What is a sentinel or warning headache?

Sentinel or Warning Headache in Subarachnoid Hemorrhage

A sentinel or warning headache is a sudden, intense headache that precedes a major aneurysmal subarachnoid hemorrhage (aSAH) by days to weeks, representing a minor hemorrhage or "warning leak" from an intracranial aneurysm that signals impending catastrophic rupture. 1, 2

Clinical Characteristics of Sentinel Headaches

• Reported in 10-43% of patients who subsequently experience major aneurysmal rupture 1
• Typically occurs 2-8 weeks before overt aSAH 1
• Usually milder than the headache associated with major rupture but still sudden in onset 1
• May persist for several days 1
• Often described as unusual in location and severity compared to any previous headache experience 3

Associated Symptoms

• Nausea and vomiting may occur 1
• Meningismus (neck stiffness) is uncommon after sentinel hemorrhage 1
• May be accompanied by transient visual disturbances 3
• Can present with strictly limited pain, such as unilateral orbital pain 4

Clinical Significance

• Increases the odds of early rebleeding 10-fold 1
• Recognition is critical as it provides an opportunity to intervene before catastrophic rupture 1
• In a study of 89 consecutive SAH patients, 27% had experienced sentinel headaches prior to major rupture 5
• Among 1752 patients with aneurysm rupture from three series, 19.4% (range 15-37%) had a history of sudden severe headache before the event leading to admission 1

Diagnostic Approach

• Non-contrast head CT is the cornerstone of diagnosis for SAH with sensitivity approaching 100% in the first 12 hours 2
• If CT is negative but clinical suspicion remains high, lumbar puncture should be performed to detect xanthochromia, especially if presentation is >6 hours from symptom onset 2
• Vascular imaging (CTA or DSA with 3D rotational angiography) should be performed to identify aneurysm location 2
• MR angiography may be considered when CTA/DSA is contraindicated 2

Common Pitfalls in Diagnosis

• Sentinel headaches are frequently misdiagnosed as migraine, tension headache, influenza, sinusitis, or neck strain 3
• Misdiagnosis of aSAH is associated with a nearly 4-fold higher likelihood of death or disability at 1 year 1
• The most common diagnostic error is failure to obtain a noncontrast head CT scan 1
• Headache is a common presenting complaint in emergency departments, with aSAH accounting for only 1% of all headaches evaluated 1

Clinical Implications

• High index of suspicion is warranted in patients presenting with sudden severe headache 1
• Early recognition and treatment of the underlying aneurysm can be lifesaving 1, 2
• Securing the aneurysm as early as possible (ideally within 24 hours) reduces rebleeding risk 2
• Treatment options include endovascular coiling and surgical clipping, with the decision made by a multidisciplinary team 2

Recognizing sentinel headaches represents one of the best opportunities to improve outcomes in patients with intracranial aneurysms by enabling intervention before catastrophic rupture occurs. Any patient presenting with a sudden, severe headache should be evaluated promptly with appropriate neuroimaging to rule out subarachnoid hemorrhage.