38ournal ofNeurology, Neurosurgery, and Psychiatry 1997;62:38-42

Measurement of post-traumatic amnesia:how reliable is it?

N S King, S Crawford, F J Wenden, N E G Moss, D T Wade, F E Caldwell

AbstractObjective-To develop and test a clinicalprotocol for deterni"iLng post-traumaticamnesia by retrospective questioning. Toestablish its limits and factors whichinfluence reliability.Design-Two independent assessmentsusing the Rivermead post-traumaticamnesia protocol were undertaken byseparate observers on various groups ofpatients at various time intervals.Analysis investigated the correlationsbetween assessments, the percentage dif-ference between assessments, the numberof patients changing category, and thedifferences between these analyses in thedifferent patient subgroups. Assessmentswere undertaken both in hospital and inthe patients' homes. Four differentpatient groups were studied. These weregroup A: 12 inpatients with very severehead injury late after injury; Group B: 40patients interviewed at home six monthsafter injury; group C: 22 patients inter-viewed within a few weeks of injury athome; group D: 116 patients interviewedinitially within a few weeks and then at sixmonths, on both occasions at home. TheRivermead post-traumatic amnesia pro-tocol involved clinical questioning of thepatient to establish how long after injury(in hoursldays/weeks) the patientregained continuous day to day memory.All periods of coma were included.Severity was categorised with standardcriteria.Results-Overall correlation was good(Spearman's r 0.79), but the correlationwas lower for patients with post-trau-matic amnesia < 24 hours and when therewas a long delay between assessments. Inall groups 19%/o-25% of patients changedcategories between assessments, but only2% changed by two categories.Conclusions-The assessment of post-traumatic amnesia with the Rivermeadpost-traumatic amnesia protocol is rea-sonably reliable. The misclassificationrate however, is significant enough thatsome caution should be taken in individ-ual cases. Other evidence does show post-traumatic amnesia to be valid, and itprobably remains the best simple prog-nostic item available. In clinical practiceone should avoid placing too much weighton post-traumatic amnesia alone.

(7 Neurol Neurosurg Psychiatry 1997;62:38-42)

Keywords: post-traumatic amnesia; measurement relia-bility

The period of post-traumatic amnesia is usu-ally defined as the time between receiving ahead injury and the resumption of normalcontinuous memory.'-3 It includes any periodsof unconsciousness, confusion, and disorienta-tion.

As single measures, post-traumatic amnesiaand the Glasgow coma scale (GCS)4 arewidely considered the two best single predic-tors of outcome after head injury. The GCS ismost useful if given when a patient is firstadmitted to hospital5 and cannot be used as aretrospective measure of severity of headinjury. The facts that post-traumatic amnesiacan be assessed relatively quickly and after therecovery of the patient are therefore majorclinical advantages.6 In addition, somepatients have significant post-traumatic amne-sia with short or negligible coma. In these cir-cumstances the amnesia correlates better thanGCS with radiological measures of severity ofhead injury.7

Russell and Smith' put forward a taxonomyof severity of head injury based on post-trau-matic amnesia as follows-mild head injury:post-traumatic amnesia less than one hour;moderate head injury: post-traumatic amnesiabetween one and 24 hours; severe head injury:post-traumatic amnesia between one andseven days; and very severe head injury: post-traumatic amnesia more than seven days.Used as a broad measure of severity of headinjury, post-traumatic amnesia has consis-tently shown an ability to predict importantoutcomes. Day to day living abilities (as mea-sured by instruments such as the Glasgow out-come scale8), for example, have shown goodcorrelation with duration of post-traumaticamnesia.9 Similarly, a range of neuropsycho-logical performance variables have shown astrong relation with duration of amnesia.'0-"2 Arecent study has suggested that the conven-tional classifications of severity of head injurybased on post-traumatic amnesia may not bethose which most accurately predict out-come.'2 However, it did confirm the efficacy ofpost-traumatic amnesia in predicting func-tional outcome. Thus the reliability of themeasurement of post-traumatic amnesia maybe a very important issue.

