The Warning Signs of a Serious Brain Injury Can Be Easy to Miss

Signs of a Serious Brain Injury After an Accident You Should Never Ignore

Some warning signs always mean you need emergency care. These are: passing out, a headache that keeps getting worse, throwing up again and again, seizures, confusion, slurred speech, weak arms or legs, and pupils that are not the same size. Any one of these means you need emergency medical care right away.

This guide follows the way a scared family really lives through a head injury. First, what to watch for right after the accident. Next, what can show up hours or days later. Finally, the red flags that mean call 911 now.

It also covers something most guides skip. It shows how to spot a brain injury in a child. And it explains why an injured person often can’t see their own symptoms.

This page is educational. It is not medical advice. When in doubt, see a doctor.

Why a serious brain injury can be easy to miss

Serious brain injuries don’t always show up right away. After a crash, fall, or attack, a rush of adrenaline can hide the early signs. A person may feel “fine” for hours. Then they can get much worse as bleeding or swelling builds inside the skull.

A traumatic brain injury (TBI) is damage to how the brain works. It happens when a blow, bump, or jolt to the head — or violent shaking — disrupts the brain. According to the Mayo Clinic, you don’t need a visible cut, a bump, or even a loss of consciousness to have one.

That’s why “walking away” from a wreck doesn’t mean the brain is fine. In the catastrophic-injury cases our attorneys handle, families often say the same thing. The injured person seemed okay at the scene. Then they got worse over the next day or two. Knowing the warning signs — and who is watching — can save a life.

Mild versus serious: what the difference looks like

A concussion is the mildest kind of TBI. Moderate and severe TBIs can cause lasting or permanent damage. You can’t grade the injury yourself. But a few clues you can see point to a more serious problem:

• How long confusion or memory loss lasts. Brief confusion is one thing. Confusion that won’t go away is a warning sign.
• Loss of consciousness. Even a few seconds matters. Longer means a more serious injury.
• Whether symptoms get worse. A mild injury tends to get better. Symptoms that grow worse over hours are a red flag.

Here’s the honest truth. Symptoms alone cannot rule out a serious injury. Only a medical exam and imaging — usually a CT scan — can show how bad it really is. For a full look at TBI types and severity, see our Traumatic Brain Injury Guide.

Timeline of warning signs

Right after the accident (scene to first hour)

Physical signs

• A severe headache, or one that keeps getting worse
• Throwing up or feeling sick again and again
• Dizziness or loss of balance
• Blurred or double vision

Neurological signs (signs from the brain and nerves)

• Passing out, even briefly
• Confusion or trouble answering simple questions
• Slurred speech
• Weak or numb arms or legs
• Pupils that are not the same size

Emergency red flags — call 911

• Convulsions or seizures
• Clear fluid or blood draining from the nose or ears
• Throwing up again and again, or a seizure in someone who was awake

These match public guidance from the CDC and the National Institute of Neurological Disorders and Stroke (NINDS). If you see any of them, don’t wait.

Delayed signs (hours to days later)

Bleeding or swelling can build slowly. So serious symptoms may show up a day or two later:

Thinking changes

• Worse confusion
• Memory problems and trouble focusing
• Slow or foggy thinking

Sense and body changes

• Headaches that won’t go away
• Trouble with bright light or loud noise
• Ringing in the ears
• Changes in sleep
• Very sleepy, or hard to wake up — this is a red flag; treat it as an emergency

Any symptom that shows up late or gets worse over time is a warning. Sometimes the brain has damage all over without an obvious injury on the outside. See our explainer on diffuse axonal injury.

When should you go to the ER after hitting your head?

Go to the emergency room right away for any of these: passing out, throwing up again and again, seizures, a bad or worsening headache, confusion, slurred speech, weakness, or uneven pupils. If none of these are present but you took a hard hit, watch closely for 24 to 48 hours. Have someone check on you.

Some people should be checked sooner, even with mild symptoms:

• Anyone taking blood thinners
• Older adults
• People hurt in high-speed or truck crashes
• Walkers or cyclists hit by a vehicle
• Anyone hurt in a violent attack

Early imaging can catch bleeding or swelling before it becomes deadly. When you’re not sure, get checked. It’s the safer choice.

