What Do MRI and CT Scans Show After a Traumatic Brain Injury?

By Lane Foster, Personal Injury Lawyer

Updated May 2026

A CT scan and an MRI can identify serious traumatic brain injuries, but they do not answer the same questions. A CT scan is often performed shortly after significant head trauma to look for urgent injuries such as bleeding, swelling or skull fractures. An MRI provides more detailed images of brain tissue and can become important where neurological symptoms continue after the immediate emergency has passed.

Neither scan rules out every brain injury. According to the Government of Canada, a concussion cannot be seen on routine imaging scans such as an MRI or CT scan. A person can therefore have serious headaches, memory problems, dizziness, slowed thinking, fatigue or difficulty returning to work even though routine imaging does not show a visible injury.

That distinction is often confusing after a collision. One person can have a brain bleed or contusion that appears on a scan. Another can have continuing cognitive and physical symptoms despite a normal CT or MRI.

For people dealing with lasting changes after an accident, the imaging report is important, but it is not the entire medical picture. Our Ontario brain injury lawyers represent people who have suffered concussions and serious traumatic brain injuries.

Can an MRI Detect a Brain Injury After a Car Accident?

Yes. An MRI can detect some traumatic brain injuries after a car accident, including structural abnormalities affecting brain tissue. Depending on the nature and severity of the trauma, an MRI can show areas of bleeding, cerebral contusions and other findings that help doctors understand the injury.

An MRI is not usually the first scan performed immediately after serious head trauma. In the emergency setting, doctors are often concerned with whether the person has bleeding, swelling or another injury requiring urgent treatment. A CT scan is generally used first for that purpose because it can be completed quickly.

MRI becomes important when injured people continue to experience neurological or cognitive problems after the acute stage. Ongoing memory loss, reduced concentration, speech changes, balance difficulties or unusual behavioural changes can lead to a more detailed neurological investigation.

An MRI still has limits. A normal MRI does not establish that no brain injury occurred. Routine MRI does not ordinarily show a concussion in the same way it can show a visible structural injury.

MRI Terms That Can Appear in Serious Traumatic Brain Injury Reports

MRI reports in serious brain injury cases often describe findings that are difficult to see, or not visible at all, on an initial CT scan. This is particularly important where the person’s neurological condition is more serious than the first CT results appeared to suggest.

A report can describe T2 or FLAIR hyperintensity. These terms refer to areas of abnormal signal within brain tissue on particular MRI sequences. In a traumatic case, the finding can be associated with edema, contusion or other injury, depending on its location, timing and appearance.

An MRI can also refer to susceptibility foci, susceptibility blooming or microhemorrhages seen on SWI or GRE sequences. These sequences are particularly sensitive to small amounts of blood product within the brain. In a serious trauma case, scattered microhemorrhages can be important because they can be associated with traumatic axonal injury even where the initial CT scan did not show the full extent of the injury.

Another term sometimes seen is restricted diffusion on diffusion-weighted imaging, or DWI. Restricted diffusion can identify areas where water movement within injured tissue has changed. In the trauma setting, the significance of that finding depends on the pattern, the location and the radiologist’s interpretation.

MRI reports can also describe corpus callosum lesions, brainstem lesions or lesions at the gray-white matter junction. Those locations are important because they are recognized sites where traumatic axonal injury can appear following strong acceleration, deceleration or rotational forces.

The significance of an MRI report does not come from one technical term. A finding has to be considered together with mechanism of the accident, the injured person’s level of consciousness, neurological condition, cognitive changes and subsequent recovery.

What Does a CT Scan Show After a Head Injury?

A CT scan is commonly used after acute head trauma because it can identify serious structural injuries quickly. In a collision case, it can show bleeding inside the skull, subdural or epidural hematomas, brain contusions, swelling, pressure affecting the brain and skull fractures.

The American College of Radiology identifies CT head imaging as the usual initial imaging examination where imaging is required after acute head trauma.

