Diagnosis of migraine in children attending a pediatric headache clinic

The International Headache Society (IHS) criteria for migraine are not sufficient to diagnose migraine in children. Specifically, the duration and localization of the headache are different in children and adults with migraine. This study compared the formal IHS criteria with pediatric-amended IHS criteria and IHS criteria with the duration factor removed in children younger than 18 years. In addition, the older criteria by Vahlquist and by Prensky and Sommer were also compared. Finally, clinical diagnosis of migraine was compared with IHS criteria with the duration factor removed. The study showed that many children with a shorter duration headache have migraine and also that a number of children with a very long duration of headaches still fit the diagnosis of migraine. Unilateral headache is quite uncommon. The majority of children with migraine complained of bilateral headaches. It is concluded that the IHS criteria for pediatric migraine should be revised. We suggest making the duration factor a minor criteria for migraine in children or to exclude headaches lasting longer than 72 hours only in children younger than 15 years.     

Outcome of juvenile headache in outpatients attending 23 Italian headache clinics. Italian Collaborative Study Group on Juvenile Headache (Società Italiana Neuropsichiatria Infantile [SINPI])

A multicenter 3-year follow-up study was carried out on young patients with headache referred to tertiary headache centers or pediatric clinics. Three years after the first examination in 1993, 442 (of an original sample of 719) young outpatients with headache (226 females and 216 males) were re-examined. The diagnostic criteria of the International Headache Society (IHS) and those modified for migraine without aura by Winner et al were applied at both the baseline evaluation and the 3-year re-examination. At the follow-up, 290 children still had headache, 101 were in clinical remission, and 51 had dropped out. Using the current diagnostic criteria, only 46.2% of patients having migraine without aura, 50% of those having migraine with aura, and 35.3% of those suffering from migraine disorders which do not fulfill IHS criteria for migraine received the same diagnosis at the time of follow-up. The percentage of patients receiving a diagnosis of migraine without aura rose significantly when new modified criteria were used (60.5%), whereas a drop in the frequency of migraine disorders not fulfilling IHS criteria was observed at follow-up, both in patients with the diagnosis of migraine without aura at the first examination (4.6%) and in patients with migraine not always fulfilling IHS criteria at the first examination (6.2%). Among all patients who received this latter diagnosis at the first examination, it was possible to make a diagnosis of migraine with aura at the follow-up in 8.8% of cases and that of migraine without aura in 26.5%. No significant variations in the frequency of either episodic tension-type headache or chronic tension-type headache were found, with the exception of a slight decrease in the percentage of tension-type headache which did not fulfill IHS criteria, but the difference between the first examination and the follow-up values does not reach the level of statistical significance (5% versus 12%). As far as the evolution of migraine is concerned, 17.4% of patients with migraine were headache-free at the 3-year follow-up. In tension-type headache, the percentage of patients who were headache-free was particularly high in those with the episodic form (32.9%) and in those suffering from tension-type headache not fulfilling IHS criteria (29.1%). The majority of patients who had been diagnosed as having unclassifiable headache at the first examination received a correct diagnosis at the follow-up with the exception of one patient. As observed in adult patients, variations in the headache characteristics were also observed in children and adolescents (that is, migraine with aura can change to migraine without aura, or the latter can transform into episodic tension-type headache or chronic tension-type headache can change into the episodic form). This follow-up study was aimed at reaching a better understanding of headache disturbances in children and adolescents, examining, in particular, variations of headache with time in this stage of life.     

Migraine without aura and migrainous disorder in children; International Headache Society (IHS) and revised IHS criteria

The widely used criteria of the IHS to define migraine without aura in children are highly specific but show poor sensitivity, with a large percentage of headaches being classified as migrainous disorder (MD). The objective of this study was to assess how many headache patients in a series of children met the diagnostic criteria of the IHS for migraine without aura or MD and to determine the changes required to convert the greatest number of MD into migraine without aura, without affecting classification of the remaining headache types. A prospective study was undertaken of 131 patients under 15 years old referred to our centre for headache. Patients were classified according to the IHS criteria and according to a modification of these criteria consisting of: (1) reduction of minimum time required for classification into migraine without aura from 2 h to 1 h; (2) acceptance of bifrontal location in addition to hemicranial; (3) acceptance of either phonophobia or photophobia as valid criteria instead of requiring presence of both. Using the IHS criteria, 51 (39%) children were diagnosed as having migraine without aura and 26 (20%) as having MD. According to our revised IHS criteria, 68 (52%) were diagnosed as migraine without aura and nine (7%) as MD. When the three modified criteria were applied, three tension headaches and one unclassifiable headache changed category. When only reduced duration and bifrontal location were applied, none of the headaches other than MD changed category. Application of two modifications to the IHS criteria--reduction in duration of headache to 1 h and acceptance of bifrontal location--increased sensitivity without reducing specificity in classifying migraine without aura in children.     

