What are the appropriate steps for evaluating and managing headaches with red flag signs, such as sudden onset, fever, confusion, or stiff neck, and potential underlying conditions like meningitis, subarachnoid hemorrhage, or brain tumors?

Headache Red Flag Signs

Any patient presenting with thunderclap headache (sudden onset reaching maximum intensity within seconds to minutes), altered mental status, fever with neck stiffness, or focal neurological deficits requires immediate hospital evaluation and neuroimaging to rule out life-threatening conditions including subarachnoid hemorrhage, meningitis, or intracranial mass lesions. 1, 2

Critical Historical Red Flags Requiring Urgent Evaluation

Immediate Life-Threatening Presentations

• Thunderclap headache (sudden onset reaching maximum intensity within 1 minute) strongly suggests subarachnoid hemorrhage and mandates immediate CT imaging 3, 1, 4
• "Worst headache of life" with abrupt onset indicates serious vascular pathology requiring emergent investigation 3, 1, 2
• Headache onset after age 50 suggests secondary headache and consideration of temporal arteritis or other serious pathology 1, 2
• Progressive headache worsening over time could indicate an intracranial space-occupying lesion 1, 2

High-Risk Clinical Scenarios

• Headache awakening patient from sleep may indicate increased intracranial pressure 1, 2
• Headache aggravated by Valsalva maneuvers (coughing, sneezing, exercise) suggests intracranial hypertension or space-occupying lesion 1, 2
• Persistent headache following head trauma may indicate intracranial injury including subdural hematoma 1, 2
• Marked change in headache pattern (significant change in previously stable characteristics) is a red flag for secondary headache 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 Findings

• Focal neurological symptoms or signs (weakness, sensory changes, visual deficits) suggest secondary headache requiring urgent evaluation 1, 2, 4
• Altered consciousness or confusion is a critical finding, particularly when combined with fever and headache, suggesting meningitis or encephalitis 3
• Uncoordination may indicate cerebellar pathology 1, 2, 4
• Impaired memory and/or altered personality suggests secondary headache 1, 2

Meningeal Signs

• Neck stiffness is a possible indicator of meningitis or subarachnoid hemorrhage, though it is present in less than 50% of bacterial meningitis cases 3, 1, 2
• Unexplained fever combined with headache may indicate meningitis 3, 1, 2
• Important caveat: The classic triad of fever, neck stiffness, and altered consciousness is present in less than 50% of bacterial meningitis cases 3
• Kernig's and Brudzinski's signs should NOT be relied upon for diagnosis due to very low sensitivity (as low as 5%) despite high specificity 3

Ottawa SAH Rule for Subarachnoid Hemorrhage Screening

For alert patients >15 years with new severe nontraumatic headache reaching maximum intensity within 1 hour, investigation for subarachnoid hemorrhage is required if ANY of the following are present: 1, 4

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 Are Present

Neuroimaging Strategy

• Neuroimaging is mandatory when red flags are present to rule out secondary causes of headache 1, 2, 4
• For suspected subarachnoid hemorrhage presenting >6 hours from onset or with new neurological deficit: perform noncontrast head CT and, if negative, proceed to lumbar puncture 1, 4
• For suspected subarachnoid hemorrhage presenting <6 hours from onset without new neurological deficit: noncontrast head CT on a high-quality scanner interpreted by a board-certified neuroradiologist is reasonable 1, 4
• MRI is preferred over CT for most secondary headache evaluations due to higher resolution and absence of radiation exposure 1, 2, 4
• CT without contrast is recommended when acute intracranial hemorrhage is suspected, as CT has 98% sensitivity for acute subarachnoid hemorrhage 3, 1, 2, 4

Meningitis Evaluation

• All patients where meningitis is suspected should be referred to hospital for further evaluation and consideration of lumbar puncture 3
• Rapid admission via emergency ambulance should be arranged so the patient arrives within 1 hour of assessment in the community 3
• Document presence or absence of: headache, altered mental status, neck stiffness, fever, rash (of any description), seizures, and signs of shock (hypotension, poor capillary refill time) 3

Special Population Considerations

Elderly Patients

• 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: Listeria or pneumococcal disease is more common in older people 3

Meningococcal Sepsis

• When rash is present with meningitis, the causative organism is Neisseria meningitidis in 92% of cases (petechial in 89%) 3
• However, 37% of meningococcal meningitis patients do not have a rash 3
• Patients with meningococcal sepsis can deteriorate rapidly and must be monitored frequently even if initially appearing well 3

Common 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 3
• Relying solely on neuroimaging without considering the complete clinical picture is a critical error 1
• Overlooking the need for neuroimaging when red flags are present can result in missed life-threatening diagnoses 2
• Individual red flag signs (fever, vomiting, headache, neck stiffness) occur frequently and are poor discriminators when considered independently—combinations of symptoms are more useful for identifying serious disease 3
• Misdiagnosis of subarachnoid hemorrhage occurred in 12% of cases in recent data, emphasizing the need for high clinical suspicion 3