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					    When Mild Is Severe –
    Contradictions In TBI
Classification Using GCS And
             PTA

          Olli Tenovuo
     Department of Neurology
       University of Turku
             Finland
            Introduction
• Glasgow Coma Scale (GCS) and
  duration of post-traumatic amnesia
  (PTA) are two by far the most common
  measures of TBI severity

• The pathophysiology behind these
  measures is largely unknown
Introduction, continued
• The relationship between GCS and PTA is
  poorly studied

• In a series of 157 consecutive mild TBIs
  (GCS 13-15), 48 patients (= 30.6 %) had a PTA
  > 24 hrs, in 22 of these PTA was over 7 days
  (= 14 %) and in 7 patients (= 4.5 %) PTA was
  over two weeks1

  1Dikmen    S, Machamer J, Temkin N. Mild head injury: facts and
  artifacts. J Clin Exp Neuropsychol 2001;23:729-38.
       Purpose of the study
• To study the eventual contradictions in
  TBI classification using the GCS and
  the duration of PTA

• To study the eventual reasons for
  discordant classifications using these
  two measures
                  Methods
• A database of 1029 TBI patients, treated at
  the neurological outpatient clinic at the
  University of Turku, Finland during the years
  1993 – 2005

• The outpatient clinic receives most TBI
  patients admitted to the hospital due to acute
  TBI + patients having suspected sequels of
  TBI within the region (= ½ million inhabitants)
               Methods
• A sample of 112 TBI patients, selected
  in random from the database
• Exclusion criteria:
  - age < 18 or > 65 at injury
  - GCS or PTA not available
  - CT within 3 days of injury lacking
• After exclusion, 95 patients formed the
  study group
    Material, demographics (n = 95)
Age ± SD                36.6 ± 13.1
Sex (M / F)             64 / 31
Education
  - elementary school   25.3 %
  - college             47.4 %
  - high school         16.8 %
  - ND                  10.5 %
Work status
  - employed            63.2 %
  - unemployed          12.6 %
  - student             20.0 %
  - other                4.2 %
  Material, injury characteristics
Injury type
  - traffic         60.0 %
  - fall            30.5 %
  - other            9.5 %
GCS (mean ± SD)     10.7 ± 4.1
PTA (mean ± SD)     10.5 ± 9.2 days
           Material, risk factors
Earlier TBIs
  - none                70.5 %
  - one mild             8.4 %
  - several mild         5.3 %
  -  moderate           3.2 %
  - not known           12.6 %
Psychiatric history
  - none                67.4 %
  - yes                 24.2 %
  - not known            8.4 %
Drug/alcohol abuse
  - none                67.4 %
  - mild                11.6 %
  - moderate            10.5 %
  - not known           10.5 %
   Classification of TBI severity
• GCS 3 – 8 = severe TBI
• GCS 9 – 13 = moderate TBI
• GCS 14 – 15 = mild TBI

• PTA > 7 days = severe TBI
• PTA 1 – 7 days = moderate TBI
• PTA < 24 hrs = mild TBI

GCS was assessed at arrival to the hospital
PTA was assessed with the Rivermead method
                 Results
• GCS and PTA yielded discordant
  classification of severity in 48.9 % of
  patients

• In 91 % of these, PTA suggested a more
  severe injury

• A difference of two classes of severity
  (= mild vs. severe) was found in 12.8 %
  of patients
                      Results, continued
                                Concordant       Discordant      p
Age                             34.5 ± 13.0      38.5 ± 13.2     0.151
Gender                          63 / 37 %        74 / 26 %       0.235
Low / high education            36 / 64 %        20 / 80 %       0.015*
Previous TBIs                   17 %             23 %            0.867
Psychiatric history             27 %             26 %            0.910
Injury type (traf / fall / o)   64 / 25 / 11 %   54 / 37 / 9 %   0.205
Abuse history                   35 %             15 %            0.076°
Confounding factors             56 %             35 %            0.053°
               Discussion

The results suggest that
• GCS and PTA reflect different aspects
  of TBI,
• they may give clearly discordant
  assessment of severity in a large
  portion of patients,
• pre-injury or injury-related factors do
  not seem to explain this discordance
              Conclusions

• There is a fairly common type of injury,
  where the consciousness is well
  preserved, but where the PTA may be
  long as a sign of more severe injury.
• The classification of TBI severity based
  solely on GCS is inadequate, and
  probably one of the main reasons for
  the conflicting views of the outcome in
  “mild” TBIs.

				
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posted:9/13/2012
language:English
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