Electroencephalogram alterations associated with psychiatric disorders in temporal lobe epilepsy with mesial sclerosis: A systematic review

MRI findings in patients with psychogenic non-epileptic seizures: Prevalence, distribution, and classification of the findings. A single tertiary epilepsy center experience

OBJECTIVE

Psychogenic non-epileptic seizures (PNES) mimic epileptic seizures without electroencephalographic correlation. Although classified as psychiatric disorders, their neurobiological or structural basis remains unclear. This study aimed to assess the prevalence and characteristics of MRI abnormalities in patients with PNES and those with comorbid epilepsy, compared to the general population, to enhance radiological evaluation and management.

METHOD

We retrospectively identified patients with a definitive diagnosis of PNES, evaluated in the refractory epilepsy unit of our tertiary epilepsy center. Patients were classified into two groups according to their comorbidity with epilepsy (PNES and PNES+). The MRI findings were evaluated and classified by two radiologists, who reported the category of the findings, laterality, and location. The two groups were compared using the chi-square test, as well as the frequencies of findings in the general population extracted from the literature.

RESULTS

Forty-six patients fulfilled the inclusion criteria. Thirty females and 16 males. MRI findings were present in 25/35 (71.4%) patients in the PNES group and 9/11 (81.8%) In the PNES + group, showing statistically significant differences in the frequency of findings with the general population (8.4-28.1%).

SIGNIFICANCE

MRI anomalies are common in PNES patients and even more prevalent in complex cases referred to epilepsy units, underscoring the necessity of correlating MRI findings with clinical-electrical patterns.

PLAIN LANGUAGE SUMMARY

In this article, we observed a higher frequency of cerebral magnetic resonance findings in patients with psychogenic non-epileptic seizures than in the general population. We also observed a higher frequency of this pathology among women, as well as right cerebral hemisphere affections. The exposed findings suggest a potential structural basis of this pathology. This hypothesis requires confirmation with larger studies.

Prevalence and associated factors of psychiatric comorbidities in epilepsy in the Casablanca-Settat region of Morocco: A cross-sectional study

OBJECTIVE

To determine the estimated prevalence of anxiety, depression, and anxiety-depression syndrome (ADS) and to identify the associated factors in Moroccan people with epilepsy (PWE).

METHOD

A cross-sectional study was conducted among adult PWE (June 2021-December 2022) in the Casablanca-Settat region. PWE were interviewed by completing a questionnaire collecting sociodemographic and clinical data. Anxiety and depression were assessed by the Hospital Anxiety and Depression Scale (HADS). Out of 21 points, a score ≥8 is in favor of considerable anxiety/depression symptoms and a sum of the two scores ≥15 indicates the presence of ADS. Data were analyzed using Statistical Package for Social Sciences (SPSS) 21.0. p-values ≤0.05 were considered statistically significant and logistic regression was performed to determine the associated factors.

RESULTS

Among 294 PWE, the median age was 39 years (interquartile range [IQR]: 25.75-54.00). The median anxiety, depression, and ADS scores were 8 (IQR: 5.00-10.00), 7 (IQR: 4.00-10.00), and 15 (IQR: 10.00-20.00), respectively. Anxiety, depression, and ADS were revealed in 51.4%, 44.9%, and 51.0% of PWE, respectively. Depression was the only predictor for anxiety (aOR = 24.20; 95%CI: 12.45-47.01). Antiseizure polytherapy (aOR = 3.35; 95%CI: 1.72-6.54) and anxiety (aOR = 24.04; 95%CI: 12.12-47.67) were the factors associated with depression. The risk of ADS was increased by female gender (aOR = 2.83; 95%CI: 1.68-4.78), antiseizure polytherapy (aOR = 2.75; 95%CI: 1.62-4.65), structural epilepsy (aOR = 1.73; 95%CI: 1.01-2.94), and the presence of concomitant conditions with epilepsy (aOR = 1.96; 95%CI: 1.16-3.31).

SIGNIFICANCE

Our study reports high psychiatric comorbidity prevalence in epilepsy, which supports the bidirectional link hypothesis. Associated factors found are important in the prognosis and prevention.

