Headache is the fifth most common symptom presenting to the ED in the United States, with a total of 2.1 million visits per year.¹ Overall, headaches affect people across all ethnic, geographic, and economic levels, with an estimated global prevalence of 47% in adults.²

In the ED, the approach to headache focuses on identifying patients at risk for rapid deterioration, morbidity, and mortality; rapidly identifying high-risk headache syndromes; and providing appropriate headache therapy.

The brain parenchyma has no pain sensors.³ Early theories postulating vasoconstriction and rebound vasodilatation as the cause of migraine have been refuted.⁴ Numerous physiologic mechanisms play a role in the development of the various clinical headache syndromes. For example, occipital nerve irritation may lead to the development of occipital neuralgia.⁵ Similarly, headaches associated with disturbances in intracranial pressure (both high and low) are related to compression of, or traction on, pressure-sensitive structures in the meninges.⁶ The pathophysiologic mechanisms of other headache syndromes, such as migraine headaches, cluster headaches, and toxic and metabolic headaches, are less clear. Discussion of these mechanisms is beyond the scope of this chapter.

Most patients with headache have conditions that are painful but benign in etiology. Identifying those at high risk is the first step in management (Table 165-1). A high-risk cause for headache accounts for only 4% of all headaches but 10% to 14% of acute-onset (“thunderclap”) headaches.^7,8 Although headaches are typically classified as primary headaches when there is no underlying cause (such as migraine or cluster headaches) and secondary headaches if associated with an underlying cause (such as tumor, meningitis, or subarachnoid hemorrhage), this distinction is not clinically useful in the ED setting.

HISTORY

Features associated with high-risk headaches are as follows:

Patient Age

Patients >50 years of age, with a new or worsening headache, represent a high-risk group. The incidence of migraine, cluster, and tension headaches decreases with age, raising the likelihood of ominous pathology for older patients.⁹

Onset of Symptoms

The abrupt onset of severe headache, or “thunderclap” headache, requires immediate and thorough evaluation.¹⁰ Thunderclap headache associated with intracerebral aneurysmal leak (“sentinel hemorrhage” or “herald bleed”) may precede catastrophic aneurysmal rupture. Associated symptoms may include neck stiffness, nausea, vomiting, loss of consciousness, neurologic deficit, or altered mentation.¹¹ Onset of thunderclap headache during periods of exertion raises suspicion for subarachnoid hemorrhage or arterial dissection of the carotid or vertebrobasilar circulation. Headaches associated with the Valsalva maneuver may herald an intracranial abnormality.¹² Rarely, spontaneous intracranial hypotension and acute hydrocephalus associated with third ventricular colloid cyst may present with thunderclap headache.¹³ Other causes for thunderclap headache are listed in Table 165-2.

Headache Quality

A change in pattern, frequency, quality, or intensity of a preexisting headache syndrome needs the same evaluation as a new-onset headache syndrome.

Fever

Fever raises concern for CNS infection, such as meningitis, encephalitis, or brain abscess. However, the absence of fever does not exclude a CNS infection, especially in patients at the extremes of age and with immunocompromised states.

Medication History

Ask about over-the-counter medications, anticoagulants, antiplatelet agents, chronic steroids, immunomodulatory agents, or antibiotics (prescribed or not) to identify patients at high risk for infection (e.g., eculizumab and its elevated risk for meningococcal infection). Chronic use of analgesic and anti-inflammatory agents may result in rebound or withdrawal headaches. Medication overuse is defined as use >10 times a month and is notable for ergots, triptans, and opioids.¹² Anticoagulants and antiplatelet agents increase the risk for hemorrhage, both spontaneous and traumatic.¹⁴ The recent use of antibiotics may present with a falsely reassuring clinical appearance due to partial treatment of a potentially dangerous CNS infection.

Prior Headache History

A prior history suggestive of migraine, tension, or cluster-type headaches, and response to specific therapy, may obviate the need for extensive ED evaluation (Tables 165-3 and 165-4).

Substance Use History

Use of adrenergic agents such as cocaine, amphetamine, or derivative compounds such as methamphetamine increases risk of intracranial hemorrhage or the less common entity of reversible cerebral vasoconstriction syndrome.¹⁵ Patients with a history of alcohol abuse are at increased risk of intracranial bleeding due to falls, interpersonal violence, and the potential for liver dysfunction associated with prolonged coagulation times and thrombocytopenia.

Family History

Known aneurysm or sudden death in first-degree relatives raises the suspicion for intracranial aneurysm.¹⁶ The incidence of aneurysm in patients with a family history is three to five times higher than in those without a family history. A personal or family history of autosomal dominant polycystic kidney disease also increases the risk for intracranial aneurysm. In patients with autosomal dominant polycystic kidney disease, aneurysmal rupture is more likely to occur at a younger age. The presence of migraine in a first-degree relative is associated with a two- to four-fold increased risk of developing migraine.¹⁷

PHYSICAL EXAMINATION

Vital Signs

Headache is a common symptom associated with fever. For example, headache is seen in up to 60% of patients with upper respiratory tract infection symptoms.^7,18 However, the persistence of headache in the presence of a normalized temperature suggests consideration for further evaluation of a possible CNS infection. The presence of fever in association with neck stiffness and altered mental status represents the classic triad of meningitis. Ninety-five percent of patients with bacterial meningitis present with at least two of the four findings (classic triad plus headache).¹⁹

Severe hypertension can be associated with headache and the development of acute changes in mental status and neurologic function. Posterior reversible encephalopathy syndrome²⁰ and hypertensive urgency should be considered in such patients (see “Posterior Reversible Encephalopathy Syndrome” section).

