What is the appropriate evaluation and management of headaches with red flags, such as sudden severe headache or headache accompanied by fever, confusion, or stiff neck?

Headache Red Flags: Evaluation and Management

Immediate Recognition of Life-Threatening Presentations

Any patient presenting with thunderclap headache (sudden onset reaching maximum intensity within 1 minute), "worst headache of life," or headache with fever, confusion, or stiff neck requires urgent neuroimaging and possible lumbar puncture to rule out subarachnoid hemorrhage or meningitis. 1, 2, 3

Critical Historical Red Flags

The following features in a patient's history demand immediate evaluation:

• Thunderclap headache: Sudden onset reaching maximum intensity within seconds to minutes suggests subarachnoid hemorrhage 1, 2, 3, 4
• "Worst headache of life": Abrupt onset of severe headache indicates serious vascular pathology 1, 3, 4
• New headache after age 50: Suggests secondary headache, particularly temporal arteritis 2, 3, 4
• Progressive headache: Worsening over time indicates possible intracranial space-occupying lesion 2, 3, 4
• Headache awakening patient from sleep: May indicate increased intracranial pressure 1, 2, 4
• Headache with Valsalva maneuvers: Aggravated by coughing, sneezing, or exercise suggests increased intracranial pressure 1, 4
• Persistent headache following head trauma: May indicate intracranial injury 1, 2, 4
• Marked change in headache pattern: Significant change in previously stable characteristics 1, 2, 4

Critical Physical Examination Red Flags

Focal neurological deficits, altered consciousness, fever with neck stiffness, or papilledema mandate immediate neuroimaging. 2, 3

Key examination findings requiring urgent evaluation:

• Focal neurological symptoms or signs: Weakness, sensory changes, visual deficits suggest secondary headache 1, 2, 3, 4
• Altered consciousness or confusion: Particularly with fever, suggests meningitis or encephalitis 3
• Neck stiffness: Indicates possible meningitis or subarachnoid hemorrhage, though present in less than 50% of bacterial meningitis cases 1, 2, 3, 4
• Unexplained fever: May indicate meningitis 2, 4
• Uncoordination: May indicate cerebellar pathology 1, 2, 4
• Limited neck flexion: Part of the Ottawa SAH Rule criteria 1, 2

Ottawa SAH Rule for Risk Stratification

For alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour, additional investigation is required if ANY of the following are present: 1, 2

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 Algorithm Based on Presentation Timing

For Suspected Subarachnoid Hemorrhage

Patients presenting <6 hours from symptom onset without new neurological deficit:

• Noncontrast head CT on high-quality scanner interpreted by board-certified neuroradiologist is sufficient to exclude SAH with 98.7% sensitivity 1, 3

Patients presenting >6 hours from symptom onset OR with new neurological deficit:

• Perform noncontrast head CT immediately 1, 3
• If CT is negative for SAH, proceed to lumbar puncture for xanthochromia evaluation (performed >6-12 hours after symptom onset for optimal sensitivity) 1
• Spectrophotometric analysis for xanthochromia has 100% sensitivity and 95.2% specificity 1

For Other Red Flag Presentations

When red flags are present (excluding acute SAH presentation):

• MRI is preferred over CT due to higher resolution and absence of radiation exposure 2, 3, 4
• CT without contrast is recommended when acute intracranial hemorrhage is suspected 2, 3, 4
• Neuroimaging should be considered in patients with atypical headache patterns or neurologic signs 1

Critical Pitfalls to Avoid

Failure to obtain noncontrast head CT is the most common diagnostic error in subarachnoid hemorrhage, historically associated with nearly 4-fold higher likelihood of death or disability. 1, 3

Additional pitfalls include:

• Relying solely on neuroimaging without considering the complete clinical picture 2, 3
• Overlooking the need for neuroimaging when red flags are present 3, 4
• Missing sentinel bleeds: 20% of patients with aneurysmal SAH report a sudden severe headache (warning leak) 2-8 weeks before major rupture 1
• Failing to recognize atypical presentations such as primary neck pain, syncope, or seizure as possible SAH 1

Special Considerations

Elderly patients with meningitis are more likely to have altered consciousness and less likely to have neck stiffness or fever compared to younger patients. 3

• Age-related causative organisms differ, with Listeria or pneumococcal disease being more common in older people 3
• Maintain high index of suspicion even with atypical presentations 1

When Neuroimaging is NOT Routinely Warranted

In patients with normal neurologic examination and headache meeting strict definition of migraine without red flags, neuroimaging is usually not warranted 1

However, if the headache has atypical features or does not meet strict migraine criteria, a lower threshold for imaging should apply 1