PLAIN LANGUAGE SUMMARY

The neural mechanisms underlying epilepsy tend to expose PWE to psychiatric disorders. Our study aims to quantify the rate of psychiatric comorbidities and their predictive factors in Moroccan PWE. The estimated prevalences of significant symptoms of anxiety, depression, and ADS were 51.4%, 44.9%, and 51.0%, respectively. Depression was the predictor of anxiety. Antiseizure polymedication and anxiety were the associated factors with depression. The risk of SAD was increased by female gender, antiseizure polymedication, structural epilepsy, and concomitant diseases with epilepsy. Our results are important for considering the psychiatric aspect of PWE and improving their care and quality of life.

Leukocyte differential gene expression prognostic value for high versus low seizure frequency in temporal lobe epilepsy

BACKGROUND

This study was performed to test the hypothesis that systemic leukocyte gene expression has prognostic value differentiating low from high seizure frequency refractory temporal lobe epilepsy (TLE).

METHODS

A consecutive series of patients with refractory temporal lobe epilepsy was studied. Based on a median baseline seizure frequency of 2.0 seizures per month, low versus high seizure frequency was defined as ≤ 2 seizures/month and > 2 seizures/month, respectively. Systemic leukocyte gene expression was analyzed for prognostic value for TLE seizure frequency. All differentially expressed genes were analyzed, with Ingenuity® Pathway Analysis (IPA®) and Reactome, to identify leukocyte gene expression and biological pathways with prognostic value for seizure frequency.

RESULTS

There were ten males and six females with a mean age of 39.4 years (range: 16 to 62 years, standard error of mean: 3.6 years). There were five patients in the high and eleven patients in the low seizure frequency cohorts, respectively. Based on a threshold of twofold change (p < 0.001, FC > 2.0, FDR < 0.05) and expression within at least two pathways from both Reactome and Ingenuity® Pathway Analysis (IPA®), 13 differentially expressed leukocyte genes were identified which were all over-expressed in the low when compared to the high seizure frequency groups, including NCF2, HMOX1, RHOB, FCGR2A, PRKCD, RAC2, TLR1, CHP1, TNFRSF1A, IFNGR1, LYN, MYD88, and CASP1. Similar analysis identified four differentially expressed genes which were all over-expressed in the high when compared to the low seizure frequency groups, including AK1, F2R, GNB5, and TYMS.

CONCLUSIONS

Low and high seizure frequency TLE are predicted by the respective upregulation and downregulation of specific leukocyte genes involved in canonical pathways of neuroinflammation, oxidative stress and lipid peroxidation, GABA (γ-aminobutyric acid) inhibition, and AMPA and NMDA receptor signaling. Furthermore, high seizure frequency-TLE is distinguished prognostically from low seizure frequency-TLE by differentially increased specific leukocyte gene expression involved in GABA inhibition and NMDA receptor signaling. High and low seizure frequency patients appear to represent two mechanistically different forms of temporal lobe epilepsy based on leukocyte gene expression.

Perturbed Information Processing Complexity in Experimental Epilepsy

Comorbidities, such as cognitive deficits, which often accompany epilepsies, constitute a basal state, while seizures are rare and transient events. This suggests that neural dynamics, in particular those supporting cognitive function, are altered in a permanent manner in epilepsy. Here, we test the hypothesis that primitive processes of information processing at the core of cognitive function (i.e., storage and sharing of information) are altered in the hippocampus and the entorhinal cortex in experimental epilepsy in adult, male Wistar rats. We find that information storage and sharing are organized into substates across the stereotypic states of slow and theta oscillations in both epilepsy and control conditions. However, their internal composition and organization through time are disrupted in epilepsy, partially losing brain state selectivity compared with controls, and shifting toward a regimen of disorder. We propose that the alteration of information processing at this algorithmic level of computation, the theoretical intermediate level between structure and function, may be a mechanism behind the emergent and widespread comorbidities associated with epilepsy, and perhaps other disorders.SIGNIFICANCE STATEMENT Comorbidities, such as cognitive deficits, which often accompany epilepsies, constitute a basal state, while seizures are rare and transient events. This suggests that neural dynamics, in particular those supporting cognitive function, are altered in a permanent manner in epilepsy. Here, we show that basic processes of information processing at the core of cognitive function (i.e., storage and sharing of information) are altered in the hippocampus and the entorhinal cortex (two regions involved in memory processes) in experimental epilepsy. Such disruption of information processing at the algorithmic level itself could underlie the general performance impairments in epilepsy.

