Traumatic Brain Injury
Injury
Side view
Midline view
Damage to the brain caused by an external force - such as a blow, jolt, or penetrating injury - ranging from mild concussion to severe, life-altering injury.
Common Signs & Symptoms
- Headache, confusion, or dizziness
- Temporary or prolonged loss of consciousness
- Memory problems or difficulty concentrating
- Mood or personality changes
- In severe cases, seizures or impaired arousal
Why These Symptoms Happen
Each symptom can be traced, at least in part, to the job a particular part of the brain normally does. These links are simplified: real symptoms usually come from several connected regions.
| Symptom | Brain region | Why it happens |
|---|---|---|
| Impulsiveness, irritability, or personality change | Frontal Lobe | The undersides and tips of the frontal lobes rub against bony ridges inside the skull when the head stops suddenly. These areas help regulate behaviour and emotion, so damage can change how a person acts and reacts. |
| Memory problems | Temporal Lobe | The tips of the temporal lobes sit in hollows of the skull and are also easily bruised. They hold memory-related structures, including the hippocampus. |
| Difficulty concentrating and slowed thinking | Frontal Lobe | Rapid acceleration and rotation can stretch long nerve fibres throughout the brain (diffuse axonal injury). Communication between regions slows, and the frontal lobe's attention and planning networks are especially sensitive to this. |
| Loss of consciousness and, in severe cases, problems with breathing or heart rate | Brain Stem | The brain stem keeps us awake and alert and controls breathing and heart rate. Twisting forces or swelling that press on it can disrupt these vital functions. |
Overview
Traumatic brain injury (TBI) results from an external force to the head - a fall, vehicle collision, sports impact, or penetrating injury - that disrupts normal brain function. Severity ranges from mild TBI (concussion), which usually resolves within days to weeks, to moderate or severe injury, which can cause lasting cognitive, physical, and emotional changes. The case of Phineas Gage, discussed on our frontal lobe page, remains one of history's most famous examples of TBI's effect on personality.
Affected Brain Regions
The frontal lobe is particularly vulnerable in TBI because of its position directly behind the forehead and the bony ridges of the skull it can strike against during rapid deceleration, which is why personality change, impulsivity, and impaired judgment are common after significant TBI. The tips of the temporal lobes are vulnerable for the same reason, which helps explain the memory problems that often follow. Because the brain stem controls basic survival functions and arousal, injury there - more likely in severe or penetrating trauma - can affect consciousness, breathing, and heart rate, making it a critical factor in TBI severity and prognosis.
Injury often happens twice in one impact: the brain hits the skull at the point of the blow, then rebounds and hits the opposite side. Doctors call this a "coup-contrecoup" injury.
How It's Studied
In emergency care, severity is often judged with the Glasgow Coma Scale, developed by Graham Teasdale and Bryan Jennett in 1974. It scores how well a person opens their eyes, responds verbally, and moves, giving a total from 3 (no response) to 15 (fully alert). CT scans are used quickly to look for bleeding, swelling, or skull fractures that may need surgery. Concussion, however, usually doesn't show up on standard scans at all; it's diagnosed from symptoms and examination. Research using advanced MRI techniques, such as diffusion imaging that traces nerve-fibre pathways, is trying to make these subtle injuries visible.
Common Myths
"You have to be knocked out to have a concussion."
Most concussions happen without any loss of consciousness. Headache, dizziness, confusion, feeling "foggy", or sensitivity to light after a blow to the head can all be signs of concussion.
"A normal brain scan means the brain isn't injured."
CT scans are designed to find bleeding and fractures. The microscopic damage behind concussion is usually invisible to them, so a normal scan doesn't rule out a brain injury.
"It's fine to play on if you feel OK."
A second blow before the brain has recovered can cause much worse injury. Anyone with a suspected concussion should stop the activity and not return until they've been assessed and their symptoms have cleared.
Current Research Directions
Concussion research has increasingly focused on the risks of returning to activity (particularly contact sports) too soon after injury, and on the cumulative effects of repeated head impacts over time. Advanced imaging techniques are improving the ability to detect subtle injury that standard scans miss, and rehabilitation research is exploring how structured cognitive and physical therapy can support recovery after moderate-to-severe TBI.
Key Terms
Related Brain Regions
Explore the regions involved in traumatic brain injury in more depth:
This article is for general education and isn't a substitute for professional medical advice or diagnosis. Seek emergency care for any head injury involving loss of consciousness, confusion, repeated vomiting, or worsening symptoms.
Sources & Further Reading
- Traumatic Brain Injury (TBI) - National Institute of Neurological Disorders and Stroke
- Head injury and concussion - NHS
- Assessment of coma and impaired consciousness: a practical scale - Teasdale & Jennett (1974), The Lancet
- Traumatic brain injury: integrated approaches to improve prevention, clinical care, and research - Maas et al. (2017), The Lancet Neurology
- About Traumatic Brain Injury - Centers for Disease Control and Prevention