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Headache Appropriate Use Criteria

UC Headache AUC Criteria (pdf)

Priority Clinical Area Coverage

This AUC reasonably addresses common and important clinical scenarios within the "Headache (traumatic and nontraumatic)" Priority Clinical Area (PCA) and thus meets the minimum requirement for qCDSM to cover that PCA. However, by CMS definition of relevancy, it is not considered relevant to that PCA, as further described (See AUC Overview).

Search Strategy and Sources – Completed 2023-04-24

  • Limits:  English, 15 years publication, and adult, 19+
  • Extensive PubMed (Medline), Supplemental: EMBase, Web of Science, and Cochrane Database of Systematic Reviews.

(Headache AND diagnostic imaging(major) AND investigative technique(major)   OR
Headache AND diagnostic imaging AND investigative technique AND review/document type OR
((Headache AND diagnostic imaging  OR craniocerebral trauma/diagnostic imaging (major) ) ) AND

 (practice guidelines as topic OR decision support techniques OR sensitivity and specificity
OR predictive value of tests OR evidence based medicine) )

  • Inclusion of references cited in ACR AC and ACEP guidelines.
    Search expanded to include specific terms including: headache with aura, temporal arteritis, positional headache, trigeminal neuralgia and trigeminal autonomic cephalgia.

Results:

397 publications were identified. Less than 40 were determined to be relevant to the question of appropriateness of imaging of headache in the acute care setting. Many are retrospective or database review and therefore limited due to pre-test bias of who received imaging. Others are limited as "abnormal imaging" is broadly inclusive of findings that may not be causative/associated with headache (e.g. arachnoid cyst, small meningiomas), or present no other outcome measure other than the presence of an abnormality on imaging. The expanded search based on specific terms (listed above) yielded an additional 268 related articles. 63 articles were selected and submitted to the team for grading. 61 were chosen for the AUC.

Recommendations:

The Oxford Centre for Evidence Based Medicine is used for assigning AUC grades. The grades are based on the level of evidence of the references according to the following:

Grade A = Level 1

Grade B = Level 2

Grade C = Level 3 or less

Sudden Onset/Severe/Thunderclap

1a. Non-contrast head CT is appropriate in patients with sudden onset, severe or "thunderclap" headache, given risk for subarachnoid hemorrhage and morbidity associated with ruptured aneurysms.  Evidence Grade: A
Two prospective studies attempted to identify a subset of adult ED patients with acute headache where subarachnoid hemorrhage (SAH) could be excluded. These 2 studies included 4130 patients of which 262 (6.3%) were diagnosed with SAH. Perry et al (Perry 2010) identified 3 clinical decision rules, all with 100% sensitivity in identifying SAH. The same group attempted to externally validate these 3 rules in a follow up study (Perry 2013). A combination of age 40 years or older, neck pain or stiffness, witnessed loss of consciousness, or onset during exertion had a 98.5% (95%CI, 94.6%-99.6%) sensitivity and 27.5% (95%CI, 25.6%-29.5%) specificity for SAH. The addition of “thunderclap headache” and “limited neck flexion on examination,” the Ottawa SAH rule (Medical Advisory Secretariat, 2010) resulted in 100% sensitivity (95%CI, 97.2%-100.0%) and 15.3% specificity (95%CI, 13.8%-16.9%). Strict application of the latter rule would increase CT utilization by about 3%.  The Ottawa SAH rule is the most rigorously defined combination of clinical findings that identify low risk patients with acute, sudden onset, non-traumatic headache that may not require imaging or workup for SAH.  While sensitive for identifying SAH, this rule is not specific and has not been demonstrated to be better than clinical practice and thus cannot be recommended at this time.

 

1b. CTA and MRA are appropriate for sudden onset headache evaluation when concerned for RCVS, although overall clinical utility is low. Evidence Grade: B
Reversible cerebral vasoconstrictive syndrome (RCVS) may also present as an acute onset severe headache, recurring over 1-2 weeks. This is more common in, but not exclusive to women and has been associated with triggers including sexual activity, exertion, Valsalva, emotion, and bathing, or secondary in the post-partum setting or following exposure to vasoactive substances (Oleson ICHD-3 2018). The primary CT, CTA or MRI may be normal (Rocha 2019, Oleson ICHD-3 2018), however clinical symptoms do not accurately predict imaging yield (Lee 2018). The disease is by definition reversible, however stroke can occur in the setting of RCVS.

