Acute headache: diagnosis

Approaching a patient with acute headache
Article section 3 of 11.  Previous  Next

By Stephanie J Nahas MD

An important first step in acute headache diagnosis is to distinguish a primary from a secondary headache. Most patients who have an acute headache have a primary headache disorder (Friedman and Grosberg 2009), but the probability of secondary headaches increases in the emergency department.

Certain “red flags” suggest the possibility of secondary headache. Once these features are identified, the physician must conduct the workup indicated by the red flag (Table 1) and diagnose the secondary headache disorder if one is present.

Table 1. Red Flags in the Diagnosis of Headache

Red flag


Possible investigations


Sudden-onset headache

• Subarachnoid hemorrhage, first and foremost

• See Table 2 for complete differential diagnoses


• Neuroimaging

• Lumbar puncture (after neuroimaging evaluation)



• Mass lesion

• Subdural hematoma

• Medication overuse


• Neuroimaging

Headache with cancer,

HIV, or other systemic

illness (fever, neck

stiffness, cutaneous rash)

• Meningitis

• Encephalitis

• Lyme disease

• Systemic infection

• Collagen vascular disease

• Arteritis


• Neuroimaging

• Lumbar puncture

• Biopsy

• Blood tests

Focal neurologic signs or

symptoms other than

typical visual or sensory



• Mass lesion


• Collagen vascular disease

• Neuroimaging

• Collagen vascular evaluation


• Mass lesion

• Idiopathic intracranial hypertension

• Encephalitis

• Meningitis


• Neuroimaging

• Lumbar puncture (after neuroimaging evaluation)

Triggered by cough,

exertion or Valsalva


• Subarachnoid hemorrhage

• Mass lesion

Posterior fossa pathology


• Neuroimaging

• Considerer lumbar puncture

Headache during

pregnancy or postpartum

• Cortical vein or cranial sinus thrombosis

• Carotid dissection

• Pituitary apoplexy

• Neuroimaging

Modified from: (Lipton et al 2008)

Table 2. Differential Diagnoses of Thunderclap Headache

Vascular etiologies

Subarachnoid hemorrhage
Cervical artery dissection
Aneurysmal thrombosis or expansion
Cerebral venous thrombosis
Hypertensive crisis
Reversible cerebral vasoconstriction syndrome
Pituitary apoplexy
Retroclival hematoma

Nonvascular etiologies

Spontaneous intracranial hypotension/hypovolemia
Colloid cyst of the third ventricle
Sinusitis (especially sphenoid)
Primary cough, sexual, and exertional headache
Primary thunderclap headache (idiopathic)

In This Article

Approaching a patient with acute headache
Identifying secondary headaches
Diagnosing a primary headache disorder
Low-to-moderate frequency headaches of long duration
High-frequency headaches of long duration
Headaches of shorter duration
References cited