IQ-Memory Differences in Traumatic Brain Injury

Abstract Objective: WMS-III Memory Index scores that are significantly lower than a patient’s IQ suggest acquired memory impairment. This comparison can be made using obtained IQ and Memory Index scores or by comparing obtained Memory Index scores to the Index scores predicted from IQ by regression. This study compared the sensitivity of obtained IQ-memory discrepancies and predicted Index discrepancy scores in a group of 75 patients with moderate or severe traumatic brain injuries. Data selection: Patients averaged 12.8 months post-TBI with a median admission GCS of 8 and abnormal head CT/MRI in 91% of cases. Average WAIS-III FSIQ was 84 (s = 14.4). Data Synthesis: WMS-III Immediate (M= 77.1, s = 19.0) and General Memory (M= 78.6, s = 20.1) Indexes were significantly lower than obtained IQ and IQ predicted Immediate (M= 90.8, s = 8.3) and General Memory (M= 90.2, s = 8.7) Indexes. Predicted memory discrepancies correlated significantly with length of unconsciousness (r’s \u3e 0.21), admission GCS (r’s \u3e 0.25), and length of PTA (r’s = 0.23). Obtained IQ-memory discrepancies were not significantly correlated with injury severity. Immediate Memory Indexes were 1S.D. lower than predicted in 52% of the group, but 1S.D. lower than FSIQ in only 28% of cases. Predicted General Memory discrepancy was also more sensitive than a direct comparison with FSIQ (45% vs. 27% abnormal cases). Conclusions: IQ predicted memory index differences appear to be more sensitive to TBI than direct differences between IQ and memory