Kaplan Award 1998. Epidemiology of chronic daily headache in the general population

Background and Objectives.—Although chronic daily headache, mainly transformed migraine, is an important reason for consultation in headache clinics, its actual prevalence is unknown. This study analyzes the prevalence of the different types of chronic daily headache in an unselected population.
Methods.—A questionnaire exploring headache frequency was distributed to 2252 unselected subjects. Those having headache 10 or more days per month were given a headache diary and were seen by a neurologist who classified their headaches. The varieties of chronic daily headache were classified according to the second revision of IHS criteria proposed by Silberstein et al published in Neurology 1996;47:871.
Results.—The questionnaire was returned by 1883 subjects (83.5%). One hundred thirty-five admitted to headache 10 or more days per month. Chronic daily headache criteria were fulfilled by 89 individuals (4.7%). Eighty were women. Forty-two (47.2% of subjects with chronic daily headache and 2.2% of all subjects) had chronic tension-type headache. Analgesic overuse was found in 8 (17%). Transformed migraine was diagnosed in 45 (50.6% of subjects with chronic daily headache and 2.4% of all subjects). Fourteen (31.1%) individuals with this form of chronic daily headache overused ergots or analgesics. The remaining 2 cases in this series met the criteria of new daily persistent headache. No one was diagnosed as having hemicrania continua.
Conclusions.—Almost 5% of the general population (9% of women) suffers from chronic daily headache, the proportion of chronic tension-type headache and transformed migraine being quite similar. Less than one third overuse analgesics. The prevalence of chronic daily headache subtypes shown here differs from data obtained from headache clinics, emphasizing that caution is needed in extrapolating data from specialized units to the general population.     

Prevalence and Clinical Features of Chronic Daily Headache in a Headache Clinic

Although chronic daily headache is regarded as a syndrome encountered in headache clinics, clinical characteristics have only rarely been studied and the condition has not been documented in Thailand. To investigate the prevalence as well as clinical features of chronic daily headache in Thai patients, 220 patients visiting Chulalongkorn Headache Clinic were examined. Sixty cases (27.3%) were diagnosed as suffering from chronic daily headache (male to female ratio, 1:5.7).
The average age of these patients was 32.7 ± 9.6 years. Based on the International Headache Society (IHS) criteria, 30% of patients with chronic daily headache could be diagnosed as suffering from migraine end 36.7% from chronic tension-type headache, whereas the remainder had combined features of both headache types and were not classifiable. Diffuse steady pain was the most common headache type reported (65%), however, associated features characteristic of migraine were often noted. These included photophobia (70%), phonophobia (56.7%) and nausea (43%). Thirty-four cases (56.7%) reported that their headache could be aggravated by stress. Daily use of analgesics was reported in 58.3% of cases. We concluded that chronic daily headache is a common problem. Although the mechanism has not been fully clarified, the prevalence of associated psychological factors and analgesic overuse imply their involvement in the pathogenesis of this condition. The criteria of the IHS are not entirely suitable for diagnosis and classification of this disorder, and modification of this classification system is needed.     

Chronic daily headache. How should it be included in the IHS classification?

A number of patients attending specialty headache centers complain of very frequent, almost continuous or continuous headaches, which are usually grouped together under the term chronic daily headache , a category which does not appear in the International Headache Society (IHS) classification. On the basis of the IHS criteria, these patients can only be classified as having a chronic tension-type headache with the possible addition of migraine, if migrainous attacks are superimposed on the "background" headache. However, several studies have demonstrated that most patients with chronic daily headache originally suffered from migraine and that their migraine has transformed, in the course of time, into a chronic headache picture in which isolated migraine attacks may or may not persist. Despite some differences in the personal opinions of authors involved in the care of patients with chronic daily headache, some views seem to be generally accepted: (1) the great majority of chronic daily headaches are transformations of an original episodic migraine and cannot be included in the chronic tension-type headache category, (2) the current IHS classification does not allow many patients presenting with chronic daily headache to be classified correctly, (3) an important nosological category (transformed migraine) has emerged from all the studies on this subject, (4) it is impossible to diagnose transformed migraine merely by "photographing" the picture of single attacks. Although some theoretical problems remain unresolved, it seems to us that the next revision of the IHS classification can no longer ignore the existence of chronic daily 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.     

