What are the red flags for headaches in a patient?

Red Flags for Headaches Requiring Immediate Evaluation

Any patient presenting with thunderclap headache (sudden onset reaching maximum intensity within seconds to minutes), "worst headache of life," or headache with focal neurologic signs requires immediate neuroimaging to rule out life-threatening secondary causes such as subarachnoid hemorrhage, intracranial hemorrhage, or stroke. 1

Critical Historical Red Flags

Onset and Temporal Pattern

• Thunderclap headache: Sudden onset reaching peak intensity within 1 minute suggests subarachnoid hemorrhage and requires emergent evaluation 1
• "Worst headache of life": Abrupt onset of severe headache may indicate serious vascular pathology including subarachnoid hemorrhage or arterial dissection 1
• New headache after age 50: Raises concern for temporal arteritis, mass lesion, or other secondary causes 1, 2
• Progressive headache: Worsening over time suggests possible intracranial space-occupying lesion 1
• Marked change in headache pattern: Significant change in previously stable headache characteristics warrants investigation for secondary causes 2, 1

Situational and Positional Features

• Headache awakening patient from sleep: May indicate increased intracranial pressure from mass lesion or idiopathic intracranial hypertension 2, 1
• Headache with Valsalva maneuvers: Pain triggered by coughing, sneezing, or straining suggests increased intracranial pressure 1, 3
• Exertional headache: Onset during physical exertion is part of the Ottawa SAH Rule criteria 1
• Headache during sexual activity: Can indicate vascular pathology 3

Trauma and Associated Symptoms

• Persistent headache following head trauma: May indicate intracranial injury including subdural or epidural hematoma 2, 1
• Headache with weight loss and/or cognitive changes: Suggests secondary headache from systemic disease or intracranial pathology 1
• Atypical aura: May indicate transient ischemic attack, stroke, epilepsy, or arteriovenous malformations rather than typical migraine 1

Physical Examination Red Flags

Neurologic Findings

• Focal neurologic symptoms or signs: Including weakness, sensory deficits, visual field cuts, or reflex abnormalities indicate structural brain pathology 2, 1, 4
• Uncoordination: May indicate cerebellar pathology 2, 1
• Altered consciousness or personality changes: Suggests serious intracranial process 1, 4
• Papilledema: Indicates elevated intracranial pressure 4

Meningeal and Systemic Signs

• Neck stiffness: Possible indicator of meningitis or subarachnoid hemorrhage 1, 4
• Limited neck flexion on examination: Part of the Ottawa SAH Rule criteria 1
• Unexplained fever: May indicate meningitis or other infectious process 1

Ottawa Subarachnoid Hemorrhage Rule

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

• 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 Based on Red Flags

Acute Severe Headache (<6 hours from onset)

• Without new neurologic deficit: Non-contrast head CT on high-quality scanner interpreted by board-certified neuroradiologist is reasonable 1
• With new neurologic deficit OR >6 hours from onset: Non-contrast head CT followed by lumbar puncture if CT is negative for subarachnoid hemorrhage 1

When Red Flags Are Present

• Suspected hemorrhage: CT without contrast is preferred as first-line imaging 1, 5
• Other secondary causes: MRI is preferred over CT due to higher resolution and better detection of masses, ischemia, and posterior fossa pathology 1, 5
• Normal imaging with high suspicion for SAH: Proceed to lumbar puncture for CSF analysis 1, 5

Common Pitfalls to Avoid

Do not rely solely on neuroimaging without considering the complete clinical picture, as emphasized by expert consensus—the history and physical examination remain paramount in headache evaluation 1. The U.S. Headache Consortium specifically notes that neuroimaging should only be pursued when results would change management or when the patient is at higher risk than the general population 2.

Rapidly increasing headache frequency, history of uncoordination, and focal neurologic signs increase the odds of positive neuroimaging findings and should lower your threshold for ordering studies 2. However, the absence of red flags in a patient with typical features of primary headache disorder generally does not require neuroimaging 2, 4.