The burden of headache disorders worldwide
The most recent World Health Organization Global Burden of Disease Study (2019) ranked migraine as the second most disabling non-fatal medical condition in terms of years lived with disability, and the global age-standardised prevalence for migraine was 14% (1) (2). Eurolight, a large cross-sectional survey from more than 10 European countries, confirmed that depression and anxiety are more common in migraineurs and are even more strongly associated with medication-overuse headache (MOH), chronic migraine (CM) (3). This may increase the overall societal burden of migraine and MOH because symptoms of comorbid illness are expected to create a vicious cycle (3).
Tension-type headache (TTH) is considered to be very common, with a lifetime prevalence in the general population ranging from 30–78% on the basis of different studies (4). Frequent episodic or chronic TTH can be associated with some disability (4); however, patients with TTH rarely seek medical advice from their primary care physicians/general practitioner (GP) (these terms are used interchangeably throughout this manuscript) and pure TTH is a rare condition in hospital settings (5).
Cluster headache (CH), despite being relatively rare (lifetime population prevalence of 0.12%) (6), is considered to be an excruciating primary headache disorder (7) and carries a significant burden of disability. The anxiety caused by the ‘fear’ of having an attack affects the planning of events, socialising, productivity and integration into activities for patients with CH (8).
Headache/Migraine diagnostic challenges in primary care
The International Headache Society is responsible for headache classification globally and publishes the International Classification of Headache Disorders periodically, the most recent being the 3rd edition (ICHD-3). This document is the internationally accepted classification of all primary and secondary headache disorders, including migraine (4). However, not all physicians are familiar with the ICHD diagnostic criteria (9), nor do they have the clinical skills and/or experience which is necessary to be able to diagnose primary headache disorders easily (10).
Migraine is the most common primary headache disorder seen in general practice; in one study, based on longitudinal data after an expert panel review, 94% of patients were diagnosed with migraine or probable migraine (5). However, in a UK primary care database study of 91,121 adults with new-onset headache (patients who had not consulted for headache in the previous year), 70% were not given a ‘diagnostic label’ or proper diagnosis, suggesting a very significant unmet need for additional headache/migraine education, training and diagnostic support in primary care (11). Lifting the Burden (LTB), a multinational group established to raise awareness of headache disorders, further highlighted the lack of headache diagnosis accuracy in primary care (12). In one study, almost all centres inaccurately captured and/or assessed headache history, especially temporal profile, and 20% of patients received a non-specific classification code, rather than a specific diagnosis (12). Overall, this study concluded that a lack of knowledge among GPs is a common cause of suboptimal treatment of patients presenting to primary care with headache (12).
After secondary headache disorders are ruled out, it is important to distinguish between the different types of primary headache conditions (such as migraine, CH, TTH, etc.), as their underlying pathophysiology differs and distinct acute and preventive treatments are used for the separate conditions (13). For example, typical acute treatments for migraine include simple analgesics, non-steroidal anti-inflammatory drugs (NSAIDs) and triptans; whereas simple analgesics and NSAIDs are generally used for TTH and normally triptans, high-flow oxygen and external vagus nerve stimulation are used for the acute treatment of CH (13).
Migraine is classified as being either CM or episodic migraine (EM), and diagnosis follows clearly defined clinical criteria, i.e. the ICHD-3 criteria (4, 14). In the primary care setting, making a migraine diagnosis is often difficult for many reasons (including lack of time, deficits in clinical experience/training and complex clinical history), and it often involves exclusion of other primary or secondary headache disorders (14). Furthermore, unlike other neurological disorders (15), there are no specific tests or biomarkers that are currently used to support the clinical diagnosis of primary headache conditions, such as migraine (4). In addition, CM specifically is often complicated by the practice of medication overuse (MO), which can lead to MOH (4, 16). According to ICHD-3, MOH is defined as a headache occurring on 15 or more days per month in a patient with a pre-existing primary headache disorder (typically migraine) and is proven to become more chronic and frequent due to regular overuse of acute or symptomatic headache medication (on 10 or more or 15 or more days per month, depending on the medication) for more than 3 months (4). In the clinic, it is common to say a patient is practicing MO, but patients are rarely diagnosed with MOH.
