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Ms. M is a 34-year-old woman who comes to an outpatient practice complaining of intermittent headaches.

image What is the differential diagnosis of headache? How would you frame the differential?


Figure 20-1.

Diagnostic approach: headache.

Headache is one of the most common physical complaints. Because < 1% of all headaches are life-threatening, the challenge is to reassure and appropriately treat patients with benign headaches while finding the rare, life-threatening headache without excessive evaluation.

Headaches are classified as primary or secondary. Primary headaches are syndromes unto themselves rather than signs of other diseases. Although potentially disabling, they are reliably not life-threatening. Secondary headaches are symptoms of other illnesses. Unlike primary headaches, secondary headaches are potentially dangerous.

The distinction between primary and secondary headaches is useful diagnostically. Primary headaches, such as tension headaches, are diagnosed clinically, sometimes using diagnostic criteria (the most commonly used are published by the International Headache Society, IHS). Traditional diagnostic studies (laboratory studies, radiology, pathology) cannot verify the diagnosis. Secondary headaches, such as headaches caused by central nervous system (CNS) tumors, often can be definitively diagnosed by identifying the underlying disease of which the headache is a symptom.

Clinically, primary and secondary headaches can be difficult to distinguish. The single most important question when developing a differential diagnosis for a headache is, “Is this headache new or old?” Chronic headaches tend to be primary, while new-onset headaches are more likely to be secondary. This is the first and most important pivotal point in diagnosing headaches. This distinction is not perfect. There are some chronic headaches that are secondary headaches (headaches caused by cervical degenerative joint disease for example) and even classic, primary headaches (such as migraines) can present as a new headache. The differentiation of old versus new also depends on how rapidly a patient brings his or her symptoms to medical attention. This being said, the classification of headaches as primary versus secondary and new versus old provides not only a memorable framework for the differential diagnosis but also a clinically useful structure by which the differential can be organized by pivotal points. The differential diagnosis appears below. Figure 20-1 shows the potential diagnoses in a more algorithmic form as they are often considered clinically. The IHS’s classification website ( is also a terrific resource for an annotated differential diagnosis.

  1. Old headaches

    1. Primary

      1. Tension headaches

      2. Migraine headaches

      3. Cluster headaches

    2. Secondary

      1. Cervical degenerative joint disease

      2. Temporomandibular joint syndrome

      3. Cranial neuralgias (maybe either primary or secondary)

      4. Headaches associated with substances or their withdrawal

        1. Caffeine

        2. Nitrates

        3. Analgesics (often presenting as chronic daily headaches)

        4. Ergotamine

  2. New headaches

    1. Primary

      1. Benign cough headache

      2. Benign exertional headache

      3. Headache associated with sexual activity

      4. Benign thunderclap headache

      5. Idiopathic intracranial hypertension (pseudotumor cerebri)

    2. Secondary

      1. Infectious

        1. Upper respiratory tract ...

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