The International Headache Society (IHS) Headache Classification as applied to a headache clinic population

Four hundred patients attending a headache clinic were classified using the IHS criteria. The majority required more than two, often three or four, diagnoses. Even though migraine was the most common diagnosis, only 1/4 of those with a migraine diagnosis had it as the only diagnosis. Seventy-five percent of migraine patients had coexistent chronic tension-type headache (CTTH), drug-induced headache or both. Ninety-six percent of patients diagnosed as having migraine with aura also suffered from migraine without aura. More than 1/3 of patients (37.7%) attending the clinic suffered from chronic daily headache (CDH) (chronic cluster headache excluded), which is not included as a separate entity in the IHS classification. Pure CTTH formed only a small minority of CDH, whereas 86.6% of CDH had migraine as one of the diagnoses. Drug-induced headache was a prominent second or third diagnosis. The advantages and disadvantages of multiple verses single diagnosis in CDH and the need to recognize the natural history of headache disorders in the classification are discussed.     

Chronic tension-type headache in children and adolescents

In this study, the causes, predisposing factors and clinical features of chronic daily headache in children and adolescents were studied within the population of patients attending a specialist headache. The International Headache Society's (IHS) criteria for the diagnosis of chronic tension type headache (CTTH) were assessed for their applicability in the paediatric age group. Over a period of three years, demographic and clinical data were collected prospectively on all children who attended the clinic and suffered from daily attacks of headache. One hundred and fifteen children and adolescents (32% of all clinic population) had chronic daily headache, of whom 93 patients (81%) fulfilled the IHS criteria for the diagnosis of CTTH. They were between 3-15 years of age (mean: 11.1, SD: 2.3) and their female to male ratio was 1.2 : 1. Around one third of the patients also suffered from migraine (mainly migraine without aura). The headache was described as mild in 60.9%, moderate 36.5% and severe 2.6%. Headache was located at the forehead in 53% or over the whole of the head in 29.6%. Pain was described as 'just sore' or dull by 73.9%. During attacks of headache, at least half the patients reported light intolerance, noise intolerance, anorexia or nausea. Thirty-two percent of patients had at least one underlying chronic disease that may have contributed to the pathogenesis of the CTTH. Eleven percent had serious stressful events related to family illnesses and in four patients headaches were triggered by family bereavement. Fourteen percent were investigated with neuroimaging and 22% were referred for clinical psychology assessment and management. In conclusion, CTTH is a common cause of headache in children attending a specialist headache clinic. The clinical features closely match those of adult population and the IHS criteria for the diagnosis of CTTH can be adapted for use in children. Predisposing stressful risk factors, physical or emotional, are present in a large proportion.     

Chronic daily headache: correlation between the 2004 and the 1988 International Headache Society diagnostic criteria

