Concussion Symptoms and Diagnostic Criteria
A concussion diagnosis requires at least one of four key signs following head trauma: altered mental state immediately after injury, posttraumatic amnesia for less than 24 hours, loss of consciousness for less than 30 minutes, or other focal and transient neurologic dysfunction. 1
Diagnostic Criteria
The diagnosis can be established when a patient experiences direct or indirect transmission of kinetic energy to the head AND demonstrates at least one of the following within 24 hours 2:
Immediate neurologic signs:
- Loss of consciousness (any duration up to 30 minutes) 1, 2
- Convulsions or tonic posturing 2
- Posttraumatic amnesia (lasting less than 24 hours) 1
- Focal neurological deficits 2
- Ataxia or balance problems 2
- Visual disturbances 2
Acute mental status changes:
- Confusion or disorientation 2
- Altered mental status 1
- Unusual behavior 2
- Feeling "in a fog" or not feeling right 2
- Difficulty concentrating 2
- Feeling slowed down or drowsy 2
Symptom Presentation
Concussion symptoms manifest across three distinct domains 3, 4:
Physical symptoms:
- Headache (most frequently reported) 3, 4
- Dizziness and balance problems 3, 4
- Nausea and vomiting 3, 4
- Fatigue and low energy 3, 4
- Sleep disturbances 3, 4
- Sensitivity to light and noise 3, 4
- Vision problems 1
Cognitive symptoms:
- Memory problems 3, 4
- Difficulty concentrating or paying attention 3, 4
- Confusion 3
- Slowed thinking 1
- Problems with executive functions 1
Emotional and behavioral symptoms:
Clinical Course and Risk Stratification
Most patients (80-85%) achieve complete symptom resolution within 3 months, but 15-20% develop persistent postconcussion syndrome requiring specialist referral. 3, 1
High-risk patients for prolonged recovery include those with:
- The triad of headache, nausea, and dizziness at initial presentation (50% chance of postconcussion syndrome at 6 months) 3
- Female gender 3
- Age over 40 years 3
- Pre-existing mood disorders 3
- High initial symptom burden 3
- History of multiple concussions 1
Red Flag Symptoms Requiring Emergency Evaluation
Patients must return immediately to the emergency department if they develop: 1, 5
- Repeated vomiting 1, 5
- Worsening headache 1, 5
- Increased sleepiness or passing out 1
- Seizures 1
- Focal neurologic deficits 1
- Abnormal behavior 1
- Confusion 1
- Problems remembering 1
Important Clinical Caveats
The symptoms are non-specific and can overlap with other conditions including depression, post-traumatic stress disorder, and anxiety disorders, requiring careful differential diagnosis. 6, 4, 7 The diagnosis requires that symptoms cannot be explained by drug, alcohol, medication use, cervical injuries, peripheral vestibular dysfunction, or other comorbidities. 1
For patients with negative head CT or deemed too low risk for neuroimaging, home observation including frequent waking or pupil assessment is not supported by literature and is not recommended. 1