Investigating headache

Published in MedicineWise News

Date published: About this date

Clinical content may change after this date. This information is not intended as a substitute for medical advice from a qualified health professional. Health professionals should rely on their own expertise and enquiries when providing medical advice or treatment.

Key messages

  • Headache is common with many types and causes but most are benign
  • Diagnose type of headache by taking a detailed history and performing a targeted examination
  • Neuroimaging is not needed for people with normal neurological examination and no 'red flags'
  • Discuss risks and costs of neuroimaging

Headache is common but most are benign

Global 1-year prevalence data show that about 1 in 2 people have had a headache: with 4 in 10 a tension-type headache and 1 in 10 a migraine. (Cluster headache was not reported because there are few population-based studies using International Headache Society criteria.)1

Discuss your diagnosis and provide information about how to manage headache

Explain that most headaches are benign (also known as primary headache). Diagnostic tests and investigations are not usually needed for primary headache.2 To help with the right diagnosis, suggest people use a headache diary for a few weeks (e.g. 4–6 weeks).2-4 A headache diary can be used to record details such as frequency, severity, suspected triggers and medicines use; and is more likely to be an accurate account than recollection alone.3 This information can inform discussion of symptoms
and the impact of headache on quality of life, guide therapy and ensure appropriate follow up.4

Download or order copies of the NPS headache diary

Take a detailed history and perform a targeted examination

An accurate diagnosis, and distinguishing primary from secondary headache is important.7 This depends on a detailed history, and targeted physical and neurological examination.7

There are many different types of headache (see Table 1 for the International Headache Society diagnostic criteria for 3 types of primary headache: tension-type, migraine and cluster).8

Often people suffer from episodes of both tension-type and migraine headaches. Other types of headache are not discussed in this publication (e.g. medication-overuse headache: refer to NPS News 38 ).5

Most headaches are self-limiting and non-disabling: provide information, reassurance and suggestions for treating symptoms as needed. Most people can manage their headache symptomatically with over-the-counter analgesics and/or non-drug strategies (for more information, see NPS News 38 and NPS News 79).5,6 Identifying and eliminating trigger factors (e.g. lack of sleep) can reduce headaches.

Table 1: Diagnostic criteria for three types of primary headache in adults

(Adapted from the International Classification of Headache Disorders, 2nd edition8)

Episodic tension-type Migraine Cluster

Headache lasting 30 minutes to 7 days

At least two of:
  • bilateral location
  • non-pulsating quality
  • mild to moderate pain intensity
  • not worsened by routine physical activity

Neither of:

  • nausea and/or vomiting
  • photophobia and phonophobia (but may have one or the other)

Headache lasting 4–72 hours

At least two of:

  • unilateral location
  • pulsating quality
  • moderate to severe pain intensity
  • worsened by routine physical activity

At least one of:

  • nausea and/or vomiting
  • photophobia and phonophobia

Differentiating between migraine without aura and episodic tension-type headache may be difficult:

  • without aura: at least 5 attacks
  • with aura: at least 2 attacks

Headache lasting 15–180 minutes

Both of:

  • unilateral location
  • severe to very severe pain around and/or above the eye and/or temple
At least one of:
  • conjunctival injection and/or lacrimation
  • nasal congestion and/or rhinorrhoea
  • eyelid oedema
  • forehead and facial sweating
  • constricted pupil and/or
  • drooping of the upper eyelid
any of these must be on the same side of the face as the headache pain
  • restlessness or agitation.
At least 5 attacks: from one attack every other day up to 8 attacks a day
Be alert for 'red flags' when diagnosing headache

Identifying a serious cause of secondary headache is an essential part of the initial diagnosis. 'Red flag' symptoms and signs are listed in Box 1. Consider secondary headache in anyone with new-onset acute headache or headache different from their usual headache.4 In the context of a comprehensive history and, careful physical and neurological examinations, the presence of red flag symptoms and signs may indicate the need for investigation, such as neuroimaging.7

Box 1: Some 'red flags' when diagnosing headache3,9

A 'new-onset' headache in a person

  • having seizures but who is not an epileptic
  • who is pregnant or post-partum
  • who is taking an anticoagulant
  • who has taken amphetamine or cocaine
  • > 50 years
  • who is young and obese
  • with a history of cancer or immunodeficiency

Headache associated with

  • head injury, especially with loss of consciousness
  • the person being woken from sleep
  • confusion, drowsiness or vomiting
  • fever or neck stiffness
  • focal neurological deficit not seen before in a migraine aura
  • symptoms worsening by coughing or physical activity
  • stroke-like symptoms or signs
  • abrupt onset ('thunderclap') and intense
  • progressive worsening

Neuroimaging is often not needed

Neuroimaging is not usually needed unless a red flag is present.2,10 Neuroimaging is unlikely to show the cause of primary headache and can result in incidental findings. Consider neuroimaging for people whose history and physical and neurological examinations suggest that their headache may be secondary to a serious cause (see above).