 

Chronic primary headache, no new features and headache, new neurologic SX

2a. Imaging is usually not appropriate in patients with chronic primary headache and no new features.
2b. Imaging may be appropriate in patients with chronic headache and new neurological symptoms.  Evidence Grade: B

Ten articles discussed primary headache imaging. In a prospective study, MR imaging in the presence of neurological symptoms (confusion, change in personality, hemianopia, imbalance) found 5.5% clinically important findings, a significant number (Clarke 2010).  Stratifying primary versus secondary headaches (thunderclap, neurologic signs, vomiting, syncope, fever, neck stiffness, recent onset, worsening headache, or persistent) resulted in 64% specificity (Grimaldi, 2009).  A survey of ED visits in the US found that in imaging of non-migraine headache in the ED, the yield was 5.2% using both MRI and CT (Gilbert 2012).  In a prospective imaging study of every patient with a headache, the only variable that appeared to correlate with abnormal imaging was an abnormal exam (Sempere 2005).

There is no benefit to imaging patients with chronic migraine who lack neurologic deficits.  In a prospective study of sequential patients, the yield of imaging (MRI and CT) migraine patients was 0.4%, and tension headache 0.8%.  In the discussion section it was noted that age greater or equal to 65 may increase the yield from 0.6% to 1.1%.  A meta-analysis of migraine and tension headache found 0.2% had abnormal imaging (Sempere 2005).   Another prospective study found a similarly low rate of significant abnormalities in migraine presentation of 1.2% and 0.9% in tension type (Clarke 2010). In a retrospective study using MRI in chronic recurrent headaches only 0.7% were clinically important (Tsushima 2005).  In a US ED survey using CT or MRI found pathological findings in 1% of those with a migraine diagnosis (Gilbert 2012).

The primary concern regarding migraine with aura is overlap of symptoms with TIA or acute stroke (Lebedeva 2017)Diffusion weighted MRI is the most sensitive way to discriminate. Decreased cerebral perfusion has been described in MRI studies of migranous aura patients as not conforming to an arterial territory (Floery 2012, Forster 2014). MR angiography has not shown to contribute to diagnosis or alter management in the setting of migraine with or without aura (Paemeleire 2005). There are many papers which have described the number, size, distribution and natural history of small white matter lesions in patients with migraine with aura compared to migraine alone, and other non-headache cohorts (Dinia 2013, Gaist 2016, Kruit 2005). However, most of these lesions are clinically silent, their distribution did not correlate with aura symptoms and detection of these lesions did not result in changes to clinical management (Rossato 2010).  Recent population based studies in Australia (Vijaratnam 2016) and the UK (Clarke 2010) have not shown any clinical value in imaging of patients with migraine with aura.

If patients do not meet criteria for primary headache, imaging may be helpful.   The overall yield of imaging all non-traumatic headaches in the ED in the US is between 3.5% and 5.5% (Gilbert 2012, Goldstein 2006).  This is similar to rates in the ambulatory care setting of 5% (Becker 1993). Only 0.01% led to neurosurgical intervention in an HMO study of chronic headache and normal exam (Weingarten 1992).  A review of 8 CT studies from 1973-1993 of patients with headache and normal exams found: 0.8% brain tumor, AVM 0.3%, hydrocephalus 0.3%, SDH 0.2%, cerebrovascular 1.2% (Frishberg 1994).  In comparison using MRI of the asymptomatic population there are 0.6% to 1.1% incidental findings (Sempere 2005). 

 

Headache after minor head trauma

3.  Non-contrast head CT may be appropriate for patients with headache in the setting of minor acute head trauma, however must be considered in the context of the entire clinical exam. Evidence Grade: A

There is discrepancy in the two major head trauma imaging algorithms as to the prognostic value of headache in the setting of recent minor head trauma.

The Canadian CT Head Rule (CCHR) (Stiell 2001) was a prospective cohort of 3121 head trauma patients presenting with GCS 13-15 across 10 Emergency departments. 2078 were imaged with non-contrast head CT. 1% required neurological intervention and 8% had brain injury that required observation. Headache was a presenting symptom in 45% of enrolled patients. The presence of headache in the setting of minor head trauma was not identified to be an independent high-risk factor to necessitate imaging.