Migrainous disorder and headache of the tension-type not fulfilling the criteria: a follow-up study in children and adolescents

In this follow-up study in children and adolescents with recurrent headaches classified as migrainous disorder (IHS 1.7) and headache of the tension-type not fulfilling the criteria (IHS 2.3), 28.6% were headache-free and 71.4% still had headaches 2-5 years after the first examination. The majority remained in the same one-digit IHS diagnosis, whereas 20% changed from migraine to tension-type headache or vice versa. The number of IHS criteria fulfilled increased significantly from the first to the second examination. The reason for diagnosing IHS 1.7 and IHS 2.3 most often was a short headache duration or headache characteristics not meeting the criteria. By reducing the minimum headache duration to 1 h, 11 of 58 patients could be diagnosed as migraine without aura. There was a remarkable overlap in the diagnostic criteria for migraine without aura and tension-type headache. In IHS 1.7 and IHS 2.3 this overlap exceeded 80%, with a trend to decrease at the second examination.     

Diagnosis of headache in childhood and adolescence: a study in 437 patients

We investigated whether the criteria for idiopathic headache published by the International Headache Society (IHS) are useful in childhood and adolescence and compared the diagnoses according to this classification with those of Vahlquist. We used a semi-structured questionnaire to examine a total of 437 children and adolescents referred consecutively to a headache outpatient clinic. Twenty-eight of 437 patients were excluded because of symptomatic or unclassifiable headache. Of 409 patients with idiopathic headache, 70.4% had definite migraine or tension-type headache (IHS 1.1, 1.2, 2.1, 2.2), 20.5% had a migrainous disorder (IHS 1.7) and 9.1% had headache of the tension-type not fulfilling the criteria (IHS 2.3). In the differential diagnosis of migraine and tension-type headache the intensity of pain, aggravation of headache by physical activity, nausea and vomiting were the most important features. The quality of pain, photo- and phonophobia were less helpful and location least important. The duration of migraine attacks was less than 2 h in 19.0% of the migraine patients. In general, the diagnostic criteria of migraine were highly specific but less sensitive, and those of tension-type headache highly sensitive but less specific. The agreement between IHS criteria and those of Vahlquist was marked (kappa = 0.57). We conclude that the IHS criteria are useful for classifying headache in children and adolescents referred to a headache outpatient clinic. A forthcoming modification of the IHS criteria should consider a reduction of the minimum duration of migraine attacks from 2 h to I h and should try to increase the sensitivity of the criteria for migraine and the specificity of the criteria for tension-type headache.     

American Headache Society members' assessment of headache diagnostic criteria

OBJECTIVE: We assessed the views of physicians interested in headache as to the diagnosis of the most commonly occurring and currently controversial headaches. BACKGROUND: The International Headache Society (IHS) classification system has received wide professional endorsement and considerable empirical support, but in the United States, their adoption by clinicians may be proceeding more slowly. Questions remain, including what diagnostic criteria for migraine and tension-type headache clinicians may continue to favor over those outlined by the IHS, to what extent is the "transformed migraine" diagnosis used in clinical practice, and how is analgesic rebound headache diagnosed with regard to the various quantitative measures of analgesic use. METHODS: Members of the American Headache Society rated the importance of IHS and non-IHS diagnostic criteria for migraine and tension-type headache and for analgesic rebound headache. Respondents also described their use of the proposed transformed migraine diagnosis. RESULTS: Two-thirds (67.3%) of the respondents reported use of the IHS criteria or the IHS criteria in conjunction with clinical judgment. For migraine and tension-type headache, IHS criteria were rated with high importance, but some respondents reported using additional non-IHS diagnostic criteria and de-emphasizing certain IHS criteria. For chronic headache, almost two-thirds (63%) of respondents reported using the transformed migraine diagnosis. For analgesic rebound headache, respondents preferred to make the diagnosis based on medication consumption that is lower than amounts stipulated in the IHS classification system. CONCLUSIONS: There remains a number of physicians interested in headache who do not use the IHS classification system, who modify the IHS criteria in practice, and who use the "transformed migraine" diagnosis for patients with chronic daily headache.     