Difficulties in measuring post-traumaticamnesia have been well documented. It can beunderestimated due to "islands of memory".2These are recollections of isolated events,

Oxford Head InjuryService, RivermeadRehabilitation Centre,Abingdon Road,Oxford OX1 4XD, UKN S KingS CrawfordF J WendenN E G MossD T WadeF E CaldwellCorrespondence to:Dr N S King.Received 19 February 1996and in revised form3 June 1996Accepted 27 August 1996

38 on January 17, 2021 by guest. P

rotected by copyright.http://jnnp.bm

j.com/

J Neurol N

eurosurg Psychiatry: first published as 10.1136/jnnp.62.1.38 on 1 January 1997. D

ownloaded from

Measurement ofpost-traumatic amnesia: how reliable is it?

which on closer examination do not occurwithin a continuous memory for events andare reported by about one third of patientswith mild and moderate head injury.'3 It canalso be underestimated if the patients aredeemed to be out of post-traumatic amnesiaonce they are oriented in time and place.Gronwall and Wrightson have shown thatthere is often little relation between respond-ing correctly to orientation questions and sub-sequently remembering that such questionshad been asked.'3 It is suggested that post-traumatic amnesia can be overestimated byincluding periods of natural sleep or impairedconsciousness due to medication, alcohol, ordrugs.2 It seems, for some, to end sharply andto coincide with a memorable event such asbeing in an ambulance, leaving hospital, orgoing home. For others, recovery seems to be aslow and protracted process. This variabilitycan further complicate its measurement.

In response to these types of difficulties,specific methodologies have been proposed tomeasure post-traumatic amnesia, one of whichis the Galveston orientation and amnesia test(GOAT).'4 It has major limitations, however;patients can attain normal scores even whenunable to answer questions relating to amne-sia; it seems to measure post-traumatic disori-entation rather than amnesia'5; it is dependenton the assessor knowing a great deal about thepatient; and it is only appropriate for longperiods of post-traumatic amnesia (more thanthree days). Artiola et al'6 and Shores et al '7have also published measures and theseinvolve both orientation questions and simplelearning tasks. Such measures mean that post-traumatic amnesia becomes "a measurableclinical entity on which independent observerscan agree".'6 These measures are limited,however, because they require repeatedadministration over at least three consecutivedays and therefore require intensive resourcesand are only appropriate for amnesia longerthan three days. They have obvious researchutility but are severely limited as clinical tools.

Clinically, post-traumatic amnesia is invari-ably measured by asking the patient to recall inchronological order, the events they canremember after their injury."3 This method,although widely used, presents difficulties.Firstly, much of the published literature doesnot describe the procedure or protocolused.'718 Secondly, when used in mild headinjury, test-retest reliability can be poor."3Although this is an important finding, its clini-cal relevance is probably limited, because fewclinicians use post-traumatic amnesia as a finegrained measure of severity of head injury.The use of post-traumatic amnesia as a broadmeasure of severity is, however, widespreadand it is an integral part of most neurologicaland neuropsychological assessments.The reliability of measuring post-traumatic

amnesia by retrospective questions across thefull range of severity of head injury thus hasgreat clinical importance. A recent study hasshown good reliability between prospectiveand retrospective measures in a populationwith severe head injury three and a half to six

years after the injury.'9 As yet, however, nodata have been reported on the interrater relia-bility of retrospective measurements in a morerepresentative sample of patients with headinjury. This study aims (1) to describe explicitlya method for measuring post-traumaticamnesia by retrospective questioning-theRivermead post-traumatic amnesia protocol;(2) to assess the interrater reliability of thismethod across a wide range of severity of headinjury and clinically relevant situations.

MethodsTo obtain data from various clinical situations,patients were recruited from four differentsources. These were chosen to be representa-tive of variables including severity of headinjury, time between assessments, and time atwhich post-traumatic amnesia was firstassessed. There was no overlap of patientsbetween these sources. In all cases theRivermead post-traumatic amnesia protocolwas used to measure post-traumatic amnesia.This protocol was derived from descriptions ofmeasurement of post-traumatic amnesia in theliterature and from clinical experience.

