The levels of evidence (class I-IV) supporting the recommendations and ratings of recommendations (A-C) are defined at the end of the "Major Recommendations" field.
Electroencephalogram (EEG)
Routine EEG with Standard Visual Interpretation
Interictal EEG is not routinely indicated in the diagnostic evaluation of headache patients. Interictal EEG is only indicated if the clinical history suggests a possible diagnosis of epilepsy, e.g., in the case of (i) unusually brief headache episodes; (ii) unusual aura symptoms (e.g., gastric/olfactory sensations, circular visual symptoms); (iii) headache associated with unusually brief auras or aura-like phenomena; (iv) headache associated with severe neurological deficits; and (v) other risk factors for epilepsy. Ictal EEG is indicated during episodes suggesting complicated aura and during auras associated with decreased consciousness or confusion.
Quantitative EEG Methods (Frequency Analysis with or without Topographic Mapping)
Current quantitative EEG methods are not routinely indicated in the diagnostic evaluation of headache patients.
Quantitative frequency analysis of EEG must always be recorded with raw EEG data and interpreted by a skilled physician in order to avoid misinterpretation of technical artifacts, normal state fluctuations and various physiological rhythms.
Analysis of Photic Driving
Photic driving may be increased in migraine and tension-type headache (TTH) patient groups as compared with headache-free subjects. The specificity of the method is not yet sufficiently documented.
There is not enough evidence to suggest that the photic driving methods that are currently in use can reliably discriminate either between migraine and nonmigraine primary headache patients or between primary headache patients and headache-free subjects.
This is a class II level of evidence and the grade of recommendation is B.
Evoked Potentials (EPs)
The literature data, often conflicting, failed to demonstrate the usefulness of EPs as a diagnostic tool in migraine. Findings should therefore be replicated before visually evoked potentials (VEPs) can be recommended in the diagnosis of migraine (not enough data are available for other types of headache). In conclusion, the Task Force does not recommend the use of EPs in the diagnosis of headache disorders.
This is a class II level of evidence, but the literature contains contrasting data and the clinical significance of abnormalities is poorly understood. The grade of recommendation is B.
Reflex Responses
Most of the neurophysiological investigation techniques have only limited usefulness in the diagnosis of headache. Further research in large populations is needed in order to establish which electrophysiological markers could be relevant in clinical practice.
This is a class IV level of evidence for nociceptive flexion reflex (not blinded studies), and class III for corneal reflex and blink reflex. The grade of recommendation is C and B respectively. As for exteroceptive suppression of masticatory muscle activity, only few blinded studies (class III) fail to confirm previous investigations: the grade of recommendation is C.
Autonomic Tests
Studies of autonomic functions in migraine and cluster headache were mostly focused on autonomic systems innervating specific target organs which, anatomically and functionally, are not necessarily related to the supposed autonomic origin of the pain. Autonomic parameters are confounded by effector organ response characteristics. Therefore, there is no clear evidence justifying the recommendation of autonomic tests for the routine clinical examination of headache patients.
This is a class IV level of evidence and the grade of recommendation is C.
Clinical Tests, Pressure Pain Thresholds (PPTs), and Electromyography (EMG) (with Special Reference to TTH)
Tenderness recorded by manual palpation is the most specific and sensitive test in patients with TTH, and can therefore be recommended as a routine clinical test in contrast to EMG and pressure pain thresholds. However, this manual palpation is non-specific and cannot be used to discriminate between different coexisting primary or secondary headaches.
This is a class IV level of evidence and the grade of recommendation is C (few blinded studies mainly concerning methodology in healthy volunteers).
Neuroimaging
When neuroimaging is warranted, the most sensitive method should be used, and magnetic resonance imaging (MRI) and not computed tomography (CT) is recommended in these cases.
The grade of recommendation is C, as most studies are non-analytical and although there exist a few randomized clinical trials, some of them are not directly relevant to these recommendations (class IV).
Specific recommendations are:
- In adult and paediatric patients with migraine, with no recent change in pattern, no history of seizures, and no other focal neurological signs or symptoms, the routine use of neuroimaging is not warranted.
- In patients with atypical headache patterns, a history of seizures, and/or neurological signs or symptoms, or symptomatic illness such as tumours, acquired immunodeficiency syndrome (AIDS), and neurofibromatosis, MRI may be indicated (to be carefully evaluated in each case).
Single-Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET)
If attacks can be fully accounted for by the standard headache classification (International Headache Society), a PET or SPECT scan will generally be of no further diagnostic value. Nuclear medicine examinations of cerebral circulation and metabolism can be carried out in subgroups of headache patients for diagnosis and evaluation of complications. Regional cerebral blood flow (rCBF) recordings can be of particular value in patients in whom the standard classification (International Headache Society) cannot be fully applied, when patients experience unusually severe attacks, or the quality or severity of attacks has changed. rCBF recordings should then be carried out both during an attack (if possible several repeated scans) and interictally (at a time interval of >5 days after an attack). Quantifiable rCBF measurements are preferable to distribution images.
This is a class IV level of evidence, i.e., most studies are case reports or case series, and therefore the grade of recommendation is C. There is insufficient evidence to make specific recommendations.
Transcranial Doppler
Transcranial Doppler examination is not helpful in headache diagnosis. It is, however, a non-invasive examination with excellent temporal resolution which is useful for studying the vascular aspects of the headache pathophysiology and the vascular effects of anti-headache medication. The information obtained using this method is easier to interpret if side-to-side comparisons are made or if it is combined with rCBF measurements.
This is a class IV level of evidence and the grade of recommendation is C.
Definitions:
Evidence Classification Scheme for a Diagnostic Measure
Class I: A prospective study in a broad spectrum of persons with the suspected condition, using a 'gold standard' for case definition, where the test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class II: A prospective study of a narrow spectrum of persons with the suspected condition, or a well-designed retrospective study of a broad spectrum of persons with an established condition (by 'gold standard') compared to a broad spectrum of controls, where test is applied in a blinded evaluation, and enabling the assessment of appropriate tests of diagnostic accuracy
Class III: Evidence provided by a retrospective study where either persons with the established condition or controls are of a narrow spectrum, and where test is applied in a blinded evaluation
Class IV: Any design where test is not applied in blinded evaluation OR evidence provided by expert opinion alone or in descriptive case series (without controls)
Rating of Recommendations
Level A rating: (established as useful/predictive or not useful/predictive) requires at least one convincing class I study or at least two consistent, convincing class II studies
Level B rating: (established as probably useful/predictive or not useful/predictive) requires at least one convincing class II study or overwhelming class III evidence
Level C rating: (established as possibly useful/predictive or not useful/predictive) requires at least two convincing class III studies