This is why someone taken to hospital after a serious crash often undergoes a CT scan before an MRI. The immediate question is whether there is an injury that requires monitoring, specialist involvement or emergency intervention.

A normal CT scan can be reassuring because it means the scan did not identify certain urgent structural injuries. It does not prove that the person did not suffer a concussion, and it does not necessarily explain continuing symptoms after the accident.

What Do Common CT Findings Mean After a Serious Brain Injury?

In serious traumatic brain injury cases, a CT report often contains more specific language than simply stating that there was “bleeding” or “swelling.” The location and type of the abnormality can will potentially help explain the seriousness of the initial injury, the need for emergency treatment and the risks facing the injured person.

Traumatic subarachnoid hemorrhage refers to blood in the space surrounding the brain, often described on CT as blood within the sulci or cisterns. In a trauma case, this can be evidence that the force of the impact caused bleeding over the surface of the brain.

Subdural hematoma refers to a collection of blood between the dura and the surface of the brain. It is often described as a crescent-shaped extra-axial collection. A larger subdural hematoma can compress the underlying brain and contribute to mass effect or midline shift.

Epidural hematoma, sometimes called an extradural hematoma, is bleeding between the skull and the dura. It is commonly described as a biconvex or lens-shaped collection. This type of bleeding can enlarge quickly and require emergency neurosurgical treatment.

Intraparenchymal hemorrhage refers to bleeding within the brain tissue itself. Where the bleeding is caused by trauma, it can appear together with a brain contusion or other injury to the surrounding tissue.

Hemorrhagic contusions are bruises of the brain that contain bleeding. They commonly occur where the brain strikes the irregular inner surface of the skull, particularly in the frontal and temporal lobes. A report can describe contusions as evolving or blossoming because the amount of visible hemorrhage and surrounding swelling can increase on later imaging.

CT reports in serious brain injury cases can also refer to cerebral edema, mass effect, effacement of the sulci or basal cisterns, and midline shift. Cerebral edema means swelling in the brain. Mass effect means that blood or swelling is pressing on nearby structures. Midline shift means that pressure has displaced the brain away from its normal central position. These terms can indicate a dangerous increase in pressure inside the skull and the need for urgent neurological or neurosurgical care.

CT Scan vs. MRI for Traumatic Brain Injury: What Is the Difference?

A CT scan and an MRI are both used to investigate head injuries, but they play different roles.

Scan	Common Role After Head Trauma	Important Limitation
CT scan	Often used shortly after the injury to identify bleeding, hematomas, swelling, significant contusions or fractures	A normal CT scan does not rule out concussion
MRI	Provides more detailed imaging of brain tissue and can assist where neurological symptoms continue or further investigation is required	A normal MRI does not rule out concussion or every traumatic brain injury

In practical terms, CT is often the emergency scan. MRI can become important later where the injured person continues to have neurological difficulties or where doctors require more detailed brain-tissue imaging.

The fact that the initial scan was normal does not mean that every later medical concern has been answered. The appropriate investigation depends on the symptoms, the timing of the injury and the clinical questions that remain.

Can MRI or CT Scans Be Normal After a Concussion?

Yes. Routine MRI and CT scans can both be normal after a concussion.

A concussion, also called a mild traumatic brain injury, does not necessarily produce a visible structural abnormality on ordinary imaging. The injured person can still experience symptoms that interfere substantially with work, school, driving, family responsibilities and day-to-day life.

After an accident, these symptoms can include headaches, dizziness, difficulty concentrating, reduced memory, unusual fatigue, disrupted sleep, sensitivity to light or noise, irritability and reduced tolerance for screens or busy environments.

This is one reason the term mild traumatic brain injury can be misunderstood. The term describes the initial severity of the brain injury, not the outcome.

What Can an MRI Show in a More Serious Brain Injury?

In moderate and severe traumatic brain injury cases, MRI findings can provide important objective evidence of damage caused by the accident.