The New Orleans Criteria (NOC) (Haydel 2000) was defined by a prospective cohort of 520 consecutive patients with minor head trauma (GCS 15) and no neurological deficit, and tested against a group of 909 additional patients with similar presentation. 6.9% of the initial group and 6.3% of the 2nd group had abnormal CT scans. 0.4% of patients required neurosurgical intervention. Headache was a presenting symptom in 24% of enrolled patients, with p=0.16 and likelihood ratio of 2.0 of a positive scan. The addition of headache to the other risk factors of short-term memory deficits, intoxication, age >60 yr and seizure did not affect sensitivity (97%) and resulted in decreased specificity from 31 to 25%.

Comparison of the two rules was performed prospectively in large cohorts of adults with head trauma and GCS 15 by the Canadian group in 1822 patients (Stiell 2005), in the Netherlands across 3181 patients (Smits 2005), and in Tunisia in 1582 patients (Bouida 2013). The presence of headache was not statistically predictive of the presence of brain injury on head CT in the Canadian study (p= 0.69) or Tunisian study (k=0.44). On the Dutch study, 5 patients with traumatic findings were identified by the NOC due to headache, and would have been missed if CCHR alone was applied in isolation. The Tunisian study discussed that the inclusion of headache as a screening factor added on to the CCHR would improve the model to reduce unnecessary head CTs without missing a significant intracranial injury.

 

Suspected intracranial hypertension

4a. Patients with suspected intracranial hypertension should undergo brain MRI as part of initial presentation evaluation.
4b. If papilledema is present, or new onset unexplained visual changes, dedicated venography should be performed concurrently.  Evidence Grade: B

Idiopathic intracranial hypertension (IIH) most commonly presents in obese young women and occasionally children, and may occur without or with papilledema (Peng 2012).The identification of papilledema is the gold standard.  Acknowledging that a dilated eye exam may not be possible in all clinical scenarios, new onset unexplained visual changes may influence the urgency of imaging, and the inclusion of MR venography as part of the initial exam. CT and CT venography are complimentary if patients cannot have MR imaging. MRI may reveal secondary signs of chronic IIH such as dilatation of the optic nerve sheath, decreased volume/height of the pituitary gland (Dong 2016), as well as exclude a space-occupying intracranial process and cerebral venous thrombosis. Ultimately, lumbar puncture can be both diagnostic and therapeutic. Recent literature focuses on techniques for venography, but not the prevalence of imaging findings of IIH or cerebral venous thrombosis (CVT) in the setting of positional headache, or accuracy of imaging modalities. Radiology protocols for MR venography without or with contrast may vary by site and scanner.

 

New non-trauma HA with Horner's, meningitis, encephalitis, vomiting or neurosurgery within 30 days

5.  Imaging for patients with new non-traumatic headache in the setting of other new features (focal neurological deficit, Horner's syndrome, vomiting, suspected meningitis or encephalitis) should be guided on these features, not that the patient has a headache.  Evidence: Panel consensus

 

Trigeminal neuralgia and Trigeminal autonomic cephalgias (TAC)

6a. MR imaging of the trigeminal nerves without and with contrast and head MRA may be appropriate in patients with classic trigeminal neuralgia however must be considered in the context of the entire clinical exam.
6b. MR imaging of the brain, brainstem and cranial nerves without and with contrast may be appropriate in patients with symptomatic trigeminal neuralgia, however must be considered in the context of the entire clinical exam.
Evidence Grade: C
The AAN guidelines found Level C evidence for MR imaging in patients with trigeminal neuralgia to discriminate between classic (idiopathic or associated with vascular compression) from symptomatic (associated with multiple sclerosis lesions, skull base abnormalities or tumors). Because of a high diagnostic accuracy, MRI might reasonably be foregone in a patient with normal trigeminal reflexes (Gronseth 2008).

Given association with symptomatic trigeminal neuralgia, MRI is recommended for patients are under age 40 or presenting with bilateral symptoms. 

For classic trigeminal neuralgia, MRI is the preferred imaging modality to evaluate suspected vascular compression using a combination of anatomic, angiographic and post-contrast sequences, reporting sensitivity >95% across platforms ranging from 0.5T – 3T (Kuncz 2006, Anderson 2006, Tanrikulu 2016, Vergani 2011), however data in the literature varies across differing techniques (Gronseth 2008). CTA may be an alternative (Balaizin 2017) for patients unable or unwilling to have MRI.

