A careful history and physical examination should aim to identify causes of acute headache that require immediate treatment. These causes can be broadly classified as imminent or completed vascular events (intracranial hemorrhage, thrombosis, cavernous sinus thrombosis, vasculitis, malignant hypertension, arterial dissection, cerebral venous thrombosis, transient ischemic attack, or aneurysm), infections (abscess, encephalitis, or meningitis), intracranial masses causing intracranial hypertension, preeclampsia, and carbon monoxide poisoning. Having the patient carefully describe the onset of headache can be helpful in diagnosing a serious cause. Report of a sudden-onset headache that reaches maximal and severe intensity within seconds or a few minutes is the classic description of a “thunderclap” headache; it should precipitate workup for subarachnoid hemorrhage, since the estimated prevalence of subarachnoid hemorrhage in patients with thunderclap headache is 43%. Thunderclap headache during the postpartum period precipitated by the Valsalva maneuver or recumbent positioning may indicate reversible cerebral vasoconstriction syndrome. Other historical features that raise the need for diagnostic testing include headache brought on by the Valsalva maneuver, cough, exertion, or sexual activity.
The medical history can also guide the need for additional workup. Under most circumstances (including a normal neurologic examination), new headache in a patient older than 50 years or with HIV infection warrants immediate neuroimaging (Table 2–5). When the patient has a history of hypertension—particularly uncontrolled hypertension—a complete search for other features of “malignant hypertension” is appropriate to determine the urgency of control of hypertension (see Chapter 11). Headache and hypertension associated with pregnancy may be due to preeclampsia. Episodic headache associated with the triad of hypertension, palpitations, and sweats is suggestive of pheochromocytoma. In the absence of thunderclap headache, advanced age, and HIV infection, a careful physical examination and detailed neurologic examination will usually determine acuity of the workup and need for further diagnostic testing. A history consistent with hypercoagulability is associated with an increased risk of cerebral venous thrombosis.
Table 2–5.Clinical features associated with acute headache that warrant urgent or emergent neuroimaging. ||Download (.pdf) Table 2–5. Clinical features associated with acute headache that warrant urgent or emergent neuroimaging.
Prior to lumbar puncture
Abnormal neurologic examination
Abnormal mental status
Abnormal funduscopic examination (papilledema; loss of venous pulsations)
Emergent (conduct prior to leaving office or emergency department)
Abnormal neurologic examination
Abnormal mental status
Urgent (scheduled prior to leaving office or emergency department)
Age > 50 years (normal neurologic examination)
Symptoms can also be useful for diagnosing migraine headache in the absence of the “classic” migraine pattern of scintillating scotoma followed by unilateral headache, photophobia, and nausea and vomiting (Table 2–6). The presence of three or more of these symptoms (nausea, photophobia, phonophobia, and exacerbation by physical activity) can establish the diagnosis of migraine (in the absence of other clinical features that warrant neuroimaging studies), and the presence of only one or two symptoms (provided one is not nausea) can help rule out migraine. A systematic list called the SNNOOP10 has been developed as a screening method for secondary causes of headache (Table 2–7).
Table 2–6.Summary likelihood ratios (LRs) for individual clinical features associated with migraine diagnosis. ||Download (.pdf) Table 2–6. Summary likelihood ratios (LRs) for individual clinical features associated with migraine diagnosis.
|Clinical Feature ||LR+ (95% CI) ||LR– (95% CI) |
|Nausea ||19 (15–25) ||0.19 (0.18–0.20) |
|Photophobia ||5.8 (5.1–6.6) ||0.24 (0.23–0.26) |
|Phonophobia ||5.2 (4.5–5.9) ||0.38 (0.36–0.40) |
|Exacerbation by physical activity ||3.7 (3.4–4.0) ||0.24 (0.23–0.26) |
Table 2–7.SNNOOP10 list of “red” flags for secondary causes of headache. ||Download (.pdf) Table 2–7. SNNOOP10 list of “red” flags for secondary causes of headache.
|Sign or Symptom ||Related Secondary Headaches |
|Systemic symptoms1 ||Headache attributed to infection, nonvascular intracranial disorders, carcinoid, or pheochromocytoma |
|Neoplasm in history ||Neoplasms of the brain; metastasis |
|Neurologic deficit/dysfunction ||Headaches attributed to vascular, nonvascular intracranial disorders; brain abscess and other infections |
|Onset of headache is sudden or abrupt ||Subarachnoid hemorrhage and other headache attributed to cranial or cervical vascular disorders |
|Older age (> 50 years) ||Giant cell arteritis and other headache attributed to cranial or cervical vascular disorders; neoplasms and other nonvascular intracranial disorders |
|Pattern change or recent onset of headache ||Neoplasms, headaches attributed to vascular, nonvascular intracranial disorders |
|Positional headache ||Intracranial hypertension or hypotension |
|Precipitated by sneezing, coughing, or exercise ||Posterior fossa malformations; Chiari malformation |
|Papilledema ||Neoplasms and other nonvascular intracranial disorders; intracranial hypertension |
|Progressive headache and atypical presentations ||Neoplasms and other nonvascular intracranial disorders |
|Pregnancy or puerperium ||Headaches attributed to cranial or cervical vascular disorders; postdural puncture headache; hypertension-related disorders (eg, preeclampsia); cerebral sinus thrombosis; hypothyroidism; anemia; diabetes mellitus |
|Painful eye with autonomic features ||Pathology in posterior fossa, pituitary region, or cavernous sinus; Tolosa-Hunt syndrome (severe, unilateral headaches with orbital pain and ophthalmoplegia due to extraocular palsies); other ophthalmic causes |
|Posttraumatic onset of headache ||Acute and chronic posttraumatic headache; subdural hematoma and other headache attributed to vascular disorders |
|Immune system pathology, eg, HIV ||Opportunistic infections |
|Painkiller overuse or new drug at onset of headache ||Medication overuse headache; drug incompatibility |
Critical components of the physical examination of the patient with acute headache include vital signs, neurologic examination, and vision testing with funduscopic examination. The finding of fever with acute headache warrants additional maneuvers to elicit evidence of meningeal inflammation, such as Kernig and Brudzinski signs. The absence of jolt accentuation of headache cannot accurately rule out meningitis. Patients older than 60 years should be examined for scalp or temporal artery tenderness.
