Which clinical and experimental data link temporal lobe epilepsy with depression?

An exploratory study of brain temperature and choline abnormalities in temporal lobe epilepsy patients with depressive symptoms

OBJECTIVE

Epilepsy and depression share neurobiological origins, and evidence suggests a possible bidirectional relationship that remains poorly understood. This exploratory, cross-sectional study aimed to investigate this relationship by employing magnetic resonance spectroscopic imaging (MRSI) and thermometry (MRSI-t) in patients with temporal lobe epilepsy (TLE) with comorbid depressive symptoms and control participants. This is the first study to combine MRSI and MRSI-t to examine brain temperature and choline abnormalities in regions implicated in seizure onset and depression.

METHODS

Twenty-six patients with TLE and 26 controls completed questionnaires and underwent imaging at 3T. Volumetric echo-planar MRSI/MRSI-t data were processed within the Metabolite Imaging and Data Analysis System (MIDAS). Choline (CHO) was quantified as a ratio over creatine (CRE; CHO/CRE). Brain temperature (TCRE ) was calculated based on the chemical shift difference of H2 O relative to CRE's stable location on the ppm spectrum. The Hospital Anxiety and Depression Scale measured anxiety and depressive symptoms. The Chalfont Seizure Severity Scale measured seizure severity in patients with TLE. Two sets of voxelwise independent sample t tests examined group differences in CHO/CRE and TCRE maps. Voxel-based multimodal canonical correlation analysis (mCCA) linked both datasets to investigate if, how, and where CHO/CRE and TCRE abnormalities were correlated in TLE participants and controls.

RESULTS

Compared to controls, patients with TLE reported more depressive symptoms (P = 0.04) and showed CHO/CRE and TCRE elevations in left temporal and bilateral frontal regions implicated in seizure onset and depressive disorders (pFWE  < 0.05). For the TLE group, CHO/CRE levels in temporal and frontal cortices were associated with elevated TCRE in bilateral frontal and temporal gyri (r = 0.96), and decreased TCRE in bilateral fronto-parietal regions (r = -0.95).

SIGNIFICANCE

Abnormalities in TCRE and CHO/CRE were observed in seizure-producing areas and in regions implicated in depression. These preliminary findings suggest that common metabolic changes may underlie TLE and depression. Our results suggest further investigations into the proposed bidirectional mechanisms underlying this relationship are warranted.

Targeting GABA receptors with chalcone derivative compounds, what is the evidence?

INTRODUCTION

In medicinal chemistry, privileged structures have been frequently exploited as a successful template for drug discovery. Common simple scaffolds like chalcone are present in a wide range of naturally occurring chemicals. Chalcone exhibits extensive biological activity and has drawn attention in this context due to its function in the GABA receptor. Epilepsy and GABA receptors are related. It is a chronic neurological condition that affects globally.

AREAS COVERED

Numerous neurological disorders, including anxiety and epilepsy, have been related to GABA, the brain's most prevalent inhibitory neurotransmitter. We go through the role of GABA receptors in anxiety and epilepsy in this review. The structure-activity relationship of chalcone and its derivatives on the GABA receptor is covered in our final section.

EXPERT OPINION

GABA is a potential therapeutic target for issues associated with the nervous system. We talk about the potential effects of chalcone as a treatment for epilepsy and anxiety on the GABA receptor. Therefore, thorough research is necessary in this regard; the value of in silico tools in developing and enhancing GABA agonists is significant.

Reward-based decision-making in mesial temporal lobe epilepsy patients with unilateral hippocampal sclerosis pre- and post-surgery

BACKGROUND

Correct functioning of the reward processing system is critical for optimizing decision-making as well as preventing the development of addictions and/or neuropsychiatric symptoms such as depression, apathy, and anhedonia. Consequently, patients with mesial temporal lobe epilepsy due to unilateral hippocampal sclerosis (mTLE-UHS) represent an excellent opportunity to study the brain networks involved in this system.

OBJECTIVE

The aim of the current study was to evaluate decision-making and the electrophysiological correlates of feedback processing in a sample of mTLE-UHS patients, compared to healthy controls. In addition, we assessed the impact of mesial temporal lobe surgical resection on these processes, as well as general, neuropsychological functioning.

METHOD

17 mTLE-UHS patients and 17 matched healthy controls completed: [1] a computerized version of the Game of Dice Task, [2] a Standard Iowa Gambling Task, and [3] a modified ERP version of a probabilistic gambling task coupled with multichannel electroencephalography. Neuropsychological scores were also obtained both pre- and post-surgery.

