Older adults represent the fastest-growing population of individuals with epilepsy with an incidence that peaks after age 65. Patients with late-onset epilepsy (LOE) have a multitude of risk factors for accelerated cognitive and brain aging, including vascular and metabolic risk factors. Despite this, there are few studies investigating the cognitive profiles of older adults with LOE, a neglected area in aging research. We examine the cognitive profiles of older adults with LOE and determine the contribution of demographic and vascular risk factors to impairment.

Participants were part of the Atherosclerosis Risk in Communities Study (ARIC) and the incidence of epilepsy was identified using ARIC hospitalization records and Centers for Medicare and Medicaid Services claims data from 1991 to 2015. Approximately 1.8% of the participants with sufficient Medicare coverage data were classified as having LOE (LOE n=281; Non-LOE n=9808). Vascular, lifestyle, and cognitive data were obtained from the ARIC Neurocognitive Study (ARIC-NCS) which consisted of three visits since 2011. Participants with ARIC-NCS visits completed after the onset of seizures were included in the final sample. Non-LOE participants with normal cognition (Black: n=603 and White: n=2543 participants independently) were used to generate z-scores across tests of language, memory, executive function, and processing speed/attention. Impairment was defined as <1.5 standard deviations below the mean of the normative sample. Stepwise regressions were conducted to examine the contribution of demographic (age, race, sex, education) and vascular risk factors (hypertension, diabetes, hyperlipidemia, obesity, smoking) to cognitive performance.

Average age of first seizure of all LOE participants (n=281) was 76.23 (SD=6.24), 55.9% female, 30.7% Black/African American, and the majority had either a college (28.1%) or high school degree (26%). Fifty-six LOE participants had ARIC-NCS visits after the onset of seizures (average age=79.84, SD=5.17, 57.1% female, 32.1% Black). Approximately 67.9% of the sample had at least one vascular risk factor with 81.5% having hypertension, 37% diabetes, 26.4% hyperlipidemia, 20.4% obesity (BMI>30), and 4.5% current smoker. The most frequently impaired domains were language (naming=29.7%; animal fluency=20%; letter fluency=30%) and memory (prose immediate recall=18.4%; prose delayed recall=44.7%; word delayed recall=19.4%). Higher education was associated with better naming (b=0.801, p=0.040). Female sex (b=-0.799, p=0.017) and lower education levels (b=0.418, p=0.050) were associated with poorer immediate prose recall. Older age was associated with poorer delayed prose recall (b=-0.191, p=0.036). Hypertension was associated with worse digit span backward (b=-0.942, p=0.002).

In older adults with LOE, language and memory were the most commonly impaired cognitive domains, similar to studies in early onset epilepsy. Vascular risk factors were prevalent among LOE and hypertension was associated with worse working memory. Further, important demographic factors (sex, education, and age) were associated with the extent of cognitive impairment. Characterizing cognitive profiles in LOE and determining the contribution of demographic and vascular factors to impairment could help to identify patients at risk for future cognitive decline and/or the development of LOE itself, as well as interventions aimed at reducing the risk of further decline.

Memory impairment is a common comorbidity in individuals with temporal lobe epilepsy (TLE). Further, in medication-resistant epilepsy the frontline option, neurosurgical epileptogenic zone destruction, places memory at significant risk. Research has highlighted that TLE causes whole-brain network efficiency disruption, but it is not established how this may explain pre- and post-surgical cognition. Here we examine whether white matter structural network organization predicts pre-operative memory function and/or risk for post-operative memory decline.

Patients with drug-resistant TLE were recruited from two epilepsy centers in a prospective longitudinal study. The pre-operative sample included 51 individuals with left TLE (L-TLE), 52 with right TLE (R-TLE), and 57 healthy controls who underwent T1- and diffusion-weighted MRI (dMRI), and neuropsychological tests of verbal and visual memory. Forty-four patients (n=21 L-TLE) subsequently underwent temporal lobe surgery (36 anterior temporal lobectomy; 7 stereotactic laser amygdalohippocampectomy; 1 amygdalohippocampectomy) and completed post-operative memory testing. Whole-brain connectomes were generated via diffusion tractography and analyzed using graph theory, focusing on network integration (path length) and specialization (transitivity). In the preoperative dataset, first we compared TLE versus controls with analysis of covariance (ANCOVAs) controlling for age. Next, linear regressions examined the association between memory scores and network efficiency between L-TLE, R-TLE and controls. In the post-operative sample, bivariate correlations examined the association between pre- to post-operative memory change and 1) global network efficiency and 2) asymmetry of mesial temporal efficiency (i.e., local efficiency of the hippocampal, parahippocampal, and entorhinal nodes). Finally, efficiency metrics were entered into stepwise regressions along with established predictors of memory decline.