It is important for the referring physician to be aware of institutional protocols, with radiologist consultation to ensure adequate coverage and sequences.

7.  Brain MR imaging without and with contrast is usually appropriate for initial evaluation of patients with trigeminal autonomic cephalgias (TAC). Evidence Grade: C

The trigeminal autonomic cephalgias (cluster headache, paroxysmal hemicrania, hemicrania continua, Short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), short-lasting unilateral neuralgiform headache with cranial autonomic symptoms (SUNA)) are primary headache disorders (Olesen 2018).Some symptoms may overlap with trigeminal neurovascular compression syndromes, prompting authors to advocate for MRI in these patients (Favoni 2013, Kitahara 2015), based on case reports totaling 36 patients who have undergone microvascular decompression. Case series/review revealed 31 structural lesions associated with TAC or TAC-like symptoms identified on MRI including intracranial vascular abnormalities and pituitary tumors, among others (Favier 2007). It is important for the referring physician to be aware of institutional protocols, with radiologist consultation to ensure adequate coverage and sequences.

 

Suspected temporal arteritis

8.  If a headache is suspected to be due to temporal arteritis, appropriate clinical management should be undertaken. Evidence: Panel consensus

The American College of Rheumatology established criteria in 1990 for the diagnosis of temporal (giant cell) arteritis, when 3 of the following 5 findings are established: 1) age of onset >50 yrs, 2) new onset headache, 3) temporal artery tenderness or decreased pulse, 4) ESR > 50 mm/hr, and 5) positive biopsy result, with high sensitivity of the first 4 criteria, and biopsy as the specific metric.

Multiple case series in the Rheumatology literature have evaluated the ability of ultrasound (Karassa 2005, Monti 2018, Karahaliou 2008, Habib 2011, Croft 2015, Maldini 2010), MRI (Bley 2007, Klink 2014, Veldhoen 2014, Rheaume 2017) and PET/CT (Larieviere 2016) to diagnose temporal arteritis, which is beyond the scope of this guideline. There is no current identified literature supporting imaging in this setting.

 

Headache in patient of advancing age

9.  Advancing age is an independent factor for appropriateness of imaging of new onset or progressive headache, however there is not a discrete age threshold. Evidence Grade: C

Multiple studies have identified a higher odds ratio for intracranial pathology identified on imaging in the setting of non-traumatic, new onset or progressive headache with increasing age, however studies vary with the lower threshold of the cohort ranging between 50 - 65 years old as summarized below. Other studies which have looked at this issue predate the range of the current literature search however do not add additional clarity.

≥ 50     Goldstein 2006, Gilbert 2012

≥ 55     Bent 2015

≥ 60     Tung 2014

 

New/progressive headache in pregnancy

10.  Non–contrast CT or MRI may be appropriate in pregnancy for evaluation of isolated new, progressive headache or change in pattern of pre-existing headaches. The presence of any other suspicious features should pre-empt headache as the underlying indication for imaging. Evidence Grade: C
There is limited recent data to address this concern. A retrospective review of 63 pregnant women with new or progressive headache during pregnancy was limited as 43% had additional abnormal neurological findings and headaches were often accompanied by additional symptoms such as photophobia, meningismus, nausea, vomiting, fever or seizures (Ramchandren 2007). The article did not address isolated headache as a predictive factor for intracranial abnormality. A more recent retrospective study of 76 pregnant women who had MR imaging for headache within 24 hours of neurological consult (Raffaelli 2018). Imaging revealed findings in 21 (27.6%) related to symptoms, including intracranial hemorrhage, cerebral venous thrombosis, infarct, PRES and acute sinusitis. Three of those patients also had seizures, 4 had change in consciousness and 3 had fever, confounding headache as the primary indication.

There is more extensive literature regarding the management of headache in pregnancy, not addressing the role of imaging specifically. Concerns are for pre-eclampsia, venous sinus thrombosis, pituitary apoplexy, ruptured AVM or aneurysm, hypertensive infarct, idiopathic intracranial hypertension, or meningitis, as well as management of chronic headache disorders due to medication changes during pregnancy.

Imaging via CT or MRI should be based on institutional protocols. Contrast is not indicated as part of the first line evaluation of headache in pregnancy.