BACKGROUND: In a previous study, we compared the 1988 International Headache Society (IHS) criteria and the Silberstein-Lipton criteria (S-L) in a subspeciality clinic sample of 638 patients with chronic daily headache (CDH) assessed both clinically and with headache diaries. Both systems allowed for the classification of most patients with CDH. The 1988 IHS classification required multiple diagnoses and was more complex to apply. OBJECTIVES: The aim of this study was to revisit the same database, now comparing the prior classification systems with the new 2004 IHS classification. In contrast with the 1st edition, the 2nd edition includes criteria for chronic migraine (CM), new daily persistent headache (NDPH), and hemicrania continua (HC). METHODS: We reviewed the clinical records and the headache diaries of 638 patients seen between 1980 and 2001 at a headache center. All patients had primary CDH according to the S-L criteria. RESULTS: Using the S-L criteria as a reference, of the 158 patients with transformed migraine (TM) without medication overuse, just 9 (5.6%) met 2004 IHS criteria for CM. Most of the subjects were classified using combinations of migraine and CTTH diagnoses, much like the 1988 IHS classification. Similarly, using the new IHS system, just 41/399 (10.2%) subjects with TM with medication overuse were classified as probable CM with probable medication overuse. Most patients with NDPH without overuse were easily classified using the 2004 criteria (95.8%). Regarding NDPH with medication overuse, the diagnostic groups were much like results for the 1st edition. All patients with chronic tension-type headache (CTTH) and hemicrania continua (HC) according to the S-L system were easily classified using the 2004 IHS criteria. CONCLUSIONS: We conclude that the 2004 IHS criteria facilitate the classification of NDPH without medication overuse and HC. For subjects with TM according to the S-L system, the new IHS criteria are complex to use and require multiple diagnoses. Very few patients with TM in the S-L system could be classified with a single diagnosis in the 2004 IHS classification. In fact, CM was so rare that it would be virtually impossible to conduct clinical trials of this entity using the 2004 IHS criteria. Clinical trials of this entity should therefore be conducted using the S-L criteria. Finally, we propose that in the 3rd edition of the IHS classification, the diagnosis of NDPH be revised so as not to exclude migraine features.     

Intravenous valproate sodium in the treatment of daily headache

BACKGROUND: Treatment of chronic daily headache/transformed migraine is challenging, especially when it is complicated by overuse of analgesics, triptans, or both. One common approach involves the use of repetitive intravenous dihydroergotamine. We investigated the use of intravenous valproate sodium in the treatment of chronic daily headache/transformed migraine in patients who had contraindications to the use of or had failed treatment with dihydroergotamine. METHODS: We administered intravenous valproate sodium (Depacon) to patients with chronic daily headache/transformed migraine (loading dose 15 mg/kg, followed by 5 mg/kg every 8 hours). All analgesics and triptans were discontinued prior to treatment with divalproex sodium, and preventative medications for migraine were begun or continued. All patients received instruction in behavioral modification and the proper use of analgesics and triptans. RESULTS: Improvement in headache was reported by 80% of the patients treated, and valproate sodium was tolerated well by most. CONCLUSION: Intravenous valproate sodium may be of assistance in the initial management of patients with chronic daily headache/transformed migraine and analgesic/triptan overuse, especially when dihydroergotamine is ineffective or contraindicated.     

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.     

Comorbidity of depressive and anxiety disorders in chronic daily headache and its subtypes

OBJECTIVE: To investigate the frequency of depressive and anxiety disorders in patients with chronic daily headache. BACKGROUND: There is a lack of data in the literature on the extent of psychiatric comorbidity in patients with different subtypes of chronic daily headache. METHODS: We recruited consecutive patients with chronic daily headache seen in a headache clinic from November 1998 to December 1999. The subtypes of chronic daily headache were classified according to the criteria proposed by Silberstein et al. A psychiatrist evaluated the patients according to the structured Mini-International Neuropsychiatric Interview to assess the comorbidity of depressive and anxiety disorders. RESULTS: Two hundred sixty-one patients with chronic daily headache were recruited. The mean age was 46 years, and 80% were women. Transformed migraine was diagnosed in 152 patients (58%) and chronic tension-type headache in 92 patients (35%). Seventy-eight percent of patients with transformed migraine had psychiatric comorbidity, including major depression (57%), dysthymia (11%), panic disorder (30%), and generalized anxiety disorder (8%). Sixty-four percent of patients with chronic tension-type headache had psychiatric diagnoses, including major depression (51%), dysthymia (8%), panic disorder (22%), and generalized anxiety disorder (1%). The frequency of anxiety disorders was significantly higher in patients with transformed migraine after controlling for age and sex (P =.02). Both depressive and anxiety disorders were significantly more frequent in women. CONCLUSION: Psychiatric comorbidity, especially major depression and panic disorders, was highly prevalent in patients with chronic daily headache seen in a headache clinic. These results demonstrate that women and patients with transformed migraine are at higher risk of psychiatric comorbidity.     

