Is a concussion with a 20-minute loss of consciousness (LOC) and mild post-traumatic amnesia considered mild, moderate, or severe?

Classification of Concussion with 20-Minute Loss of Consciousness and Mild Post-Traumatic Amnesia

This presentation meets criteria for mild traumatic brain injury (mTBI), not moderate or severe TBI, based on established guideline definitions that classify any loss of consciousness under 30 minutes with post-traumatic amnesia less than 24 hours as mild TBI. 1

Definitional Framework

The American Congress of Rehabilitation Medicine and CDC criteria explicitly define mild TBI as including:

• Any loss of consciousness less than 30 minutes with a Glasgow Coma Scale (GCS) score of 13-15 after the period of unconsciousness 1
• Post-traumatic amnesia lasting less than 24 hours 1
• Any alteration in mental state at the time of injury 1

Your scenario with 20 minutes of unconsciousness and mild post-traumatic amnesia falls squarely within these mild TBI parameters 1.

Critical Clinical Considerations

The term "mild" refers to the initial injury classification, not the potential severity of outcomes or complications. 1 This is a crucial distinction that causes significant confusion in clinical practice:

• 5-15% of patients with mild TBI may have compromised function 1 year after injury 1
• Patients with intraparenchymal lesions despite GCS scores of 13-15 can perform on neuropsychological testing similar to those with moderate TBI (GCS 9-12) 1
• Up to 15% of patients with GCS score of 15 will have acute lesions on head CT 1

Essential Management Algorithm

This patient requires:

1. Immediate head CT imaging - Loss of consciousness is an independent predictor of intracranial injury with odds ratio of 1.9 (95% CI 1.3-2.6) 1

2. Serial GCS assessments - A single GCS score has limited prognostic value; serial determinations are essential for detecting deterioration 1, 2

3. Documentation of specific amnesia characteristics:

   • Duration of retrograde amnesia (memory loss before injury) 3
   • Duration of anterograde amnesia (inability to form new memories after injury) 3
   • These are more reliable indicators of injury severity than loss of consciousness alone 1, 3

Important Clinical Pitfalls

Do not dismiss this as "just a mild concussion" based solely on the classification. 1 Common errors include:

• Assuming "mild" means benign outcomes - The classification reflects initial presentation criteria, not prognosis 1, 4
• Relying on a single GCS determination - The GCS was designed for serial assessments in comatose patients, not for diagnosing mild TBI 1
• Ignoring post-concussive symptoms - These may be more important than loss of consciousness duration for predicting outcomes 1, 5

Severity Grading Context

The 2001 Vienna Consensus specifically rejected traditional concussion grading scales that attempted to stratify severity based primarily on loss of consciousness duration 1. Instead, modern approaches emphasize:

• Combined measures of recovery rather than single-point classifications 1
• The burden and duration of post-concussive symptoms 1, 5
• Neuropsychological testing results 1, 5
• Serial clinical assessments 1, 2

Follow-Up Requirements

This patient needs specialized follow-up given the documented loss of consciousness and amnesia 1:

• Standardized symptom assessment using validated scales 1
• Neuropsychological testing if symptoms persist beyond expected recovery timeframe 1, 6, 4
• Education about post-concussive syndrome risk factors 4
• Activity modification guidance with gradual return to normal activities 1, 4

The classification as "mild" TBI is based on initial presentation criteria, but this patient requires comprehensive evaluation, imaging, and close monitoring given the 20-minute loss of consciousness and documented amnesia. 1