Compared to controls, TLE showed longer path length (p < .05; ηp2 = .03) and lower transitivity (p = .01; ηp2 = .04). Pre-operatively, better verbal learning and memory were associated with both shorter path length (β = -0.23 to -0.32; psadjusted < .05) and increased transitivity (β = 0.20 to 0.31; psadjusted < .05). These associations were greater in L-TLE than R-TLE (i.e., a significant interaction; β = -0.29 to 0.25; psadjusted <.05). Post-operatively, global metrics predicted decline on list learning for LTLEs (rs = -.57 to .58; ps < .01), and were marginal on list recall (rs = -.42 to .40; ps < .10). Leftward asymmetry of mesial temporal local efficiency predicted greater decline across most verbal memory measures for L-TLE (rs -.47 to -59; psadjusted <.05), but not R-TLE. Asymmetry of mesial network efficiency uniquely explained at least 20 to 43% of the variance in list learning, recall, and story learning for L-TLE, outperforming hippocampal asymmetry and preoperative score (psadjusted <.05).

Our findings suggest that global white matter network abnormalities contribute to verbal memory impairment pre-operatively and vulnerability to decline post-operatively in L-TLE. Asymmetry of a predefined mesial temporal sub-network may help predict post-operative memory function following left temporal lobe surgery, such that greater efficiency in the to-beresected mesial temporal network may be an important risk factor for decline. Our findings extend the importance of network approaches in TLE to include the relationships between neurobiological networks and memory function.

Hippocampal pathology is a consistent feature in persons with temporal lobe epilepsy (TLE) and a strong biomarker of memory impairment. Histopathological studies have identified selective patterns of cell loss across hippocampal subfields in TLE, the most common being cellular loss in the cornu ammonis 1 (CA1) and dentage gyrus (DG). Structural neuroimaging provides a non-invasive method to understand hippocampal pathology, but traditionally only at a whole-hippocampal level. However, recent methodological advances have enabled the non-invasive quantification of subfield pathology in patients, enabling potential integration into clinical workflow. In this study, we characterize patterns of hippocampal subfield atrophy in patients with TLE and examine the associations between subfield atrophy and clinical characteristics.

High-resolution T2 and T1-weighted MRI were collected from 31 participants (14 left TLE; 6 right TLE; 11 healthy controls [HC], aged 18-61 years). Reconstructions of hippocampal subfields and estimates of their volumes were derived using the Automated Segmentation of Hippocampal Subfields (ASHS) pipeline. Total hippocampal volume was calculated by combining estimates of the subfields CA1-3, DG, and subiculum. To control for variations in head size, all volume estimates were divided by estimates of total brain volume. To assess disease effects on hippocampal atrophy, hippocampi were recoded as either ipsilateral or contralateral to the side of seizure focus. Two sample t-tests at a whole-hippocampus level were used to test for ipsilateral and contralateral volume loss in patients relative to HC. To assess whether we replicated the selective histopathological patterns of subfield atrophy, we carried out mixed-effects ANOVA, coding for an interaction between diagnostic group and hippocampal subfield. Finally, to assess effects of disease load, non-parametric correlations were performed between subfield volume and age of first seizure and duration of illness.

Patients had significantly smaller total ipsilateral hippocampal volume compared with HC (d=1.23, p<.005). Contralateral hippocampus did not significantly differ between TLE and HC. Examining individual subfields for the ipsilateral hemisphere revealed significant main-effects for group (F(1, 29)=8.2, p<0.01), subfields (F(4, 115)=550.5, p<0.005), and their interaction (F(4, 115)=8.1, p<0.001). Post-hoc tests revealed that TLE had significantly smaller volume in the ipsilateral CA1 (d=-2.0, p<0.001) and DG (d = -1.4, p<0.005). Longer duration of illness was associated with smaller volume of ipsilateral CA2 (p=-0.492, p<0.05) and larger volume of contralateral whole-hippocampus (p=0.689, p<0.001), CA1 (p=0.614, p < 0.005), and DG (p=0.450, p<0.05).

Histopathological characterization after surgery has revealed important associations between hippocampal subfield cell loss and memory impairments in patients with TLE. Here we demonstrate that non-invasive neuroimaging can detect a pattern of subfield atrophy in TLE (i.e., CA1/DG) that matches the most common form of histopathologically-observed hippocampal sclerosis in TLE (HS Type 1) and has been linked directly to both verbal and visuospatial memory impairment. Finally, we found evidence that longer disease duration is associated with larger contralateral hippocampal volume, driven by increases in CA1 and DG. This may reflect subfield-specific functional reorganization to the unaffected brain tissue, a compensatory effect which may have important implications for patient function and successful treatment outcomes.

The International Classification of Cognitive Disorder in Epilepsy (IC-CoDE) is a new consensus-based taxonomy that classifies patients into one of four cognitive phenotypes (i.e., cognitively intact, single-domain impairment, bi-domain impairment, generalized impairment). The IC-CoDE has been effectively applied to patients with temporal lobe epilepsy (TLE), but little is known about the relationship between pre-operative cognitive phenotype and post-operative cognitive outcome following epilepsy surgery. The purpose of this study was to examine whether the IC-CoDE classifications are related to memory decline following surgery for TLE.