RESULTS

Behavioral analyses showed a pattern of increased risk for the mTLE-UHS group in decision-making under ambiguity compared to the control group. A decrease in the amplitude of the Feedback Related Negativity (FRN), a weaker effect of valence on delta power, and a general reduction of delta and theta power in the mTLE-UHS group, as compared to the control group, were also found. The beta-gamma activity associated with the delivery of positive reward was similar in both groups. Behavioral performance and electrophysiological measures did not worsen post-surgery.

CONCLUSIONS

Patients with mTLE-UHS showed impairments in decision-making under ambiguity, particularly when they had to make decisions based on the outcomes of their choices, but not in decision-making under risk. No group differences were observed in decision-making when feedbacks were random. These results might be explained by the abnormal feedback processing seen in the EEG activity of patients with mTLE-UHS, and by concomitant impairments in working memory, and memory. These impairments may be linked to the disruption of mesial temporal lobe networks. Finally, feedback processing and decision-making under ambiguity were already affected in mTLE-UHS patients pre-surgery and did not show evidence of clear worsening post-surgery.

Comorbid epilepsy and depression—pharmacokinetic and pharmacodynamic drug interactions

Background: Major depressive disorder may be encountered in 17% of patients with epilepsy and in patients with drug-resistant epilepsy its prevalence may reach 30%. This indicates that patients with epilepsy may require antidepressant treatment.

Purpose: Both pharmacodynamic and pharmacokinetic interactions between antiepileptic (antiseizure) and antidepressant drugs have been reviewed. Also, data on the adverse effects of co-administration of antiepileptic with antidepressant drugs have been added. This article was submitted to Neuropharmacology, a section of the journal Frontiers in Pharmacology.

Methods: The review of relevant literature was confined to English-language publications in PUBMED databases. Table data show effects of antidepressants on the seizure susceptibility in experimental animals, results of pharmacodynamic interactions between antiepileptic and antidepressant drugs mainly derived from electroconvulsions in mice, as well as results concerning pharmacokinetic interactions between these drugs in clinical conditions.

Conclusion: Antidepressant drugs may exert differentiated effects upon the convulsive threshold which may differ in their acute and chronic administration. Animal data indicate that chronic administration of antidepressants could reduce (mianserin, trazodone) or potentiate the anticonvulsant activity of some antiepileptics (fluoxetine, reboxetine, venlafaxine). There are also examples of neutral interactions (milnacipran).

Perceived stress, resilience, and stress coping in patients with drug resistant epilepsy and functional dissociative seizures

PURPOSE

Depression and anxiety are psychiatric disorders related to chronic stress, commonly found in patients with drug-resistant epilepsy (DRE) and functional dissociative seizures (FDS). The present study compares the levels of perceived stress, resilience, and the styles of stress coping among patients with DRE (n=60), FDS (n=28), and controls (n=31).

METHODS

We performed a cross-sectional study. All patients underwent Video Electroencephalography to confirm the diagnosis and completed the psychiatric assessment (SCID I and II of DSM IV) supported by several instruments validated in Spanish.

RESULTS

FDS scored higher in perceived stress (p = 0.004) with lower levels of resilience compared to controls (p = 0.01). Stress coping subscales show higher scores in negative self-focus and hostility in patients with FDS compared to controls (p=0.003). Similarly, DRE patients scored higher in perceived stress (p = 0.001), and presented lower levels of resilience (p = 0.004) with higher levels of hostility compared to controls (p=0.02). However, no significant differences were found between FDS and DRE on stress coping variables. Anxiety scores and depression rates were higher in the FDS group compared to DRE (p=0.008) and higher in DRE compared to controls (p<0.05). A positive correlation between depression and perceived stress was found (r = 0.6, p=0.0001).

CONCLUSIONS

Our results delineate a more detailed picture of the psychological profile of this population, emphasizing the importance of stress factors in patients with FDS and DRE. Combined intervention strategies which enhance stress coping may be appropriate to direct treatment and psychotherapy.

Intrinsic Brain Activity in Temporal Lobe Epilepsy With and Without Depression: Insights From EEG Microstates

Background: Depression is the most common psychiatric comorbidity of temporal lobe epilepsy (TLE). In the recent years, studies have focused on the common pathogenesis of TLE and depression. However, few of the studies focused on the dynamic characteristics of TLE with depression. We tested the hypotheses that there exist abnormalities in microstates in patients with TLE with depression.