MEASUREMENT OF POST-TRAUMATIC AMNESIA:THE RIVERMEAD POST-TRAUMATIC AMNESIAPROTOCOLPost-traumatic amnesia is taken as the timebetween receiving a head injury and theresumption of normal continuous memory,including all periods of unconsciousness, con-fusion, and disorientation for whatever reason.

Patients are asked to recall their memoriesafter the injury in chronological order. It isemphasised that they should relate what theycan actually recall rather than what they havebeen told. After each event, the patient isasked "what is the next thing you remember?"and thus it is clarified whether each memory isan isolated one or part of a longer memorysequence. This process is continued until theassessor is satisfied that normal continuousmemory is being described. The patient isthen asked if this is the point at which he orshe thinks that normal continuous memory forevents returned. The patient might need tocompare memory for that point with memoryfor a time a few days or weeks before the injury(when it was normal). If the assessor andpatient disagree after discussion, the assessor'smeasure is used.The Rivermead post-traumatic amnesia

protocol is designed to be used by clinicianswith experience in head injury assessment andall the clinicians in this study fulfilled this crite-rion.

SOURCES OF PATIENTSGroup A Rivermead Rehabilitation Centre(RRC) (n = 12)Patients who had sustained a very severe headinjury sufficient to warrant inpatient or out-patient treatment at the RivermeadRehabilitation Centre were included if theyhad received their injury within two years ofthe study and consented to take part in it. An

39

on January 17, 2021 by guest. Protected by copyright.

http://jnnp.bmj.com

/J N

eurol Neurosurg P

sychiatry: first published as 10.1136/jnnp.62.1.38 on 1 January 1997. Dow

nloaded from

King, Crawford, Wenden, Moss, Wade, Caldwell

Table 1 Group characteristics for each source ofpatients

Rivermead OXHIS earlyrehabilitation Six month OXHIS early follow up andcentre follow up only follow up six monthn = 12 (A) n = 40 (B) n = 22 (C) n = 116 (D)

Age:Mean (SD) (y) 39 (12-3) 34 (13-1) 36 (14-5) 34 (13-6)Range 17-61 17-60 17-63 16-65

Sex:Male 8 (66 7%) 25 (62 5%) 17 (77 3%) 68 (58 6%)Female 4 (33-3%) 15 (37 5%) 5 (22 7%) 48 (41 4%)

PTA:Mean (SD) 11 (7 7) weeks 65 (192 6) hours 76 (154 4) hours 19 (78 6) hoursRange 1-7 months 1 minute-6 weeks 20 minutes-4 weeks 1 minute-4 weeks

Time from head injury to first assessment:Mean (SD) 38 (25 8) weeks 27 (1 4) weeks 4 (5 4) weeks 11 (9 2) daysRange 11-84 weeks 25-30 weeks 0-5-26 weeks 4 days-12 weeks

Time delay between assessments:Mean (SD) 17 (2 6) days 9 (4 0) days 14 (9 9) days 26 (2) weeksRange 13-21 days 3-20 days 3-46 days 21-34 weeks*

*One missing as date of head injury unclear. PTA = post-traumatic amnesia.

investigator interviewed the patient forbetween 10 and 30 minutes and used theRivermead post-traumatic amnesia protocol toassess length of post-traumatic amnesia. Thepatient was then told that a second investiga-tor would discuss their head injury with themagain in between one and three weeks. A sec-ond investigator then repeated the procedureone to three weeks later. Factual informationsuch as date of head injury, age, etc, weretaken from medical records. Patients wereapproached consecutively over a four monthperiod of admissions to Rivermead and thesample included those who were already inpa-tients at the time of the study.