 

Isolated headache, cancer (known or suspected)

11.  Imaging is appropriate for evaluation of isolated headache in oncologic patients. Evidence Grade: C

There is limited recent data to address this concern. A study of 68 cancer patients presenting with new or changing headache underwent MRI and structured exam. 32% were found to have intracranial metastases. Significant clinical predictors were headache ≥ 10 weeks, non-tension type headache, and emesis however few patients would be excluded from MR imaging given low specificity factors (Christiaans 2002)

MRI without and with contrast is preferred. CT may be done based on acuity and severity of symptoms, and available resources.

 Suspected sinus-related headache; Suspected odontogenic-related headache and Suspected orbital-related headache

12.  Imaging for patients with suspected dental, sinus or orbital etiology for headache should be guided on these features, co-morbidities, and clinical exam findings. Evidence: Panel Consensus

Imaging should be tailored to the suspected site, such as non-contrast sinus CT for suspected sinus-related headache, post-contrast maxillofacial CT for suspected odontogenic infection as a source of headache, or post-contrast orbital CT for suspected orbital process as a source of headache.

 

References Cited and OCEDM Level of Evidence:

  1. Anderson, V. C., et al. (2006). High-resolution three-dimensional magnetic resonance angiography and three-dimensional spoiled gradient-recalled imaging in the evaluation of neurovascular compression in patients with trigeminal neuralgia: a double-blind pilot study. Neurosurgery 58(4): 666-673; discussion 666-673. Level 2
  2. Aranda-Valera, I. C., et al. (2017). Diagnostic validity of Doppler ultrasound in giant cell arteritis. Clin Exp Rheumatol 35 Suppl 103(1): 123-127. Level 2
  3. Aschwanden, M., et al. (2015). The ultrasound compression sign to diagnose temporal giant cell arteritis shows an excellent interobserver agreement. Clin Exp Rheumatol 33(2 Suppl 89): S-113-115. Evidence: Level 3
  4. Baliazin, V. A., et al. (2017). Computed Tomography in the Diagnosis of Classical Trigeminal Neuralgia. J Comput Assist Tomogr 41(4): 521-527. Level 3
  5. Becker, L. A., et al. (1993). Use of CT scans for the investigation of headache: a report from ASPN, Part 1. J Fam Pract 37(2): 129-134. Level 2
  6. Bent, C., et al. (2015). Clinical scoring system may improve yield of head CT of non-trauma emergency department patients. Emerg Radiol 22(5): 511-516. Level 2
  7. Bley, T. A., et al. (2007). Diagnostic value of high-resolution MR imaging in giant cell arteritis. AJNR Am J Neuroradiol 28(9): 1722-1727. Level 3
  8. Bouida, W., et al. (2013). Prediction value of the Canadian CT head rule and the New Orleans criteria for positive head CT scan and acute neurosurgical procedures in minor head trauma: a multicenter external validation study. Ann Emerg Med 61(5): 521-527. Level 1
  9. Christiaans, M. H., et al. (2002). Prediction of intracranial metastases in cancer patients with headache. Cancer 94(7): 2063-2068. Level 3
  10. Clarke, C. E., et al. (2010). Imaging results in a consecutive series of 530 new patients in the Birmingham Headache Service. J Neurol 257(8): 1274-1278. Level 2
  11. Cox, B., et al. (2016). Magnetic resonance neurography in the management of peripheral trigeminal neuropathy: experience in a tertiary care centre. Eur Radiol 26(10): 3392-3400. Level 4
  12. Croft, A. P., et al. (2015). Cranial ultrasound for the diagnosis of giant cell arteritis. A retrospective cohort study. J R Coll Physicians Edinb 45(4): 268-272. Level 3
  13. Dinia, L., et al. (2013). White matter lesions progression in migraine with aura: a clinical and MRI longitudinal study. J Neuroimaging 23(1): 47-52.  Level 3
  14. Dong, C., et al. (2016). Morphometric MRI changes in intracranial hypertension due to cerebral venous thrombosis: a retrospective imaging study. Clin Radiol 71(7): 691-697.  Level 3
  15. Favier I, Van Vliet JA, Roon KI et al. (2007) Trigeminal autonomic cephalagias due to structural lesions: A review of 31 cases. Arch Neurol. 64(1):25-31. Level 3
