A concussion can happen without a blow to the head and without blacking out. Knowing the signs others can see, the symptoms only the injured person feels, and the red flags that mean "go to the ER now" is the difference between a concussion caught early and one that lingers.
The short version
A concussionA mild traumatic brain injury from a blow or jolt to the head. Symptoms can include headache, dizziness, and trouble concentrating; most people recover with proper rest and follow-up care. is a mild traumatic brain injury. It changes the way the brain works for a time, usually without changing the way the brain looks on a standard CTA test that combines many X-ray images into detailed cross-section pictures of bones and tissues; it is fast and especially good for bone detail. or MRIMagnetic Resonance Imaging — an imaging test that uses strong magnets and radio waves (no X-ray radiation) to make detailed pictures of soft tissues such as muscles, ligaments, and spinal discs. scan. That is exactly why concussions get missed: the scan comes back clean, the person is walking and talking, and everyone assumes nothing happened.
Two beliefs cause most missed concussions:
- “You have to hit your head.” You doA medical doctor — "MD" or "DO" — with four years of medical school plus a multi-year residency in a chosen field. not. A concussion happens when the brain moves rapidly inside the skull. A direct blow does that — but so does a whiplash-type motion when the body is hit hard. Car crashes, hard tackles, falls onto the body rather than the head, and some workplace impacts can all produce a concussion.
- “You have to be knocked out.” You do not. Only about 10% of concussions involve any loss of consciousness. Most people stay awake and aware the whole time.
Signs other people can see
These are the things a parent, coach, athletic trainer, co-worker, or teammate may notice — often before the injured person notices anything:
- Appears dazed, stunned, or has a blank stare
- Is confused about the play, the assignment, the score, or where they are
- Moves clumsily or seems unsteady on their feet
- Answers questions slowly, or repeats the same question
- Cannot recall events just before or just after the hit
- Any loss of consciousness, even brief
- A change in mood, personality, or behavior that is unlike them
Symptoms the injured person feels
Physical: headache (the most common and often the most persistent symptom), pressure in the head, nausea or vomiting, dizziness, balance problems, a sense that things are spinning, blurred or double vision, sensitivity to light, sensitivity to noise, feeling tired or drained.
Thinking and memory: feeling “foggy” or “slowed down,” trouble concentrating, trouble remembering new information, slower reaction time, difficulty reading or looking at screens.
Emotional and mood: irritability, sadness, anxiety or nervousness, feeling more emotional than usual.
Sleep: sleeping much more than usual, sleeping much less than usual, trouble falling asleep, drowsiness.
A person may have one of these or many. The pattern matters — it is what a concussion specialistA provider who focuses on one area of medicine, such as orthopedics, cardiology, or neurology. You often reach a specialist through a referral. uses to work out which clinical profile of concussion is present and which treatment fits. See the companion article on the concussion profiles model.
Symptoms can be delayed — keep watching
This is the part most people miss. Symptoms may not appear until hours or even days after the injury. Someone can walk off a field, finish a shift, or drive home from a collision feeling fine, and wake up the next morning with a headache, light sensitivity, and no ability to concentrate.
If someone has taken a significant hit to the head or body, it is worth watching them over the following days for changes in how they feel, how they think, and how they behave — not just in the first hour.
Red flags: seek emergency care immediately
Most concussions are not emergencies. But a small number of head injuries involve bleeding, swelling, or a skull fracture, and those need emergency evaluation, not an outpatient appointment.
Call 911 or go to the nearest emergency department right away if a person with a head injury has any of the following:
- A headache that keeps getting worse
- Repeated vomiting
- Loss of consciousness for more than a brief moment
- One pupil larger than the other, or unequal pupils
- A seizure or convulsion
- Difficulty waking up, or unusual drowsiness you cannot rouse them from
- Slurred speech
- Weakness, numbness, or decreased coordination in the arms or legs
- Increasing confusion, agitation, or restlessness
- Clear fluid or blood draining from the nose or ears
- Neck pain after the injury, or any concern about a neck or spine injury
- For infants and toddlers: will not stop crying, will not nurse or eat, or has any bump or bruise on the head
These can indicate a more serious traumatic brain injury. An outpatient concussion clinic — including Aptiva Health — is not an emergency service.
Children, teens, and student athletes
Children and adolescents deserve a lower threshold for evaluation. A young person may not have the vocabulary to describe feeling “foggy,” and may under-report symptoms to stay in a game or avoid missing school. Watch for a child who is unusually tired, irritable, off their schoolwork, or reluctant to do things they normally enjoy after a head or body impact.
An unrecognized concussion in a student can quietly damage a semester’s grades and a young person’s mood before anyone connects it to the injury.
What to do if you suspect a concussion
- Stop the activity. Anyone suspected of having a concussion should be removed from play, practice, or the activity immediately, and should not return the same day.
- Check for red flags. If any of the emergency signs above are present, go to the ER or call 911.
- Get evaluated promptly. If there are no red flags, arrange an evaluation with a concussion specialist — ideally within the first week. Early specialist care is associated with faster recovery.
- Do not drive if you are dizzy, foggy, or your reactions feel slowed.
- Tell someone. Make sure a family member, coach, or co-worker knows what happened and can watch for changes over the next few days.
Smart questions to ask
- Based on my symptoms, which type of concussion do I most likely have?
- What warning signs should send me to the emergency room?
- When is it safe for me to drive, return to school or work, and exercise?
- Who should I follow up with, and how soon?
- What will the evaluation and follow-up cost, and is it covered by my plan?
Sources
- CDC — HEADS UP: Concussion Signs and Symptoms
- MedlinePlus — Concussion
- Consensus statement on concussion in sport — 6th International Conference, Amsterdam 2022 (British Journal of Sports Medicine, 2023)
- Aptiva Health — Concussion Treatment & Neuropsychology