Group B: Oxford Head Injury Service (OXHIS)six month follow up team (n = 40)The service aims to register all patientsbetween 16 and 65 years who sustain any typeof head injury requiring hospital treatment inOxfordshire. During a routine follow up aspart of a pilot study of outcomes at six monthsafter injury, those patients who consentedwere interviewed at home by one of the followup team (SC, FJW). The investigator assessedthe patient's post-traumatic amnesia using theRivermead post-traumatic amnesia protocoland administered other follow up question-naires. A brief structured interview was usedto establish basic epidemiological information.About 10 days later, the other member of thefollow up team visited the patient andrepeated the procedure. The two investigatorsalternated between interviewing patients onthe first or second visit. Patients wereapproached consecutively over a six monthperiod of notifications to the register.

Group C: OXHIS early intervention team (n =22)A member of OXHIS (NSK, FEC, NEGM)routinely assessed a random half of all regis-tered patients 7-10 days after injury. Patientswere interviewed in their homes and coun-selling and ongoing treatment were providedas required. During the first interview, post-traumatic amnesia was established using theRivermead post-traumatic amnesia protocoland consent was requested for another mem-ber of the team to revisit in the near future.

Consenting patients were then interviewed intheir homes 7-14 days later and the amnesiawas reassessed. The investigators alternatedbetween seeing patients on the first or secondvisit. Patients were approached consecutivelyover a 10 month period of notifications to theregister which included several months whenthe register was not fully operational. Patientsmeasured as having no post-traumatic amnesiaat first assessment were excluded.

Group D: OXHIS early Intervention and sixmonth follow up teams combined (n = 116)Many patients received visits from both theOXHIS intervention team at 7-10 days afterinjury and the follow up team at six monthsafter injury. On both occasions post-traumaticamnesia was established using the Rivermeadpost-traumatic amnesia protocol. Patientswere approached consecutively over a 13month period of notifications to the registerand were excluded if amnesia was zero onboth assessments.

Table 1 summarises the characteristics ofeach of these groups for age, sex, duration ofpost-traumatic amnesia, time from head injuryto first assessment, and time delays betweenassessments.A Spearman's rank correlation coefficient

(r) was generated for post-traumatic amnesiaassessments from first and second interviewsfor all patients. Coefficients were also gener-ated for subgroups of the sample according to(a) duration of post-traumatic amnesia, (b)time at which post-traumatic amnesia was firstassessed, and (c) time between the two assess-ments. The data were also analysed to deter-mine the difference between the twoassessments, the results being expressed as apercentage of the longer post-traumatic amne-sia estimate.

ResultsTable 2 shows Spearman's r for measures ofpost-traumatic amnesia at the first and secondassessments. It displays coefficients for thesample as a whole and for subsamples selectedaccording to severity of head injury, time offirst assessment, and time between assess-ments. It also shows the percentage of patients

40 on January 17, 2021 by guest. P

rotected by copyright.http://jnnp.bm

j.com/

J Neurol N

eurosurg Psychiatry: first published as 10.1136/jnnp.62.1.38 on 1 January 1997. D

ownloaded from

Measurement ofpost-traumatic amnesia: how reliable is it?

Table 2 Reliability ofPTA assessment

Significant Percentage ofdifference sample who

No of Spearman's between changed categorySample patients r correlations n (%l)Whole sample 190 0-79 - 39 (21)PTA:< 24 hours 139 0-59 * 27 (19)> 24hours 51 0-82 12 (24)

Time between assessments:< 6 weeks 74 0-90 ** 14 (19)> 6 months 116 0-64 25 (22)

Time until first assessment:< 3 months 142 0-76 NS 27 (19)> 6 months 48 0-87 12 (25)

*P < 0-05; **P < 0-01. PTA = post-traumatic amnesia.

Table 3 Number ofpatients who changed head injury severity categories betweenassessments for the whole sample

PTA classification PTA Classification at 2nd assessmentat 1stassessment Mild Moderate Severe Very severe Totals

Mild 75 12 EI2 0 89Moderate 12 37 6 Liii 56Severe m 2 21 1 25Very severe 0 0 2 18 20Totals 88 51 31 20 190

Patients in boxes changed by more than one category.

who changed categories of severity of headinjury between assessments using the criteriaof Russell and Smith.' It indicates that post-traumatic amnesia was less reliably assessed inpatients in whom post-traumatic amnesia wasbrief and in patients with a long time delaybetween assessments.