Methods: Participants were classified into patients with TLE with depression (PDS) (n = 19) and patients with TLE without depression (nPDS) (n = 19) based upon the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V). Microstate analysis was applied based on 256-channel electroencephalography (EEG) to detect the dynamic changes in whole brain. The coverage (proportion of time spent in each state), frequency of occurrence, and duration (average time of each state) were calculated.

Results: Patients with PDS showed a shorter mean microstate duration with higher mean occurrence per second compared to patients with nPDS. There was no difference between the two groups in the coverage of microstate A–D.

Conclusion: This is the first study to present the temporal fluctuations of EEG topography in comorbid depression in TLE using EEG microstate analysis. The temporal characteristics of the four canonical EEG microstates were significantly altered in patients with TLE suffer from comorbid depression.

Mood Disturbances, Anxiety, and Impact on Quality of Life in Patients Admitted to Epilepsy Monitoring Units

Introduction: The overall combined prevalence of anxiety and depression in patients with epilepsy has been estimated at 20.2 and 22.9%, respectively, and is considered more severe in drug-refractory epilepsy. Patients admitted to epilepsy monitoring units constitute a particular group. Also, patients with psychogenic non-epileptic seizures can reach more than 20% of all admissions. This study aims to characterize these symptoms in a large cohort of patients admitted for evaluation in a tertiary epilepsy center.

Materials and Methods: The study was conducted among 493 consecutive patients (age: 38.78 ± 12.7, 57% females) admitted for long-term video EEG from January 2013 to February 2021. Demographic, clinical, and mood disorder patients' data were collected. Anxiety and depression symptoms were assessed through the Hospital Anxiety Depression Scale (HADS-A and HADS-D), the State Trait Anxiety Inventory (STAI), and Beck Depression Inventory (BDI-II). Quality of life was determined using the QOLIE-10. Patients were divided into three groups: patients with epilepsy (n = 395), psychogenic non-epileptic seizures (PNES) (n = 56), and combined (n = 33). A univariate and multivariate regression analysis was performed for variables associated with quality of life.

Results: Of 493 patients, 45.0% had structural etiology, and considering epilepsy classification, 43.6% were of temporal lobe origin. In addition, 32.45% of patients had a previous psychiatric history, 49.9% of patients had depressive symptoms in BDI, and 30.9% according to HADS-D; 56.42 and 52.63% of patients presented pathological anxiety scores in STAI-T and STAI-S, respectively; and 44.78% according to HADS-A. PNES and combined groups revealed a higher incidence of pathologic BDI scores (64.29 and 78.79%, p < 0.001) as well as pathologic HADS-A scores (p = 0.001). Anxiety and depression pathologic results are more prevalent in females, HADS-A (females = 50.7%, males = 36.8%; p = 0.0027) and BDI > 13 (females = 56.6%, males = 41.0%; p = 0.0006). QOLIE-10 showed that 71% of the patients had their quality of life affected with significantly higher scores in the combined group than in the epilepsy and PNES groups (p = 0.0015).

Conclusions: Subjective anxiety, depression, and reduced quality of life are highly prevalent in patients with refractory epilepsy. These symptoms are more evident when PNES are associated with epilepsy and more severe among female patients. Most of the cases were not previously diagnosed. These factors should be considered in everyday clinical practice, and specific approaches might be adapted depending on the patient's profile.

Predictive factors of quality of life in temporal and extratemporal lobe epilepsy: association with affective temperament profiles and psychiatric comorbidities

BACKGROUND

Investigating predictive factors of reduced quality of life (QOL) of patients and their association with focal epilepsy can improve management and treatment strategies.

OBJECTIVE

This study aimed to investigate the relationship between affective temperaments, depression, anxiety, disease characteristics, and QOL and to explore the predictors of QOL in patients with temporal lobe epilepsy (TLE) and extratemporal lobe epilepsy (ETLE).

METHODS

A total of 50 patients with TLE, 51 patients with ETLE, and 70 controls were enrolled. Affective temperaments were evaluated using the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego-Autoquestionnaire (TEMPS-A). QOL was assessed by the Short-Form Health Survey (SF-36). Beck Depression Inventory and Beck Anxiety Inventory were used to explore depression and anxiety severity, respectively.

RESULTS

Compared with the controls, patients with TLE and ETLE had significantly higher scores on all TEMPS-A scales, except on hyperthymic temperament. All the SF-36 subscale scores were lower in the TLE and ETLE groups. Linear regression analysis revealed that depressive symptoms, anxiety, depressive and irritable temperament, and seizure frequency were significant predictors of QOL in TLE. Patients with ETLE with temperamental disturbances, depressive symptoms, and polytherapy had a poorer QOL.