Effect of age on the fulfilment of the IHS criteria for migraine in children at a headache clinic

In a headache clinic, 247 children suffering from severe recurrent headaches were studied in relation to the IHS criteria for migraine. Of the 247, 163 had migrainous headache, with 110 (67.5%) of these having migraine in accordance with the IHS criteria. The remaining 53 (32.5%) had headache attacks fulfilling all but one of the IHS criteria. Coverage of the IHS criteria for migraine was 93%. Symptoms of unilateral headache, aggravation by physical activity, and nausea showed the greatest differences in frequency between those with migraine and those with probable migraine. All children with aura fulfilled criteria for migraine. Children with migraine with aura (11.8, 95% CI: 11.0–12.6 years) were older than those without aura (10.1, 9.4–10.8 years; p = 0.001). Children with pulsating headache were slightly older than children without pulsating headache. No differences in age were detected for the other IHS criteria.     

IHS criteria and gender: a study on migraine and tension-type headache in children and adolescents

The aim of this study was to investigate whether the IHS criteria for migraine and tension-type headache depend on gender. Among 409 children and adolescents with recurrent idiopathic headache seen at a university outpatient clinic, girls had significantly more often migraine with aura. Also, there was a trend towards a higher frequency of tension-type headache in girls. In migraine, aggravation of headache by physical activity and occurrence of aura symptoms were more common in females, whereas vomiting and phonophobia occurred more often in males. In tension-type headache, females more often reported mild intensity of headache. All other criteria were similar in both sexes. Age influenced the expression of some of the accompanying symptoms in the various types of migraine, but had only minimal influence on other diagnostic criteria of migraine and tension-type headache in females as well as in males. Our study suggests that the frequency of migraine (except that of migraine with aura) is similar among girls and boys, that tension-type headache may occur more often in girls, and that gender has some influence on the IHS criteria for migraine, but almost no influence on those of tension-type headache.     

Migraine in childhood and adolescence. A critical study of the diagnostic criteria and of the influence of age on clinical findings

We studied 253 children aged <15 years. Phase 1 included 193 children with migraine (1.1 and 1.2) divided into two groups (<10 and ≥ 10 years). We studied the relationship between age and migraine type, headache characteristics, and associated symptoms of the International Headache Society (IHS) definition. A higher frequency of migraine with aura, pulsatile quality, and unilateral location was observed in older children. In phase 2 we studied 176 children with headache (excluding migraine with aura), comparing diagnostic criteria, definition items, sensitivity, and specificity. The results showed that item B of the definition was the most frequent cause of exclusion in the 1.7 diagnostic group. Compared with Vahlquist and the IHS, the Prensky criteria were the most sensitive. Sensitivity was >70% for pain of moderate/severe intensity, duration between 2 and 48 h, isolated photophobia, isolated phonophobia, and aggravation with physical activity. Specificity was >70%, for nausea, vomiting, phonophobia and photophobia, isolated photophobia, aggravation with physical activity, and isolated phonophobia. Based on three alternative definitions, each modifying one item of the IHS definition, the sensitivity and specificity of these alternative definitions were compared with the "extended" criteria (children with migraine without aura and migrainous disturbance, according to the IHS criteria, grouped together). Exclusion of headache duration increased sensitivity by 10%, compared to restrictive IHS criteria, without decreasing specificity.     

Responsiveness of non-IHS migraine and tension-type headache to sumatriptan

In a long-term efficacy and satiety study, 424 patients were treated with sumatriptan (6 mg sc) for 1,904 migraine attacks. The patients were diagnosed with migraine based on IHS criteria but individual migraine attacks treated in the study were physician diagnosed; not necessarily required to meet IHS criteria. A re-analysis of the treatment response to open label sumatriptan (6 mg sc) indicated that 43 patients had treated at least one migraine that fulfilled IHS criteria for tension-type headache. Analysis of this population revealed they treated 232 headaches. Of these headaches, 114 were classified per IHS criteria as migraine; 76 as tension-type; and 42 as. non-IHS migraine (not classifiable as IHS migraine or IHS tension-type headache). Of the 114 migraines a positive response to sumatriptan occurred in 109 (96%) cases; of the 76 tension-types, 73 responded to sumatriptan (97%); of the 42 non-IHS migraine, 40 (95%) responded to sumatriptan. An equivalent response to sumatriptan among three diagnostic groups of headache supports the concept of a common biologic mechanism involving 5HT₁ receptors that spans a range of clinical presentations.     