Table 3 shows the number of patients whochanged categories of severity of head injurybetween assessments using the criteria ofRussell and Smith. The numbers in boxes indi-cate the four patients who changed by morethan one category. Three of these patients werefrom group D and one was from group B.

Table 4 shows the data described as the per-centage difference between first and secondassessments of post-traumatic amnesia. Thiswas calculated using the formula (a-b)/a wherea is the higher and b is the lower of the twomeasures, which minimises the sensitivity ofthe data to the severity of head injury. Thetable displays the percentage of change for thewhole sample and for the subsamples selectedaccording to severity of head injury, time offirst assessment, and time between assess-ments. When one of the assessments of post-traumatic amnesia was zero this artificiallycaused the percentage change to be 100% (n =50) and this is highlighted in the table. The

other assessors' measurement of post-trau-matic amnesia for these 50 patients rangedfrom one minute to 48 hours; mean 2-3 hours,median 5 (SD 9 5) minutes. Forty three wereassessed as mild, five as moderate, two assevere, and none as very severe.

DiscussionTable 2 shows that, using a defined clinicalprotocol, the retrospective assessment of post-traumatic amnesia has reasonable reliabilitywith a correlation coefficient of 0 79 and with79% of patients being allocated to the samegrade of severity by both assessors. Thisapplied to all levels of severity and at varioustime points after injury. Table 3 however,indicates that a significant minority of patientscan be misclassified, with 2% being allocatedto widely differing categories of severity by twodifferent assessors.As would be expected, table 2 indicates that

measurement was more reliable for longerdurations of post-traumatic amnesia and whentime intervals between assessments wereshorter. The second finding accords withmany reliability studies which show decreasingreliability as time intervals between testingincreases. The finding that post-traumaticamnesia is measured more reliably for moresevere head injuries has not been previouslyreported, but is consistent with the findings ofGronwall and Wrightson."3 They found thatassessing post-traumatic amnesia by retrospec-tive questioning was often unreliable inpatients with mild head injury. It is also con-sistent with the finding of McMillan et al thatgood reliability exists in severe head injuriesbetween prospective and retrospective assess-ments.'9 Their Spearman's r of 0-87 is remark-ably similar to a coefficient of 0-82 for thepatients with more severe head injury in thepresent study (see table 2).The Rivermead post-traumatic amnesia

protocol was developed to reflect normal clini-cal practice and to be usable by clinicians on aday to day basis without difficulty. It is proba-bly a method similar to that used by most clin-icians who regularly assess patients with headinjury and the definition of post-traumaticamnesia underlying the Rivermead post-traumatic amnesia protocol is generallyaccepted.'-3 The study shows that using theRivermead protocol is reasonably reliable, butthere is scope for variability in measurement.

Table 4 Percentage change in post-traumatic amnesia (PTA) between first and second assessment

Range ofpercentage change in PTA

0 1-24% 25-49% 50-74% 75-99% 100% * Totals

Whole sample (n (%)) 34 (18) 16 (8) 34 (18) 19 (10) 37 (20) 50 (26) 190PTA < 24 hours (n(%)) 23 (17) 10 (7) 16 (11) 12 (9) 29 (21) 49 (35) 139PTA > 24hours 11 (22) 6 (12) 18 (35) 7 (14) 8 (16) 1 (2) 51Time between assessments< 6weeks (n(%)) 19 (26) 9 (12) 18 (24) 6 (8) 12 (16) 10 (14) 74

Time between assessments> 6 months (n (%)) 15 (13) 7 (6) 16 (14) 13 (11) 25 (22) 40 (34) 116

Time until first assessment< 3 months (n(%)) 22 (16) 12 (8) 24 (7) 16 (11) 27 (19) 41 (29) 142

Timne until first assessment> 6 months 12 (25) 4 (8) 10 (21) 3 (6) 10 (21) 9 (19) 48

Numbers in parentheses indicate percentage of total number for each range of change.*50 patients were assessed as having no PTA on one of the assessments, giving a percentage change of 100%.

