What Is a Mild Traumatic Brain Injury (MTBI) in Ontario—and Why Is It Often Misunderstood?
- 2 days ago
- 4 min read
By Lane Foster, Personal Injury Lawyer
Last updated: April 2026
A mild traumatic brain injury (MTBI), often called a concussion, is a brain injury that may not appear on CT or MRI scans but can still cause serious and long-lasting symptoms. In Ontario, these injuries are frequently misunderstood—especially when they significantly affect a person’s ability to work and function.
What Counts as a Mild Traumatic Brain Injury (MTBI)?
A mild traumatic brain injury is typically caused by a blow to the head or a sudden acceleration or deceleration—common in car accidents.
In practical terms:
A concussion is a form of MTBI
Loss of consciousness is not required
Imaging is often normal
Diagnosis is based on reported symptoms, clinical assessment, and observed changes in cognitive and day-to-day functioning.
Why the Term “Mild” Is Misleading
The word “mild” refers to how the injury presents initially—not how serious it becomes.
Some people recover quickly. Others experience persistent symptoms that interfere with nearly every aspect of daily life.
We often see individuals who were working, independent, and functioning at a high level before the accident struggle afterward with memory, focus, fatigue, and emotional regulation. In those cases, there is nothing “mild” about the impact.
Most People Recover — But Not Everyone
Most people who suffer a mild traumatic brain injury will recover within weeks or a few months.
However, a smaller subset experience persistent symptoms that do not resolve. These individuals may develop ongoing cognitive, emotional, and physical difficulties that interfere with their ability to work and function day-to-day.
The challenge is that, in the early stages, there is often no reliable way to predict which path a person will follow. What initially appears to be a “minor” injury can, over time, become a much more serious and long-lasting condition.
We often see clients come to us several months after a concussion, having initially assumed they would recover, only to realize their symptoms are not improving.
How Ontario Courts Treat MTBI Cases
Ontario courts recognize that mild traumatic brain injuries can result in serious and lasting impairment—even where imaging is normal.
In decisions such as Legree v. Origlieri, 2021 ONSC 7650 and Graul v. Kansal, 2022 ONSC 1958, the court accepted detailed evidence of cognitive, behavioural, and functional decline despite the absence of clear findings on CT or MRI.
In both cases, the analysis focused on how the individual’s functioning had changed after the accident—including their ability to work, think clearly, and manage daily life.
These decisions reflect a broader reality: brain injury claims are often decided based on real-world impact—not just imaging or diagnostic labels.
Common Symptoms of MTBI
Symptoms can vary, and they don’t always appear right away.
They generally fall into three categories:
Cognitive
Memory problems
Slowed thinking
Difficulty concentrating
Emotional
Irritability
Anxiety or depression
Personality changes
Physical
Headaches
Dizziness
Sensitivity to light or noise
These symptoms are often most noticeable when someone tries to return to work or resume their normal routine.
Why MTBI Cases Are Often Disputed
MTBI claims are frequently challenged by insurance companies.
The main reasons are consistent:
Imaging is often normal
Symptoms are subjective
Early complaints may be underestimated
Documentation is sometimes inconsistent
That does not mean the injury is minor. It means the case depends heavily on clear, consistent evidence of how the injury affects daily life over time.
The MIG Issue
In Ontario, many MTBI claims are initially placed in the Minor Injury Guideline (MIG). This can create real problems as it limits access to necessary treatment.
The MIG is intended for minor soft tissue injuries, but brain injuries are sometimes placed improperly there early in the process. A car accident lawyer in Ontario will often formally dispute this designation with the insurer to increase access to treatment.
When an MTBI Becomes a Serious Claim
An MTBI becomes a significant brain injury claim when it leads to lasting functional impairment.
This can include:
Inability to return to work
Reduced capacity or productivity
Ongoing cognitive or psychological symptoms
Loss of independence
In Ontario, this often becomes a key issue in determining whether an injury meets the legal threshold for compensation.
The key issue is not the label “mild”—it is the real-world impact over time.
A Practical Reality
MTBI cases are common, but they are often misunderstood. They frequently involve:
Symptoms that are not visible
Normal imaging
A gradual realization that something is not right
When properly documented, however, these cases can represent serious and life-altering injuries.
Frequently Asked Questions
Is a concussion considered a brain injury in Ontario?
Yes. A concussion is a form of mild traumatic brain injury and is treated as a brain injury in Ontario claims.
Can an MTBI be serious?
Yes. While some people recover quickly, others experience long-term symptoms that affect their ability to work and function.
Why do insurers downplay MTBI claims?
Because symptoms are often subjective and imaging is usually normal, insurers may argue the injury is minor—even where functional impairment is significant.
How long does it take to recover from an MTBI?
Most people recover within weeks or months, but some experience persistent symptoms that can last much longer.