CONCLUSIONS

Affective temperaments, psychiatric disorders, and clinical factors may predict impaired QOL in patients with TLE and ETLE. Further studies are needed to identify predictors of QOL in various epilepsy subtypes.

Effect of lacosamide on neuroinflammation-mediated seizures comorbid with depression in C57BL/6 mice- Role of kynurenine pathway

Comorbid conditions in persons with epilepsy (PWE) are very common with depression being highly prevalent. Lacosamide (LCM) is used to treat patients with seizures, but the underlying pathways associating the seizures and comorbid depression are still unknown. Kynurenine pathway (KP) has a major role in seizures, inflammation as well as depression, considering which we evaluated the effect of LCM on kynurenine levels in murine model of neuroinflammation-mediated seizures. We then evaluated the effects on the depressive symptoms associated with seizures. Lipopolysaccharide (LPS) primed pilocarpine (PILO) is an established model for neuro-inflammation-mediated seizures. The anti-seizure and anti-depressive effects of 21 days of LCM administration were studied in this model. After 24 h of seizure termination, behavioral parameters viz. forced swimming test and sucrose preference test were performed to study its antidepressant effect. Biochemical estimations of levels of kynurenine, inflammatory cytokines, and oxidative markers were also evaluated. Lacosamide significantly reduced hippocampal kynurenine levels in LPS and LPS + PILO groups but did not show significant reduction in the PILO alone group. Levels of inflammatory cytokines and oxidative stress markers were also reduced significantly. Lacosamide has shown positive effects against neuroinflammation-mediated model of seizures comorbid with depression by reducing hippocampal kynurenine levels. No reduction in the PILO group is suggestive of the principal contribution of its anti-inflammatory and antioxidant activity in its anti-seizure potential in this model via KP.

Psychiatric alterations after previous temporal lobectomy: Report of cases and review

INTRODUCTION

Anterior temporal lobectomy (LTA) is a surgical procedure commonly used for the treatment of temporal lobe epilepsy refractory to medical management, with high success rates in the control of seizures. However, an important association with psychiatric illnesses has been described that can alter the postoperative outcome in these patients.

METHODS

A series of 2 cases of patients who, despite successful crisis control, developed psychiatric complications in the postoperative period of anterior temporal lobectomy.

RESULTS

The cases included a male patient with no history of previous mental illness, who developed a major depressive episode in the postoperative period, and a female patient with previous psychosis who presented as a surgical complication exacerbation of psychosis, diagnosed with paranoid schizophrenia.

CONCLUSIONS

Psychiatric disorders can occur in postoperative temporal lobe epilepsy patients with or without a history of mental illness. The most frequent alterations reported are depression, anxiety, psychosis and personality disorders. The inclusion of psychiatric evaluations in the pre- and post-surgical protocols can lead to an improvement in the prognosis of the neurological and mental outcomes of the patients undergoing the intervention.

Stress-Associated Molecular and Cellular Hippocampal Mechanisms Common for Epilepsy and Comorbid Depressive Disorders

The review discusses molecular and cellular mechanisms common to the temporal lobe epileptogenesis/epilepsy and depressive disorders. Comorbid temporal lobe epilepsy and depression are associated with dysfunction of the hypothalamic-pituitary-adrenocortical axis. Excessive glucocorticoids disrupt the function and impair the structure of the hippocampus, a brain region key to learning, memory, and emotions. Selective vulnerability of the hippocampus to stress, mediated by the reception of glucocorticoid hormones secreted during stress, is the price of the high functional plasticity and pleiotropy of this limbic structure. Common molecular and cellular mechanisms include the dysfunction of glucocorticoid receptors, neurotransmitters, and neurotrophic factors, development of neuroinflammation, leading to neurodegeneration and loss of hippocampal neurons, as well as disturbances in neurogenesis in the subgranular neurogenic niche and formation of aberrant neural networks. These glucocorticoid-dependent processes underlie altered stress response and the development of chronic stress-induced comorbid pathologies, in particular, temporal lobe epilepsy and depressive disorders.