The IHS Classification Criteria for Migraine Headaches in Adolescents Need Minor Modifications

The operational and diagnostic criteria for migraine and all other headache disorders released in 1988 by the International Headache Society are universally considered reliable and exhaustive. These criteria, however, cannot be considered as satisfactory for population-based studies on migraine prevalence, especially if adolescents are the subjects of the study.
Using these diagnostic criteria, we conducted an epidemiological study in order to assess the prevalence of migraine headache in a student population aged 11 to 14 years. Our survey made it possible to code IHS 1.1 (migraine without aura) in 2.35%, IHS 1.2 (migraine with aura) in 0.62%, IHS 1.7 (migrainous disorders not fulfilling migraine criteria) in 1.52%, and IHS 13 (headache not classifiable) in 1.38% of the examined pupils.
In adolescents, the low prevalence estimates of migraine headache coded IHS 1.1 and the relatively high prevalence estimates of headaches coded IHS 1.7 and IHS 13 have appeared to be a consequence of the rigidity of some operational diagnostic criteria of the recent IHS classification rather than of the geographical, environmental, or socioeconomical pecularities of the cohort.
Therefore, in order to improve the reliability and the exhaustiveness of the IHS classification by increasing its sensitivity, we believe that minor modifications of the diagnostic criteria are necessary. Within these revised criteria, the subitem "moderate or severe intensity" of pain headache should become mandatory, whereas the lower limit of the criterion "duration of pain" should be reduced to 1 hour.     

A structural representation of migraine diagnostic criteria: the experts' view

OBJECTIVE: To generate an empirically derived structural representation of migraine diagnostic criteria in a group of international headache experts using the Pathfinder network scaling algorithm in order to evaluate the validity of the migraine criteria used in the International Headache Society (IHS) classification system. BACKGROUND: Because it is a disease entity that lacks objective defining markers, developing valid diagnostic criteria for migraine is a challenge. The IHS committee relied on expert consensus to develop their classification system in 1988. Expert consensus also was used to evaluate the validity of the IHS classification system, but further studies employing alternative methods still are needed. METHODS: Headache experts representing the Executive Committee of the IHS and the Board of Directors of the American Headache Society analyzed 14 criteria (7 IHS and 7 non-IHS) considered relevant in diagnosing migraine. Their ratings were submitted to the Pathfinder algorithm to generate a network structure reflecting the experts' conceptualization of migraine diagnostic criteria. RESULTS: The expert network had 3 groupings: headache characteristics (eg, phonophobia, unilateral pain, throbbing pain), biological contributing factors (eg, family history, hormonal relationship, relief with sleep), and triggering factors (eg, worse with stress, food triggers). The IHS criteria were clustered together in the center portion of the network. A t test showed that each IHS criterion was closer conceptually to other IHS criteria than to non-IHS criteria. Graph theory indices revealed that the most central criteria were unilateral pain, moderate/severe intensity, and nausea/vomiting. CONCLUSION: The structural representation of migraine diagnostic criteria from these international headache experts is consistent with the migraine diagnostic criteria set forth in the IHS classification system and thus provides further support for the validity of migraine criteria in the IHS system.     

Diagnosis of migraine: empirical analysis of a large clinical sample of atypical migraine (IHS 1.7) patients and proposed revision of the IHS criteria

The International Headache Society (IHS) diagnostic criteria for headache improved the accuracy of primary headache diagnoses, including migraine. However, many migraineurs receive an 'atypical migraine' diagnosis according to the IHS nosology (IHS 1.7), indicating that they approximate but do not fully meet all IHS criteria. This study characterized and sub-classified patients with atypical migraine. Within a clinical sample of 382 headache sufferers, 83 patients met IHS criteria for 'atypical migraine'. Patients receiving the IHS 1.7 designation did not converge to form a homogeneous group. Rather, distinct and clinically relevant subgroups were empirically derived (e.g. migraine with atypical pain parameters, brief migraine, chronic migraine). The results call for revisions of the IHS diagnostic criteria for migraine that would minimize the number of patients receiving an atypical diagnosis. Revisions would include decreasing the minimum headache duration criteria from 4 h to 2 h, and developing a classification for 'chronic migraine' for migraine greater than 15 days per month. The proposed revision provides a means of diagnosing the daily and near-daily headache commonly observed in clinical populations.     

