Concussion Warning Signs: What to Watch For After a Head Injury
A concussion specialist explains what to watch for after a head injury; emergency red flags, symptoms that show up late, and the signs your recovery needs expert help.
Shan Patel, PsyD
8/3/20263 min read
Someone takes a hit on the field, in a car, on the stairs, and the first question is always the same: how do I know if this is serious? After years of specializing exclusively in concussion care, here’s how I’d answer that question when things matter: the first hours, the first days, and the weeks after.
First: The Emergency Signs (Don’t Wait On These)
Most concussions are not medical emergencies, but a small number of head injuries involve something more dangerous, and the window to act matters. Go to the emergency department or call 911 if you see any of these after a head injury:
• A headache that keeps getting worse, or is sudden and severe
• Repeated vomiting
• One pupil larger than the other
• Seizures or convulsions
• Weakness, numbness, or loss of coordination
• Slurred speech or increasing confusion
• Unusual behavior, extreme drowsiness, or inability to stay awake
• Loss of consciousness — even briefly
This list aligns with the danger signs published by the CDC’s HEADS UP initiative [1]. The rule I give every parent and coach: when in doubt, get it checked. An unnecessary ER visit costs an evening. A missed brain bleed can cost far more.
The Myth That Delays Care
Here’s the misconception I encounter most: “They were never knocked out, so it can’t be a concussion.” Most people with a concussion never lose consciousness. A concussion is diagnosed by the mechanism of injury and the symptoms that follow, not by being knocked out, and not by a scan. In fact, CT scans and MRIs are usually completely normal after a concussion, because the injury is functional, not structural. A normal scan rules out emergencies; it does not rule out a concussion.
The First Few Days: What to Monitor
Concussion symptoms don’t always show up immediately, some emerge hours or even days later, once the person returns to school, work, or screens. Watch for changes across four areas:
Physical: headaches, dizziness, nausea, balance problems, fatigue, sensitivity to light or noise, visual changes
Thinking: brain fog, slowed thinking, trouble concentrating or remembering, difficulty with schoolwork or job tasks that used to be easy
Mood: irritability, anxiety, feeling overwhelmed or “not themselves,” sadness
Sleep: trouble falling asleep, sleeping much more or less than usual, waking unrefreshed
In kids and teens, the tells are often behavioral before they’re verbal: a chatty kid gets quiet, grades dip, they come home from school exhausted, they melt down over small things. If the person seems different after a head injury, take it seriously, even if they insist they’re fine. Athletes, especially, are motivated to minimize. One more thing worth watching: symptoms that spike with activity. If screens, exertion, busy environments, or schoolwork reliably make symptoms worse, that’s not a sign of damage, but it is a sign the recovery needs active management, not just time.
The Weeks After: When “Give It Time” Stops Being the Answer
Most people recover from a concussion within roughly two to four weeks, per the international Consensus Statement on Concussion in Sport [2]. The warning sign at this stage isn’t any single symptom, it’s the calendar. If it’s been three or four weeks and symptoms aren’t clearly improving, or you’re stuck in a loop of feeling better, trying normal life, and crashing again, waiting longer is not the plan. Lingering symptoms usually mean specific, treatable factors are maintaining them: a vestibular or visual system that needs rehabilitation, disrupted sleep, deconditioning, a migraine pattern the injury set off, or anxiety about the symptoms themselves. These respond to targeted treatment [3, 4]. They rarely respond to more rest. Research has shown that prolonged strict rest does not improve recovery and may prolong symptoms [5].
This is the single most common story I hear from patients: weeks or months of “just rest and see,” normal scans, reassurance without a plan, and a recovery going nowhere. If that’s you or your child, that’s precisely the situation specialty evaluation exists for.
The Bottom Line
• First hours: know the emergency signs; when in doubt, get checked.
• First days: monitor the four symptom areas; expect some symptoms to appear late; believe behavior changes.
• Beyond a few weeks: if you’re not clearly improving, stop waiting and get a specialist’s evaluation.
A concussion is highly treatable at every one of those stages, but the treatment has to match what’s actually driving the symptoms. That starts with an evaluation designed to find out.
References
1. Centers for Disease Control and Prevention. HEADS UP: Concussion Danger Signs. cdc.gov/headsup
2. Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport, Amsterdam 2022. British Journal of Sports Medicine. 2023.
3. Collins MW, Kontos AP, Okonkwo DO, et al. Statements of Agreement From the Targeted Evaluation and Active Management (TEAM) Approaches to Treating Concussion Meeting. Neurosurgery. 2016.
4. Kontos AP, Sufrinko A, Sandel N, et al. Sport-Related Concussion Clinical Profiles: Clinical Characteristics, Targeted Treatments, and Preliminary Evidence. Current Sports Medicine Reports. 2019.
5. Thomas DG, Apps JN, Hoffmann RG, et al. Benefits of Strict Rest After Acute Concussion: A Randomized Controlled Trial. Pediatrics. 2015.
6. Leddy JJ, Haider MN, Ellis MJ, et al. Early Subthreshold Aerobic Exercise for Sport-Related Concussion: A Randomized Clinical Trial. JAMA Pediatrics. 2019.
About the author:
Shan Patel, PsyD, is a neuropsychologist and concussion specialist who completed his fellowship through the UPMC Sports Medicine Concussion Program. He is the Owner and CEO of the Patel Concussion Institute (PCI), a telehealth-based practice serving patients nationally via PSYPACT, and serves as Clinical Director of the University Orthopedic Care, Concussion Program, and Integrative Behavioral Health Program, overseeing operations across 14 hospital-based clinics in Florida.
