There is no more important issue for the diagnosis and determination of prognosis after a brain injury than the length and severity of amnesia. Amnesia is defined as the loss of memory for events, both before and after the accident. Loss of memory for events before the accident is called retrograde amnesia, i.e. similar to the use of the term retroactive, i.e. something that relates back to a time prior to the event. Loss of memory for events after the accident is called anterograde amnesia. This also includes problems with new learning. See http://tbilaw.com/AboutMildBrain16.html In non-coma brain injury cases, there is rarely any significant retrograde amnesia, and the term Post Traumatic Amnesia, (“PTA”) is often used generally to describe the loss of memory following an event.
One of the leading text’s in the Field of Brain Injury, Lezak’s Neuropsychological Assessment, now in its 4th Edition, clearly states the prevailing opinion, that it is the length of Post Traumatic Amnesia that is the biggest predictor of outcome after a brain injury. The 4th Edition contains this chart with respect to amnesia:
TABLE 7.1 Estimates of Severity of Injury Based on Posttraumatic Amnesia (PTA) Duration
PTA Duration Severity
<5 minutes Very Mild
5-60 minutes Mild
1-24 hours Moderate
1-7 days Severe
1-4 weeks Very Severe
More than 4 weeks Extremely Severe
Now the problems with prognosticating brain injury from determinations of PTA is that this measure is rarely properly assessed by treating doctors after a head injury. Lezak explains this dilemma as follows:
“However, difficulties in defining and therefore determining the duration of PTA have made its usefulness as a measure of severity questionable in some cases (Jennett, 1972; Macartney-Filgate, 1990). For example, while it is generally agreed that PTA does not end when the patient begins to register experience again but only when registration is continuous, deciding when continuous registration returns may be difficult with confused or aphasic patients (Gronwall and Wrightson, 1980). Moreover, many patients with relatively mild head are discharged home while still in PTA, leaving it up to the examiner to attempt at some later date to estimate PTA duration from reports by the patient or family members, who often have less reliable memories. These considerations have led such knowledgeable clinicians as Jennett (1979) and N. Brooks (1989) to assert that fine-tuned accuracy of estimation is not necessary as judgments of PTA in the larger time frames of hours, days, or weeks will usually suffice for clinical purposes (e.g., Table 7.1). Length of PTA as more accurate than coma duration in predicting cognitive status two years after injury(D.N. Brooks, Aughton, et al., 1999). Yet failures to discriminate between moderately and severely impaired patients suggest that it may not classify patients with sufficient sensitivity for research (N. Brooks, McKinlay, et al., 1987).”
What does this all mean? It means that someone who is comatose for a week but has a rapid return of memory and a reasonably quick end to PTA may be expected to have a better outcome than someone who is never knocked out but continues to have PTA for more than a month. YES. I DID SAY THAT. Someone without a loss of consciousness can have a worse outcome than someone who is in a coma, if they have a longer period of PTA.
But alas, I am a lawyer, and how do I prove that someone has PTA that persists for weeks after a seemingly routine concussion? If the medical professionals would do their job of follow-up, my job would be so much easier.
I met with a client recently who was amnestic for as much as three months post accident. Among the highlights of what she doesn’t remember is an airline trip to visit a doctor, meeting her lawyer, the last four months of a pregnancy. While not remembering a lawyer might be a good thing, forgetting one of her first airline trips and a significant portion of her pregnancy, are undeniably abnormal. But are these memory gaps clearly documented in her medical records? One month post accident, she is seen by her family doctor, because her significant other is concerned about her memory problems and seizure episodes she is having. The doctor documents the seizure episodes but asks no probing questions about memory or even notes her boyfriend’s concerns about memory.
Why can’t doctors learn how critical documenting amnesia is? Is it so hard to ask questions of a person with Post Concussion Syndrome questions that will test whether that person is imprinting current memories to that person’s long term memory? The brain has a memory mechanism quite analogous to a computer’s RAM conversion to hard drive memory process. If you are creating a document on a computer and lose power or your computer crashes before you save the document, all will be lost and what was held in your computer’s RAM, will not be saved to your computer’s hard drive. Amnesia is the failure of the brain to convert short term memories into long term memory, in essence saving the memory to a different part of the brain.
In order to test for amnesia, it is necessary to ask questions of a person that determine what they remember about a few hours ago, what they remember of yesterday. Why is this so hard? It isn’t hard – it is just that it has never been made to seem important enough. Yet all of 50 steps of the classic neurological exam will tell us far less than simply asking someone what an injured person ate for dinner the night before the follow-up exam.
For more on my thoughts about identifying amnesia, see my YouTube videos at:http://youtube.com/profile?user=braininjuryattorney