Post-traumatic amnesia

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Post-traumatic amnesia (PTA) is a state of confusion that occurs immediately following a traumatic brain injury in which the injured person is disoriented and unable to remember events that occur after the injury.[1] The person may be unable to state his or her name, where he or she is, and what time it is.[1] When continuous memory returns, PTA is considered to have resolved.[2] While PTA lasts, new events cannot be stored in the memory.[3] 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.[3] During PTA, the patient's consciousness is "clouded".[4] Because PTA involves confusion in addition to the memory loss typical of amnesia, the term "posttraumatic confusional state" has been proposed as an alternative.[4]

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).[5] Both retrograde and anterograde forms may be referred to as PTA,[6] or the term may be used to refer only to anterograde amnesia.[7]

Frequently the last symptom to ameliorate after a loss of consciousness,[6] anterograde amnesia may not develop until hours after the injury.[8] 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.[9]

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.[10]

[edit] Measure of TBI severity

Levels of TBI severity[11]
  GCS PTA LOC
Mild 13 to 15 <1
hour		 <30
minutes
Moderate 9 to 12 30 minutes
to 24 hours		 1 to 24
hours
Severe <8 >1 day >24
hours

PTA has been proposed to be the best measure of head trauma severity,[9] but it may not be a reliable indicator of outcome.[3] However, PTA duration may be linked to the likelihood that psychiatric and behavioral problems will occur as consequences of TBI.[4]

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,[9] 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.[3]

Longer periods of amnesia or loss of consciousness immediately after the injury may indicate longer recovery times from residual symptoms from concussion.[12] Increased duration of PTA is associated with a heightened risk for TBI complications such as post-traumatic epilepsy.[13]

[edit] 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).[3] The Galveston Orientation and Amnesia Test (GOAT) exists to determine how orientated a patient is and how much material they are able to recall.[4]

[edit] References

  1. ^ a b Lee LK (2007). "Controversies in the Sequelae of Pediatric Mild Traumatic Brain Injury". Pediatric Emergency Care 23 (8): 580–583; quiz 584–586. doi:10.1097/PEC.0b013e31813444ea. PMID 17726422. 
  2. ^ Petchprapai N, Winkelman C (2007). "Mild Traumatic Brain Injury: Determinants and Subsequent Quality of Life. A Review of the Literature". Journal of Neuroscience Nursing 39 (5): 260–272. PMID 17966292. 
  3. ^ a b c d e van der Naalt J (2001). "Prediction of Outcome in Mild to Moderate Head Injury: A Review". Journal of Clinical and Experimental Neuropsychology 23 (6): 837–851. doi:10.1076/jcen.23.6.837.1018. PMID 11910548. 
  4. ^ a b c d Trzepacz PT, Kennedy RE (2005). "Delerium and Posttraumatic Amnesia", in Silver JM, McAllister TW, Yudofsky SC: Textbook Of Traumatic Brain Injury. American Psychiatric Pub., Inc, 175–176. ISBN 1585621056. Retrieved on 2008-03-06. 
  5. ^ Shaw NA (2002). "The Neurophysiology of Concussion". Progress in Neurobiology 67 (4): 281–344. doi:10.1016/S0301-0082(02)00018-7. PMID 12207973. 
  6. ^ a b Cantu RC (2001). "Posttraumatic Retrograde and Anterograde Amnesia: Pathophysiology and Implications in Grading and Safe Return to Play". Journal of Athletic Training 36 (3): 244–248. PMID 12937491. 
  7. ^ Sivák Š, Kurča E, Jančovič D, Petriščák Š, Kučera P (2005). "An Outline of the Current Concepts of Mild Brain Injury with Emphasis on the Adult Population" (PDF). Časopis Lėkařů Českých 144 (7): 445–450. 
  8. ^ Binder LM (1986). "Persisting Symptoms after Mild Head Injury: A Review of the Postconcussive Syndrome". Journal of Clinical and Experimental Neuropsychology 8 (4): 323–346. doi:10.1080/01688638608401325. PMID 3091631. 
  9. ^ a b c Rees PM (2003). "Contemporary Issues in Mild Traumatic Brain Injury". Archives of Physical Medicine and Rehabilitation 84 (12): 1885–1894. PMID 14669199. 
  10. ^ McCaffrey RJ (1997). "Special Issues in the Evaluation of Mild Traumatic Brain Injury", The Practice of Forensic Neuropsychology: Meeting Challenges in the Courtroom. New York: Plenum Press, 71-75. ISBN 0-306-45256-1. 
  11. ^ Rao V, Lyketsos C (2000). "Neuropsychiatric Sequelae of Traumatic Brain Injury". Psychosomatics 41 (2): 95–103. PMID 10749946. 
  12. ^ Masferrer R, Masferrer M, Prendergast V, Harrington TR (2000). "Grading Scale for Cerebral Concussions". BNI Quarterly 16 (1). Barrow Neurological Institute. ISSN 0894-5799. 
  13. ^ Chadwick D (2005). Adult Onset Epilepsies. E-epilepsy - Library of articles, National Society for Epilepsy.