Epidemiology

Up to 85% of the U.S. adult population reports significant headaches at least occasionally, and 15% does so on a regular basis. Headache as a primary complaint represents 3 to 5% of all emergency department (ED) visits. The vast majority of patients who have a primary complaint of headache do not have a serious medical cause for the problem. Tension headache accounts for approximately 50% of patients visiting the ED, another 30% have headache of unidentified origin, 10% have migraine-type pain, and 8% have headache from other potentially serious causes (e.g., tumor, glaucoma). It is estimated that less than 1% of patients who come to the ED with headache have a life-threatening organic disease.¹ These percentages can create a false sense of security, and headache is disproportionately represented in emergency medicine malpractice claims. Although still rare, the most commonly encountered life-threatening cause of severe sudden head pain is subarachnoid hemorrhage (SAH); approximately 20,000 potentially salvageable cases of SAH are seen in EDs each year. It is estimated that 25 to 50% of these are missed on the first presentation to a physician.² The other significant, potentially life-threatening causes of headache occur even less frequently. Meningitis, carbon monoxide poisoning, temporal arteritis, acute angle-closure glaucoma, intracranial hemorrhage (ICH), cerebral venous sinus thrombosis, and increased intracranial pressure can often be linked with specific historical elements and physical findings that facilitate their diagnosis.

Pathophysiology

The brain parenchyma is insensitive to pain. The pain-sensitive areas of the head include the coverings of the brain (the meninges), the blood vessels (both arteries and veins supplying the brain) and the various tissues lining the cavities within the skull. The ability of the patient to specifically localize head pain is often poor. Much of the pain associated with headache, particularly with vascular headache and migraines, is mediated through the fifth cranial nerve. Such pain may proceed back to the nucleus and then be radiated through various branches of the fifth cranial nerve to areas not directly involved. A specific inflammation in a specific structure (e.g., periapical abscess, sinusitis, or tic douloureux) is much easier to localize than the relatively diffuse pain that may be generated by tension or traction headaches. Pains in the head and neck may easily overlap. They should be thought of as a unit when complaints of headache are considered.

Differential Considerations

The differential diagnosis of headache is complex because of the large number of potential disease entities and the diffuse nature of many types of pain in the head and neck region (Table 20-1). However, in evaluating the patient with a headache complaint, the top priority is to exclude the life-threatening causes: SAH and ICH, meningitis, encephalitis, and mass lesions. Carbon monoxide is an exogenous toxin, the effects of which may be reversible by removing the patient from the source and administering oxygen. Carbon monoxide poisoning is a rare example of a headache in which relatively simple interventions may quickly improve a critical situation. On the contrary, returning the patient to the poisoned environment without a diagnosis could be lethal.

Rapid Assessment and Stabilization

If the patient is in a critical or comatose state, initial stabilization, including airway management, is prioritized and, if at all possible, preceded by a neurologic examination. For purposes of the initial assessment, headache can be divided into two categories: accompanied by altered mental status and without altered mental status. Whenever a patient’s mental status is impaired, brain tissue is initially assumed to be compromised. The principles of care centered on cerebral resuscitation address the seven major causes of evolving brain injury: lack of substrate (glucose, oxygen), cerebral edema, intracranial mass lesion, endogenous or exogenous toxins, metabolic alterations (fever, seizure), ischemia, or elevated intracranial pressure.

Pivotal Findings