From the Guidelines
Red flags for headache diagnosis include sudden onset of severe headache, neck pain or stiffness, witnessed loss of consciousness, onset during exertion, thunderclap headache, and limited neck flexion on examination, as outlined in the Ottawa SAH Rule 1. These red flags are critical in identifying patients who may have a subarachnoid hemorrhage (SAH) or other serious conditions that require immediate medical attention. The Ottawa SAH Rule is a reliable method to screen out individuals with a low likelihood of SAH, with a sensitivity of 100% and specificity of 13.6% 1.
Key Red Flags
- Age ≥40 years
- Neck pain or stiffness
- Witnessed loss of consciousness
- Onset during exertion
- Thunderclap headache (instantly peaking pain)
- Limited neck flexion on examination If any of these red flags are present, patients should undergo additional investigation, including noncontrast head CT and possibly lumbar puncture (LP) for xanthochromia evaluation, especially if they present > 6 hours from ictus 1.
Importance of Prompt Evaluation
Prompt evaluation is necessary to rule out life-threatening causes, such as SAH, meningitis, or brain tumor, which can cause rapid deterioration and permanent neurological damage if left untreated 1.
Diagnostic Approach
High-quality CT scanners can detect SAH with high sensitivity, especially when images are interpreted by fellowship-trained, board-certified neuroradiologists 1.
Limitations and Considerations
It is essential to note that many analyses do not apply to patients with atypical presentations, such as primary neck pain, syncope, seizure, or new focal neurological deficit, and that the lack of a classic presentation should still prompt appropriate imaging and workup 1.
From the Research
Red Flags for Headache Diagnosis
The following are red flags that may indicate a serious cause of headache:
- Sudden and severe onset 2, 3, 4
- Head trauma 2, 4
- Cancer 2
- Immunocompromised state 2, 4
- Pregnancy 2, 4
- Age 50 years or older 2, 4
- Related to activity or position 2
- Focal neurological signs or seizure 3
- Systemic signs 3
- Precipitation by physical activity 3
- New neurological deficit 4
- History of neoplasm 4
- Recent head trauma (2-7 days prior) 4
Clinical Significance of Red Flags
Red flags are important in identifying patients at higher risk of a serious secondary headache cause 4. However, their low specificity may result in increased rates of CT scanning 4. A well-taken history and targeted physical examination coupled with appropriate investigations can enable secondary headache syndromes to be recognized consistently and thus allow their timely and appropriate treatment 3.
Diagnosis and Management
Imaging such as CT, MRI, or noninvasive vascular imaging may be necessary to identify a treatable cause in patients presenting with red flags 2. The predictive performance of red flag criteria can be estimated individually and in combination to identify patients with serious secondary headache 4. A step-wise approach to emergency department and inpatient management of headache is necessary, including review of red flags and consideration of treatment options such as intravenous fluids, anti-dopaminergic agents, and nerve blocks 5.