Post-Traumatic Amnesia Is Factor in Concussion Management

Types of amnesia

There are two major types of amnesia:

Post-traumatic amnesia (PTA) or anterograde amnesia is characterized by a reduced ability to form new memories after a brain injury, which may lead to decreased attention and inaccurate perception. Anterograde memory is frequently the last function to return after the recovery from a loss of consciousness (LOC). Following the recovery of consciousness patients may be unable to recall little or anything that occurred for days, weeks, or even months after their injury.

Retrograde amnesia (RGA) is characterized by the partial or total loss of the ability to recall events that have occurred during the period immediately preceding brain injury. RGA may extend backwards for seconds, minutes, hours, days, months or even years depending on the severity of the injury. The duration of retrograde amnesia usually progressively decreases.

Testing for RGA

When checking for orientation and RGA, the Sport Concussion Assessment Tool 2 (SCAT2) issued in conjunction with the Concensus Statement on Concussion in Sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008¹ calls for the team physician or ATC, to ask the following questions on the sideline (modified Maddocks questions):

1. At what venue are we today?
2. Which half is it now?
3. Who scored last in this match?
4. What team did you play last week/game?
5. Did your team win the last game?

Testing for PTA

When checking for PTA or anterograde amnesia deficits, the Zurich consensus statement recommends that the team physician or ATC conduct three cognitive assessment tests:

1. An orientation test: What month is it? What is the date today? What is the day of the week? What year is it? What time is it right now?
2. An immediate memory test: using random, unrelated words, reading each word at a rate of one word per second, and asking the athlete to recall the words both immediately and after a delay (not informing the athlete of the delayed testing until after tests 2 and 3 below, and choosing a different set of words each time the test is performed at follow-up exams);
3. A concentration test in which the athlete is asked to recite backwards two sets of increasingly long strings of digits, and then recite the months of the year in reverse order starting with the last month.

PTA: Still a factor in treatment

Until the early 2000's, the most widely followed concussion management guidelines focused on loss of consciousness (LOC) and PTA in determining the severity, or grade, of a concussion and return-to-play protocol. Many considered the duration of PTA the best indicator of traumatic brain injury severity and the most dependable factor in predicting outcome, even in mild cases.

Beginning in 2001 with the Vienna international consensus statement on concussion in sport, and continuing with the consensus statement on concussion in sport of the 2nd International Conference on Concussion in Sport in Prague in 2004, the trend was away from using PTA as a surrogate measure of injury severity:

• Studies suggested that the nature, severity, and duration of clinical post-concussion symptoms such as headache, dizziness, confusion, disorientation, and blurred vision are more common than amnesia (A 2000 study of 1003 concussions sustained by high school and college football players reported that amnesia was present in only 27% of all cases), and may be more important than the presence or duration of amnesia alone.


• Studies have also shown that, because RGA varies with the time of measurement after injury, it is a poor measure of injury severity.

The current consensus statement on concussion statement¹issued in May 2008 swings back the other way, reporting  "renewed interest" in the role of PTA as a surrogate measure of injury severity." It therefore includes post-traumatic amnesia as a "'modifying' factor" that may predict the potential for prolonged or persistent concussion symptoms and influence concussion investigation and management.  Noting that retrograde amnesia "varies with the time of measurement post-injury," the statement continues the expert  trend in the 2000s viewing RGA as "poorly reflective" of concussion severity.

1. Consensus Statement on Concussion in Sport: the 3rd International Conference on Concussion in Sport held in Zurich, November 2008.  Br. J. Sports Med. 20090: 43:i76-i84

Revised June 19, 2009