Red Flags for Headaches Requiring Immediate Medical Attention
Headaches with any of the following red flags require immediate medical attention as they may indicate life-threatening conditions such as subarachnoid hemorrhage, meningitis, or intracranial space-occupying lesions.
Patient History Red Flags
- Thunderclap headache - sudden onset headache reaching maximum intensity within seconds to minutes, which may indicate possible subarachnoid hemorrhage 1
- "Worst headache of life" - abrupt onset of severe headache may indicate serious vascular pathology 1
- Marked change in headache pattern - significant change in previously stable headache characteristics 1
- New headache onset after age 50 - suggests secondary headache and consideration of temporal arteritis 1
- Progressive headache - worsening over time could indicate an intracranial space-occupying lesion 1
- Headache awakening patient from sleep - may indicate increased intracranial pressure 1, 2
- Headache aggravated by postures or maneuvers that raise intracranial pressure (coughing, sneezing, exercise) 1
- Persistent headache following head trauma - may indicate intracranial injury 1
- Headache associated with weight loss and/or change in memory or personality - suggests secondary headache 1
- Atypical aura - may indicate transient ischemic attack, stroke, epilepsy, or arteriovenous malformations 1
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
- Uncoordination - may indicate cerebellar pathology 1, 2
- Impaired memory and/or altered consciousness or personality - suggests secondary headache 1
- Limited neck flexion on examination - part of the Ottawa SAH Rule 2
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 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
For patients with acute onset of severe headache who present >6 hours from symptom onset or who have a new neurological deficit: A noncontrast head CT and, if negative for subarachnoid hemorrhage, lumbar puncture should be performed 2
For patients with acute onset of severe headache who present <6 hours from symptom onset and without new neurological deficit: A noncontrast head CT performed on a high-quality scanner and interpreted by a board-certified neuroradiologist is reasonable 2
When red flags are present: Neuroimaging is indicated to rule out secondary causes of headache 1
MRI is 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
Clinical Significance
The sensitivity of red flag criteria for detecting serious secondary headaches has been reported as 96.5%, though specificity is low at only 5.1% 3
New neurological deficit, history of neoplasm, older age (>50 years), and recent head trauma are independent predictors of a serious secondary headache diagnosis 3
Only rarely does serious underlying disease give rise to a headache that exactly mimics a migraine or tension headache - there are almost always atypical features or warning signals 4
Overlooking the need for neuroimaging when red flags are present is a common pitfall that can lead to missed diagnosis of life-threatening conditions 1, 5
Aneurysms account for the majority of fatal vascular cases (22.9%), with loss of consciousness, occipital headache, neck pain, and focal neurological deficits seen more commonly in these cases 5
Remember that while most headaches are benign, recognizing these red flags and acting promptly can be life-saving for patients with serious underlying conditions 5, 6.