Classification of chronic daily headache by International Headache Society criteria: limits and new proposals

We conducted a retrospective study of 150 patients with chronic daily headache (CDH) to determine how to categorize their headache according to the classification of the International Headache Society (IHS). All patients were first evaluated at Parma and Pavia Headache Centres (from January 1992 to March 1993) and had had headache for at least 15 days a month during the previous 6 months. Four patients were thereafter excluded due to poor reliability. The 146 patients who met our CDH criteria (92 with and 54 without clear-cut migraine attacks) could be classified into four groups: (i) chronic tension-type headache (CTTH)-27 patients; (ii) coexisting migraine plus CTTH-65 patients; (iii) unclassifiable daily headache-27 patients; and (iv) migraine and an unclassifiable interval headache-27 patients. Seventy-two percent of patients with CDH had migraine as the initial form of their headache. We therefore propose to revise the IHS classification for migraine, taking into account its evolution, and add two subcategories, migraine with interparoxysmal headache and chronic migraine.     

Classification of Daily and Near-Daily Headaches: Proposed Revisions to the IHS Criteria

SYNOPSIS
The International Headache Society (IHS) headache classification, while a major advance, does not adequately classify the daily and near-daily headache disorders known as chronic daily headache (CDH). We believe that chronic daily headache is a group of disorders which includes chronic tension-type headache (CTTH), transformed migraine (TM), new daily persistent headache (NDPH), and hemicrania continua (HC). We propose specific criteria for transformed migraine, new daily persistent headache, and hemicrania continua, and have modified the criteria for chronic tension-type headache.     

Chronic daily headache in children and adolescents presenting to tertiary headache clinics

BACKGROUND: Adults with chronic daily headache often describe a transformation from episodic migraine and partial retention of migrainous features. Although chronic daily headache has not been investigated as carefully in the pediatric population, one study showed a predominance of coexisting daily headache and episodic migraine, without a clear history of transformation. OBJECTIVE: To identify the clinical features of chronic daily headache in children and adolescents, to evaluate the efficacy of current headache classification criteria, and to compare the features of coexistent daily and episodic headaches so as to determine whether they represent separate syndromes or different stages in the "transformation" process. DESIGN: We surveyed 189 consecutive patients, 18 years of age or younger, who presented for initial evaluation of daily or near daily headache at one of 9 tertiary headache clinics. Data were collected in semistructured interviews employing a standard questionnaire and analyzed using Statistical Analysis Systems and Stata statistical software computer programs. RESULTS: Of the patients enrolled, 70% were female and 87% were white. Mean age was 13.0 +/- 3.1 years. Male gender was associated with a higher degree of reported disability. A family history of headache (typically migraine) was described in 79%. Use of nonsteroidal anti-inflammatory drugs 5 days per week or more was reported by 44% of patients. The International Headache Society (IHS) criteria failed to classify 64% of patients and criteria proposed by Silberstein et al failed to classify 31% of patients. Participating physicians misclassified patients according to criteria of the IHS and Silberstein et al in one third of cases. Nearly one quarter of patients reported two separate headache types with distinguishing characteristics. "Baseline" headache was present 27.3 +/- 4.1 days per month with a mean pain intensity of 5.9 +/- 2.1 on a 10-point scale. Superimposed episodic headache occurred 4.7 +/- 3.8 days per month with a mean pain intensity of 8.4 +/- 1.4, and was more often accompanied by other migrainous symptoms. After logistic regression to control for pain intensity, the only statistically significant difference between the two headache types was a lower prevalence of tension-type head pain with the superimposed headache. CONCLUSIONS: Our data suggest that rather than having two coexistent headache types, children and adolescents with chronic daily headache have a single syndrome that, in many cases, will paroxysmally worsen and gather migrainous features.     

Evaluation of chronic daily headache—comparison to criteria for chronic tension-type headache

The purpose of this study was to evaluate the adequacy of the International Headache Society (IHS) criteria for chronic tension-type headache and, if appropriate, suggest modifications of the IHS classification. We evaluated 100 consecutive patients with chronic daily headache. Approximately two-thirds of our patients fulfilled the criteria for chronic tension-type headache. Most of the patients who failed to meet the criteria did so because they had more than one migrainous feature. Approximately 50% of patients took excessive amounts of analgesic medication. We conclude that the IHS criteria should be modified to include chronic daily headache evolving from migraine; subtypes with and without medication overuse should be distinguished.     