Neuroimaging is unlikely to show the cause of primary headache

Most people who present with headache have a primary headache disorder such as tension-type, migraine or cluster headache (Table 1).7 These people are likely to have normal examinations and are unlikely to have any red flag symptoms and signs. Neuroimaging is unlikely to show a cause because primary headaches do not result from structural brain abnormalities.7

Consider neuroimaging for people whose history and examination suggest that their headache may be secondary to a serious cause

People with an abnormal neurological examination are more likely to show a serious cause of headache with neuroimaging.4,11

For example, in a recent 5-year case series of 3655 people with acute headache, 530 had neuroimaging. Some of these people had a red flag indicating a possible serious cause of secondary headache while others did not (but, for example, some had hemiplegic migraine or cluster headache). All 11 serious causes of headache identified by neuroimaging had a red flag.12 Neuroimaging showed many insignificant findings that were unrelated to the headache: in about 1 in every 3 CT scans and about 1 in every 2 MRIs. The number of insignificant abnormalities seen is greater with MRI than with CT imaging (46% and 25%, respectively).12

Box 2: Some serious causes of secondary headache2,3

  • brain tumour
  • carotid or vertebral artery dissection
  • cerebral venous thrombosis
  • encephalitis
  • giant cell arteritis
  • herpes zoster
  • hypertensive encephalopathy
  • idiopathic intracranial hypertension
  • intracranial abscess
  • meningitis
  • primary angle-closure glaucoma
  • reversible cerebral vasoconstriction syndrome
  • subarachnoid or intracranial haemorrhage
  • subdural collection
Neuroimaging can result in incidental findings

Bear in mind the medical, practical and ethical issues associated with incidental findings — neurological abnormalities incidental to the reason for neuroimaging. Incidental findings may cause patient anxiety and clinician uncertainty (which may result in further inappropriate investigations and/or treatment with associated risks).

A recent Canadian audit of CT scans detected incidental findings in about 20% of cases (compared with about 2% of findings potentially related to headache).13

A meta-analysis showed one incidental finding for every 37 people who did not have neurological symptoms and who had a brain MRI (for research purposes or, occupational, clinical or commercial screening).14

Discuss risks and costs of neuroimaging

Neuroimaging has risks and costs. These include risks of the procedure (e.g. exposure to ionising radiation, adverse effects of contrast agents), risks in interpreting the results (e.g. incidental findings, false positives/negatives); and financial and logistic costs (e.g. out-of-pocket expenses to the individual, cost to the health system, waiting time, transport to and from the imaging facility).

Exposure to ionising radiation from a single head CT scan is estimated to increase the average lifetime attributable risk of death from cancer by 0.005% for a 45 year old person.15 Although the individual risk is small, increasing CT use contributes to increased mortality at a population level.15 Radiation dose varies depending on the source: there is no "safe" dose and all doses contribute to lifetime risk (Table 2).16 A 2005 report found that Australian GPs ordered a CT of the brain or head in about 1 in 10 headache problems.17 Avoid ionising radiation in pregnancy or when there is a possibility of pregnancy.9

Table 2: Some radiation sources and doses16

Source of radiation exposure Radiation dose millisieverts (mSv) Range (mSv)
Background radiation
(Average yearly dose Australians are unavoidably exposed to)
Chest X-ray 2 views 0.08 0.05–2
CT scan 3 1–15
MRI 0 0
Expert reviewers

Alessandro S Zagami

Senior Staff Specialist in Neurology, Institute of Neurological Sciences, Prince of Wales Hospital Conjoint Associate Professor, Prince of Wales Clinical School, University of New South Wales

Randall Jones
Consultant Neuroradiologist, Neurological Intervention and Imaging Service of Western Australia

Any correspondence regarding content should be directed to NPS. Declarations of conflicts of interest have been sought from all reviewers.

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