  16. Favoni, V., et al. (2013). SUNCT/SUNA and neurovascular compression: new cases and critical literature review. Cephalalgia 33(16): 1337-1348. Level 3
  17. Floery, D., et al. (2012). Acute-onset migrainous aura mimicking acute stroke: MR perfusion imaging features. AJNR Am J Neuroradiol 33(8): 1546-1552.  Level 3
  18. Forster, A., et al. (2014). Perfusion patterns in migraine with aura. Cephalalgia 34(11): 870-876. Level 3
  19. Frishberg, B. M. (1994). The utility of neuroimaging in the evaluation of headache in patients with normal neurologic examinations. Neurology 44(7): 1191-1197. Level 3
  20. Gaist, D., et al. (2016). Migraine with aura and risk of silent brain infarcts and white matter hyperintensities: an MRI study. Brain 139(Pt 7): 2015-2023. Level 2
  21. Gilbert, J. W., et al. (2012). Atraumatic headache in US emergency departments: recent trends in CT/MRI utilisation and factors associated with severe intracranial pathology. Emerg Med J 29(7): 576-581.  Level 3
  22. Goldstein, J. N., et al. (2006). Headache in United States emergency departments: demographics, work-up and frequency of pathological diagnoses. Cephalalgia 26(6): 684-690. Level 2
  23. Grimaldi, D., et al. (2009). Risk stratification of non-traumatic headache in the emergency department. J Neurol 256(1): 51-57.  Level 2
  24. Gronseth, G., et al. (2008). Practice parameter: the diagnostic evaluation and treatment of trigeminal neuralgia (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology and the European Federation of Neurological Societies. Neurology 71(15): 1183-1190. Guidelines, not primary literature.
  25. Habib, H. M., et al. (2012). Color duplex ultrasonography of temporal arteries: role in diagnosis and follow-up of suspected cases of temporal arteritis. Clin Rheumatol 31(2): 231-237. Level 3
  26. Haydel, M. J., et al. (2000). Indications for computed tomography in patients with minor head injury. N Engl J Med 343(2): 100-105. Level 1
  27. Honningsva LM, et al. (2016). Intracranial abnormalities and headache: A population-based imaging study (HUNT MRI). Cephalalgia 36(2): 113-121.  Level 1
  28. Karahaliou, M., et al. (2006). Colour duplex sonography of temporal arteries before decision for biopsy: a prospective study in 55 patients with suspected giant cell arteritis. Arthritis Res Ther 8(4): R116.  Level 3
  29. Karassa, F. B., et al. (2005). Meta-analysis: test performance of ultrasonography for giant-cell arteritis. Ann Intern Med 142(5): 359-369. Level 3
  30. Kitahara, I., et al. (2015). Pathogenesis, Surgical Treatment, and Cure for SUNCT Syndrome. World Neurosurg 84(4): 1080-1083.  Level 3
  31. Klink, T., et al. (2014). Giant cell arteritis: diagnostic accuracy of MR imaging of superficial cranial arteries in initial diagnosis-results from a multicenter trial. Radiology 273(3): 844-852.  Level 3
  32. Kruit, M. C., et al. (2005). Infarcts in the posterior circulation territory in migraine. The population-based MRI CAMERA study. Brain 128(Pt 9): 2068-2077. Level 3
  33. Kruit, M. C., et al. (2009). Iron accumulation in deep brain nuclei in migraine: a population-based magnetic resonance imaging study. Cephalalgia 29(3): 351-359.  Level 3
  34. Kuncz, A., et al. (2006). Comparison of clinical symptoms and magnetic resonance angiographic (MRA) results in patients with trigeminal neuralgia and persistent idiopathic facial pain. Medium-term outcome after microvascular decompression of cases with positive MRA findings. Cephalalgia 26(3): 266-276.  Level 3
  35. Lariviere, D., et al. (2016). Positron emission tomography and computed tomography angiography for the diagnosis of giant cell arteritis: A real-life prospective study. Medicine (Baltimore) 95(30): e4146.  Level 4
  36. Lebedeva, E. R., et al. (2017). Prospective testing of ICHD-3 beta diagnostic criteria for migraine with aura and migraine with typical aura in patients with transient ischemic attacks. Cephalalgia: 333102417702121.  Level 2
  37. Lee M.J., et al. (2018). Serial testing of the ICHD-3 beta diagnostic criteria for probable reversible cerebral vasoconstriction syndrome: A prospective validation study. Cephalalgia 38(10):1665-71.  Level 2
