The first tests
Evaluation starts with a history and a neurologic examination: alertness, speech, strength, pupils, gait, and other findings. A non-contrast head CT is the usual first imaging test because it is fast, widely available, and excellent at showing extra-axial blood and mass effect.
How it looks
How acute and chronic collections can look
These simplified CT-style drawings show where blood collects. They are educational illustrations, not patient scans. Actual scans can have mixed appearances and need clinical interpretation.
Reading a CT report in plain language
Reports use a short vocabulary. These words are descriptions, not a care plan:
| Term | Plain meaning |
|---|---|
| Hyperdense | Brighter than brain. Typical of acute blood. |
| Hypodense | Darker than brain. Typical of older (chronic) blood or fluid. |
| Isodense | Similar to brain; can be easy to miss without careful review. |
| Crescentic | Moon-shaped collection along the inner skull—typical of subdural blood. |
| Mass effect | The collection is compressing nearby brain. |
| Midline shift | The brain’s midline is pushed off center, measured in millimeters. |
| Mixed density | Bright and dark blood together; may mean different ages or rebleeding. |
A fuller list lives in the glossary.
When MRI is used
MRI can help when CT is equivocal, when the collection is small or isodense, or when the team needs more detail about blood of different ages. It is slower and is not the first test in an unstable patient.
Images plus the exam
A modest collection in a deteriorating patient can be more urgent than a larger collection in someone who is stable. Repeat scans matter when symptoms change. Treatment is not decided from a millimeter measurement alone.
If you have been told there is “some shift,” ask what the number is, whether it has changed, and how it fits with your exam. Those three facts are more useful than a screenshot of one slice.
Bring the actual images
Radiology reports are summaries. Specialists planning drainage or MMA embolization need the DICOM images themselves, not only a printout. Ask the hospital or imaging center for a disc or a secure electronic transfer. Do not send identifiable medical records through ordinary email.
Sources & further reading
- MedlinePlus / National Library of Medicine — Subdural hematoma
- Neurovascular Centers — Dr. Wled Wazni and the practice
Educational content from Neurovascular Centers. Individual treatment decisions require a clinical examination and review of your imaging.