Summary

Patients with headaches who display certain red flags should undergo neuroimaging to rule out serious pathology. Key red flags include:

• Sudden onset (thunderclap): A headache that reaches peak intensity within seconds to minutes may indicate subarachnoid hemorrhage or vascular emergencies ¹.
• New-onset headache in older patients: New headaches, especially in patients older than 50, can be a harbinger of temporal arteritis, intracranial neoplasm, or other pathologies ¹².
• Focal neurological deficits: Any focal weakness, sensory changes, or other localized deficits should prompt imaging to evaluate for stroke, mass lesion, or demyelinating disease ².
• Altered mental status or impaired consciousness: This may indicate increased intracranial pressure, hemorrhage, or infection ¹.
• Signs of increased intracranial pressure: The presence of papilledema or new-onset seizure raises concerns for intracranial mass, hydrocephalus, or hemorrhage ².
• Systemic symptoms or immunocompromise: Fever, weight loss, or immunosuppression can raise suspicion for meningitis, brain abscess, or other infections ¹.
• Headache with a history of trauma: Recent head trauma with a headache may suggest intracranial hemorrhage, particularly in higher risk patients (e.g., on anticoagulation) ².

At a Glance

Red Flag Feature	Potential Concern	Action
Sudden onset, severe ("thunderclap") headache	Subarachnoid hemorrhage, vascular event	Immediate imaging (CT/MRI)
New-onset headache in patients >50	Temporal arteritis, neoplasm, cerebrovascular etiology	Advanced imaging
Focal neurological deficits	Stroke, mass lesion, demyelinating disease	Urgent neuroimaging
Altered mental status/impairment	Increased intracranial pressure, hemorrhage/infection	Emergent imaging
Signs of increased intracranial pressure (papilledema)	Brain mass, hydrocephalus, hemorrhage	Neuroimaging evaluation
Systemic symptoms (fever/weight loss) or immunosuppression	Meningitis, abscess	Consider contrast imaging
Recent head trauma	Intracranial hemorrhage	CT head evaluation

Recognizing these red flags in the context of headache is crucial, as timely imaging—often with non-contrast head CT or MRI—can be life-saving and guide further management ¹².