CONSISTENCY OF WITHIN-DAY AND ACROSS-DAY PERFORMANCE AFTER MILD BRAININJURY

The objective of this study was to determine whether inconsistent and erratic within-day and across-day performance is a symptom of mild to moderate traumatic brain injury (TBI), and to determine whether impair ed consistency of performance can coexist, in the same patient, with i ntact or ''normal'' performance on single administrations of neuropsyc hological and other cognitive tests. The design was a matched-pair stu dy in which a computerized cognitive test battery was administered 30 times over 4 days to all subjects. Performance patterns between TBI an d control subjects were compared. Subjects also received traditional n europsychological testing. The setting was a rehabilitation hospital o utpatient department. The subjects were 12 adult volunteers, six with documented TBI and six with no history of TBI, neurologic illness, or injury. Control subjects showed consistent improvement of performance over days 1 to 4, whereas subjects with TBI showed erratic and inconsi stent performance across days. In addition to inconsistent performance , some subjects with TBI showed worsening performance across days. The main outcome measures were performance on the Automated Neuropsycholo gical Assessment Metrics (ANAM) battery and performance on traditional neuropsychological tests. Some patients with TBI in the study who hav e normal initial performance on traditional clinical neuropsychologica l tests and newly developed computerized cognitive tests show abnormal ities of sustained performance. Such abnormalities are most apparent w hen performance is observed over multiple days, and are characterized by erratic and inconsistent across-day performance. Inconsistent perfo rmance was observed even in those subjects with TBI whose initial perf ormance was equal to or better than that of the control subjects. Defi cits in dynamic performance may explain why some patients with TBI who have excellent neuropsychological test performance nonetheless compla in of functional decrement from premorbid ability.