity to the normal pulsating of cranial vessels rather than primarily a classical nociceptive response to a change in vessel diameter. At its simplest level tension type headache is featureless headache: no nausea, no photophobia or phonophobia, no aggravation with movement and no throbbing. Extending this view it is unsurprising that some migraine sufferers might have fully blown migraine on some days and aborted forms of the attack on others. They would phenotypically appear as having migraine on some days and tension type headache on others, but their real biology would be simply that of migraine, thus earning the diagnostic label of chronic migraine.

By diagnosing patients who have disabling attacks that are clearly migraine on some days, and headache that is not disabling and largely featureless on other days, as one syndrome of chronic migraine we overdiagnose the migrainous aspect. Simultaneously, we underestimate the co-occurrence of the two biologies: migraine and tension type headache. However, considering epidemiology,⁴ treatment responses,¹⁴ responses to triggering,¹⁵ or indeed biochemistry,¹⁶ it is becoming clear that chronic tension type headache as a phenotype defined by the IHS harbours at least two distinct biologies, one of which is indistinguishable from migraine. This error of over estimation seems pragmatic; chronic migraine patients respond to preventative anti-migraine treatments, and since triggers perceived to be those of tension type headache, such as stress, are just as likely to trigger migraine,¹⁷ lifestyle advice is generic for both headaches. It is noteworthy in this context that the data demonstrate co-morbidity of depression with migraine,¹⁸ and that migraine can certainly be a generalised headache. Unfortunately, the more one examines the data on chronic tension type headache, the more difficult it is to define it by any positive feature; this sets out very clearly the need for careful research on patients with very pure chronic tension type headache.

There seems little point in telling a patient with migraine on some days and phenotypic tension type headache on another that they have two problems, or using the term mixed headache, without any biological justification. From a research perspective one must characterise headache phenotype prospectively in sufficient detail to seek correlations with biological markers, but this is not possible in clinical practice in the absence of those markers. Faced with a problem that fills clinics, and in which a biologically reliable differentiation is impossible, our pragmatic approach seems appropriate and serves us well. If one accepts this approach and recognises chronic migraine as an entity, defined by frequent headache with features, and chronic tension type headache as frequent completely featureless headache—no nausea, photophobia, phonophobia, aggravation with movement, nor throbbing qualities—then the overwhelming challenge in neurology outpatients is the management of chronic migraine. In a referral centre such as ours with patients from both neurologists and general practitioners we see very few patients with pure chronic tension type headache. We recognise every clinician is captive of who is referred to them, or comes to see them.

Chronic migraine: clinical approach

We find it useful to obtain certain key clinical facts during the consultation. This is not an exhaustive list but serves to illustrate some important principles.

How long have you been having headaches?

It is remarkable although not surprising that patients with headache assume everyone else has headaches, or has had disabling headache at some time. This assumption often extends to their doctors. One suspects that if a parent or sibling has headache, then the sufferer just assumes that it is normal. To those of us who do not have headache, nor a family history of headache, the experience is so rare as to be a novelty. It is useful to be sure that the response of relatively recent onset does not actually mean that the headache changed, became more frequent or more severe, or both, in recent times, although the patient has always been somewhat “headachey”.

How often do you have a headache?

This may lead to many and varied responses but the key is how many days are affected and how many days have significant disability. If the patient is unsure how many days of headache they have, we find turning the question around to “how often is your head completely normal”, or some variation of this, often elicits a very illuminating single digit response. If any doubt remains one can ask the patient to keep a diary. The patient records the days on which they have headache and lists all medications taken that day. It is crucial for management that all medications are recorded, particularly over-the-counter (OTC) preparations (see below). Patients sometimes do not think of these preparations as “drugs”.

Tell me about your worst attacks.

If one accepts the concept of chronic migraine then the most illuminating history is that of the most severe attacks. In isolation such attacks will have some migrainous features, and this greatly aids in the diagnosis. A careful discussion of how these are treated will help plan management.

Triggering and family history.

Migraine genes seem to confer a set of sensitivities to various triggers. In essence the migraine brain has a varying level of sensitivity, which explains why triggers work on some days and not others. This variability is perfectly compatible with the current view of migraine as a channelopathy.¹⁹ Triggering of headache by changing sleep pattern (sleeping in or getting tired), changing eating habit (skipping meals), changing weather (pressure change or hot weather), changing female hormone levels (menses), physical change (over exertion), or emotional change (stress or relaxation from stress), all—with the exception of stress—seem rather migrainous. It helps to establish that a first degree family member is “headachy”, and a bonus if they clearly have or have had migraine. The latter is particularly true in paediatric practice where CDH certainly occurs as chronic migraine—the fact that the headaches run in the family is very reassuring for all concerned.