Examination of the Head and Neck

Meningismus is an important clinical clue to the presence of infection or hemorrhage.¹⁹ Examine the ears, nose, and throat to identify otitis media and sinusitis, both of which may cause headache and contribute to the extension of infection to the CNS. Palpate for scalp tenderness and tenderness over the temporal arteries to assess for possible temporal arteritis.

Examination of the Eye

Headache can occur with acute angle-closure glaucoma, scleritis, and endophthalmitis. Consider acute angle-closure glaucoma even when there is no focal ocular complaint, because the pain can be so severe the patient may fail to localize pain to the eye. Measure intraocular pressure to exclude glaucoma. Check visual acuity and visual fields and examine the pupils and eyelids, checking for signs of Horner’s syndrome.

Funduscopic Examination

Papilledema can be seen in the presence of raised intracranial pressure. However, there is typically a delay in the onset of papilledema once intracranial pressure begins to elevate, and papilledema can persist once intracranial pressure returns to normal.²¹ The ability to recognize papilledema by routine direct ophthalmoscopy alone (particularly with nondilated pupils) is limited, but using a panoptic ophthalmoscope provides a more reliable view of the retina.²² Bedside US of the optic nerve sheath can also assess for papilledema.^23,24 The presence of papilledema requires CT imaging before lumbar puncture.²⁵

Neurologic Examination

A baseline neurologic assessment includes the following: mental status assessment; cranial nerve examination, including pupillary examination (for asymmetry or ptosis, which may suggest third nerve compression by posterior communicating artery aneurysms); assessment for other cranial neuropathies (which may raise suspicion for carcinomatous meningitis); motor examination to detect extremity weakness (particularly subtle weakness with pronator drift); reflex examination for subtle asymmetry or a Babinski reflex; and gait and coordination testing (which may be impaired in cerebellar lesions).

There are many causes of headache, each of which is diagnosed and managed differently. See discussions of specific causes of headache below.

Routine blood testing is of limited utility in the diagnosis of acute headache and should be guided by the patient’s age, history, relevant comorbidities, and medication history.

The laboratory evaluation of patients with high-risk headaches may include basic metabolic profile, CBC, coagulation panel, erythrocyte sedimentation rate, and blood cultures for possible infection.

Selecting an appropriate imaging study depends on the history, physical examination findings, and differential diagnosis of headache,^26,27,28 as well as the resources available to the emergency provider. Table 165-5 summarizes some of the American College of Radiology recommendations for appropriate imaging. When MRI is immediately unavailable and diagnostic uncertainty regarding the possibility of an underlying lesion prevails, further imaging may be necessary, the timing of which will depend on the clinical circumstances and likelihood of the patient being able to follow-up in a reliable fashion.²⁶

If the patient presents with a typical history of headache that responds to typical measures and a normal neurologic examination, avoiding imaging may be prudent to reduce the risk for radiation exposure. For most patients in the ED with headache, a noncontrast head CT is the fastest and most appropriate initial imaging study, as well as the most sensitive for detecting acute intracranial hemorrhage.^28,29

Contrast (iodinated contrast and gadolinium-based magnetic resonance contrast agents) is contraindicated for patients with renal insufficiency due to risk for renal toxicity and nephrogenic systemic fibrosis.³⁰ Gadolinium is also relatively contraindicated in pregnancy and breastfeeding women. MRI can be limited by claustrophobia. A discussion with the radiologist and/or radiology technical staff can clarify the safety of MRI in patients with devices or foreign bodies.

Magnetic resonance angiography is useful in detecting arterial disease (stenosis, congenital anomalies, dissection, CNS vasculitis) and should be considered in any case where there may be arterial pathology underlying the patient’s symptoms. Discuss concerns for dissection with the radiologist to determine the most appropriate MRI method.

If MRI is unavailable or not clinically feasible, consultation with radiology regarding other appropriate imaging modalities is prudent.

After the clinical assessment, blood work, and imaging, the next step is to determine whether or not to perform a lumbar puncture (LP) and, if so, the timing of LP. LP can serve as both a diagnostic tool (as in meningitis, subarachnoid hemorrhage, intracranial hypotension, carcinomatous meningitis) and therapeutic tool (as in pseudotumor cerebri).

Ideally, perform the LP with the patient in the lateral decubitus position in order to allow for the accurate measurement of opening pressure. Seated LP does not allow for accurate assessment of opening pressure. Opening pressure provides critical information about the patient’s intracranial pressure, should be performed routinely, and should be considered a routine procedure when performing LP.

The possibility of herniation in association with LP is a frequent concern of emergency providers. There is no randomized controlled trial assessing the question of when it is safe to perform an LP. The cumulative evidence suggests that in patients without a history of immunosuppression, who have a normal sensorium, and who have no focal neurologic deficits, it is safe to proceed with LP without imaging prior to LP.^31,32