From the Guidelines
For headaches, a CT scan without contrast is typically the initial imaging choice, as it is sufficient for detecting most serious conditions like bleeding, tumors, or structural abnormalities that might cause headaches 1. When considering the use of contrast in a CT scan for headaches, it's essential to weigh the benefits against the potential risks, such as allergic reactions or kidney problems. The decision to use contrast depends on specific symptoms, medical history, and what the doctor suspects might be causing the headaches.
- Key factors that might lead to the use of contrast include:
- Sudden severe headache
- Headache with neurological symptoms
- Headaches that are worsening despite treatment In these cases, contrast can provide more detailed information, such as when looking for specific vascular abnormalities, distinguishing between tumor types, or evaluating infection 1. However, for most cases, especially in the emergency setting where speed and sensitivity for detecting acute blood products are crucial, a non-contrast CT scan of the head is the imaging modality of choice, particularly for suspected subarachnoid hemorrhage (SAH) from a ruptured aneurysm or arteriovenous malformation (AVM) 1. It's also important to consider alternative imaging modalities, such as MRI, which may be indicated if it is not possible to perform a CT scan, or if further evaluation is needed after initial imaging 1.
From the Research
CT Scan with or without Contrast for Headaches
- The use of computed tomography (CT) scans with or without contrast for evaluating headaches is a topic of discussion in the medical field 2, 3, 4, 5, 6.
- A study published in 2018 found that CT angiography (CTA) can be useful in detecting vascular abnormalities in patients with acute severe headache, normal neurological examination, and normal noncontrast head CT, but its added value remains controversial 2.
- Another study published in 2021 suggested that patients with atraumatic subarachnoid hemorrhage who have a negative computed tomography (CT) scan of the head obtained more than 6 hours after symptom onset may not require a subsequent lumbar puncture to rule out the diagnosis 3.
- The role of lumbar puncture in early detection of subarachnoid hemorrhage after negative head CT was investigated in a study published in 2019, which found that modern CT scanners seem to have high sensitivity and specificity in the diagnosis of subarachnoid hemorrhage when performed within 24 hours of symptom onset 4.
- A retrospective observational study published in 2018 found that a CT scan taken within 6 hours of onset of sudden headache is sufficient for confirming or ruling out subarachnoid bleeding in patients with sudden headache who have no neurologic deficits 5.
- The American College of Radiology Appropriateness Criteria for Headache, published in 2019, provide evidence-based guidelines for initial imaging strategies for headaches associated with various features, including severe and sudden onset, optic disc edema, and "red flags" 6.
Key Findings
- CT scans with or without contrast can be useful in evaluating headaches, but their use depends on the specific clinical scenario 2, 3, 4, 5, 6.
- The added value of CTA in detecting vascular abnormalities is controversial, and its use may be justified in the emergency setting due to possible therapeutic consequences 2.
- Lumbar puncture may not be required to rule out subarachnoid hemorrhage in patients with a negative CT scan obtained more than 6 hours after symptom onset 3.
- Modern CT scanners have high sensitivity and specificity in diagnosing subarachnoid hemorrhage when performed within 24 hours of symptom onset 4.
- A CT scan taken within 6 hours of onset of sudden headache can confirm or rule out subarachnoid bleeding in patients with no neurologic deficits 5.