Abstract
Dr Seshia and colleagues raise a number of important issues regarding headache classification in their paper. They recommend the introduction of a diagnosis called chronic daily headache, but at the same time realize that this is not an actual diagnosis but a collective description of headaches that occur very frequently. Even the fathers of the term, Stephen Silberstein and Richard Lipton, acknowledge that chronic daily headache is not a medical diagnosis. Seshia et al. point out that the word ‘chronic’ is used with three different meanings in the Headache Classification. The first meaning is in migraine and tension-type headache, where chronic actually means frequent; the second meaning is in cluster headache, where chronic means unremitting; and the third meaning is in the secondary headaches, where chronic means that the headache has persisted for > 3 months. The Headache Classification Committee was aware of this problem and intensely debated whether it could be rectified. Unfortunately, no ideal solution was found to a change of nomenclature. The most logical solution to this problem would be to call chronic migraine and chronic tension-type headache frequent migraine and frequent tension-type headache. Chronic cluster headache could be called unremitting or non-periodic and the term chronic could then be preserved for secondary headaches that persist for > 3 months. This is the usual meaning of chronic in disease nomenclature. Chronic low back pain, for example, means chronic back pain persisting for > 3 months.
However, I am not sure that such a change of frequently used diagnostic terms would be possible at the present time. Most members of the committee felt that to use the term frequent migraine instead of chronic migraine, frequent tension-type headache instead of chronic tension-type headache, would not convey the seriousness and importance of these headache entities. Another possibility would obviously be to call them daily, as in chronic daily headache. However, the problem is that most of these headaches are not daily. They just occur on 15 days a month or more, so they should be called near-daily, which is very clumsy.
Chronic daily headache as originally proposed by Silberstein and Lipton is very problematic. As mentioned, it is not usually daily but near-daily. Almost all primary headaches are chronic in the sense that they continue for > 3 months, and the term as proposed covers a wide spectre of diagnoses including not only migraine, tension-type headache and new daily persistent headache but also some cases of long-lasting cluster headache attacks, chronic post-traumatic headache and other chronic secondary headaches. To divide the whole headache classification up into two categories, those occurring < 15 days/month and those more frequent, would almost double the whole classification document. Besides, there are several other suggestions for dividing the classification. For example, it has been suggested to divide migraine up into sensitizing and non-sensitizing types. Another more recent suggestion has been to divide migraine into medication-responsive and medication-refractory. Menstrual and non-menstrual migraine is a third way—one could go on.
In fact, my personal belief is that the first edition of the Headache Classification was the best regarding migraine. It required a diagnosis of all the component headaches and did not distinguish according to frequency.
I understand that many physicians want to be able to diagnose their chronic headache patients with a single diagnosis, but this is going to serve neither patients nor headache science in the future. Only by precise diagnosis based as far as possible on aetiology, pathophysiological mechanisms or clinical features can headache science progress and thereby also headache treatment.