41

on January 17, 2021 by guest. Protected by copyright.

http://jnnp.bmj.com

/J N

eurol Neurosurg P

sychiatry: first published as 10.1136/jnnp.62.1.38 on 1 January 1997. Dow

nloaded from

King, Crawford, Wenden, Moss, Wade, Caldwell

The clinician has to interpret informationobtained from the patient and the informationitself may potentially be inconsistent. Thisstudy shows the extent of that variability. It isnot known to what extent the underlying phe-nomenon of post-traumatic amnesia itselfvaries, but clinical experience certainly sug-gests that some patients can seem to be out ofpost-traumatic amnesia when seen on a ward(are oriented and can recall events from 24-48hours before) yet have no recall of seeing theassessor when reviewed four weeks later.Unfortunately there is no gold standard withwhich measurements of post-traumatic amnesiacan be compared. Prospective measures havebeen developed,'4 16 but they cannot be usedroutinely and they are not applicable in mildhead injuries. Indeed, the validity of post-trau-matic amnesia as a measure of severity waslargely established using clinical procedureswhich were not detailed. 'The findings of this study, which indicate

the variability in assessments of post-traumaticamnesia, should be interpreted cautiously.The duration of post-traumatic amnesia isoften used in group studies to characterise thesample and to measure severity (prognosis).The fact that studies have repeatedly demon-strated that duration of post-traumatic amne-sia correlates with outcome,9 radiologicalfindings,7 and neuropsychological abnormali-ties'102 demonstrates the validity of post-trau-matic amnesia as a measure. It also suggeststhat reliability must have been at least reason-able otherwise no association would have beenfound. The study starts to quantify the uncer-tainty associated with a clinical assessment ofpost-traumatic amnesia. It should informgroup studies, but does not limit the useful-ness of post-traumatic amnesia.The findings highlight some of the risks

associated with relying solely on post-trau-matic amnesia as a measure of severity in indi-vidual patients and in using it to define rigidtaxonomies of severity. Certainly post-trau-matic amnesia should be used as a major fac-tor when considering the severity of a patient'shead injury, but it should not necessarily bethe sole determining factor. Indeed, manyyears after the event residual problems (if any)need to be born in mind when determiningcurrent severity even if these do not necessarilyreflect the severity of the original brain dam-age.The study does have some potential limita-

tions and weaknesses. The sample was col-lected opportunistically and is not entirelycomplete epidemiologically. Epidemiologicalstudies suggest that at least 75% of all headinjuries are mild20 and as few as 8% may besevere.'6 The sample in this study comprised73% mild and moderate head injuries and27% severe or very severe injuries. Patientswith major head injury are therefore probablyoverrepresented. This, however, was a deliber-ate choice. The numbers would be too smallto allow subgroup analysis if a "pure" epi-demiological sample were relied on, when theresults appertaining to minor head injurieswould dominate any analysis. In addition the

methodology allowed sampling across a widerange of clinically relevant situations which,otherwise, might have been impossible. Thuswe believe that the sample is adequately repre-sentative of general clinical practice.

In conclusion, measuring post-traumaticamnesia by retrospective questioning had goodreliability when the explicit method describedin this study was used. The Rivermead post-traumatic amnesia protocol may therefore be auseful way of measuring the duration of post-traumatic amnesia in clinical practice. Theprotocol standardises the procedure of assess-ment, but is associated with a 21% misclassifi-cation rate. In only 2% of cases however, isthis category change of unequivocal clinicalsignificance (a change of over more than onecategory). This is probably as good as can beachieved in routine clinical practice. Futureresearch should concentrate on improving theclinical assessment of post-traumatic amnesia,developing other better measures of severity ofhead injury and prognosis, and investigatingmore definitive measures of post-traumaticamnesia for use as a gold standard.