Mental Health of Adolescents With Epilepsy in Enugu, Nigeria: A Cross-Sectional Study

Adolescence is an important period, marked by significant changes in biological and psychosocial domains. Epilepsy is a chronic neurologic disorder associated with social stigma and prejudice. The etiology of depression in epilepsy appears to be a complex interplay between psychosocial and neurobiologic factors. This period may be too taxing for the adolescent with epilepsy to steer, as epilepsy can affect the development of independence by its social, educational, and mental health effects. The study aimed to compare the burden of depression in adolescents with epilepsy with the general population.One hundred forty-five adolescents with epilepsy and their classmates matched for age and gender were studied over a 9-month period. Zung Self-rating Depression Scale was used to determine the burden of depression in the study population.Among the subjects, 70 (48.3%) had scores in the depressive range to varying degrees compared to 38 (26.2%) controls. The difference in scores was significant (OR=2.628, P < .001). Among the population with positive scores, mild depression category was the commonest for both groups (40% and 22.8%, respectively). There was a statistically significant relationship between gender, seizure type, and depression, whereas there was no significant relationship between age, social class, number of antiepileptic drugs, seizure frequency in the last 12 months, and depression.Adolescents with epilepsy had higher rates of depression than the general population. Hence, there might be need for routine screening of adolescents with epilepsy for early detection and management of depression to improve their overall well-being and quality of life.

Sex Differences in the Epilepsies and Associated Comorbidities: Implications for Use and Development of Pharmacotherapies

The epilepsies are common neurologic disorders characterized by spontaneous recurrent seizures. Boys, girls, men, and women of all ages are affected by epilepsy and, in many cases, by associated comorbidities as well. The primary courses of treatment are pharmacological, dietary, and/or surgical, depending on several factors, including the areas of the brain affected and the severity of the epilepsy. There is a growing appreciation that sex differences in underlying brain function and in the neurobiology of epilepsy are important factors that should be accounted for in the design and development of new therapies. In this review, we discuss the current knowledge on sex differences in epilepsy and associated comorbidities, with emphasis on those aspects most informative for the development of new pharmacotherapies. Particular focus is placed on sex differences in the prevalence and presentation of various focal and generalized epilepsies; psychiatric, cognitive, and physiologic comorbidities; catamenial epilepsy in women; sex differences in brain development; the neural actions of sex and stress hormones and their metabolites; and cellular mechanisms, including brain-derived neurotrophic factor signaling and neuronal-glial interactions. Further attention placed on potential sex differences in epilepsies, comorbidities, and drug effects will enhance therapeutic options and efficacy for all patients with epilepsy. SIGNIFICANCE STATEMENT: Epilepsy is a common neurological disorder that often presents together with various comorbidities. The features of epilepsy and seizure activity as well as comorbid afflictions can vary between men and women. In this review, we discuss sex differences in types of epilepsies, associated comorbidities, pathophysiological mechanisms, and antiepileptic drug efficacy in both clinical patient populations and preclinical animal models.

Psychiatric Alterations after Previous Temporal Lobectomy: Report of Cases and Review

INTRODUCTION

Anterior temporal lobectomy (LTA) is a surgical procedure commonly used for the treatment of temporal lobe epilepsy refractory to medical management, with high success rates in the control of seizures. However, an important association with psychiatric illnesses has been described that can alter the postoperative outcome in these patients.

METHODS

A series of 2 cases of patients who, despite successful crisis control, developed psychiatric complications in the postoperative period of anterior temporal lobectomy.

RESULTS

The cases included a male patient with no history of previous mental illness, who developed a major depressive episode in the postoperative period, and a female patient with previous psychosis who presented as a surgical complication exacerbation of psychosis, diagnosed with paranoid schizophrenia.

CONCLUSIONS

Psychiatric disorders can occur in postoperative temporal lobe epilepsy patients with or without a history of mental illness. The most frequent alterations reported are depression, anxiety, psychosis and personality disorders. The inclusion of psychiatric evaluations in the pre- and post-surgical protocols can lead to an improvement in the prognosis of the neurological and mental outcomes of the patients undergoing the intervention.

