Abstract
The International Headache Society (IHS) criteria for headache related to haemo-dialysis consider that the headaches must begin during haemodialysis and terminate within 24 h. Twenty-eight patients whose headaches started by the time they entered the dialysis programme were prospectively studied. We were not able to classify eight patients that presented the headaches between the sessions. Despite the small number of patients in our study being too low to provide a basis for change in the IHS classification, it serves as an observational report demonstrating possible varieties of headache related to haemodialysis.
Introduction
The International Headache Society (IHS) classification and diagnostic criteria for headache disorders, cranial neuralgia and facial pain (1) are a bench mark and made it possible to standardize terms used in different settings and by different investigators. Headaches are classified as primary or secondary, respectively, if there is or there is not any underlying structural (or metabolic) disorder. The increasing interest in the study of headache brought important contributions, mainly in the field of primary headache disorders (2).
The IHS classification contains six subcategories pertaining to headaches associated with metabolic disorders (1). These criteria mandate symptoms and/or signs of metabolic disorder; confirmation by laboratory investigations when specified under the subform; the headache intensity and/or frequency is related to variations in the metabolic disorder with a specified time lag; the headache disappears after normalization of the metabolic state. One of these subcategories concerns headache related to haemodialysis (HD) (item 10, subitem 5). The diagnostic criteria according to the IHS are (1): (i) onset during HD and termination within 24 h after dialysis; (ii) has occurred at least half of HD and at least three times; (iii) can be prevented by changing dialysis parameters.
The aim of this study is to report eight patients that started to present headaches after the beginning of the HD programme, the headaches occurring mainly between the sessions, hence not fulfilling the IHS criteria.
Methods
We prospectively studied chronic renal failure patients attending three dialysis services from the town of Ribeirão Preto, State of São Paulo, Brazil, from January 1998 to December 1999. The three clinics are part of the same public health care programme, have similar equipment as well as follow similar procedures defined by the Brazilian Unified Health System. All subjects agreed to participate in the study, expressed by signing a written informed consent approved by the University Hospital Research Ethics Committee. All the patients were followed by one of the authors (A.L.A.).
Subjects under HD programme were studied to identify those who did not report chronic headaches before the beginning of the HD sessions and whose headaches started by the time they entered the dialysis programme. They were prospectively evaluated and followed up for at least 6 months. Forms of headaches were classified according to IHS criteria (1). Exclusion criteria were the following: (i) time of HD < 6 months; (ii) inability to report the information needed; (iii) cognitive impairment.
Results
One hundred and thirty-two patients were studied to identify 28 subjects whose headaches started by the time they entered the dialysis programme. All patients had headaches at least twice a week. The types of headaches are depicted in Table 1.
Classification of the headaches presented by subjects in haemodialysis programme according the criteria proposed by the International Headache Society
We were not able to classify eight patients (28.6%). After a careful follow-up, it was observed that the attacks occurred> 50% of the time in-between the sessions, hence not fulfilling the criterion (ii) of item 10.5 of the IHS classification.
Five patients fulfilled criteria for migraine without aura, two for episodic tension-type headache and one for chronic tension-type headache. For all individuals, the pattern of headache remained unchanged throughout the follow-up period. No one had severe hypertension or had their headaches related to acute hypertension, thereby not fulfilling the criteria for headache and arterial hypertension (item 6.8 of the IHS classification).
No differences were found regarding age (43.2 vs. 40.6 years), sex (60% vs. 62.5% males) or length of HD sessions (4 h in both groups) comparing the group that presented pain mainly during the sessions with the one that presented mainly between the sessions. Other possible triggering factors such as electrolyte levels did not differ between both groups and where described elsewhere (3), as well as the detailed phenotype characterization and treatment (3, 4).
Discussion
Before 1988, the taxonomy of headache was not uniform and diagnostic criteria were rarely based on operational rules. In 1988 the IHS instituted a classification system that had become the standard for headache diagnosis and clinical research. The classification was endorsed by all the national headache societies represented in the IHS and also by the World Federation of Neurology (5). It is accepted that it is more difficult to classify secondary than primary headaches (6), especially because much less is known about secondary headaches. Specifically considering the HD headaches, a previous study showed that around 70% of the patients receiving dialysis treatment complain about headaches related to the sessions (7). Our study shows that almost all these headaches can be classified using the IHS system (1). However, we could identify a rather important group of individuals where headaches could not be classified. All these patients presented a form of dialysis-related headache occurring between HD sessions.
Currently, headaches occurring after the beginning of the HD sessions can fit into one out of the following forms: (i) those beginning simultaneously with the dialytic programme, in patients without headache antecedents, thereby fulfilling the item 10.5 of the IHS classification (headache related to dialysis); (ii) those occurring during the dialysis but in patients with antecedents of primary headaches. Such cases, according to IHS criterion (i), should be classified as the primary headache form, worsened by a causal factor; (iii) those starting simultaneously with the dialytic programme, in patients without headache antecedents, but the headaches occurring between the sessions> 50% of the time, hence not fulfilling item 10.5 of the IHS classification.
There are two possibilities regarding the classification of such patients: (i) to consider them as presenting primary headaches, therefore they should be placed somewhere in IHS items 1–4 (1). Proceeding in such way, it would be possible to classify every patient. Nevertheless, it seems to be quite artificial to classify subjects whose headaches start in close temporal relationship with a potential metabolic disorder situation, as presenting primary headaches; (ii) to consider such patients as presenting a headache disorder not classifiable (item 13 of the IHS classification).
Despite being a well-recognized complication of HD treatment, headaches occurring in these situations remain poorly studied (7). Theoretically a wide array of possibilities may be involved in the underlying mechanisms of these headache disorders, including hypoxaemia that occurs at the beginning of the sessions, hyponatraemia, changes in serotonin levels, disturbances regarding urea and analogous, renin-aldosterone, 18-hydroxi-II-deoxycorticosterone and dialysis disequilibrium syndrome (8–12). It is not reasonable to consider that all these substances and situations have to be controlled within 24 h after dialysis. It could be argued that those headaches would be related to the chronic renal failure (uraemia and increasing of toxic catabolites that occur between HD sessions), therefore they should be classified as item 10.6—headache related to other metabolic abnormality. Against these arguments we could list three others: (i) chronic renal failure is not listed in item 10.6 of the IHS classification. It would be necessary to include this situation in this classification system; (ii) no patients reported headaches before the beginning of the HD sessions, even though they already presented other symptoms and signs of renal failure; (iii) some patients presented headaches both during and between the HD sessions.
It seems to be more reasonable to consider these patients as also presenting headaches related to dialysis. Despite the small number of patients in our study being too low to provide a basis for change in the IHS classification, it serves as an observational report demonstrating possible varieties of headache related to haemodialysis. We think that further studies should evaluate a slightly modified version of item 10.5 of the IHS classification (Table 2). This subject must be considered of special importance, especially now that the IHS classification is being intensely studied and revised.
Classification of dialysis headache. Comparison of the criteria of the International Headache Society and the modifications proposed to such criteria
Footnotes
Acknowledgement
The authors thank Dr Fred D. Sheftell for the careful review of the manuscript.