International Headache Society headache diagnostic patterns in pain facility patients

OBJECTIVE: Previous studies have indicated that many patients with chronic pain (PWCP) referred to pain facilities for the treatment of neck and/or low back pain complain of associated headaches. The purpose of this study was to characterize the nature of these headaches according to International Headache Society (IHS) headache diagnostic criteria. DESIGN: In preparation for this study, a questionnaire that reflected IHS headache diagnostic criteria was developed. All consecutive patients admitted to our pain facility complaining of headache completed this questionnaire and received a physical and neurologic examination focused on key aspects of headache. A headache interview was also conducted, using the questionnaire as a question guide. All questionnaires were entered in a computerized database, and IHS diagnoses were arrived at for each patient. As many IHS diagnoses as possible were assigned to each PWCP as long as IHS criteria were fulfilled. In addition, a frequency distribution for headache precipitants and neck-associated symptoms was developed and evaluated by discriminant analysis to determine the diagnostic value of these factors in relation to each IHS diagnostic group. SETTING: Pain facility (multidisciplinary pain center). PATIENTS: Consecutive PWCP. RESULTS: Of 1,466 PWCP, 154 (10.5%) were identified as suffering from severe headache interfering with function. Of these, 55.8% indicated that their headaches were related to an injury for which they were seeking treatment and 83.7% had neck pain. Migraine headache represented the most common diagnostic group (90.3%), with cervicogenic headache representing the second most common (33.8%). Of the total group, 44.2% had more than one headache diagnosis, that is, there was overlap. Cervicogenic headache patients had the greatest percentage of overlap (94.2%), with migraine patients being second (68.3%). The most frequent headache precipitant was mental stress, followed by neck position and activity/exercise. The migraine and cervicogenic headache groups had a statistically significant greater number of neck-associated symptoms when compared with the remaining patients. Of the total headache group, 74.6% complained that they had a tender point at the back of their neck. Cervicogenic, migraine, and tension PWCP had the greatest frequency of head or neck tender points. The discriminant analysis for neck-associated symptoms yielded the following symptoms as the most common predictors of headache across IHS diagnostic groups: clues to onset were severe headache beginning at the neck or tender point and numbness in arms and legs; headache brought on by neck position and arms overhead; and neck symptoms consisting of a tender point in the neck and feeling severe headache in the neck. CONCLUSIONS: Headache can and should be considered a frequent comorbid condition in PWCP. Because of the overlap data, more precise diagnostic criteria may be required to separate cervicogenic headache from migraine headache. Neck-associated symptoms seem to be important even to those PWCP diagnosed with migraine headache.     

A nationwide survey of migraine in France: prevalence and clinical features in adults

In November 1990 a nationwide survey of migraine was conducted in France on a representative sample of residents aged 15 years and older. The diagnosis of migraine was based on the International Headache Society (IHS) classification. In a previous study, we validated a diagnostic algorithm which classifies headache sufferers as IHS migraine, "borderline" migraine, possible migraine and non-migrainous headache. The overall prevalence of migraine patients with the IHS criteria in the present study was 8.1%; another 4% were classified as "borderline" migraine, which we in fact considered as definite migraine. Age, gender and occupation were found to be risk factors for migraine. Neither frequency and duration of attacks nor length of time of disease differed with gender. Expressed intensity of attacks, however, was greater in females.     

A nationwide survey of migraine in France: prevalence and clinical features in adults. GRIM.

In November 1990 a nationwide survey of migraine was conducted in France on a representative sample of residents aged 15 years and older. The diagnosis of migraine was based on the International Headache Society (IHS) classification. In a previous study, we validated a diagnostic algorithm which classifies headache sufferers as IHS migraine, "borderline" migraine, possible migraine and non-migrainous headache. The overall prevalence of migraine patients with the IHS criteria in the present study was 8.1%; another 4% were classified as "borderline" migraine, which we in fact considered as definite migraine. Age, gender and occupation were found to be risk factors for migraine. Neither frequency and duration of attacks nor length of time of disease differed with gender. Expressed intensity of attacks, however, was greater in females.     

