Is a non-contrast computed tomography (CT) scan an appropriate diagnostic test for new-onset headache in patients over 50 years old?

From the Guidelines

A non-contrast computed tomography (CT) scan is an appropriate initial diagnostic test for new-onset headache in patients over 50 years old, as it can quickly identify most life-threatening causes of headache, including hemorrhage, large mass lesions, and hydrocephalus, with a high sensitivity of 98.7% and specificity of 99.9% for detecting subarachnoid hemorrhage within 6 hours of symptom onset 1.

Key Considerations

• The Ottawa SAH Rule can be used to screen out individuals with a low likelihood of subarachnoid hemorrhage, but it has a low specificity of 7.6-15.3% 1.
• Patients over 50 with new headaches, especially those with "thunderclap" onset, neurological deficits, or signs of increased intracranial pressure, require prompt imaging to rule out serious underlying conditions.
• If the CT is negative but clinical suspicion remains high, further evaluation with MRI may be warranted as it offers better visualization of posterior fossa structures, small lesions, and vascular abnormalities.

Diagnostic Approach

• The non-contrast approach is preferred initially because it avoids potential contrast agent complications while still providing sufficient diagnostic information for most acute scenarios.
• Clinicians should combine imaging with thorough history and physical examination to guide further management decisions.
• The American College of Radiology recommends noncontrast head CT as the initial imaging test for patients with acute head trauma, including those with mild head trauma who meet certain criteria, such as age over 60 years, drug or alcohol intoxication, or physical evidence of trauma above the clavicle 1.

Important Notes

• The sensitivity and specificity of noncontrast CT for detecting subarachnoid hemorrhage are high, but not 100%, and clinical judgment should be used to determine the need for further evaluation or imaging.
• The use of clinical decision rules, such as the Ottawa SAH Rule, can help identify patients who are unlikely to have subarachnoid hemorrhage and may avoid unnecessary imaging and workup.

From the Research

Diagnostic Considerations for New-Onset Headache in Patients Over 50

• The diagnosis of new-onset headache in patients over 50 years old requires careful consideration of potential underlying causes, including subarachnoid hemorrhage (SAH) 2.
• A non-contrast computed tomography (CT) scan is often used as an initial diagnostic test to rule out SAH, with studies suggesting that it is highly sensitive for detecting SAH within 6 hours of symptom onset 3, 4.
• The sensitivity of modern multislice CT for SAH has been reported to be 99.6% for aneurysmal SAH and 99.0% for all SAH at 48 hours after headache onset 4.
• However, if the CT scan is negative, a lumbar puncture (LP) may still be necessary to rule out SAH, particularly if the patient presents with a sudden-onset severe headache 5, 6.
• The diagnostic workflow of an LP after a negative CT head for a patient presenting with a sudden-onset severe headache has been observed to have a high enough proportion to warrant its continued use despite the sensitivity of modern CT scanners 5.

Specific Patient Populations

• Patients over 50 years old with new-onset headache may require a more thorough diagnostic evaluation due to the increased risk of underlying conditions such as SAH 2.
• The use of non-contrast CT scans and LPs in this patient population should be guided by clinical judgment and consideration of individual patient risk factors 3, 5, 4, 6.

Diagnostic Test Characteristics

• The sensitivity and specificity of non-contrast CT scans and LPs for diagnosing SAH have been reported in various studies, with modern multislice CT scanners showing high sensitivity for detecting SAH 3, 4.
• The use of LPs after a negative CT head has been shown to have a high enough proportion to warrant its continued use in certain patient populations 5.