Careful assessment of visual acuity, ocular gaze, visual fields, pupillary defects, optic disks, and retinal vein pulsations is crucial. Diminished visual acuity is suggestive of glaucoma, temporal arteritis, or optic neuritis. Ophthalmoplegia or visual field defects may be signs of venous sinus thrombosis, tumor, or aneurysm. Afferent pupillary defects can be due to intracranial masses or optic neuritis. In the setting of headache and hypertension, retinal cotton wool spots, flame hemorrhages, and disk swelling indicate acute severe hypertensive retinopathy. Ipsilateral ptosis and miosis suggest Horner syndrome and in conjunction with acute headache may signify carotid artery dissection. Finally, papilledema or absent retinal venous pulsations are signs of elevated intracranial pressure—findings that should be followed by neuroimaging prior to performing lumbar puncture (Table 2–5). On nonmydriatic fundoscopy, up to 8.5% of patients who arrive at the emergency department complaining of headache had abnormalities; although few had other significant physical examination findings, 59% of them had abnormal neuroimaging studies. Among pregnant women receiving inpatient neurologic consultation, more than one-third have a hypertensive cause that argues for a low threshold for neuroimaging and evaluation for preeclampsia.
Complete neurologic evaluations are also critical and should include assessment of mental status, motor and sensory systems, reflexes, gait, cerebellar function, and pronator drift. Any abnormality on neurologic evaluation (especially mental status) warrants emergent neuroimaging (Table 2–5).
Neuroimaging is summarized in Table 2–5. Under most circumstances, a noncontrast head CT is sufficient to exclude intracranial hypertension with impending herniation, intracranial hemorrhage, and many types of intracranial masses (notable exceptions include lymphoma and toxoplasmosis in HIV-positive patients, herpes simplex encephalitis, and brain abscess). When needed, a contrast study can be ordered to follow a normal noncontrast study. A normal neuroimaging study does not exclude subarachnoid hemorrhage and should be followed by lumbar puncture. One study supported a change of practice wherein a lumbar puncture can be withheld when a head CT scan was performed less than 6 hours after headache onset and showed no evidence of subarachnoid hemorrhage (negative predictive value 99.9% [95% CI, 99.3–100.0%]).
In patients for whom there is a high level of suspicion for subarachnoid hemorrhage or aneurysm, a normal CT and lumbar puncture should be followed by angiography within the next few days (provided the patient is medically stable). Lumbar puncture is also indicated to exclude infectious causes of acute headache, particularly in patients with fever or meningeal signs. Cerebrospinal fluid tests should routinely include Gram stain, white blood cell count with differential, red blood cell count, glucose, total protein, and bacterial culture. In appropriate patients, also consider testing cerebrospinal fluid for VDRL (syphilis), cryptococcal antigen (HIV-positive patients), acid-fast bacillus stain and culture, and complement fixation and culture for coccidioidomycosis. Storage of an extra tube with 5 mL of cerebrospinal fluid is also prudent for conducting unanticipated tests in the immediate future. Polymerase chain reaction tests for specific infectious pathogens (eg, herpes simplex 2) should also be considered in patients with evidence of central nervous system infection but no identifiable pathogen.
The Ottawa subarachnoid hemorrhage clinical decision rule had 100% sensitivity (and 13–15% specificity in different studies) in predicting subarachnoid hemorrhage. According to it, patients who seek medical attention in an emergency department complaining of an acute nontraumatic headache should be evaluated for subarachnoid hemorrhage if they have one or more of the following factors: age 40 years or older, neck pain or stiffness, witnessed loss of consciousness, onset during exertion, thunderclap headache (instantly peaking pain), or limited neck flexion on examination.
In addition to neuroimaging and lumbar puncture, additional diagnostic tests for exclusion of life-threatening causes of acute headache include erythrocyte sedimentation rate (temporal arteritis; endocarditis), urinalysis (malignant hypertension; preeclampsia), and sinus CT (bacterial sinusitis, independently or as a cause of venous sinus thrombosis).
A prospective multicenter observational cohort study found that the biomarker copeptin was associated with serious secondary headache (OR 2.03, 95% CI 1.52–2.70, P < 0.0001).
Optic nerve ultrasonography (optic nerve sheath diameter sonography) has been proposed as a noninvasive, quick method for diagnosing increased intracranial pressure.