Opiate use to control bowel motility may induce chronic daily headache in patients with migraine

OBJECTIVES: To investigate whether opiate overuse might cause chronic daily headache in those with migraine, we studied patients who were taking codeine (or other opiates) for control of bowel motility after colectomy for ulcerative colitis. BACKGROUND: Analgesic overuse is considered by many to be one factor which can result in the transformation of migraine into a chronic daily headache pattern. Most of the evidence for this comes from patients with migraine who are taking increasing amounts of analgesia for headache. Many of these patients revert to an intermittent migraine pattern once the analgesics are stopped. METHODS: Women who were 1 year postcolectomy for ulcerative colitis were identified in several colorectal surgery practices in Calgary. They were sent a questionnaire designed to determine if they had a history of migraine prior to surgery, if they currently had chronic daily headache, what medications they were taking to control bowel motility, and what medications they were taking for headache. RESULTS: Twenty-eight patients who met our inclusion criteria returned completed questionnaires. Eight of these exceeded the recommended limits for opiate use in patients with headache. Eight patients met diagnostic criteria for migraine. Two patients had chronic daily headache starting after surgery. Both used daily opiates beginning after their surgery, and both had a history of migraine. The other six patients who used opiates daily did not have a history of migraine and did not have chronic daily headache. All patients with migraine who used daily opiates to control bowel motility following surgery developed chronic daily headache after surgery. CONCLUSIONS: Patients with migraine who use daily opiates for any reason are at high risk of developing transformed migraine with chronic daily headache. This risk appears much lower in patients without a history of migraine who use opiates for nonpain indications.     

Does chronic daily headache arise de novo in association with regular use of analgesics?

BACKGROUND: The prevalence of chronic daily headache in association with regular use of analgesics is about 2%. Whether regular use of analgesics has a causal or consequential relationship to daily headache has not been established. A causal relationship has been suggested consequent to the observation of improvement or resolution of headache following analgesic withdrawal in patients attending headache clinics, but this observation has not been validated by controlled trials. PURPOSE: The aim of our investigation was to determine whether regular use of analgesics is associated with the development of chronic daily headache de novo and to characterize the clinical phenotype of those headaches by carefully studying chronic daily headache in patients with regular use of analgesics for a nonheadache indication. METHODS: Patients attending a rheumatology-monitoring clinic of second-line agents were interviewed by a training neurologist with regard to their analgesic and headache history. Headache classification was according to the criteria of the International Headache Society. Daily headache characteristics were surveyed via a standardized questionnaire, and headache features were further explored by a trained medical interviewer. RESULTS: Of 110 patients presenting to a rheumatology-monitoring clinic, 73% had a diagnosis of rheumatoid arthritis, 23% had seronegative arthritis, and 4% comprised a miscellaneous group. One hundred three were using one or more analgesics regularly for their arthritis. Of this group, 8 (7.6%) reported a history of chronic daily headache, each of whom reported a history of migraine. The onset of migraine occurred before the onset of chronic daily headache in 7 patients and at about the same time as the chronic daily headache in 1 patient. In those with onset of migraine prior to chronic daily headache, the mean interval before the onset of headache was 30 years (range, 10 to 50 years). Regular use of analgesics preceded the onset of daily headache in 5 patients by a mean of 5.4 years (range, 2 to 10 years). In 1 patient, analgesic use and the development of daily headache occurred at about the same time. In 1 patient, the onset of daily headache preceded regular use of analgesics by almost 30 years. Five of those with regular use of analgesics had been taking an opiate-based preparation in combination with a nonsteroidal anti-inflammatory agent in 4. Two had been on a combination of acetaminophen (paracetamol) and a nonsteroidal anti-inflammatory drug. The minimum number of tablets per week was 7, and the mean was 48 (range, 7 to 87). Of those patients who did not have daily headache, 41% had a history of migraine and 27% reported a history of tension-type headache. CONCLUSION: These findings suggest that individuals with primary headache, specifically migraine, are predisposed to developing chronic daily headache in association with regular use of analgesics.     

