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Neurologists diagnose headaches according to the International Headache
Society (I.H.S.) Classification System. This system recognizes four primary
headache types. The phrase, "primary headache type" means that
the headache is not caused by some other disease process. These headache
types are migraine, tension, cluster and chronic paroxysmal hemicrania,
and miscellaneous. Of these, cluster is by far the most severe headache.
The headache intensity is severe enough to make some patients contemplate
These headaches are called cluster because the patient will experience
a "cluster" or series of headaches for some period of time
and they will then disappear for several months before they recur.
described by an allergist named Horton, they were felt to be allergic-or
histamine-related because he had a series of patients that would have
these horrible headaches the same period every year. In addition, histamine
(known to be important for allergic reactions) would trigger the headache
in a susceptible patient. Other known triggers include red wines and
A typical cluster headache will be described as an "ice-pick"
type pain in the eye or just above one eye. It is typically a relatively
short headache and most patients would rather walk around during the headache
than lie down. It tends to occur at night and will wake patients from
their sleep. It is associated with eye findings on the affected side.
Cluster headaches and migraines are sometimes referred to as vascular
headaches. I do not like this categorization because research is demonstrating
that cluster and migraine are clearly different entities and grouping
them causes unneeded confusion. In addition, patients will sometimes be
told that they have "cluster migraines" and this is the worst
of all as it fails to convey to the patient which diagnosis they have
- i.e., cluster or migraine.
This series of web pages reviews the IHS definition of cluster headache
and chronic paroxysmal hemicrania. It has epidemiological data, a few
words of the origin of cluster headache, and articles on the treatment
of acute attacks and prevention of future attacks.
I.H.S. Cluster Headache