What are the diagnostic criteria for cerebral concussion?

Diagnostic Criteria for Cerebral Concussion

Concussion is diagnosed clinically based on a history of closed head injury or transmitted force to the brain, combined with specific acute indicators including disorientation/confusion, impaired balance within 24 hours, slower reaction time within 2 days, and impaired verbal learning/memory within 2 days—no loss of consciousness is required for diagnosis. 1

Core Diagnostic Requirements

Primary diagnostic criteria include:

• History of biomechanical force: Direct impact to the head or transmitted forces to the brain from closed head injury 2
• Glasgow Coma Scale score of 13-15 at presentation 3
• Temporal relationship: Symptoms must have clear temporal connection to the injury mechanism 4

Most Reliable Acute Indicators (Within 3 Days)

The following indicators provide the strongest diagnostic evidence when present:

• Disorientation or confusion immediately following injury is the most reliable immediate indicator 1
• Impaired balance assessed within the first 24 hours using standardized tools (Balance Error Scoring System or Sensory Organization Test) 1
• Slower reaction time measured within 2 days of injury 1
• Impaired verbal learning and memory within 2 days provides objective cognitive dysfunction evidence 1

Clinical Assessment Components

Perform a comprehensive evaluation including:

• Detailed injury history: Mechanism of injury, events surrounding trauma, presence/absence of loss of consciousness (occurs in <10% of cases), posttraumatic amnesia, and any witnessed disorientation 2, 1
• Previous concussion history: Number, duration, and intervals between prior concussions 2
• Symptom assessment: Headache (most common), dizziness, nausea, cognitive difficulties, mood changes, sleep disturbance 3, 4
• Neurological examination: Mental status, cranial nerves, motor/sensory function, reflexes 2
• Gait and balance testing: BESS, Romberg test, tandem gait 2
• Cognitive assessment: Sport Concussion Assessment Tool (SCAT) or Standardized Assessment of Concussion (SAC) 2
• Vestibular and ocular-motor examination: Vestibular ocular reflex, smooth pursuits, saccades, convergence 5
• Cervical spine examination: Often accompanies concussion 1, 5

Five Recognized Concussion Subtypes

Evaluate for all five subtypes as they are not mutually exclusive and may change over time: 2

1. Cognitive subtype: Attention deficits, impaired reaction time, slowed processing, memory problems (>1 SD below baseline or 1.5 SD below normal on testing) 2
2. Ocular-motor subtype: Impaired smooth pursuits, saccades, convergence insufficiency 2
3. Headache/migraine subtype: Post-traumatic headache with or without migraine features 2
4. Vestibular subtype: Dizziness, imbalance, visual motion sensitivity 2
5. Anxiety/mood subtype: Nervousness, emotional lability, depressed mood, irritability triggered or exacerbated by injury 2

Associated Conditions to Assess

• Sleep disturbance: Commonly present and should be systematically evaluated 1
• Cervical strain: Frequently accompanies concussion 1, 5

Exclusion Criteria

Do not diagnose concussion if: 2

• Pre-existing psychiatric or neurological disability prevents accurate self-report
• Medical condition confounds accurate assessment
• Medication, drug, or substance use confounds assessment

Neuroimaging Considerations

Conventional CT and MRI are typically normal in concussion by definition 2, 6

Obtain emergent CT imaging if any red flags present: 2

• Glasgow Coma Scale <15 at 2 hours post-injury
• Suspected open or depressed skull fracture
• Worsening headache
• Repeated vomiting
• Focal neurological deficits
• Altered mental status progression
• Seizure
• Irritability on examination

CT is the test of choice within first 24-48 hours to rule out intracranial hemorrhage (subdural, epidural, intracerebral, subarachnoid) 2

Critical Diagnostic Pitfalls to Avoid

• Never require loss of consciousness for diagnosis—LOC occurs in less than 10% of sport-related concussions and is not necessary for concussion diagnosis 2, 1
• Do not rely on neuroimaging to diagnose concussion—there is no objective biomarker or imaging test that definitively diagnoses concussion; it remains a clinical diagnosis 1, 6
• Avoid delayed evaluation—the most reliable diagnostic indicators are present within the first 48 hours 1
• Do not minimize injury with terms like "ding" or "getting your bell rung" during documentation, though these terms may help elicit history from athletes 2
• Recognize that symptoms are nonspecific—diagnosis requires establishing temporal relationship between appropriate injury mechanism and symptom onset 4

Monitoring and Follow-up

• Provide clear instructions on which signs/symptoms warrant return to emergency department: progressive symptoms, repeated vomiting, severe worsening headache, seizure, focal deficits, altered consciousness 2
• Reassess for subtype predominance changes as clinical presentation may evolve over time 1
• Women, older adults, less educated persons, and those with previous mental health diagnoses are at higher risk for persistent symptoms beyond 2 weeks 3