Warning signs of a brain injury in children

Most legal guides skip children. But the signs are different, and kids often can’t say what’s wrong. After any real head injury, watch a child’s behavior:

• Crying all the time that you can’t soothe
• Refusing to eat or nurse
• Changes in sleep or play habits
• Losing skills they just learned (words, walking, using the toilet)
• Unusual sleepiness or crankiness
• Any loss of balance in a child who used to be steady

A child can’t always tell you their head hurts or their vision is blurry. When a child has a serious head injury, take them to pediatric (children’s) emergency care. It’s better to be safe.

Why the injured person may insist they’re fine — anosognosia

Do people with a brain injury know they have one? Often, no. Many injured people can’t see their own symptoms. Doctors call this anosognosia. The person may say they feel fine while acting completely unlike themselves.

This is why family watching is so important. It can make all the difference. Watch for crankiness, unusual anger, worry, sadness, mood swings, or simply acting unlike themselves. Don’t brush it off as “just stress.” If someone you love is off after an accident, you may be the only one who can see it. Trust what you’re seeing and tell their doctor.

These changes in mood and personality are among the most lasting effects of a serious brain injury. They can strain relationships, work, and daily life for years.

What to do if you suspect a serious brain injury

Here is a simple checklist. It protects the person’s health first, and saves evidence second:

1. Get an emergency medical evaluation. Health comes first, always. Tell the ER how it happened (crash speed, fall height, attack). That helps them decide on imaging.
2. Follow up with specialists. A neurologist or brain-injury team can track recovery over time.
3. Keep a symptom diary. Write down each symptom, the date and time it started, and whether it’s getting better or worse. This helps doctors. It also shows how the injury affected daily life.
4. Ask family to watch. Because of anosognosia, loved ones often catch changes the injured person cannot. Pick someone to check in during the first 24–48 hours.
5. Follow all medical limits. Don’t go back to work, driving, sports, or activity until a doctor says it’s okay. Write down the limits.
6. Save accident details. Keep photos of the scene, witness names and numbers, and incident or police report numbers. For an injury on someone else’s property, note broken locks, dark areas, or missing cameras before they’re fixed or the video is erased.

When a serious brain injury was caused by someone else

Did another person’s carelessness cause a serious, permanent brain injury? Then you and your family may have a legal claim. These claims often come from truck crashes, other serious accidents, medical negligence, or a violent attack on unsafe property.

Here’s a common example. Someone is attacked, robbed, or shot in an apartment complex, a parking garage, a hotel, a bar, or a store. The property had broken locks or gates, no working cameras, poor lighting, or no guards. A preventable attack caused a life-altering brain injury. When that happens, the property owner may share the blame.

The legal term for this is negligent security. It’s a type of premises liability claim (a claim about an unsafe property). Most people who need this help have never heard the phrase. What matters is simpler. You were hurt on someone else’s property because they didn’t keep it reasonably safe.

Serious brain injuries bring lifelong costs — surgeries, rehab, home care, and lost income. A family shouldn’t carry that burden alone when someone else’s carelessness caused it.

A few Florida facts worth knowing:

• You usually have limited time to file. For negligence claims that start on or after March 24, 2023, Florida generally gives you two years to file a personal-injury lawsuit, under Fla. Stat. §95.11.
• Shared fault matters. Florida uses a modified comparative-negligence rule. A person found more than 50% at fault generally can’t recover damages, under Fla. Stat. §768.81.

Our licensed Florida attorneys offer a free case evaluation. We’ll listen, explain your options in plain language, and answer your questions. We make no promises about any specific outcome.

To understand the most severe outcomes, read about the long-term effects of a severe TBI and the vegetative and minimally conscious states. If you’re ready to talk, you can request a free case evaluation.

Key takeaways

Some signs always mean emergency care: passing out, a worsening headache, throwing up again and again, seizures, confusion, slurred speech, weak arms or legs, and uneven pupils. Symptoms can also show up hours or days later, so keep watching. Watch children by their behavior. Family watching is key, because many injured people don’t realize how badly they’re hurt. Get medical help first. Then, if someone else’s carelessness caused the injury, a free case evaluation can help you understand your options.

Frequently asked questions