IHS Criteria for Migraine and Tension-Type Headache in Children and Adolescents

We investigated the influence of age on the IHS criteria for migraine and tension-type headache in 437 consecutive children and adolescents and found the following age-associated statistically significant differences: migraine duration, occurrence of migraine aura, and bilateral location of tension-type headache were more often fulfilled by adolescents, whereas aggravation of headache by physical activity (in migrainous disorder) and photophobia (in migraine with aura) were more often fulfilled by children, Accordingly, there are only a few, differences concerning the fulfillment of the IHS criteria for migraine and tension-type headache in children and adolescents. Independent of age, the intensity of headache and the presence or absence of nausea are most important for differentiating the two major types of idiopathic headache. The sensitivity of the IHS criteria for migraine could be increased by reducing the minimum duration of migraine and by allowing the diagnosis of migraine when severe headache is associated with nausea, even though the criteria of location, quality, and aggravation by physical activity are not fulfilled.     

Migraine in children – an evaluation of the IHS criteria

The purpose of the present study was to compare the new criteria by the International Headache Society (IHS) with criteria for the definition of childhood migraine previously used. In particular, we considered the problem of the minimally acceptable headache duration in children. In a postal questionnaire, 36.5% of 3580 children 8–9 years old reported headache attacks. Ninety-five children (2.7%) fulfilled the IHS criteria. Three percent fulfilled the previously used migraine definition of Vahlquist. Some of the children in the latter group had considerably shorter headache attacks than those of the IHS patients, but otherwise their symptoms were very similar. When the IHS criterion of headache attack duration was lowered from a minimum of 2 h to 1 h, or omitted, the number of migraine patients increased from 95 to 114 and 127, respectively.     

Presentation of a new instrument: the diagnostic headache diary

A new instrument, the Diagnostic Headache Diary, based on the operational diagnostic criteria of the International Headache Society (IHS), was tested in 61 migraine patients from a headache research clinic using the clinical diagnosis (IHS criteria) for comparison. All patients kept the diary for one to eight months. The clinical and diary diagnosis of migraine with and without aura was the same in, respectively, 72 and 87% of the patients. Nausea, photophobia and phonophobia tended to be more pronounced at the clinical interview. The diary identified 20 more cases of episodic tension-type headache and 15 fewer cases of chronic tension-type headache than the clinical interview. Two blinded observers always made the same IHS diagnoses when interpreting the diagnostic headache diary. A combination of a clinical interview and the diagnostic headache diary gives a qualitatively and quantitatively more precise diagnosis than a clinical interview alone.     

Variability of reported headache symptoms and diagnosis of migraine at 12 months

Assignment of a diagnosis of migraine has been formalized in diagnostic criteria proposed by the International Headache Society. The objective of the present study is to determine the reproductibility of the formal diagnosis of migraine in a cohort of headache sufferers over a one-year period. The study was performed in a community cohort taking part in a long-term prospective health survey, the GAZEL study. Two thousand five hundred individuals reporting headache in the GAZEL cohort were sent two postal questionnaires concerning headache symptoms and features at 12-monthly intervals. Replies to the questions allowed a migraine diagnosis to be attributed retrospectively using an algorithm based on the IHS classification scheme. The response rate was 82% for the first questionnaire and 69% for both questionnaires. Of the 1733 subjects providing information at both time-points, the agreement rate for the diagnosis of strict migraine (IHS categories 1.1 or 1.2) was 77.7% (kappa = 0.48), with 62.2% of the patients with this diagnosis (IHS categories 1.1 or 1.2) at Month 0 retaining the same diagnosis at Month 12. When diagnostic criteria were widened to include IHS category 1.7 (migrainous disorder), the agreement rate of the diagnosis was similar at 77.6% (kappa = 0.52), but 82% of the patients with this diagnosis (IHS categories 1.1 or 1.2 or 1.7) at Month 0 now retained the same diagnosis at Month 12. In conclusion, the one-year reproducibility of reporting of migraine headache symptoms is only moderate, varies between symptoms, and leads to instability in the formal assignment of a migraine headache diagnosis and to diagnostic drift between headache types. This finding is compatible with the continuum model of headache, where headache attacks can vary along a severity continuum from episodic tension-type headaches to full-blown migraine attacks.