Pyridoxine for treatment of levetiracetam-induced behavioral adverse events: A randomized double-blind placebo-controlled trial

BACKGROUND

Levetiracetam is a broad-spectrum antiseizure medication with known behavioral side effects. The possible beneficial effect of pyridoxine on improvement of these psychiatric problems has been suggested in few previous studies. This clinical trial aimed to investigate the effect of pyridoxine on behavioral side effects of levetiracetam in adult patients with epilepsy.

METHODS

This study was a randomized double-blind placebo-controlled clinical trial on 53 adult patients with epilepsy with behavioral side effects after treatment by levetiracetam. Patients who met the study criteria were randomized to receive 40 mg/day pyridoxine or placebo. Their psychiatric state was surveyed by SCL-90-R questionnaire before and three weeks after initiation of treatment.

RESULTS

There were no statistically significant differences in the behavioral adverse effects between the pyridoxine-treated group and the placebo group.

CONCLUSION

Although this study showed no statistically significant beneficial effects of pyridoxine on the behavioral adverse effects of levetiracetam, placebo-controlled trials with a larger size and higher doses are needed to determine whether it is effective or not.

Epilepsy-associated increase in gonadotropin-releasing hormone neuron firing in diestrous female mice is independent of chronic seizure burden severity

Reproductive endocrine disorders are common comorbidities of temporal lobe epilepsy (TLE). Our previous studies using the intrahippocampal kainic acid (IHKA) mouse model of TLE demonstrated that many females show prolonged estrous cycles and hypothalamic gonadotropin-releasing hormone (GnRH) neurons exhibit elevated firing during diestrus. However, it is unknown whether the degree of change in GnRH neuron activity is dependent on epilepsy severity. Here, we used 24/7 in vivo electroencephalography (EEG) and in vitro electrophysiological recordings in acute brain slices to assess GnRH neuron firing in relation to chronic seizure burden in diestrous female mice at two months after IHKA injection. We found that percentage of time in seizure activity in the 24 h prior to slice preparation is an accurate proxy of overall seizure burden. Firing rates of GnRH neurons from EEG-recorded IHKA mice were increased in comparison to controls, but no relationships were found between GnRH neuron firing and seizure burden measured in vivo. The independence of GnRH neuron firing rate in relation to seizure burden was unaffected by GnRH neuron soma location or estrous cycle length. Furthermore, GnRH neuron firing rates were not yet different from control values when measured 1 month after injection, when epileptogenesis is already complete in IHKA mice. These findings indicate that the severity of epilepsy and the degree of downstream disruption to GnRH neuron activity are independent, suggesting that susceptibility to reproductive endocrine comorbidities is driven by other risk factors.

Beyond Seizure Control: Treating Comorbidities in Epilepsy via Targeting of the P2X7 Receptor

Epilepsy is one of the most common chronic diseases of the central nervous system (CNS). Treatment of epilepsy remains, however, a clinical challenge with over 30% of patients not responding to current pharmacological interventions. Complicating management of treatment, epilepsy comes with multiple comorbidities, thereby further reducing the quality of life of patients. Increasing evidence suggests purinergic signalling via extracellularly released ATP as shared pathological mechanisms across numerous brain diseases. Once released, ATP activates specific purinergic receptors, including the ionotropic P2X7 receptor (P2X7R). Among brain diseases, the P2X7R has attracted particular attention as a therapeutic target. The P2X7R is an important driver of inflammation, and its activation requires high levels of extracellular ATP to be reached under pathological conditions. Suggesting the therapeutic potential of drugs targeting the P2X7R for epilepsy, P2X7R expression increases following status epilepticus and during epilepsy, and P2X7R antagonism modulates seizure severity and epilepsy development. P2X7R antagonism has, however, also been shown to be effective in treating conditions most commonly associated with epilepsy such as psychiatric disorders and cognitive deficits, which suggests that P2X7R antagonisms may provide benefits beyond seizure control. This review summarizes the evidence suggesting drugs targeting the P2X7R as a novel treatment strategy for epilepsy with a particular focus of its potential impact on epilepsy-associated comorbidities.

