Accelerated Cognitive Ageing in Epilepsy: A Neuropsychological Evaluation of Cognitive Deterioration

OBJECTIVE

Shed light on cognitive deterioration in Accelerated Cognitive Ageing (ACA) in epilepsy from a neuropsychological point of view in order to improve clinical diagnostics.

METHODS

We compared the IQ-profile including GAI, OPIE IV-premorbid IQ and deterioration-scores of 21 epilepsy patients with ACA with 21 matched epilepsy patients without ACA (Epilepsy Controls) and 16 age- and education-matched Healthy Controls. Memory was also evaluated.

RESULTS

Premorbid IQs were equal in all groups. Deterioration was apparent in the ACA-group in the WAIS-IV FSIQ and PRI, whereas no deterioration was found in the two control groups. PSI was impaired in both epilepsy groups, though with more impairment seen in the ACA-group. The VCI remained unimpaired. The FSIQ-GAI discrepancy was equal in both patient groups and significantly larger than in the Healthy Controls. WMS-IV memory indices were of average level in all groups. Memory impairment in ACA was not statistically different from the Epilepsy Controls. 85.7% of ACA-patients could be correctly classified through factors DET_FSIQ and PSI.

CONCLUSIONS

Cognitive deterioration in ACA is characterized by an average drop of 19 IQ-points in FSIQ and PRI. Verbal abilities remain unimpaired. Impairments in fluid functions compromise cognitive abilities in epilepsy, but only partially contribute to cognitive deterioration in ACA. PSI proved to have some diagnostic value in differentiating epilepsy patients from healthy controls, but fails to differentiate between ACA and Epilepsy Controls. A comparison made between OPIE-IV equations and obtained IQs leads to a significant better detection of cognitive deterioration in epilepsy than the use of GAI-FSIQ discrepancies alone.

Differences in the intellectual profile of children with intellectual vs. learning disability

The WISC-IV was used to compare the intellectual profile of two groups of children, one with specific learning disorders (SLDs), the other with intellectual disabilities (ID), with a view to identifying which of the four main factor indexes and two additional indexes can distinguish between the groups. We collected information on WISC-IV scores for 267 children (Mage=10.61 [SD=2.51], range 6-16 years, females=99) with a diagnosis of either SLD or ID. Children with SLD performed better than those with ID in all measures. Only the SLD children, not the ID children, revealed significant differences in the four main factor indexes, and their scores for the additional General Ability Index (GAI) were higher than for the Cognitive Proficiency Index (CPI). Children with a diagnosis of SLD whose Full-Scale Intelligence Quotient (FSIQ) was <85 showed a similar pattern. Our findings confirm the hypothesis that children with SLD generally obtain high GAI scores, but have specific deficiencies relating to working memory and processing speed, whereas children with ID have a general intellectual impairment. These findings have important diagnostic and clinical implications and should be considered when making diagnostic decisions in borderline cognitive cases.