Overview
A concussion is a mild traumatic brain injury caused by a blow to the head or by force transmitted to the head from the body. Loss of consciousness is not required. Symptoms may affect thinking, vision, balance, mood, sleep, and physical comfort, and they may begin immediately or become noticeable over the next hours or days.1
Most people improve substantially within days to weeks, but recovery is individual. Modern care has moved away from prolonged dark-room rest. After a brief period of relative rest, patients generally benefit from a gradual, symptom-limited return to ordinary activity, school, work, and exercise—with stricter safeguards for return to collision sport.423
The most important updates are:
- CT and MRI do not diagnose most concussions. Imaging is used to look for bleeding, fracture, or another structural injury when risk factors are present.1
- “Cocooning” is outdated. Twenty-four to 48 hours of relative rest is usually followed by light activity that does not cause more than mild, brief symptom worsening.42
- The 2025 CBI-M framework adds precision. It describes acute TBI across clinical findings, biomarkers, imaging, and modifiers rather than relying only on “mild, moderate, severe.” It is a characterization framework—not a replacement for bedside diagnosis or current emergency decision rules.56
- Persistent symptoms should be treated by pattern. Headache, vestibular, visual, cervical, sleep, mood, autonomic, and exertional problems often need different interventions.
- No athlete with suspected concussion should return to play the same day.43
Evidence cutoff: This article reflects publicly available evidence through August 9, 2026. Recommendations must be individualized for age, sport, occupation, pregnancy, anticoagulant use, prior injuries, and the circumstances of the current trauma.
Symptoms of Concussion
| Domain | Examples |
|---|---|
| Physical | Headache, nausea, dizziness, balance trouble, light or noise sensitivity, blurred vision, fatigue, neck pain |
| Cognitive | Feeling slowed, foggy, forgetful, distractible, or unable to process information normally |
| Emotional | Irritability, anxiety, sadness, emotional lability, reduced stress tolerance |
| Sleep | Sleeping more or less than usual, trouble falling asleep, unrefreshing sleep |
Symptoms are not specific to concussion. Migraine, cervical injury, inner-ear disorders, medication effects, sleep loss, anxiety, depression, and other medical problems can produce similar complaints. A diagnosis requires the injury context, symptom pattern, examination, and assessment for more serious trauma.
When It Is an Emergency
Call 911 or seek emergency care after head injury for:
- Worsening or severe headache, repeated vomiting, seizure, increasing confusion, agitation, unusual behavior, or inability to awaken
- Weakness, numbness, slurred speech, unequal pupils, new double vision, severe imbalance, or loss of coordination
- Clear fluid or blood from the nose or ears, a suspected skull fracture, or significant neck injury
- Loss of consciousness that is prolonged or followed by deterioration
- Use of an anticoagulant or bleeding disorder with concerning symptoms or a significant mechanism
- Any concern for abuse, assault, intoxication masking symptoms, or inability to be monitored safely
Older adults, very young children, people taking anticoagulants, and people with major trauma may need a lower threshold for emergency assessment. A person can have intracranial bleeding even if they initially appear well.
How Concussion Is Diagnosed
Diagnosis is clinical. A clinician reviews the mechanism, immediate signs, amnesia or altered awareness, symptoms, medications, prior concussion history, migraine, mood, sleep, and neurological examination. In sport, standardized symptom, balance, eye-movement, cognitive, and exertional tools can support—but not replace—clinical judgment.4
Imaging
Most uncomplicated concussions have a normal CT and conventional MRI. CT is used acutely when validated decision rules or clinical judgment indicate risk of hemorrhage or fracture. MRI may be considered when symptoms, deficits, or the course are atypical, but a normal MRI does not rule out concussion.1
Blood biomarkers
FDA-authorized blood tests can help some emergency clinicians decide whether CT is needed after mild TBI in defined adult populations. They do not diagnose concussion severity, explain persistent symptoms, determine return to sport, or predict CTE.
CBI-M: a more detailed acute-injury description
The 2025 Clinical, Biomarkers, Imaging, and Modifiers framework was designed to characterize acute TBI more precisely across multiple domains.56 It may improve research and future care pathways, but many elements are not yet routinely available, and it should not be marketed as a single new “test” for concussion.
Modern Recovery: Relative Rest, Then Gradual Activity
First 24–48 hours
- Reduce activities that clearly worsen symptoms, but normal self-care and calm daily activity are usually appropriate.
- Prioritize sleep, hydration, regular meals, and safe symptom treatment.
- Limit—not necessarily eliminate—screens, reading, bright environments, and cognitive load based on symptoms.
- Avoid alcohol, recreational drugs, driving when impaired, and situations with risk of another head impact.