Finally, it has been said that daily headache can never be migraine. This view postdates Critchley who described it to one of us as nonsense (personal communication to PJG), and seems to the authors unlikely to be correct. Biology knows few absolute rules, and given that we have no markers, the use of the concept of chronic migraine has many satisfied adherents. Patients with migraine have their biology and genotype every day of their lives, so having it expressed frequently seems certainly plausible.

ANALGESICS AND DAILY HEADACHE

Perhaps the most common association of CDH is analgesic overuse.²⁰ It is exceedingly common for patients with daily headache to be taking often large quantities of analgesics. In this context taking an acute attack medicine more than twice a week is probably overuse. Usually such patients have headache that is improved by the acute attack medicine, only to return (rebound headache) as the drug effect wears off. They take the medicine again and so a vicious cycle takes hold. It seems likely that all of the medicines used in treating acute primary headache can complicate matters to some extent in the context of overuse syndromes. Certainly this seems clear for caffeine opiate agonists, ergotamine, and triptans. The worst offenders are compound OTC analgesics with combinations of paracetamol or aspirin, with caffeine or codeine phosphate, or both. The great problem is that these compounds are available as OTCs and we cannot regulate their use. As a general rule, having to use an acute medication more than once a week probably means that a preventative medication should be considered, although the most crucial aspect is the pattern of use over time. Detoxification of patients from codeine based OTCs can be extremely difficult for both patients and doctors. The first crucial step is to recognise the problem.

Withdrawal of analgesics will often improve daily headache but in our experience only in about one third to one half of patients will it cause the problem to revert to a clearly episodic form. The headache returns to its natural episodic state and can thus be managed more easily. For those patients who continue to experience daily headache after analgesic withdrawal careful management is required to prevent a return to analgesic overuse. This will often mean initiating a preventative medication.

MANAGEMENT OF CHRONIC DAILY HEADACHE

The management of CDH can be very rewarding. Most patients overusing analgesics respond very sensibly when the problem is explained. The keys to managing daily headache are excluding treatable causes (table 2), getting a clear analgesic history, and making a diagnosis of the primary headache type involved.

Management of medication overuse: outpatients

It is essential that analgesic use be reduced and eliminated. Patients can reduce their use either by 10% every week or two, depending on their circumstances, or if they wish and there is no contraindication, by immediate cessation of use. Either approach can be facilitated by first keeping a careful diary over a month or two to be sure of the size of the problem. A small dose of a non-steroidal anti-inflammatory drug (NSAID), such as naproxen 500 mg twice daily for six weeks if tolerated, will take the edge off the pain as the analgesic use is reduced. NSAID overuse does not seem to be a common issue in daily headache when dosed once or twice daily, whereas with more frequent dosing we have seen problems develop. When the patient has reduced their analgesic use substantially a preventative medication should be introduced. It must be emphasised that preventatives simply do not work in the presence of analgesic overuse, so the patient must reduce the analgesics or the entire use of the preventative is a wasted effort. The most common cause of intractability to treatment is the use of a preventative when analgesics continue to be used regularly. For some patients this is very difficult and often one must be blunt and tell them that some degree of pain is inevitable in the first instance if the problem is to be controlled.

Management of medication overuse: inpatient

Some patients will require admission for detoxification. This comprises broadly two groups: those who fail outpatient withdrawal, and those who have a significant complicating medical indication, such as brittle diabetes mellitus, where withdrawal may be problematic as an outpatient. We admit such patients and withdraw acute medications completely on the first day, unless there is some indication not to do so. We use antiemetics—domperidone oral or suppositories—and fluids as required, as well as clonidine for opiate withdrawal symptoms. For acute intolerable pain during the waking hours we find intravenous aspirin (1 g) useful, and at night we use chlorpromazine by injection, ensuring adequate hydration. If the patient does not settle over 3–5 days we use a course of intravenous dihydroergotamine (DHE).²¹ As time goes by we feel that DHE is indispensable in this setting; administered every eight hours for three days, it can induce a significant remission that allows a preventative treatment to be established. Often 5-HT₃ antagonists, such as ondansetron or granisetron, will be required with DHE as it is essential to ensure that the patient does not have significant nausea.

Preventative treatments

We find the tricylics, amitriptyline or dothiepin, at doses up to 1 mg/kg, very useful. These are started in low dose (10–25 mg daily) and best given 12 hours before the patient wishes to wake up to avoid excess morning sleepiness. The other very useful medications for these patients are the anticonvulsants, such as valproate, gabapentin, and more recently topiramate. For valproate doses up to 1500 mg daily are used. We generally start on 200 mg twice daily, increasing to 400 mg or 600 mg twice daily as tolerated over 2–4 week intervals. The blood count and liver enzymes should be checked at baseline and the various side effects explained to patients, especially to women about the fetal abnormalities. For gabapentin we aim to dose at 1800–3600 mg daily, and find it very well tolerated, although probably less effective from a population viewpoint.