An MRI identifies structural abnormalities affecting brain tissue, including contusions and areas of bleeding. Depending on the trauma and the timing of the scan, it can also help investigate injuries that were not fully explained by the initial emergency workup.

These findings can affect more than the initial diagnosis. Where a brain injury has caused major cognitive, behavioural or physical changes, imaging can form part of the evidence used to understand prognosis, rehabilitation needs, capacity for independent living and the person’s ability to return to work.

A serious brain injury case is not assessed by the MRI report alone. The medical record can also include hospital records, neurological assessments, rehabilitation evidence, cognitive testing and evidence of how the person’s everyday functioning changed after the injury.

When Brain Imaging Matters for Catastrophic Impairment in Ontario

Brain imaging has a specific legal importance where an adult injured in a motor vehicle accident seeks catastrophic impairment designation under Ontario’s Statutory Accident Benefits Schedule based on traumatic brain injury.

Under the adult traumatic brain injury criterion, there must be positive findings on a CT scan, MRI or another medically recognized brain diagnostic technology showing accident-related intracranial pathology. The person must also satisfy the applicable Glasgow Outcome Scale Extended, or GOSE, requirement at the relevant time after the accident.

This is a particular catastrophic impairment test analyzed by Ontario catastrophic injury lawyers. It does not mean that every valid brain injury claim requires positive imaging. A person with a concussion can still have a serious claim despite normal MRI and CT scans.

For a detailed explanation of catastrophic impairment designation after a traumatic brain injury, see our guide to catastrophic impairment in Ontario.

Speaking With an Ontario Brain Injury Lawyer After a Serious Injury

CT scans and MRI scan answer important medical questions after a traumatic brain injury. Imaging can identify bleeding, contusions, swelling and other structural injuries. In serious cases, it can become important evidence about the nature and extent of the injury.

But a scan does not always explain everything a person is experiencing. Someone can continue to suffer significant concussion symptoms even after routine imaging is normal.

A brain injury claim must be assessed using the complete medical and functional record: what happened in the accident, what symptoms developed, what treatment was required and how the injury changed the person’s ability to work and live independently.

Foster Injury Law is an Ontario personal injury law firm which represents people throughout Ontario who have suffered concussions and traumatic brain injuries in serious accidents. Our Ontario brain injury lawyers can review the medical evidence, explain the available claims process and help determine what compensation and treatment funding can be pursued.

We offer free consultations and do not charge legal fees unless the claim is successfully resolved.

Frequently Asked Questions About MRI, CT Scans and Brain Injuries

Can an MRI detect a traumatic brain injury?

Yes. An MRI can detect some significant traumatic brain injuries, including brain contusions, areas of bleeding and other structural abnormalities affecting brain tissue. A normal MRI does not rule out a concussion.

What does a CT scan show after a head injury?

CTs scan can identify urgent traumatic findings such as bleeding inside the skull, hematomas, swelling, significant brain contusions and skull fractures. It is commonly used shortly after serious head trauma since it can identify injuries requiring immediate attention.

Can MRI or CT scans be normal after a concussion?

Yes. A concussion are often present even where routine MRI and CT scans are normal. Concussion is diagnosed through the injury history, symptoms and changes in the injured person’s functioning. In fact, most concussions are not apparent on either MRI or CT scans.

Is a CT scan or MRI better for a brain injury?

An MRI provides more detailed brain-tissue imaging and can become useful where neurological symptoms continue or further investigation is needed. A CT scan is often used first after serious acute head trauma because it can quickly identify bleeding or swelling. CT scans are used first because they are fast and readily available.

Does Ontario require positive brain imaging for catastrophic impairment?

For an adult seeking catastrophic impairment designation under Ontario’s traumatic brain injury criterion, the SABS requires positive findings on CT, MRI or another medically recognized brain diagnostic technology showing accident-related intracranial pathology, together with the applicable GOSE requirement. This requirement applies to that specific catastrophic impairment category, not to every concussion or brain injury claim.