After the first day or two
Begin light physical and cognitive activity below the level that causes substantial or prolonged worsening. Mild, brief symptom increase can occur during appropriate rehabilitation; major or lasting worsening means the plan should be adjusted.42
For many patients, walking and then structured aerobic exercise can be introduced early. In adults with persistent symptoms, randomized-trial evidence supports individualized subsymptom-threshold aerobic exercise as one component of rehabilitation—not as a universal cure.8
Return to School, Work, Driving, and Sport
School and work
Temporary accommodations may include reduced hours, rest breaks, lower screen brightness, extra time, limited multitasking, and postponement of high-stakes testing or hazardous duties. Complete absence for a prolonged period can make reintegration harder, so the goal is graded participation.3
Driving and safety-sensitive work
Dizziness, slowed reaction time, visual symptoms, sedating medication, and poor attention can make driving unsafe. Commercial driving, aviation, heavy equipment, military duty, and work at heights require occupation-specific clearance.
Sport
An athlete with suspected concussion is removed immediately and does not return the same day. Return-to-sport progression begins only after appropriate clinical assessment and advances stepwise. Later stages involving risk of head impact require symptom resolution, normal examination, and medical clearance consistent with the sport’s rules.43
Persistent Symptoms: Treat the Driver
Symptoms lasting beyond the usual recovery window are sometimes called persisting post-concussion symptoms. This is a description, not proof of permanent brain damage. Factors associated with prolonged recovery can include greater initial symptom burden, prior concussion, migraine, anxiety or depression, sleep disturbance, pain, female sex in some cohorts, and adverse social or occupational circumstances; none predicts an individual outcome with certainty.7
| Dominant problem | Possible targeted approach |
|---|---|
| Headache | Identify migraine, tension-type, cervicogenic, medication-overuse, or neuralgic pattern; use diagnosis-specific treatment |
| Dizziness/imbalance | Vestibular examination, BPPV maneuvers when indicated, vestibular rehabilitation |
| Visual symptoms | Assessment of eye movements, convergence, accommodation, and referral when appropriate |
| Neck pain | Cervical assessment and physical therapy; evaluate for structural injury when indicated |
| Exercise intolerance | Graded subsymptom aerobic program and evaluation for autonomic or cardiopulmonary contributors |
| Sleep/mood | Sleep treatment, psychotherapy, medication when appropriate, and crisis assessment when needed |
| Cognitive difficulty | Pacing, workplace/school accommodations, medication review, sleep and mood treatment, neuropsychological assessment in selected cases |
Passive treatments and repeated imaging are rarely enough. Recovery often improves when the care plan matches the dominant symptom mechanism.
Repeated Concussions and Long-Term Risk
A prior concussion can increase the risk of another concussion, especially before full recovery. Repeated head impacts are also relevant to long-term neurological health, but an individual concussion does not mean a person will develop CTE or dementia. Risk discussions should separate acute injury, persistent symptoms, and cumulative repetitive-head-impact exposure.
What Patients Should Know
- You do not need to be knocked unconscious to have a concussion.
- A normal CT does not mean symptoms are imaginary; it means no CT-visible acute structural injury was found.
- Brief relative rest is appropriate; prolonged inactivity is usually not.
- Return to sport is more conservative than return to ordinary daily activity.
- Persistent symptoms are not one disease and often respond best to targeted rehabilitation.
- New or worsening red flags require reassessment rather than assuming “it is just the concussion.”
Bottom line: concussion care in 2026 is active, staged, and individualized. Protect the brain from another impact, screen for dangerous injury, resume safe activity gradually, and treat the specific systems that remain impaired.
At Los Altos Neurology, concussion evaluation integrates headache, vestibular, cognitive, sleep, mood, cervical, and exertional factors rather than relying on a single score or scan.
Post-traumatic headache is one of the most treatable parts of concussion recovery — it is covered in our headache & migraine pathway. Lingering mental cloudiness is addressed in our brain fog guide.
References
- Centers for Disease Control and Prevention. Updated July 29, 2025. CDC Mild TBI Management Guideline for Adults.
- Centers for Disease Control and Prevention. Updated 2025. What to Do After a Mild TBI or Concussion.
- CDC HEADS UP. Clinical guidance. Managing Return to Activities.
- Patricios JS, Schneider KJ, Dvorak J, et al. Br J Sports Med. 2023;57:695-711. Consensus statement on concussion in sport: Amsterdam 2022.
- Manley GT, et al. Lancet Neurol. 2025;24:512-523. A new characterisation of acute traumatic brain injury: CBI-M.
- National Institute of Neurological Disorders and Stroke. 2025. New framework for classifying traumatic brain injury.
- Systematic review and meta-analysis. JAMA Netw Open. 2025. Factors associated with persisting symptoms after concussion in adults.
- Randomized clinical trial. Arch Phys Med Rehabil. 2024. Subsymptom threshold aerobic exercise for adults with persisting postconcussive symptoms.
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