What are the red flags of headache in adults?

Red Flag Headache Symptoms in Adults

When evaluating adults with headache, immediately investigate for secondary causes if any red flag features are present, as these indicate potentially life-threatening conditions requiring urgent neuroimaging or other diagnostic workup.

Critical Historical Red Flags

Acute Onset Features

• Thunderclap headache (sudden onset reaching maximum intensity within seconds to minutes) suggests subarachnoid hemorrhage and requires immediate evaluation 1, 2
• "Worst headache of life" with abrupt onset indicates serious vascular pathology 1, 2
• Headache onset after age 50 raises concern for secondary headache, particularly temporal arteritis 1, 2

Pattern and Progression Features

• Marked change in headache pattern (significant alteration in previously stable headache characteristics) warrants investigation for secondary causes 1, 2
• Progressive headache that worsens over time suggests intracranial space-occupying lesion 1
• Headache awakening patient from sleep may indicate increased intracranial pressure 1, 2

Provocative Features

• Headache aggravated by Valsalva maneuvers (coughing, sneezing, exercise) or postures that raise intracranial pressure suggests intracranial hypertension, hypotension, or space-occupying lesion 1, 3
• Headache brought on by exertion could indicate intracranial pathology 1

Associated Features

• Persistent headache following head trauma may indicate subdural hematoma or other intracranial injury 1, 2
• Atypical aura may indicate transient ischemic attack, stroke, epilepsy, or arteriovenous malformations 1, 2
• Headache associated with weight loss and/or change in memory or personality suggests secondary headache, possibly malignancy 1, 2

Critical Physical Examination Red Flags

Neurological Signs

• Focal neurological symptoms or signs strongly suggest secondary headache requiring urgent evaluation 1, 2, 3
• Uncoordination may indicate cerebellar pathology 1, 2, 3
• Impaired memory and/or altered consciousness or personality suggests secondary headache 1, 2
• Papilledema indicates increased intracranial pressure 3

Infectious/Inflammatory Signs

• Neck stiffness is a possible indicator of meningitis or subarachnoid hemorrhage 1, 2
• Unexplained fever may indicate meningitis 1, 2

Ottawa Subarachnoid Hemorrhage Rule

For alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour, investigate for subarachnoid hemorrhage if ANY of the following are present: 2

• Age ≥40 years
• Neck pain or stiffness
• Witnessed loss of consciousness
• Onset during exertion
• Thunderclap headache (instantly peaking pain)
• Limited neck flexion on examination

Diagnostic Approach Based on Red Flags

Imaging Selection

• Neuroimaging is mandatory when red flags are present to rule out secondary causes 1, 2
• MRI is preferred over CT due to higher resolution and absence of radiation exposure for most secondary headache evaluations 1, 2
• CT without contrast is recommended when acute intracranial hemorrhage is suspected (thunderclap headache, trauma) 1, 2

Timing-Based Protocol for Suspected Subarachnoid Hemorrhage

• Patients presenting >6 hours from symptom onset or with new neurological deficit: Perform noncontrast head CT followed by lumbar puncture if CT is negative 2
• Patients presenting <6 hours from symptom onset without new neurological deficit: Noncontrast head CT on high-quality scanner interpreted by board-certified neuroradiologist is reasonable 2

Common Pitfalls to Avoid

• Overlooking the need for neuroimaging when red flags are present is a critical error that can result in missed life-threatening diagnoses 1
• Relying solely on neuroimaging without considering the complete clinical picture can lead to diagnostic errors 2
• Assuming a preexisting headache disorder excludes secondary headache is dangerous, as secondary headaches can occur in patients with known primary headache disorders 4

When No Red Flags Are Present

Consider primary headache disorders (migraine, tension-type, cluster headaches) using International Classification of Headache Disorders criteria when no red flags are identified 1