Now how do we diagnose primary or secondary headaches? Well, the basis of the diagnosis of a primary headache really rests upon the symptoms themselves. Recently the International Headache Society (IHS) Classification, second edition (ICHD-2), was released to distinguish various types of headaches, the clinical features of various types of headaches. And as you can see from this slide, primary headache is based on symptoms. It's a tool that now is available to measure and monitor patient disability, whereas secondary headache disorders are based on etiology, whether it's due to stroke, subarachnoid hemorrhage, infection, sinusitis, or one of the many different causes of headache. How we distinguish between the 2 can be difficult, but in general there are red flags in both the history and on the physical exam that can separate between a primary and a secondary headache disorder.

As you see here, the red flags for secondary headaches are listed, and we use the mnemonic SSNOOP, which refers to a number of different characteristics in the headache history, clinical features, and examinations that can tip you off as to whether you're dealing with an ominous cause of headache. So the first S, systemic symptoms, is referring to weight loss or fever or joint pains or body aches, which should suggest an underlying infectious or systemic inflammatory disorder. Newly acquired neurologic signs or symptoms should always raise concern for an underlying disorder. The second S, secondary risk factors, such as an underlying disease, whether HIV or systemic cancer, should raise the specter of a more serious disorder in an immunocompromised host. Neurologic symptoms or abnormal signs on the neurologic examination, such as a change in the mental status, a waxing and waning mental status or impairment in alertness, should clue the physician that an ominous cause is probablyat play.

How does the headache begin? The onset, such as a sudden onset or the worst headache of their life or headache that crescendos rapidly, also should clue the physician that he or she is dealing with a subarachnoid hemorrhage or other form of intracerebral bleed. Headaches that begin in an older population, either a new onset of headache after age 50 or a change in an established pattern of headache after age 50, are an organic cause of headache until proven otherwise. In this subpopulation, the idea of mass lesions or systemic illness such as giant-cell arteritis always needs to be entertained. And finally, a previous headache history or a progression of a known headache -- whether the pattern has changed or that this is the first headache or a change in an established pattern of headache or whether other clinical features are at play -- need to come into the history to rule out secondary vs. primary causes of headache. When Jessie discussed her headache, none of these factorslisted under SSNOOP were evident.