Chronic daily headache relates to the daily or almost-daily occurrence
of headache. However, not all daily or almost-daily headaches fall
under this denominator, as is the case with the daily or almost-daily
headaches of (chronic) cluster headache and paroxysmal hemicrania,
as well as those of hypnic headache or nocturnal migraine. These
conditions can be referred to as paroxysmal daily headaches in which
the headaches occur in well-defined attack patterns. In cluster
headache, the attack pattern is that of headaches occurring once
or twice a day and lasting 1 to 2 hours, whereas in paroxysmal hemicrania,
it is that of headaches occurring 5 to 15 times per day and lasting
10 to 30 minutes. In hypnic headache or nocturnal migraine, the
headaches occur once a day, waking the patient from sleep at night,
usually between 4 and 6 am, and lasting for a variable amount of
time, also depending on the efficacy of treatment.
Of the nonparoxysmal daily headaches, hemicrania continua is
a condition that does not fall under the denominator of chronic
daily headache, either. However, it is discussed in this chapter because
it is very difficult, if not impossible, to distinguish from chronic
daily headache on the basis of presentation alone. It differs from
chronic daily headache in having a somewhat more consistent and
less variable intensity of the pain and in an absolute response
to preventive treatment with indomethacin.
Chronic daily headache is not the same as chronic tension-type
headache, as defined by the International Headache Society (IHS).1 The
IHS defines chronic tension-type headache as headaches with an average
frequency of 15 days per month (180 days per year) or more for at
least 6 months. In addition, the headaches must have at least two
of the following features: pressing quality, mild or moderate intensity,
bilateral location, and no aggravation by routine physical activity.
Both of the following have to apply: no vomiting and no more than
one of the following symptoms: nausea, photophobia, or phonophobia.
Finally, the following conditions must be met: the history as well
as the physical and neurologic examination do not suggest the presence
of another cause of headache; if the presence of such a cause is
suggested, it is ruled out by appropriate investigations or, if
such a cause is present, the headaches did not occur for the first
time in close temporal relation to occurrence of the disorder.
Although it is stated in the IHS classification that sometimes
migraine gradually transforms into chronic tension-type headache,
in my opinion, that is incorrect. Migraine may, however, transform
into chronic daily headache, as discussed later. The confusion stems
from the fact that the IHS identifies chronic daily headache as
a synonym for chronic tension-type headache, which is incorrect.
Chronic daily headache is, rather, a replacement for the old term,
mixed or combined headache. In the practice of medicine, the group
of patients with this condition is also the majority ...