  38. Maldini, C., et al. (2010). Limited value of temporal artery ultrasonography examinations for diagnosis of giant cell arteritis: analysis of 77 subjects. J Rheumatol 37(11): 2326-2330. Level 3
  39. Medical Advisory Secretariat (2010). Neuroimaging for the evaluation of chronic headaches: an evidence-based analysis. Ont Health Technol Assess Series [Internet]. 10(26): 1-57. Policy review, not primary literature.
  40. Monti, S., et al. (2018). The proposed role of ultrasound in the management of giant cell arteritis in routine clinical practice. Rheumatology (Oxford) 57(1): 112-119. Level 3
  41. Olesen, J. et. al. (2018). The International Classification of Headache Disorder, 3rd. Cephalalgia 38(1): 1-211. Guidelines, not primary literature.
  42. Paemeleire, K., et al. (2005). Magnetic resonance angiography of the circle of Willis in migraine patients. Clin Neurol Neurosurg 107(4): 301-305.  Level 3
  43. Peng, K. P., et al. (2012). High-pressure headaches: idiopathic intracranial hypertension and its mimics. Nat Rev Neurol 8(12): 700-710. Review article not primary literature.
  44. Perry, J. J., et al. (2013). Clinical decision rules to rule out subarachnoid hemorrhage for acute headache. Jama 310(12): 1248-1255.  Level 1
  45. Perry, J. J., et al. (2010). High risk clinical characteristics for subarachnoid haemorrhage in patients with acute headache: prospective cohort study. Bmj 341: c5204.  Level 2
  46. Raffaelli B., et al. (2018). Brain imaging in pregnant women with acute headache. J Neurol 265(8):1836-43.  Level 3
  47. Ramchandren, S., et al. (2007). Emergent headaches during pregnancy: correlation between neurologic examination and neuroimaging. AJNR Am J Neuroradiol 28(6): 1085-1087. Level 3
  48. Rheaume, M., et al. (2017). High-Resolution Magnetic Resonance Imaging of Scalp Arteries for the Diagnosis of Giant Cell Arteritis: Results of a Prospective Cohort Study. Arthritis Rheumatol 69(1): 161-168. Level 3
  49. Rocha E.A., et al. (2019). RCVS2 score and diagnostic approach for reversible cerebral vasoconstrictive syndrome. Neurology 92(7):e639-47. Level 3
  50. Rossato, G., et al. (2010). Cerebral distribution of white matter lesions in migraine with aura patients. Cephalalgia 30(7): 855-859.  Level 3
  51. Sempere, A. P., et al. (2005). Neuroimaging in the evaluation of patients with non-acute headache. Cephalalgia 25(1): 30-35. Level 2
  52. Smits, M., et al. (2005). External validation of the Canadian CT Head Rule and the New Orleans Criteria for CT scanning in patients with minor head injury. Jama 294(12): 1519-1525.  Level 2
  53. Stiell, I. G., et al. (2005). Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. Jama 294(12): 1511-1518.  Level 2
  54. Stiell, I. G., et al. (2001). The Canadian CT Head Rule for patients with minor head injury. Lancet 357(9266): 1391-1396. Level 1
  55. Tanrikulu, L., et al. (2016). New Clinical and Morphologic Aspects in Trigeminal Neuralgia. World Neurosurg 92: 189-196.  Level 3
  56. Tsushima, Y., et al. (2005). MR imaging in the evaluation of chronic or recurrent headache. Radiology 235(2): 575-579.  Level 3
  57. Tung, C., et al. (2014). Emergency room decision-making for urgent cranial computed tomography: selection criteria for subsets of non-trauma patients. Acta Radiol 55(7): 847-854. Level 3
  58. Veldhoen, S., et al. (2014). MRI displays involvement of the temporalis muscle and the deep temporal artery in patients with giant cell arteritis. Eur Radiol 24(11): 2971-2979.  Level 3
  59. Vergani, F., et al. (2011). Preoperative MRI/MRA for microvascular decompression in trigeminal neuralgia: consecutive series of 67 patients. Acta Neurochir (Wien) 153(12): 2377-2381; discussion 2382.  Level 3
  60. Vijiaratnam, N., et al. (2016). Migraine: Does aura require investigation?  Clin Neurol Neurosurg 148: 110-114.  Level 3
  61. Weingarten, S., et al. (1992). The effectiveness of cerebral imaging in the diagnosis of chronic headache. Arch Intern Med 152(12): 2457-2462.  Level 2