Trauma-induced transient brain dysfunction without imaging abnormality.
Also known as: concussion, mild TBI, mTBI, post-concussive syndrome, PCS
Overview
A complex pathophysiologic process affecting the brain induced by traumatic biomechanical forces, producing transient impairment of neurologic function. Typically GCS 13-15, loss of consciousness <30 minutes (often none), and post-traumatic amnesia <24 hours, with normal structural neuroimaging.
Epidemiology
~3-4 million sports-related concussions per year in the US; many more from falls, MVCs, military blast injuries, and assaults. Up to 40% of patients have symptoms beyond 1 month (persistent post-concussive symptoms).
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Rotational and linear acceleration forces produce shear stress on axons and a transient neurometabolic cascade: indiscriminate neurotransmitter release, ionic shifts (potassium efflux, calcium influx), hypermetabolic glucose use to restore ionic gradients, and reduced cerebral blood flow. The mismatch between energy demand and supply leaves the brain vulnerable to a second hit during this metabolic crisis (second impact syndrome).
Clinical presentation
Symptoms
Headache (most common)
Confusion, feeling 'in a fog'
Dizziness, balance problems
Nausea/vomiting
Photophobia, phonophobia
Difficulty concentrating, slowed thinking
Memory problems (especially retrograde and anterograde amnesia around the event)
Migraine triggered by trauma — Throbbing, photophobia, aura; responds to migraine therapy
Post-traumatic seizure — Witnessed convulsion, tongue bite, postictal state
Functional / psychogenic — Inconsistent exam, secondary gain, normal imaging — diagnosis of exclusion
Diagnostic workup
Diagnostic criteria
Clinical: traumatic mechanism + altered mental status / symptoms / amnesia + normal structural imaging. No single laboratory or imaging test is required.
Labs
Generally not indicated
Consider glucose, blood alcohol, drug screen if altered mental status
GFAP/UCH-L1 blood biomarker (FDA-cleared) can help rule out CT-positive injury in select adults
Imaging
Non-contrast head CT if any Canadian CT Head Rule criteria positive: GCS <15 at 2 h, suspected open/depressed skull fracture, signs of basilar fracture, vomiting ≥2 episodes, age ≥65, amnesia >30 min, dangerous mechanism
MRI not routinely needed; consider if persistent symptoms beyond expected recovery or focal findings
Cervical spine imaging per NEXUS or Canadian C-spine Rules
Tolerate cognitive/physical activity without symptom exacerbation
2
Light aerobic exercise (walking, stationary bike, <70% max HR)
Increase heart rate
3
Sport-specific exercise (running, skating drills — no head impact)
Add movement
4
Non-contact training drills, resistance training
Coordination and cognitive load
5
Full-contact practice after medical clearance
Restore confidence, assess functional skills
6
Return to play
Normal game play
Graduated return-to-play protocol following sport-related concussion (Amsterdam 2023). Progress only when asymptomatic at each step; minimum 24 h per step.
Treatment
First-line
Initial relative rest (1-2 days) — physical and cognitive — followed by GRADUAL return to activity
Symptom-limited aerobic activity (sub-symptom-threshold exercise like stationary bike) within 24-48 h is now recommended (Buffalo Treadmill Test guides intensity)
Acetaminophen for headache (avoid NSAIDs/aspirin in the first 24-48 h due to bleeding risk, though increasingly considered safe)
Sleep hygiene, hydration, avoid alcohol and recreational drugs
Return-to-learn before return-to-play — graduated school accommodations as needed
Graduated return-to-play protocol (6-step Berlin/Amsterdam consensus): only progress when asymptomatic at the prior step; no full contact until cleared by clinician
Second-line / adjunct
Targeted therapy by dominant symptom: vestibular therapy for dizziness, oculomotor therapy for visual symptoms, cervical PT for neck pain, cognitive behavioral therapy for mood/sleep
Migraine prophylaxis (amitriptyline, propranolol, topiramate) for persistent post-traumatic headache
Neuropsychological testing for prolonged cognitive symptoms
Avoid return to contact sport until full recovery; consider permanent retirement after multiple concussions or persistent symptoms
Complications
Persistent post-concussive symptoms (>1 month) in up to 30-40%
Second impact syndrome — rare but catastrophic diffuse cerebral edema from repeat head injury before recovery; pediatric athletes at highest risk
Post-traumatic epilepsy
Chronic traumatic encephalopathy (CTE) — neurodegenerative tauopathy associated with repetitive head impacts; diagnosed only postmortem
Depression, anxiety, PTSD
Vocational and academic impairment
PANCE pearls
Loss of consciousness is NOT required to diagnose concussion (occurs in <10% of sports concussions).
'Strict rest' (cocoon therapy) for >2 days is HARMFUL — early symptom-limited activity improves outcomes (Amsterdam consensus 2023).
Never return an athlete to play on the same day of a suspected concussion.
Headache patterns matter: persistent post-traumatic headache often resembles migraine and responds to migraine treatment.
Anyone with suspected concussion needs a graduated return-to-learn AND return-to-play plan — academic and athletic stepwise progression.
References
Amsterdam Consensus 2023 — Consensus Statement on Concussion in Sport — 6th International Conference (Patricios et al., BJSM 2023)
CDC mTBI 2018 — CDC Guideline on Diagnosis and Management of Mild Traumatic Brain Injury Among Children (Lumba-Brown et al., JAMA Pediatr 2018)
Canadian CT Head Rule — The Canadian CT Head Rule for Patients with Minor Head Injury (Stiell et al., Lancet 2001)
AAN 2013 — Evaluation and Management of Concussion in Sports (Giza et al., Neurology 2013)
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