The vast majority of headache is of ‘benign’ origin. Benign meaning that they are self-limiting (they will eventually go away on their own) and do not indicate that anything ‘worse’ is going on.
‘Primary’ headaches are those that do not result from another cause (e.g. intra-cranial bleeding, tumor.) Differentiating between migraine, tension-type, and cluster headaches (all of which are primary headaches) is important, as optimal treatment may differ. However, more important is knowing when to suspect the possibility of secondary headache.
Secondary headache is headache that is caused by or results from another disease or condition. Any of the following features suggest the possibility of headache as a secondary disorder and warrant further investigation:
- Unusual history or unusual character of headache.
- Age over 40 at time of first migraine.
- Headache is ‘new’, ‘different’ or substantially worse than what has previously been experienced.
- A change (especially sudden change) in the character of the headache, either in intensity, duration or frequency.
- Abnormal or unexpected neurological symptoms.
- Headaches associated with other neurological signs or symptoms (eg, diplopia, loss of sensation, weakness, trouble walking or standing) or those of unusually sudden onset.
- Headaches that are persistent (especially beyond 72 hours), or that develop after head injury or other trauma.
- Headaches that are associated with stiff neck or fever.
- Immediate, very rapid onset of severe headache – sometimes referred to as a “thunderclap headache.”
The “thunderclap headache” typically reaches peak intensity within 60 seconds. Left unattended, it may resolve over several hours – but it should not be left unattended. Thunderclap headache may represent a true medical emergency. In about 25% of cases it is caused by bleeding into the brain that can result in permanent damage or death if not promptly treated. Emergency medical care should be obtained.
One type of bleeding into the brain is called a sub-arachnoid hemorrhage. This almost always results in severe headache – typically described as “the worst headache of my life” and is often associated with a stiff neck, photophobia, nausea, vomiting, and possibly alteration of consciousness. Sub-arachnoid hemorrhage may result in a “thunderclap” headache, or it may develop somewhat more gradually.
Space occupying lesions (e.g. tumors) are another rare cause of headache, but may be missed as the symptoms sometimes mimic those of migraine (but much more often appear as “tension type” headaches.) In a recent extensive study, all patients with tumor-caused headaches that were similar to migraine had unusual symptoms such as excessively long headaches, a dramatic increase in headache frequency, new onset of seizures, confusion, prolonged nausea, and partial paralysis. This again emphasizes the need to investigate unexpected changes in headache frequency, duration or character.
It is important to note that many non-migraine headaches can respond to triptan therapy. Triptans may decrease headache pain associated with viral and bacterial infections and subarachnoid hemorrhage (bleeding into the brain.) When other symptoms raise concerns, the fact that a headache responds to an anti-migraine drug should not be taken as proof that it is a migraine.