Evaluation and Management of Post-Traumatic Amnesia After Head Injury
Immediate Assessment of Amnesia
Evaluate both retrograde amnesia (inability to recall events before the injury) and anterograde amnesia (inability to form new memories after the injury) by asking specific questions about details before and after the traumatic event. 1
- Amnesia is an important indicator of more serious injury and serves as an independent predictor of intracranial injury with an odds ratio of 1.9 (95% CI 1.3-2.6). 2
- Loss of consciousness occurs in less than 10% of concussions, but when present alongside amnesia, it signals potentially significant intracranial pathology. 1
- Document the specific duration and characteristics of both retrograde and anterograde amnesia, as this information is critical for assessing injury severity. 2
Neuroimaging Decision-Making
Obtain head CT imaging immediately for any patient with post-traumatic amnesia who also has any of the following high-risk features: 1, 3
- GCS score less than 15 within 2 hours of injury
- Age ≥65 years
- Suspected open or basilar skull fracture
- Vomiting more than once
- Focal neurologic deficit
- Coagulopathy or anticoagulant use
- Dangerous mechanism (fall >3 feet or 5 stairs)
Note that the absence of loss of consciousness or amnesia does NOT exclude the need for CT imaging if other high-risk features are present, as two well-designed studies demonstrated these factors are not sufficiently sensitive to identify all at-risk patients. 1
Validated Assessment Tools
Use the Abbreviated Westmead Post-Traumatic Amnesia Scale for efficient and standardized assessment in the emergency department setting. 4
- This tool allows 94% of patients with mild TBI to clear post-traumatic amnesia testing within 4 hours. 4
- Prospective assessment using validated tools is essential, as post-traumatic amnesia may easily go unrecognized in the acute setting. 5
- Serial assessments are necessary to determine when the patient has fully emerged from post-traumatic amnesia, defined as full orientation with return of continuous memory. 5
Discharge Criteria and Instructions
Patients can be safely discharged if they have a negative head CT (or are deemed too low-risk for imaging) AND have cleared post-traumatic amnesia testing with full orientation and continuous memory. 1, 5
Provide written and verbal discharge instructions at a sixth- to seventh-grade reading level that include: 1
- Return immediately for: repeated vomiting, worsening headache, problems remembering, confusion, focal neurologic deficit, abnormal behavior, increased sleepiness or passing out, or seizures 1
- Avoid alcohol for at least 48 hours 3
- Someone should check on the patient every 2-3 hours during the first 24 hours 3
- Limit screen time and avoid strenuous mental or physical activity until symptom-free 1
Post-Concussive Symptom Monitoring
Identify and document post-concussive symptoms at the time of assessment using a standardized symptom scale. 1
Common symptoms include: 1
- Headache (most frequently reported)
- Memory problems and difficulty concentrating
- Mental fogginess (a good predictor of slower recovery)
- Dizziness and balance problems
- Sleep disturbances
- Mood changes and irritability
Refer to a specialist in traumatic brain injury if symptoms persist beyond 3 weeks or sooner if planning to return to sports. 1, 6
Special Considerations
- Retrograde amnesia symptoms may appear to improve over time as patients hear others discuss the injury and falsely report remembering more details. 1
- Patients in post-traumatic amnesia with behavioral disturbance require behavioral and environmental interventions as the mainstay of treatment, avoiding pharmacological interventions where possible as they may worsen agitation. 5
- Up to 15% of patients with GCS score of 15 will have acute lesions on head CT, emphasizing the importance of appropriate imaging decisions. 2
- The duration of post-traumatic amnesia (defined as less than 24 hours for mild TBI) is the best single indicator of injury severity and predicts functional outcome. 2, 7