Commentary: Controversies in SIGN guidance on diagnosing and managing headache in adultsBMJ 2008; 337 doi: https://doi.org/10.1136/bmj.a2445 (Published 20 November 2008) Cite this as: BMJ 2008;337:a2445
A discussion of headache centres on two largely independent areas: diagnosis of possible serious cause (usually none is found), and pain management (typically less, not more medication is needed). The newly published guideline from the Scottish Intercollegiate Guidelines Network (SIGN)1 uses the familiar split of primary and secondary headache—that is, benign and serious headache.
It is unusual for headache to be the sole symptom of brain tumour.1 The guideline omits demographics: the approximate risk of brain tumour or other serious cause for headache is 1:1000 for headache presenting in primary care, 1:100 for headache presenting in secondary care (outpatients), and 1:10 for headache presenting in accident and emergency departments.
The guideline lists familiar “red flag” indications.1 Reassurance from a scan is supported by a single, unblinded study showing benefit at three months but not at one year.2 The guideline discusses risks of imaging, not confined to computed tomography ionising radiation. Incidental findings are common and sometimes lead to inappropriate treatment. The rate of incidental findings comes from two recent studies. In one, a quarter of 2536 healthy 20 year olds had magnetic resonance scans that were not strictly normal, of which three quarters were normal variants.3 In the other, among 2000 healthy 45 to 97 year olds, one in eight had significant intracranial abnormality, including stroke (7%), aneurysm or angioma (1.2%), benign tumour (mostly meningioma) (1.6%).4 “Sitting on a time bomb” is the typical comment from a patient with headache and an incidental abnormality. These studies overlook the common finding of nasal sinus disease: chronic sinusitis is not the cause of chronic headache. A low threshold for referring patients with headache for imaging may seem compassionate and safe, but there is a “number needed to harm” that has not yet been quantified.
Normal results on imaging can occur in secondary headache. Giant cell arteritis requires screening preferably with both erythrocyte sedimentation rate and C reactive protein; the pain is not specifically temporal.1 First, worst, or thunderclap headache with a normal CT brain scan demands lumbar puncture to look for blood products (not for red cells).1 These matters often remain overlooked, particularly by those who rely more on imaging than on clinical assessment.
Primary headaches have neural localisation and a presumed molecular pathology; these are not disorders of the psyche, blood vessels, neck, diet, or allergy.
Migraine and tension-type and cluster headache
Chronic migraine is a new diagnosis (since 2004).5 The distinction between chronic migraine and chronic tension-type headache is challenging.1 Some authorities now rarely diagnose tension-type headache, seen as a milder, featureless migraine; others reject chronic migraine. The guideline seems to regard migraine as unilateral and tension-type headache as bilateral1; certainly these can coexist, have similar localisation to the brainstem, and require similar treatments. However, the rarer group of primary headaches, the trigeminal autonomic cephalalgias (such as cluster headache) arise in the midbrain, respond to neither tricyclics nor β blockers, and are unilateral. Migraine may be more asymmetrical than unilateral; according to the International Headache Society’s criteria, migraine need not be unilateral, nor tension-type headache bilateral.5
Medication overuse headache
Medication overuse headache, technically a secondary headache,5 belongs in the context of the primary headaches (migraine and tension-type headache, not trigeminal autonomic cephalalgia), which it mimics.
The SIGN guideline states that medication overuse headache must be excluded in all patients with chronic daily headache.1 Medication overuse headache is “by far the most common cause of migraine-like headache on ≥15 days a month,”5 affecting 1 in 50 people.6 The guideline emphasises the importance of stopping medication but does not seem to support the view that drug treatment for preventing medication overuse headache is futile and may worsen headache.6 Topiramate, without medication cessation, offers a statistically significant though numerically small benefit of 3.5 fewer headache days a month.7 Recognition and treatment of medication overuse headache is the best single strategy for sorting out chronic headache.
The SIGN guideline does not cover facial pain, so I hope it will publish a further high quality guideline on that subject.
Cite this as: BMJ 2008;337:a2445
Contributor: The author is the sole contributor.
Competing interest: The author is a member of the International Headache Society and British Association for the Study of Headache. He has in the past been paid by the manufacturers of most if not all drugs licensed for the treatment of headache and migraine and currently undertakes drug trials in migraine and headache. He has a private practice that profits from both overconcern about the risk of brain tumour as a cause of headache and under-recognition of medication overuse headache.
Provenance and peer review: Commissioned; not externally peer reviewed.