We thank Mrs Ann White for typing this manuscript, theDepartment of Health for funding the Oxford Head InjuryService as part of the their traumatic brain injury initiative, andthe patients for all their cooperation.

1 Russell WR, Smith A. Post traumatic amnesia after closedhead injury. Arch Neurol 1961;5:16-29.

2 Whitty CWM, Zangwill OL. Traumatic Amnesia. In:Whitty CWM, Zangwill OL, eds. Amnesia. London:Butterworths Press, 1977:118-35.

3 Lezak MD. Neuropsychological assessment. New York:Oxford University Press, 1983;165-75.

4 Teasdale G, Jennett B. Assessment of coma and impairedconsciousness. Lancet 1974;ii:81-4.

5 Teasdale G, Jennett B. Assessment and prognosis of comaafter head injury. Acta Neurochir (Wien) 1976;34:45-55.

6 Williams JM, Gomes F, Drudge 0, Kessler M. Predictingoutcome from closed head injury by early assessment oftrauma severity.

_Neurosurg 1984;61 :581-5.

7 Wilson JTL, Teasdale GM, Hadley DM, Wiedman KD,Lang D. Post-traumatic amnesia: still a valuable yard-stick. .7 Neurol Neurosurg Psychiatry 1993;56: 198-201.

8 Jennett B, Bond M. Assessment of outcome after severebrain damage. Lancet 1975;i:480-4.

9 Brooks DN. Wechsler memory scale performance and itsrelation to brain damage after severe closed head injury. 7Neurol Neurosurg Psychiatry 1976;39:593-601.

10 Brooks DN, Aughton ME, Bond MR, Jones P, Rizui S.Cognitive sequelae in relationship to early indices ofseverity of brain damage after severe blunt head injury. 7Neurol Neurosurg Psychiatry 1980;43:529-34.

11 Karzmark P. Prediction of long-term cognitive outcome ofbrain injury with neuropsychological, severity of injuryand demographic data. Brain Inj 1992;6:213-17.

12 Bishara SN, Partridge FM, Godfrey MPD, Knight RG.Post-traumatic amnesia and Glasgow coma scale relatedto outcome in survivors in a consecutive series of patientswith severe closed head injury. Brain Inj 1992;6:373-80.

13 Gronwall D, Wrightson P. Duration of post traumaticamnesia after mild head injury. J7ournal of ClinicalNeuropsychology 1980;2:51-60.

14 Levin HS, O'Donnell VM, Grossman RG. The Galvestonorientation and amnesia test: a practical scale to assesscognition after head injury. _7 Nerv Ment Dis 1979;167:675-83.

15 Shores EA, Morosszeky JE, Sandanam J, Batchelor J.Preliminary validation of a clinical scale for measuringthe duration of post-traumatic amnesia. Med _7 Aust1986;155:569-72.

16 Artiola I, Fortuny L, Briggs M, Newcombe F, Ratcliffe G,Thomas C. Measuring the duration of post-traumaticamnesia. .T Neurol Neurosurg Psychiatry 1980;43:377-9.

17 Schacter DL, Crovity HF. Memory function after closedhead injury: a review of the quantitative research. Cortex1977;13: 150-76.

18 Forrester G, Encel J, Geffen G. Measuring post-traumaticamnesia (PTA): an historical review. Brain Inj 1994;8:175-84.

19 McMillan TM, Jongen ELMM, Greenwood RJ.Assessment of post traumatic amnesia after severe closedhead injury: retrospective or prospective? .7 NeurolNeurosurg Psychiatry 1996;60;422-7.

20 Kraus JF, Nourjah P. The epidemiology of mild uncompli-cated brain injury. Trauma 1988;28:1637-43.

42

on January 17, 2021 by guest. Protected by copyright.

http://jnnp.bmj.com

/J N

eurol Neurosurg P

sychiatry: first published as 10.1136/jnnp.62.1.38 on 1 January 1997. Dow

nloaded from