Late-Onset Epilepsy With Unknown Etiology: A Pilot Study on Neuropsychological Profile, Cerebrospinal Fluid Biomarkers, and Quantitative EEG Characteristics.

Introduction: Despite the fact that epilepsy has been associated with cognitive decline, neuropsychological, neurobiological, and neurophysiological features in patients with late-onset epilepsy of unknown etiology (LOEU) are still unknown. This cross-sectional study aims to investigate the neuropsychological profile, cerebrospinal fluid (CSF) biomarkers of Alzheimer's disease (AD), and resting-state quantitative electroencephalographic (qEEG) cortical rhythms in LOEU patients with mild cognitive impairment (LOEU-MCI) and with normal cognition (LOEU-CN), compared to non-epileptic MCI (NE-MCI) and cognitively normal (CN) controls. Methods: Consecutive patients in two clinical Units diagnosed with LOEU-CN (19), LOEU-MCI (27), and NE-MCI (21) were enrolled, and compared to age and sex-matched cognitively normal subjects CN (11). Patients underwent standardized comprehensive neuropsychological evaluation and CSF core AD biomarkers assessment (i.e., CSF Aß42, phospho-tau and total tau, classified through A/T/(N) system). Recordings of resting-state eyes-closed electroencephalographic (EEG) rhythms were collected and cortical source estimation of delta (<4 Hz) to gamma (>30 Hz) bands with exact Low Resolution Electromagnetic Tomography (eLORETA) was performed. Results: Most LOEU patients had an MCI status at seizure onset (59%). Patients with LOEU-MCI performed significantly worse on measures of global cognition, visuo-spatial abilities, and executive functions compared to NE-MCI patients (p < 0.05). Regarding MCI subtypes, multiple-domain MCI was 3-fold more frequent in LOEU-MCI than in NE-MCI patients (OR 3.14, 95%CI 0.93-10.58, p = 0.06). CSF Aß42 levels were lower in the LOEU-MCI compared with the LOEU-CN group. Finally, parietal and occipital sources of alpha (8-12 Hz) rhythms were less active in the LOEU-MCI than in the NE-MCI and CN groups, while the opposite was true for frontal and temporal cortical delta sources. Discussion: MCI status was relatively frequent in LOEU patients, involved multiple cognitive domains, and might have been driven by amyloidosis according to CSF biomarkers. LOEU-MCI status was associated with abnormalities in cortical sources of EEG rhythms related to quiet vigilance. Future longitudinal studies should cross-validate our findings and test the predictive value of CSF and EEG variables.

Hippocampal epileptogenesis in autoimmune encephalitis.

OBJECTIVE: Autoantibody-mediated forms of encephalitis (AE) include neurological disorders characterized by subacute memory loss, movement disorders, and, often, frequent, focal epileptic seizures. Yet, the electrophysiological effects of these autoantibodies on neuronal function have received little attention. In this study, we assessed the effects of CSF containing autoantibodies on intrinsic and extrinsic properties of hippocampal neurons, to define their epileptogenic potential. METHODS: We compared the effects of CSF containing leucine-rich glioma inactivated 1 (LGI1), contactin-associated protein-like 2 (CASPR2), and γ-aminobutyric acid receptor B (GABAB R) antibodies on ex vivo electrophysiological parameters after stereotactic hippocampal inoculation into mice. Whole-cell patch-clamp and extracellular recordings from CA1 pyramidal neurons and CA3-CA1 field recordings in ex vivo murine brain slices were used to study neuronal function. RESULTS: By comparison to control CSF, AE CSFs increased the probability of glutamate release from CA3 neurons. In addition, LGI1- and CASPR2 antibodies containing CSFs induced epileptiform activity at a population level following Schaffer collateral stimulation. CASPR2 antibody containing CSF was also associated with higher spontaneous firing of CA1 pyramidal neurons. On the contrary, GABAB R antibody containing CSF did not elicit changes in intrinsic neuronal activity and field potentials. INTERPRETATION: Using patient CSF, we have demonstrated that the AE-associated antibodies against LGI1 and CASPR2 are able to increase hippocampal CA1 neuron excitability, facilitating epileptiform activity. These findings provide in vivo pathogenic insights into neuronal dysfunction in these conditions.

Synaptic vesicle protein 2A tumoral expression predicts levetiracetam adverse events.

OBJECTIVE: The efficacy of levetiracetam (LEV) in controlling seizures in patients with brain tumor-related epilepsy (BTRE) depends on tumoral expression of synaptic vesicle protein 2A (SV2A). Although LEV is generally well tolerated, neuropsychiatric adverse events (NPAEs) might occur, limiting compliance and seizure control. We aimed to assess the influence of tumoral SV2A expression on the occurrence of LEV-related NPAEs in patients with glioma. METHODS: Specimens from patients enrolled in the multicenter COMPO study, with glioma and BTRE treated with LEV, undergoing neurosurgery were retrieved. Immunohistochemistry-based expression of SV2A in tumoral and peritumoral tissue was scored in a four-point scale from absent (score = 0) to strong (score = 3). Low immunoreactivity (IR) corresponded to scores < 2. Staining ratios (tumoral SV2A IR/peritumoral SV2A IR) were grouped into low (≤ 0.5) and high (> 0.5). NPAEs were assessed longitudinally with the Neuropsychiatry Inventory 12 test (NPI-12). RESULTS: Overall, 18 patients were eligible for analysis. All received LEV monotherapy, with 67% developing NPAEs. Patients with NPAEs had significantly lower median SV2A intensity score compared to patients without NPAEs (score 1 vs 0, p = 0.025). Low staining ratio (≤ 0.5) associated with higher NPAE occurrence compared to SR > 0.5 (85.7% vs 0%, p < 0.01). A SR ≤ 0.5 predicted a consistent increase in risk of NPAEs (OR 45.0; 95% CI 1.8-1128; p = 0.02). CONCLUSIONS: Our results suggest that SV2A expression in tumoral and peritumoral tissue correlates with the occurrence of LEV-related NPAEs. Thus, considering that SV2A expression also influences LEV effectiveness, SV2A staining might help in tailoring treatment to patients.