Post-traumatic amnesia

Post-traumatic amnesia (PTA) is a state of confusion that occurs immediately following a traumatic brain injury(TBI) in which the injured person is disoriented and unable to remember events that occur after the injury.cite journal |author=Lee LK |title=Controversies in the Sequelae of Pediatric Mild Traumatic Brain Injury |journal=Pediatric Emergency Care |volume=23 |issue=8 |pages=580–583; quiz 584–586 |year=2007 |pmid=17726422 |doi=10.1097/PEC.0b013e31813444ea] The person may be unable to state his or her name, where he or she is, and what time it is. When continuous memory returns, PTA is considered to have resolved.cite journal |author=Petchprapai N, Winkelman C |title=Mild Traumatic Brain Injury: Determinants and Subsequent Quality of Life. A Review of the Literature |journal=Journal of Neuroscience Nursing |volume=39 |issue=5 |pages=260–272 |year=2007 |pmid=17966292] While PTA lasts, new events cannot be stored in the memory.cite journal |author=van der Naalt J |title=Prediction of Outcome in Mild to Moderate Head Injury: A Review |journal=Journal of Clinical and Experimental Neuropsychology |volume=23 |issue=6 |pages=837–851 |year=2001 |pmid=11910548 |doi=10.1076/jcen.23.6.837.1018 ] About a third of patients with mild head injury are reported to have "islands of memory", in which the patient can recall only some events. During PTA, the patient's consciousness is "clouded".cite book| author=Trzepacz PT, Kennedy RE |chapter=Delerium and Posttraumatic Amnesia |editor=Silver JM, McAllister TW, Yudofsky SC |date=2005 | title=Textbook Of Traumatic Brain Injury |publisher=American Psychiatric Pub., Inc |isbn=1585621056 |pages=175–176
url=http://books.google.com/books?hl=en&lr=&id=3CuM6MviwMAC&oi=fnd&pg=PR13&dq=%22Silver%22+%22Textbook+Of+Traumatic+Brain+Injury%22+&ots=PBgkqDseLv&sig=dwP28Fmn63Qjvxr80Cm6So22ITc#PPA175,M1 |accessdate=2008-03-06] Because PTA involves confusion in addition to the memory loss typical of amnesia, the term "posttraumatic confusional state" has been proposed as an alternative.

There are two types of amnesia: retrograde amnesia (loss of memories that were formed shortly before the injury) and anterograde amnesia (problems with creating new memories after the injury has taken place).cite journal |author=Shaw NA |title=The Neurophysiology of Concussion |journal=Progress in Neurobiology |volume=67 |issue=4 |pages=281–344 |year=2002 |pmid=12207973 |doi=10.1016/S0301-0082(02)00018-7] Both retrograde and anterograde forms may be referred to as PTA,cite journal|author=Cantu RC |date=2001 |url=http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=155413 |title=Posttraumatic Retrograde and Anterograde Amnesia: Pathophysiology and Implications in Grading and Safe Return to Play |journal=Journal of Athletic Training |volume=36 |issue=3 |pages=244–248 |pmid=12937491 ] or the term may be used to refer only to anterograde amnesia.cite journal |author=Sivák Š, Kurča E, Jančovič D, Petriščák Š, Kučera P |year=2005
url=http://www.clsjep.cz/odkazy/clc0507_445.pdf |format=PDF |title=An Outline of the Current Concepts of Mild Brain Injury with Emphasis on the Adult Population |journal=Časopis Lėkařů Českých |volume=144 |issue=7 |pages=445–450 ]

Frequently the last symptom to ameliorate after a loss of consciousness, anterograde amnesia may not develop until hours after the injury.cite journal |author=Binder LM |title=Persisting Symptoms after Mild Head Injury: A Review of the Postconcussive Syndrome |journal=Journal of Clinical and Experimental Neuropsychology|volume=8 |issue=4 |pages=323–346 |year=1986 |pmid=3091631 |doi=10.1080/01688638608401325] A common example in sports concussion is the quarterback who was able to conduct the complicated mental tasks of leading a football team after a concussion, but has no recollection the next day of the part of the game that took place after the injury. Retrograde amnesia sufferers may partially regain memory later, but memories are not regained with anterograde amnesia because they were not encoded properly.

The term "posttraumatic amnesia" was first used in 1928 in a paper by Symonds to refer to the period between the injury and the return of full, continuous memory, including any time during which the patient was unconscious.cite book |author=McCaffrey RJ |title=The Practice of Forensic Neuropsychology: Meeting Challenges in the Courtroom |publisher=Plenum Press |location=New York |year=1997 |pages=71-75 |isbn=0-306-45256-1 |oclc= |doi= |chapter=Special Issues in the Evaluation of Mild Traumatic Brain Injury]

Measure of traumatic brain injury severity

PTA has been proposed to be the best measure of head trauma severity,cite journal |author=Rees PM |title=Contemporary Issues in Mild Traumatic Brain Injury |journal=Archives of Physical Medicine and Rehabilitation |volume=84 |issue=12 |pages=1885–1894 |year=2003 |pmid=14669199 |doi=] but it may not be a reliable indicator of outcome.However, PTA duration may be linked to the likelihood that psychiatric and behavioral problems will occur as consequences of TBI.

Classification systems for determining the severity of TBI may use duration of PTA alone or with other factors such as Glasgow Coma Scale (GCS) score and duration of loss of consciousness (LOC) to divide TBI into categories of mild, moderate, and severe. One common system is shown in the table at right.

PTA is considered a hallmark of concussion, and is used as a measure of predicting its severity, for example in concussion grading scales. It may be more reliable for determining severity of concussion than GCS because the latter may not be sensitive enough; concussion sufferers often quickly regain a GCS score of 15.

Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms from concussion.cite journal|author=Masferrer R, Masferrer M, Prendergast V, Harrington TR |year=2000 |url=http://www.emergemd.com/bniq/article.asp?article_ref_id=16-1-1 |title=Grading Scale for Cerebral Concussions |journal=BNI Quarterly |volume=16 |issue=1 |publisher=Barrow Neurological Institute |issn=0894-5799 ] Increased duration of PTA is associated with a heightened risk for TBI complications such as post-traumatic epilepsy.cite web | url=http://www.e-epilepsy.org.uk/pages/articles/show_article.cfm?id=35 |title=Adult Onset Epilepsies |author=Chadwick D| publisher=E-epilepsy - Library of articles, National Society for Epilepsy |date=2005 ]

Assessment

Duration of PTA may be difficult to gauge accurately; it may be overestimated (for example, if the patient is asleep or under the influence of drugs or alcohol for part of the time) or underestimated (for example, if some memories come back before continuous memory is regained). The Galveston Orientation and Amnesia Test (GOAT) exists to determine how orientated a patient is and how much material they are able to recall.cite book| author=Silver JM, McAllister TW, Yudofsky SC |date=2005| title=Textbook Of Traumatic Brain Injury |publisher=American Psychiatric Pub., Inc |isbn=1585621056 |page=63]

References