347 patients (ages 16-66; 57% female) with pharmacoresistant TLE completed comprehensive pre- and post-surgical neuropsychological assessments. Patients were classified into IC-CoDE phenotypes based on pre-surgical pattern of cognitive impairment using a threshold of >1.5 standard deviations (SD) below the normative mean. Change scores were calculated from delay trial scores of the following memory tests: Rey Auditory Verbal Learning Test (RAVLT), and Logical Memory (LM) and Verbal Paired Associates (VPA) subtests from the Wechsler Memory Scale - Third Edition (WMS-III). Cutoffs were applied using epilepsy-specific reliable change indices and patients were classified within the ‘decline’ group if they experienced significant decline on any of the three memory measures.

The distribution of IC-CoDE phenotypes in our sample were as follows: 57% intact, 29% single-domain, 10% bi-domain, and 5% generalized impairment. 108 patients (31%) demonstrated post-surgical memory decline. Patients who underwent dominant temporal lobectomy were more likely to show post-surgical memory decline compared to non-dominant temporal lobectomy. However, there was no significant difference in phenotype distribution between patients who underwent left versus right-sided resections; thus, analyses were conducted on the entire sample to increase power. Chi-square analyses revealed unique patterns of post-surgical memory decline across phenotypes, X2 = 8.79, p = .032. There was a significantly higher proportion of patients with memory decline in the single-domain phenotype (39%) and this was followed by the bi-domain phenotype (33%) and the intact phenotype (29%). In contrast, patients with generalized impairment were unlikely to show memory decline (.06%). Within the single domain impaired phenotype, there were no differences between the specific domains impaired and memory decline. Logistic regression model was also significant; after controlling for surgery side, the IC-CoDE phenotypes significantly predicted the likelihood of a patient experiencing post-surgical memory decline; X2 = 8.18, p = .043.

In addition to the IC-CoDE providing a useful cognitive classification scheme in epilepsy, the IC-CoDE phenotypes appear helpful in identifying those at risk for post-operative memory decline. Previous literature has suggested that those with better pre-surgical cognition are generally at highest risk for cognitive decline. Our results generally follow this trend, but interestingly, patients with single domain impairment were at the highest risk of memory decline, even above those in the cognitively intact group. Future studies are important to confirm this pattern in other samples and examine additional contributing factors and underlying mechanisms that may influence risk of memory decline across these cognitive phenotypes.

Episodic memory impairment and hippocampal pathology are hallmark features of both temporal lobe epilepsy (TLE) and amnestic mild cognitive impairment (aMCI). Pattern separation (PS), which enables the distinction between similar but unique experiences, is thought to contribute to successful encoding and retrieval of episodic memories. Impaired PS has been proposed as a potential mechanism underling episodic memory impairment in aMCI, but this association is less established in TLE. In this study, we examined behavioral PS in patients with TLE and explored whether profiles of performance in TLE are similar to aMCI.

Patients with TLE, aMCI, and age-matched, healthy controls (HCs) completed a modified recognition task that relies on PS for the discrimination of highly similar lure items, the Mnemonic Similarity Task (MST). Group differences were evaluated and relationships between clinical characteristics, California Verbal Learning Test—Second Edition scores, and MST performance were tested in the TLE group.

Patients with TLE and aMCI demonstrated poorer PS performance relative to the HCs, but performance did not differ between the two patient groups. Neither the side of seizure focus nor having hippocampal sclerosis affected performance in TLE. However, TLE patients with clinically defined memory impairment showed the poorest performance.

Memory performance on a task that relies on PS was disrupted to a similar extent in TLE and aMCI. The MST could provide a clinically useful tool for measuring hippocampus-dependent memory impairments in TLE and other neurological disorders associated with hippocampal damage.

On March 11, 2020, the World Health Organization declared an outbreak of a new viral entity, coronavirus 2019 (COVID-19), to be a worldwide pandemic. The characteristics of this virus, as well as its short- and long-term implications, are not yet well understood. The objective of the current paper was to provide a critical review of the emerging literature on COVID-19 and its implications for neurological, neuropsychiatric, and cognitive functioning.

A critical review of recently published empirical research, case studies, and reviews pertaining to central nervous system (CNS) complications of COVID-19 was conducted by searching PubMed, PubMed Central, Google Scholar, and bioRxiv.

After considering the available literature, areas thought to be most pertinent to clinical and research neuropsychologists, including CNS manifestations, neurologic symptoms/syndromes, neuroimaging, and potential long-term implications of COVID-19 infection, were reviewed.

Once thought to be merely a respiratory virus, the scientific and medical communities have realized COVID-19 to have broader effects on renal, vascular, and neurological body systems. The question of cognitive deficits is not yet well studied, but neuropsychologists will undoubtedly play an important role in the years to come.