From the Guidelines
A non-contrast Computed Tomography (CT) of the head can rule out several significant conditions, including acute intracranial hemorrhage, large brain tumors, significant brain edema, hydrocephalus, midline shift, mass effect, and skull fractures. According to the most recent and highest quality study 1, a non-contrast head CT is usually appropriate for the initial imaging of patients with acute head trauma that is mild, moderate, or severe. The study also notes that CT is particularly valuable in emergency settings because it's quick, widely available, and excellent for detecting acute bleeding, which requires immediate intervention.
Some of the key conditions that a non-contrast CT head scan can rule out include:
- Acute intracranial hemorrhage (such as subdural, epidural, subarachnoid, or intraparenchymal bleeding)
- Large brain tumors
- Significant brain edema
- Hydrocephalus
- Midline shift
- Mass effect
- Skull fractures It can also identify large ischemic strokes that have already developed, though early ischemic changes may be subtle or not visible.
However, a plain CT has limitations and cannot reliably detect:
- Small tumors
- Early or small strokes
- Demyelinating diseases like multiple sclerosis
- Vascular malformations that aren't actively bleeding
- Subtle brain injuries For these conditions, MRI is typically more sensitive 1. Additionally, CT cannot evaluate brain function or detect metabolic disorders, infections in early stages, or neurodegenerative diseases like Alzheimer's. When evaluating patients with neurological symptoms, it's essential to recognize that a normal CT doesn't completely exclude all intracranial pathology 1.
From the Research
Non-Contrast Computed Tomography (CT) of the Head
A non-contrast CT of the head can be used to rule out certain conditions, including:
- Intracranial hemorrhage, as it is sensitive for detecting acute hemorrhage 2, 3
- Acute infarct, with studies showing high sensitivity and specificity for detection 4
- Other acute abnormalities, such as mass lesions or vascular malformations 2
Limitations of Non-Contrast CT
However, a non-contrast CT of the head may not be sufficient to rule out all conditions, including:
- Subacute or chronic hemorrhage, which may be better detected with MRI 2, 3
- Underlying mass lesions or vascular malformations, which may require additional imaging such as CT angiogram or MRI 2
- Certain types of intracranial injuries, such as those caused by minor head trauma, which may require a clinical decision instrument to determine the need for CT scanning 5
Clinical Decision Making
Clinical judgment should be used to determine the need for a non-contrast CT of the head, as well as the need for additional imaging or testing 6, 5. The use of artificial intelligence algorithms may also be helpful in triaging patients and identifying those who are likely to have a normal scan 4.