Alyah asks François Stefanescu, a doctor and researcher at the Brain Institute, whether the brain can get bruised if you bump your head. The doctor explains how the skull protects the brain, what a blow to the head is, and how to avoid it.
Skull: how is the brain protected from impacts?
The skull plays a vital role in protecting the brain, a particularly fragile organ. However, in the event of a violent blow to the head, the brain can sustain injuries, including bleeding that is sometimes likened to a ‘bruise’. But how is this possible when the brain is so well protected?
Can you really get a ‘bruise’ on the brain?
Yes, a severe blow to the head can cause what is commonly known as a ‘bruise’ on the brain. In medical terms, this is known as a cerebral contusion, i.e. damage to brain tissue caused by trauma.
To understand this phenomenon, we first need to know what a bruise is. Blood circulates through our bodies via small tubes called blood vessels. When a sufficiently strong impact occurs, some of these vessels may rupture. Blood then leaks into the surrounding tissue, causing a mark that may be red or purple, and which may gradually change colour.
A similar phenomenon can occur in the brain following a head injury, that is, an injury caused by a blow to the head.
How does the skull protect the brain?
The brain is particularly well protected. It is situated inside the skull, a solid bony structure that forms a protective shell around it.
However, the brain is not directly attached to the walls of the skull. It is surrounded and bathed in a fluid called cerebrospinal fluid (CSF). This fluid helps, in particular, to cushion movements and impacts.
A brain that ‘floats’ inside the skull
The brain is a soft organ. When the head moves, the cerebrospinal fluid helps prevent it from striking the walls of the skull directly.
However, this protection is not absolute. When an impact is particularly severe, the brain can be jolted violently inside the skull and come into contact with its walls. It may then be subjected to significant forces capable of causing injury.
This is particularly what can happen during a severe head injury.
Where might injuries occur following a blow to the head?
During a severe head injury, the brain can be jolted in various directions. Injuries therefore do not necessarily occur exactly where the head was struck.
Bleeding or bruising may occur, for example, between the skull and the brain, within the brain tissue itself, or even on the side opposite to where the head was struck.
This phenomenon is due to the movement of the brain inside the skull. During a severe impact, it can shift and strike the various internal walls of the skull.
Do all blows to the head cause a serious head injury?
Fortunately, no. The minor, accidental knocks to the head that we experience on a daily basis do not usually cause a brain contusion.
The risk is more closely associated with violent impacts, high-speed collisions or repeated trauma.
The severity of a head injury depends, in particular, on the force of the impact and its effects on the brain.
What warning signs should you look out for after a blow to the head?
It is not possible to tell simply by looking at a person whether they have an injury inside the skull. However, certain symptoms should prompt you to seek medical attention promptly.
After a blow to the head, you should be particularly alert to the onset of:
- severe headaches
- unusual sensitivity to light or noise
- dizziness or a spinning sensation
- nausea or vomiting
- difficulty speaking
- extreme tiredness or a feeling of weakness
- unusual changes in behaviour, such as marked irritability.
If such symptoms appear following a blow to the head, it is important to see a doctor. In some cases, hospital treatment and further tests may be necessary to check for any injuries.
Why does a helmet protect the skull and the brain?
A helmet provides vital protection when an activity exposes the head to impacts or falls. It acts partly as armour for the brain, helping to absorb some of the energy from the impact.
Wearing a helmet is particularly important when cycling, riding a scooter, rollerblading or skiing. More generally, whenever an activity involves speed or carries a risk of falling on your head, it is essential to take precautions to protect your skull.
Protecting the skull helps to protect the brain, an organ that is essential to the functioning of the whole body.
Key facts about the skull and impacts
The skull provides essential primary protection for the brain, supplemented in particular by cerebrospinal fluid, which helps to cushion movements. Despite these protective measures, a very violent impact can cause a head injury and lead to brain damage.
Fortunately, most minor impacts do not cause a ‘bruise’ to the brain. However, following a significant impact, certain symptoms such as severe headaches, vomiting, dizziness, difficulty speaking or an unusual change in behaviour should prompt you to seek medical advice.
Finally, prevention remains essential: wearing a helmet during high-risk activities provides better protection for the skull and brain against impacts.