Secondary headache: concepts and examples

Many disorders herald their onset or presence with headache. Of particular concern are those disorders that do not present with signs and symptoms that quickly point to an underlying etiology, and may present with headache as a first or sole symptom. New headache has a very wide differential, as opposed to chronic recurrent headache. Early identification of secondary headache is made easier by identifying those at higher risk of secondary headache, based on their background along with features of the presentation, such as new onset headache, thunderclap onset headache, and headache presentations in those over 50 years old. Other examples include those with HIV and other immunocompromised states, and a history of cancer. Such patients need more rigorous evaluation. Further investigation generally entails imaging of the head, either with computed tomography (CT) or magnetic resonance imaging. CT remains useful in an urgent care setting, to rule out mass lesions, bleeding, and stroke. It is important to understand the limitations of CT scanning of the head; brain imaging may be entirely normal with raised intracranial pressure or low intracranial pressure. Posterior fossa masses may be missed, as lack of resolution along with bone artifact make assessment of the posterior fossa difficult. Carotid or vertebral dissection does not by itself show up on CT imaging. Cerebral vein or sinus thrombosis is often not seen on CT imaging. Small mass lesions in the brain can also be missed with CT, but generally those that are small would not cause headache. Meningitis or encephalitis can show no signs on CT imaging. Assessment of the new patient with headache should always include visualization of the optic disks and blood pressure measurement; failure to do so is medicolegal jeopardy. We will take a closer look at a couple of disorders and presentations of secondary headache.