Temporal Lobe Epilepsy and Psychiatric Comorbidity

Most focal seizures originate in the temporal lobe and are commonly divided into mesial and lateral temporal epilepsy, depending upon the neuronal circuitry involved. The hallmark features of the mesial temporal epilepsy are aura, unconsciousness, and automatisms. Symptoms often overlap with the lateral temporal epilepsy. However, the latter present a less evident psychomotor arrest, frequent clones and dystonic postures, and common focal to bilateral tonic–clonic seizures. Sclerosis of the hippocampus is the most frequent cause of temporal lobe epilepsy (TLE). TLE is among all epilepsies the most frequently associated with psychiatric comorbidity. Anxiety, depression, and interictal dysphoria are recurrent psychiatric disorders in pediatric patients with TLE. In addition, these alterations are often combined with cognitive, learning, and behavioral impairment. These comorbidities occur more frequently in TLE with hippocampal sclerosis and with pharmacoresistance. According to the bidirectional hypothesis, the close relationship between TLE and psychiatric features should lead to considering common pathophysiology underlying these disorders. Psychiatric comorbidities considerably reduce the quality of life of these children and their families. Thus, early detection and appropriate management and therapeutic strategies could improve the prognosis of these patients. The aim of this review is to analyze TLE correlation with psychiatric disorders and its underlying conditions.

Forced Normalization Revisited: New Concepts About a Paradoxical Phenomenon

The phenomenon of Forced Normalization (FN) was first described by Landolt in 1953, who described the disappearance of epileptiform discharges in the EEG of patients with epilepsy, concomitant with the development of psychotic symptoms. Later, Tellenbach coined the term “alternative psychosis” referring specifically to the alternation between clinical phenomena. Finally, in 1991, Wolf observed a degenerative process involved in the phenomenon, which he called “paradoxical normalization.” Initially, FN was explained through experimental models in animals and the demonstration of the kindling phenomenon, in its electrical and pharmacological subdivisions. At this stage of research on the epileptic phenomenon, repetitive electrical stimuli applied to susceptible regions of the brain (hippocampus and amygdala) were considered to explain the pathophysiological basis of temporal lobe epileptogenesis. Likewise, through pharmacological manipulation, especially of dopaminergic circuits, psychiatric comorbidities began to find their basic mechanisms. With the development of new imaging techniques (EEG/fMRI), studies in the area started to focus on the functional connectivity (FC) of different brain regions with specific neuronal networks, which govern emotions. Thus, a series of evidence was produced relating the occurrence of epileptic discharges in the limbic system and their consequent coactivation and deactivation of these resting-state networks. However, there are still many controversies regarding the basic mechanisms of network alterations related to emotional control, which will need to be studied with a more homogeneous methodology, in order to try to explain this interesting neuropsychiatric phenomenon with greater accuracy.

The Kainic Acid Models of Temporal Lobe Epilepsy

Experimental models of epilepsy are useful to identify potential mechanisms of epileptogenesis, seizure genesis, comorbidities, and treatment efficacy. The kainic acid (KA) model is one of the most commonly used. Several modes of administration of KA exist, each producing different effects in a strain-, species-, gender-, and age-dependent manner. In this review, we discuss the advantages and limitations of the various forms of KA administration (systemic, intrahippocampal, and intranasal), as well as the histologic, electrophysiological, and behavioral outcomes in different strains and species. We attempt a personal perspective and discuss areas where work is needed. The diversity of KA models and their outcomes offers researchers a rich palette of phenotypes, which may be relevant to specific traits found in patients with temporal lobe epilepsy.

Absolute spike frequency and different comorbidities in temporal lobe epilepsy

OBJECTIVE

The objective of this study was to examine if the absolute number of interictal epileptiform discharges (IED) is related to the presence of different comorbidities and refractivity in patients with temporal lobe epilepsy.

METHODS

Analysis with scalp EEG of the IED of 30 patients with temporal epilepsy. The analysis was performed in three selected periods of the record during N2-N3 sleep. We analyzed the number of IED and the sum of the values obtained in the three selected segments to determine the absolute interictal spike frequency.

RESULTS

The number of IED for patients varied from 11 to 450. The absolute interictal spike frequency showed a statistically significant relation with the presence of refractivity (p < 0.05), and neurological and/or psychiatric comorbidity (p < 0.05). Patients with an absolute interictal spike frequency ≤ 60 showed little refractoriness and no comorbidity. Patients with an absolute interictal spike frequency > 60 were mostly refractory and with neurological and/or psychiatric comorbidity. No significant relation was found of absolute interictal spike frequency with age at the onset of epilepsy, number of anticonvulsant drugs used, or base pathology (MRI).

CONCLUSIONS

The absolute interictal spike frequency is capable of differentiating patients with temporal lobe epilepsy, identifying those with temporal lobe epilepsy according to the severity of the condition. Only those patients with non-frequent spikes (≤60 over the affected temporal lobe) have a low percentage of refractoriness with little or no presence of comorbidity.