How to classify headaches

Headache is a symptom like any other patient complaint, such as back pain. The headache may be a primary headache disorder, such as a cluster headache, or it might be secondary to another issue, such as a brain tumor.

Over 90% of patients presenting to their primary care physician with headache have one of the four primary headache disorders:

1. Migraine

This can include migraine with aura or without aura, and aura without headache. An aura refers to a group of symptoms—visual, sensory, or other central nervous system symptoms—which are fully-reversible, develop gradually, and are usually followed by headache and other migraine symptoms such as nausea.

2. Tension-type headaches

This type of headache includes episodic and frequent tension-type headaches.

3. Trigeminal autonomic cephalalgias

This is a broad category that includes cluster headaches, paroxysmal hemicrania, and short-lasting, unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT).

4. Other primary headaches

Other primary headache disorders include cough headache, exercise headache, and hypnic headaches.

In general, a headache should be considered secondary if it appears or worsens during another illness, and especially if the headache fluctuates with changes in the underlying condition.

There are eight secondary headache types, each with several subtypes:

1. Headache attributable to trauma
2. Vascular disorders
3. Nonvascular intracranial disorders
4. Substance use or withdrawal
5. Infection
6. Disorders of hemostasis
7. Disorders affecting the structures of the head or neck
8. Psychiatric disorders

The International Headache Society designed a classification system to help classify the many different potential presentations of headache. Currently in its third edition, the International Classification of Headache Disorders (ICHD-3) identifies 14 major categories of headache, which themselves are divided into three broad groups: the primary headache disorders (comprising categories 1–4), the secondary headache disorders (composed of categories 5–12), and finally, categories 13 and 14, representing the cranial neuropathies and neuralgias (which we’ll cover later).

The ICHD-3 system was modeled on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V). It incorporates both clinical criteria and laboratory features to establish diagnoses. It is hierarchical and one can characterize using multiple levels of complexity that are characterized by sequential numbering (however, it often isn’t necessary to break down your patient’s headache into the smallest of subcategories). The first and second digits of the classification are useful in primary care, and the third, fourth, and fifth digits are useful for neurology and headache specialty centers.

Using the classification system

• Use the characteristics of the headache to categorize the headache type, not the characteristics of the patient.
• The headache phenotype that is present currently, and especially over the last year, is considered to be the most current diagnosis.
• All the criteria in the classification scheme must be fulfilled in order to achieve an accurate diagnosis.
• The criteria often include a specific number of attacks that must have been experienced before any one headache type can be diagnosed.
• Many patients may have more than one headache type, and multiple headache types must be assessed and diagnosed individually.

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