The deficits in diagnosis of headache disorders were further demonstrated by The Chronic Migraine Epidemiology and Outcomes Study, a US longitudinal web-based panel study with 1,254 chronic migraineurs included in the analysis. This study concluded that, of the chronic migraine patients who consulted with a healthcare professional (HCP), only 24.6% (n=126) received an accurate diagnosis and 44.4% (n=56) of those with a correct diagnosis received both acute and preventive treatment (17). In other words, only 4.5% (n=56) of those with CM traversed all three barriers to successful CM care (i.e. consulted an HCP for migraine, received an accurate diagnosis and were prescribed minimal acute and preventive pharmacological treatments). This suggests that there is a very significant unmet need for patient education and access to healthcare, as well as a need to significantly improve diagnosis and management of patients with migraine (17).
The role of the GP in the management of patients with uncomplicated EM is well established and generally straightforward. The general expectation is that GPs should feel confident to make a diagnosis, initiate therapy and manage the less refractory patients in the primary care setting (16). However, the management of CM in primary care is debated and varies between countries (16). Many of these more chronic and refractory cases warrant referral to more specialised hospital-based headache services compared with EM (18). Unfortunately, waiting times for new appointments may be long and access to these specialist clinics may be limited (12). In addition, the role of the GP is especially important in some countries because of a low level of headache expertise, even in senior neurology department positions. This will obviously lead to a shortage of headache specialists to manage referrals in the hospital setting (19).
Misdiagnosis (as well as underdiagnosis) of primary headache is also a common problem in primary care; in a study of 162,576 participants who completed a self-administered mailed headache questionnaire, only around half (56.2%) of those meeting the ICHD, 2nd edition (ICHD-2) criteria for migraine reported that they had received a diagnosis of migraine. Alternative diagnoses included sinus headache (39.0%), TTH (31.2%), stress headache (28.5%) and CH (9.9%) (20). Misdiagnosis can be caused by several factors, including lack of clinical experience/training, failure to take a thorough history and symptoms of migraine being attributed to or mimicking secondary causes, e.g. sinus congestion interpreted as meaning sinusitis (20). Diagnostic delay is a well-recognised hurdle for the appropriate management of patients with migraine (21). For example, it may result in a failure to initiate appropriate treatments, for example NSAIDs and triptans (13), and risk factor modification, e.g. reduce caffeine intake, which ultimately improve functional status and quality of life for people with migraine (14). Misdiagnosis and diagnostic delay of CH is also a widespread problem (22). Patients with CH often consult many different specialists (including medical doctors, surgeons and dentists) and receive multiple varying opinions prior to being correctly diagnosed (22). For example, in a study of 144 patients with episodic CH from Italy and Eastern Europe, the mean number of incorrect diagnoses received per patient with CH was 2.3. Furthermore, in the same study, the average delay to correct diagnosis was 5.3 ± 6.4 years, which led to the majority of patients taking inappropriate acute treatments (such as NSAIDs) and only a quarter had been using a recommended preventive CH therapy (23). Limited knowledge of CH characteristics by patients and HCPs is thought to be one of the major explanations for the delays in diagnosis of these patients (22).
The American Headache Society FrontLine Primary Care Advisory Board on the crisis of diagnosis and management of migraine, have suggested a number of strategies for improvement of headache management in primary care. These included development of important tools and resources for headache education on the front line, e.g. point-of-care applications and considerations for implementing migraine screening tools (24).
The aspiration is that introduction of different diagnostic instruments, (e.g. screening tools such as patient questionnaires), may improve migraine diagnosis in general practice. In one review of migraine screening tools (including items, instruments and scales), it was recommended that a structured intake form and a headache diary are used when diagnosing patients with headache (9). Headache-specific screening tools for doctors and HCP’s already exist: for example, ID-Migraine™, which is a three-item migraine screening questionnaire based on the ICHD-2 criteria (9, 25). Another example is the Cluster Headache Screening Questionnaire, which has been developed for rapid identification of CH (26). However, more needs to be done given the level of misdiagnosis and underdiagnosis of primary headache conditions, specifically migraine.