Cognitive and Psychosocial Outcome in Survivors of Severe Traumatic Brain Injury: Correlations with Cerebral Perfusion Pressure, Frontal Lobe Damage and Somatosensory Evoked Potentials
ABSTRACT
Objective:
To correlate neuropsychological outcome in patients after severe traumatic head injury, with neurophysiological and neuroradiological data collected during the intensive care unit (ICU) period of care.
Methods:
Patients admitted to Waikato Hospital ICU with severe traumatic head injury were studied. Respiratory difficulty at the accident site, admission Glasgow Coma Score (GCS), anatomic traumatic brain disruption as quantified by a cerebral computed tomography score, prolongation of the central conduction time (CCT) of somatosensory evoked potentials and the percentage time that the cerebral perfusion pressure was less than 70 mmHg (%CPP < 70) were measured. Neuropsychological outcome was assessed, in terms of cognitive and behavioural function, by the Controlled Oral Word Association (COWA) test (performed by the patient) and Head Injury Behaviour rating scale (HIBS, performed by their caregiver) respectively, one year following injury.
Results:
Sixty-eight patients with a median post-resuscitation GCS of 6 were able to complete the neuropsychological follow up. Most patients had significantly impaired cognitive and behavioural function (mean COWA = 32 and HIBS = 9.7). Cognitive function did not correlate significantly with behavioural function (COWA vs HIBS, r = -0.14, p = 0.27). There were no significant correlations between either GCS (r = 0.15, p = 0.28) or estimates of respiratory difficulty at the accident scene and neuropsychological outcome. Poor cognitive outcome (COWA) was correlated with %CPP < 70 (r =-0.41, p = 0.005) and prolonged CCT (r = 0.26, p = 0.03). There was an insignificant correlation between the CT score and cognitive outcome (frontal lobe score vs COWA, r = -0.12, p = 0.33). However, the group of patients with the most severe frontal lobe injury tended to have a worse behavioural outcome as assessed by the HIBS.
Conclusions:
Behavioural outcome as quantified by the caregiver (HIBS) does not correlate well with the degree of cognitive impairment as measured directly from the patient (COWA). Severely head injured patients with poor neurophysiological indicators (%CPP < 70 or prolonged CCT) have a poor neuropsychological outcome. However, anatomical disruption of the brain as estimated by the frontal lobe CT score correlated poorly with outcome. (Critical Care and Resuscitation 2000; 2: 246-252)
Key words:
Head injury, outcome, neuropsychological assessment
