Abstracts

Rationale:
Neurocognitive functioning has been well characterized in young adults with TLE; yet little is known about the potential overlaying effects of aging, which might add to or interact with already compromised cognitive abilities. This is a particular concern for left TLE (LTLE) patients, as cognitive symptoms such as naming difficulty, already evident in young LTLE patients, are also a classic cognitive symptom of Alzheimer’s disease. We previously found that in young LTLE patients, both auditory and visual naming are relatively impaired, yet auditory naming tends to be worse than visual naming performance. We hypothesized that 1) Similar to younger LTLE patients, older LTLE patients would perform more poorly on auditory naming than visual naming, whereas 2) Probable AD (PAD) patients would show comparable impairment in both.
Method:
Participants were 30 LTLE (22 women) and 42 PAD (19 women) older adult patients (mean (SD): LTLE: Age: 68.5 years (8.5), Education: 15.3 years (2.7), epilepsy onset age: 49.8 years (23. 8), FSIQ: 107.5 (15.0); PAD: Age 75.9 years (6.9), Education: 16.3 years (2.8), onset age: 70.3 (13.4), FSIQ: 100.0 (15.6)). All participants underwent neuropsychological evaluation, including the Older Adult Auditory Naming (ANT) and Visual Naming tests (VNT), and the Boston Naming Test (BNT). ANT and VNT scores were converted to z-scores using age- and education-stratified normative data. ANT and VNT scores included:  Rapid responses (number correct < 2 seconds, i.e., automatic retrieval) and Tip-of-the-tongues (“TOT”= items named 2-20 seconds or after 20 seconds following phonemic cue). BNT scores consist of total correct. Paired T tests compared ANT and VNT performance. Fisher’s Exact assessed classification based on naming performance. Positive (PPV) and negative predictive values (NPV) were calculated for classifying PAD using cut-off scores (ANT and VNT: > 1 SD below mean, BNT: raw score < 50).
Results:
At odds with hypothesis 1, older LTLE patients earned comparable, normal range scores on the ANT and VNT. Consistent with hypothesis 2, PAD patients performed below the normal range on both the ANT and VNT; however, VNT performance was poorer than ANT performance (Rapid responses: t = 2. 47, p = .02). VNT < ANT performance correctly classified 67% of PAD and misclassified only 10% of LTLE patients (p = .006). VNT Rapid responses (< 1 SD) provided a better combination of PPV (62.5%) and NPV (83.3%) than ANT Rapid responses: PPV: 45%, NPV: 90% or BNT scores (PPV: 38%, NPV: 86%).
Conclusion:
Unlike younger adults with LTLE, our sample of older LTLE patients performed normally on both auditory and visual naming, likely related to the late epilepsy onset age. By contrast, PAD patients performed poorly on both auditory and visual naming, with visual naming worse than auditory naming—a pattern unique from any of our previous epilepsy findings, not only by group comparisons, but on an individual patient basis. Results suggest 1) clinical utility of VNT-ANT difference scores and VNT time-based scores in differentiating LTLE and PAD in older adults, and 2) different neural mechanisms underlying naming deficits in LTLE and PAD.
Funding:
:R01NS083976(MJH)