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.     

A retrospective, comparative study on the frequency of abuse in migraine and chronic daily headache

OBJECTIVE: To assess and contrast the relative frequency of a past history of physical and/or sexual abuse in patients with chronic daily headache (CDH) versus migraine. BACKGROUND: A number of risk factors have been identified as risk factors for chronification of headache disorders. Limited data exist regarding the influence of physical and/or sexual abuse on primary headache disorders. METHODS: This was a retrospective chart review of 183 consecutive new headache patients seen from December 2004 through August 2005 at an outpatient tertiary-care center. Patients were included in the study if they had chronic daily headache (with criteria for medication over-use headache or chronic migraine), or migraine with or without aura. A history of physical and/or sexual abuse was systematically asked of all headache patients at their first visit in the clinic. This information was then transferred to a semi-standardized form and the relative frequency of abuse in both groups contrasted. RESULTS: Of the 161 patients included in the study, 90.1% were female with a mean age of 36.4 +/- 12.0. A total of 59.0% of the patients were diagnosed with CDH and 41.0% were diagnosed with migraine. Overall, 34.8% of all patients, 40.0% of CDH patients, and 27.3% of migraine patients had a history of physical and/or sexual abuse. The relative frequency of a history of physical and/or sexual abuse was higher in the CDH group as compared to the migraine group (P = .048). CONCLUSION: The relative frequency of abuse is higher in CDH sufferers than migraineurs, suggesting that physical and sexual abuse may be risk factors for chronification.     

An expert system for headache diagnosis: the Computerized Headache Assessment tool (CHAT)

BACKGROUND: Migraine is a highly prevalent chronic disorder associated with significant morbidity. Chronic daily headache syndromes, while less common, are less likely to be recognized, and impair quality of life to an even greater extent than episodic migraine. A variety of screening and diagnostic tools for migraine have been proposed and studied. Few investigators have developed and evaluated computerized programs to diagnose headache. OBJECTIVES: To develop and determine the accuracy and utility of a computerized headache assessment tool (CHAT). CHAT was designed to identify all of the major primary headache disorders, distinguish daily from episodic types, and recognize medication overuse. METHODS: CHAT was developed using an expert systems approach to headache diagnosis, with initial branch points determined by headache frequency and duration. Appropriate clinical criteria are presented relevant to brief and longer-lasting headaches. CHAT was posted on a web site using Microsoft active server pages and a SQL-server database server. A convenience sample of patients who presented to the adult urgent care department with headache, and patients in a family practice waiting room, were solicited to participate. Those who completed the on-line questionnaire were contacted for a diagnostic interview. RESULTS: One hundred thirty-five patients completed CHAT and 117 completed a diagnostic interview. CHAT correctly identified 35/35 (100%) patients with episodic migraine and 42/49 (85.7%) of patients with transformed migraine. CHAT also correctly identified 11/11 patients with chronic tension-type headache, 2/2 with episodic tension-type headache, and 1/1 with episodic cluster headache. Medication overuse was correctly recognized in 43/52 (82.7%). The most common misdiagnoses by CHAT were seen in patients with transformed migraine or new daily persistent headache. Fifty patients were referred to their primary care physician and 62 to the headache clinic. Of 29 patients referred to the PCP with a confirmed diagnosis of migraine, 25 made a follow-up appointment, the PCP diagnosed migraine in 19, and initiated migraine-specific therapy or prophylaxis in 17. CONCLUSION: The described expert system displays high diagnostic accuracy for migraine and other primary headache disorders, including daily headache syndromes and medication overuse. As part of a disease management program, CHAT led to patients receiving appropriate diagnoses and therapy. Limitations of the system include patient willingness to utilize the program, introducing such a process into the culture of medical care, and the difficult distinction of transformed migraine.