What are the red flag signs of headache?

Red Flag Signs of Headache

The most critical red flag signs of headache requiring immediate medical attention include thunderclap headache (sudden onset reaching maximum intensity within seconds to minutes), "worst headache of life," new focal neurological deficits, and headache with fever and neck stiffness, as these may indicate life-threatening conditions such as subarachnoid hemorrhage or meningitis. 1, 2

Patient History Red Flags

• Thunderclap headache - sudden onset headache reaching maximum intensity within seconds to minutes (may indicate subarachnoid hemorrhage) 1, 2
• "Worst headache of life" - abrupt onset of severe headache (may indicate serious vascular pathology) 1
• New headache onset after age 50 (suggests secondary headache, consider temporal arteritis) 1, 2
• Progressive headache that worsens over time (could indicate intracranial space-occupying lesion) 1, 2
• Headache that awakens patient from sleep (may indicate increased intracranial pressure) 1, 2
• Headache aggravated by Valsalva maneuvers (coughing, sneezing, exercise) 1, 2
• Persistent headache following head trauma (may indicate intracranial injury) 1, 2
• Marked change in previously stable headache pattern 1, 2
• Headache associated with weight loss and/or changes in memory or personality 1, 2
• Atypical aura (may indicate TIA, stroke, epilepsy, or arteriovenous malformations) 1, 2

Physical Examination Red Flags

• Focal neurological symptoms or signs (suggest secondary headache) 1, 2
• Neck stiffness (possible indicator of meningitis or subarachnoid hemorrhage) 1, 2
• Unexplained fever (may indicate meningitis) 1, 2
• Uncoordination (may indicate cerebellar pathology) 1, 2
• Impaired memory and/or altered consciousness or personality 1, 2
• Limited neck flexion on examination (part of the Ottawa SAH Rule) 1
• Papilledema (indicates increased intracranial pressure) 3

Ottawa SAH Rule

For alert patients >15 years of age with new severe nontraumatic headache reaching maximum intensity within 1 hour, additional investigation for subarachnoid hemorrhage is required if any of these criteria are met 1:

1. Age ≥40 years
2. Neck pain or stiffness
3. Witnessed loss of consciousness
4. Onset during exertion
5. Thunderclap headache (instantly peaking pain)
6. Limited neck flexion on examination

Diagnostic Approach When Red Flags Present

• For patients with acute onset of severe headache who present >6 hours from symptom onset or who have a new neurological deficit: perform noncontrast head CT and, if negative for subarachnoid hemorrhage, proceed to lumbar puncture 1
• For patients with acute onset of severe headache who present <6 hours from symptom onset without new neurological deficit: noncontrast head CT performed on a high-quality scanner and interpreted by a board-certified neuroradiologist 1
• MRI is generally preferred over CT due to higher resolution and absence of radiation exposure, except when acute intracranial hemorrhage is suspected, then CT without contrast is recommended 1, 2

Common Pitfalls to Avoid

• Overlooking the need for neuroimaging when red flags are present 2
• Mistaking a secondary headache for a primary headache disorder (migraine, tension-type, cluster) 4, 5
• Failing to perform lumbar puncture after a negative CT scan when subarachnoid hemorrhage is suspected 1, 6
• Assuming that a pre-existing headache disorder excludes a secondary cause 7
• Relying solely on neuroimaging without considering the complete clinical picture 8, 5

Distinguishing from Primary Headache Features

Primary headaches (migraine, tension-type, cluster) constitute nearly 98% of all headaches, but secondary headaches are important to recognize as they may be life-threatening 9. Typical migraine features include recurrent headache attacks lasting 4-72 hours, unilateral location, pulsating quality, moderate to severe intensity, aggravation by routine physical activity, and associated symptoms like nausea, vomiting, photophobia, and phonophobia 3. However, the presence of any red flags should prompt consideration of secondary causes, even in patients with a known primary headache disorder 7.