Concussion

What happens in a concussion

The brain floats in fluid inside the skull. A sudden blow or a rapid acceleration and deceleration, such as a tackle or whiplash in a car crash, makes it twist and bump against the skull. This stretches nerve fibers and triggers a short-lived energy crisis in brain cells: they need more fuel while blood flow is temporarily reduced. The result is a problem with how the brain functions, not visible structural damage, which is why CT and MRI scans are usually normal.

A concussion sits at the mild end of traumatic brain injury. "Mild" refers to the initial severity. Symptoms can still be disruptive for days or weeks.

Signs and symptoms of concussion

Symptoms usually appear immediately but can emerge over the first 24 to 48 hours.

Signs others may notice

• Appearing dazed or stunned, with a blank stare
• Moving clumsily or slowly
• Answering questions slowly, or repeating the same question
• Not remembering events just before or after the hit
• Brief loss of consciousness
• Mood or behavior changes

Concussion in children and babies

Young children cannot describe symptoms. Watch for crying that cannot be soothed, changes in feeding or sleep, loss of interest in favorite toys, and loss of new skills such as toilet training. Teenagers often take longer to recover than adults and are at higher risk if they return to sport too soon.

Causes and risk factors

• Falls, the leading cause in young children and older adults
• Contact and collision sports such as football, hockey, soccer, rugby and lacrosse
• Car, bike and motorcycle crashes
• Assaults and blast exposure
• A previous concussion, which raises the risk of another and may lengthen recovery

When a head injury is more than a concussion

Bleeding inside the skull, such as an epidural hematoma or a subdural bleed, can follow the same kind of blow and can be fatal if missed. The danger signs in the triage box above, especially a worsening headache, repeated vomiting, increasing drowsiness or confusion, and weakness on one side, point to bleeding or brain swelling. An epidural bleed can cause a "lucid interval", when the person seems fine for a few hours and then deteriorates. Older adults and people on blood thinners can develop a slow subdural bleed days to weeks later.

How concussion is diagnosed

A doctor or trained athletic trainer will ask how the injury happened, whether you lost consciousness, what you remember, and what symptoms you have. They check:

• orientation and memory (for example, recalling a list of words)
• balance and coordination
• eye movements, pupils, strength, sensation and reflexes

Sports medicine teams use standardized tools such as the SCAT6 (Sport Concussion Assessment Tool). A CT scan is done only when there are red flags, using validated rules such as the Canadian CT Head Rule or PECARN for children, to look for bleeding or a fracture. MRI is reserved for symptoms that persist or do not fit.

Concussion treatment and recovery

The first 24 to 48 hours

• Relative rest: reduce screen time, reading and demanding mental work. Complete bed rest in a dark room is no longer advised, because it slows recovery.
• Light activity: gentle walking is fine as long as it does not clearly worsen symptoms.
• Pain relief: acetaminophen (paracetamol) for headache, following the label dose. Some doctors advise avoiding ibuprofen or aspirin for the first day because of a theoretical bleeding risk.
• Avoid alcohol and recreational drugs, which slow brain recovery.
• Do not drive until you can concentrate and react normally.
• You do not need to be woken every hour through the night unless a doctor specifically tells you to.

Gradual return to activity

After the first 1 to 2 days, increase activity step by step. A small, brief rise in symptoms (no more than 2 points on a 0-to-10 scale, settling within an hour) is acceptable. A bigger or lasting rise means you need to step back for a day.

Returning to school or work

Start with shorter days, breaks in a quiet room, extra time for tests and reduced screen use. Most students return to school within a few days with these adjustments. Full academic load usually follows within 1 to 2 weeks.

Return to sport

Never return to sport on the same day as a suspected concussion: "if in doubt, sit them out". Return to play follows six stages, each lasting at least 24 hours:

1. Symptom-limited daily activity
2. Light aerobic exercise (walking, stationary bike)
3. Sport-specific exercise without head impact
4. Non-contact training drills
5. Full-contact practice, after medical clearance
6. Return to competition

Students should be back at school fully before returning to contact sport. The whole process takes at least 1 to 2 weeks after symptoms settle, and often longer in children.

Complications

• Post-concussion syndrome: symptoms lasting beyond the usual recovery period. Headache, dizziness, poor concentration and mood changes are common. Targeted rehab (vestibular therapy, graded aerobic exercise, sleep and headache management) helps.
• Second impact syndrome: a rare but often fatal brain swelling when a second blow happens before the first concussion has healed. It mainly affects teenagers and is the main reason for strict return-to-play rules.
• Post-traumatic headache and neck pain, often from an accompanying whiplash injury.
• Repeated head impacts over years are linked to chronic traumatic encephalopathy (CTE), although a single concussion is not thought to cause it.

Preventing concussion

• Wear a properly fitted helmet for cycling, skiing, skating, motorcycling and contact sports. Helmets reduce skull fractures and bleeding but cannot fully prevent concussion.
• Use seat belts and age-appropriate car seats.
• Reduce fall risks at home: stair gates for toddlers, grab bars, good lighting and a medication review for older adults.
• Follow sport rules on tackling technique and limits on heading or body checking for young players.

Frequently asked questions

How long does a concussion last?

Most adults feel back to normal within 10 to 14 days, and most children and teens within 4 weeks. A minority, roughly 10 to 30% depending on the study and age group, more often those with previous concussions, migraines, anxiety or a slow start to recovery, have symptoms for longer, which is called persistent post-concussion symptoms.

Can you sleep after a concussion?

Yes. Sleep helps the brain recover. You do not need to be kept awake. If the person is very drowsy, confused, vomiting repeatedly or getting worse, get emergency care before they go to sleep. A doctor may ask a carer to check on them during the first night.

What are the first signs of a concussion?

Common first signs are headache, dizziness, a dazed or confused look, nausea, blurred vision, and not remembering what happened just before or after the hit. Loss of consciousness happens in fewer than 1 in 10 concussions, so its absence does not rule one out.

Do you need a CT scan for a concussion?

Usually not. A CT scan shows bleeding and fractures, not concussion itself. Doctors order one only when warning signs are present, such as loss of consciousness, repeated vomiting, a worsening headache, a skull deformity, blood thinner use or older age.

How can you tell a concussion from a more serious brain injury?

A concussion causes symptoms that stay the same or slowly improve. A bleed or swelling usually causes symptoms that get worse: a severe or increasing headache, repeated vomiting, growing drowsiness or confusion, seizures, unequal pupils or weakness on one side. These need emergency care.

When can my child go back to sports after a concussion?

Only after they are symptom-free at rest, back at school without problems, have completed the stepwise return-to-play program, and have written clearance from a doctor. This takes a minimum of about 1 to 2 weeks after symptoms resolve and often longer for children.