Clinical guidance for MRI referral

MRI of the head

Unexplained chronic headache

MBS item description

Referral by a medical practitioner (excluding a specialist or consultant physician) for a scan of head for a patient 16 years or older for unexplained chronic headache with suspected intracranial pathology (R) (K) (Contrast) (Anaes.)

Key information

  • In most headache syndromes there is a lack of evidence to suggest imaging improves health outcomes.
  • Most common headache types can be diagnosed on history and examination.
  • Investigations including neuroimaging are only indicated when history or examination suggests headache is secondary to serious intracranial pathology.
  • Abnormalities detected on neuroimaging may not be clinically significant but may lead to further unnecessary investigations or interventions.
  • Neuroimaging for reassurance is not recommended.
  • ​This guidance does not cover acute headache.

Explanation
B - High-quality systematic reviews of case–control or cohort studies, directly applicable to the target population, and demonstrating overall consistency of results
or
Extrapolated evidence from high quality meta-analyses, systematic reviews of randomised controlled trials (RCTs), or RCTs with a very low risk of bias or well conducted meta-analyses, systematic reviews, or RCTs with a low risk of bias.

Recommendation
Neuroimaging should be considered in patients with headache and an unexplained abnormal finding on the neurological examination

Explanation
The US Headache Consortium achieved consensus on the recommendation in the absence of relevant RCTs

Recommendation
Neuroimaging could be considered for headache worsened by Valsalva manoeuvre, headache causing awakening from sleep, new headache in an older patient, or progressively worsening headache†

Grade: None given

Recommendation
Neuroimaging is not indicated for people diagnosed with tension-type headache, migraine, cluster headache or medication overuse headache solely for reassurance

Headache is one of the most common neurological problems presented to GPs. People with headache and their healthcare professionals can be worried about possible serious underlying disease.20,21

Headaches disorders are classified as either primary or secondary and these are further divided into specific headache type.20,22

Primary headache disorders, including migraine, tension-type and cluster headaches, account for the majority of headaches.23The aetiology of primary headaches is poorly understood and they are differentiated by their clinical patterns.22

Table 2.4 Clinical patterns of primary headaches

Table 2.4

Clinical patterns of primary headaches

Investigations, including neuroimaging, do not contribute to the diagnosis of migraine or tension-type headache. Some guidelines, but not all, recommend brain MRI in patients with cluster headache due to the small possibility of a serious underlying structural lesion.24

Secondary headaches, are attributed to underlying disorders.20 The most common secondary headache is due to medication overuse, which occurs most commonly in those taking medication for a primary headache disorder.20 Headache may also be referred from the muscles, joints and ligaments of the upper three cervical segments due to the convergence of nociceptive afferent nerves from these segments with those of the trigeminal nerve.25

Serious causes of secondary headaches include tumour, infection, bleeding and arteritis.24,26 These warrant further investigation, which may include imaging. Note that MRI will not detect all serious causes of secondary headache, such as giant cell arteritis.6

Table 2.5 Intracranial tumours

Table 2.5

Intracranial tumours


Table 2.6 Giant cell arteritis

Table 2.6

Giant cell arteritis


For detailed explanations of headache classifications go to the International Headache Society Classification page.

What findings increase the suspicion of intracranial pathology?

People with headache alone are unlikely to have serious underlying disease.22 Serious intracranial pathology as the cause of headache is rare (e.g. space-occupying lesion <1%, idiopathic intracranial hypertension <1%, chronic meningitis <1% and giant cell arteritis <1%).6

The SNOOP mnemonic is a useful reminder of clinical features that may indicate a secondary headache with serious underlying cause.27,28

Table 2.7 The SNOOP-4 mnemonic

Table 2.7

The SNOOP-4 mnemonic

History

Patients with increased intracranial pressure may report symptoms such as:

  • a frontal headache that is worse after lying down, most notable in the morning and wakes the patient from sleep but improves during the day
  • vomiting, particularly early morning and not associated with nausea
  • blurred vision
  • personality or behavioural changes.

In imaging studies, the following symptoms have been shown to increase the odds of finding a significant abnormality on neuroimaging: rapidly increasing headache frequency, history of dizziness or lack of coordination, history of subjective numbness or tingling, or history of headache causing awakening from sleep.21

Physical examination

Examination of patients presenting with headache should include:20,22

  • blood pressure
  • examination of temporal arteries
  • neck examination, including palpation for posterior cervical tenderness
  • fundoscopy (where the doctors is experienced in its use)
  • cranial nerve assessment, especially pupils, visual fields, eye movements, facial power and sensation, and bulbar function (soft palate, tongue movement)
  • assessment of tone, power, reflexes and coordination in all four limbs
  • plantar responses
  • assessment of gait, including heel–toe walking.

There should be more detailed assessment if prompted by the history. The examination should be tailored to include any focal neurological symptoms.20

An abnormal neurological examination significantly increases the likelihood of finding an abnormality on neuroimaging.21

The choice between CT and MRI may depend on the situation. In emergency situations, CT is generally recommended.

SIGN suggests that MRI is the imaging modality of choice because of its greater sensitivity.20

MRI does appear to be more sensitive in finding white matter lesions and developmental venous anomalies than CT.20,21However, this greater sensitivity appears to be of little clinical importance in the evaluation of patients with chronic headache, as MRI may just be better at identifying incidental abnormalities.21

The relative rarity of secondary headaches – compared with the large number of patients with primary headache – and the potential to reveal incidental abnormalities raise concerns about the balance between risk and benefits of neuroimaging studies (either CT or MRI) to exclude underlying causes of headache.21

The major benefit of neuroimaging is the detection of significant and treatable lesions that impact the quality of life.21 The risk is finding incidental abnormalities that may cause anxiety and potential harm with further investigations and treatments. MRI, with its greater sensitivity, may be better at finding abnormalities – both significant and insignificant.

The ‘benefit’ of alleviating patient anxiety about having an underlying pathologic condition by obtaining a negative or normal scan does not appear to be a significant or sustained benefit.20,22 A randomised controlled trial of 150 patients with chronic daily headache in a specialist clinic found that patients who received MRI had a decrease in anxiety levels at 3 months, but that the reduction in anxiety was not maintained at 1 year.20

Other risks include false reassurance from an inadequate study and the risk of over-sedation in claustrophobic patients having MRI scans.21

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