The effects of insular and mesiotemporal lesions on affective information processing: Preliminary evidence from patients with epilepsy surgery

Depressive symptoms and anxiety are common complaints in patients who have had epilepsy surgery. Recent studies have reported disturbances in emotional memory, facial and vocal emotion recognition, and affective learning after temporal lobe and/or insular resection for drug-resistant seizures, suggesting that these regions may be involved in emotional processes underlying psychological symptoms. The insula is a core component of the salience network and is thought to be involved in processing emotions such as disgust, and the role of mesial temporal lobe structures in affective processing is well established. However, to our knowledge, no study has yet investigated whether attentional processing of affective information is altered when these structures are resected as part of an epilepsy surgery. The present study examined the interference control capacity and attentional biases for emotional information in adult patients with epilepsy who underwent temporal lobe resections including the amygdala and hippocampus (n = 15) and/or partial or complete insular resections (n = 16). Patients were tested on an Emotional Stroop test and on a Dot-Probe task using fearful and disgusting pictures and were compared with a healthy control group (n = 30) matched for age, gender, and education. Repeated-measures analyses of variances revealed a significant effect of emotional words on color naming speed in the Emotional Stroop task among insular patients, which was not observed in the other groups. By contrast, the groups did not differ on Dot-Probe task performance. These preliminary findings suggest that insular damage may alter emotional interference control.

Antidepressant and anti-amnesic effects of the aqueous lyophilisate of the leaves of Leptadenia arborea on an animal model of cognitive deficit associated depression

Leptadenia arborea (Asclepiadaceae) is a plant used in traditional medicine to treat syphilis, migraine, and mental illnesses. The aim of our study was to investigate possible antidepressant and anti-amnesic effects of the aqueous lyophilisate of the leaves of Leptadenia arborea in an animal model of cognitive deficit associated depression. Swiss albino adult mice of both sexes were used for this study. A 14-day combined stress model was used to induce depression with early cognitive deficits. The forced swimming test, the open field test and plasma corticosterone level were used to assess antidepressant-like effect. The novel object recognition task (NORT), the Morris Water Maze (MWM) and neurochemical analysis of hippocampal acetylcholinesterase activity was also carried out to assess memory integrity. The aqueous lyophelisate of L. arborea increased swimming time and decreased immobility time in the forced swimming test. In the open field test they was no difference in the number of lines crossed between groups, and the lyophilisate-treated mice spent more time in the centre compared to the control. The lyophilisate decreased the plasma level of corticosterone compared to the control. The lyophilisate decreased the latency to reach the hidden platform and increased the time spent in the target quadrant in the MWM. The lyophilisate also increased the time of exploration of the novel object in the NORT and decreased the acetylcholinesterase activity in the hippocampus. L. arborea effects were decreased when it was co-administered with pCPA. Results suggest that the aqueous lyophilisate of the leaves of L. arborea possess antidepressant-like and anti-amnesic effects.

Comparison of psychiatric comorbidities and impact on quality of life in patients with epilepsy or psychogenic nonepileptic spells

OBJECTIVES

Psychiatric comorbidity is common in people with epilepsy (PWE) and psychogenic nonepileptic spells (PNES). These comorbidities can be detrimental to quality of life (QOL) and are often underdiagnosed and undertreated. Some types of epilepsy, such as focal temporal lobe epilepsy (TLE), have been associated with higher rates of psychiatric comorbidity. This study examined the impact of psychiatric comorbidity on QOL in patients admitted to two level 4 epilepsy monitoring units (EMUs).

METHODS

In this prospective observational study, 200 patients admitted to two level 4 EMUs completed standardized surveys including the Quality of Life in Epilepsy (QOLIE-31-P), Generalized Anxiety Disorder 7-item (GAD-7), Patient Health Questionnaire (PHQ-9), and Beck Depression Inventory-II (BDI-II). Hierarchal multiple regression was performed to assess impact on QOL.

RESULTS

Of the 200 participants, 113 had a diagnosis of epilepsy, 36 had a diagnosis of PNES, and 51 were excluded for nondiagnostic evaluation or dual diagnosis. Of those with epilepsy, 65 had TLE, 28 had focal extratemporal lobe epilepsy (ETLE), and 20 had nonfocal epilepsy. Patients with PNES had higher self-reported anxiety and depression levels (GAD-7: p = 0.04, PHQ-9: p < 0.01; BDI-II: p < 0.01) but similar QOL to PWE (p = 0.78). Using hierarchal multiple regression, symptoms of anxiety and depression were significant predictors of lower QOL in PWE but not in patients with PNES. There was no difference in QOL in those with ETLE and TLE.

CONCLUSIONS

Our findings suggest that self-reported anxiety and depression symptoms are common in patients admitted to level 4 EMUs regardless of diagnosis and play an important role in predicting QOL in PWE. Our findings emphasize the importance of routinely screening all EMU patients for psychiatric comorbidity.

Mechanisms of Psychiatric Comorbidities in Epilepsy

Psychiatric illnesses, including depression and anxiety, are highly comorbid with epilepsy (for review see Josephson and Jetté (Int Rev Psychiatry 29:409-424, 2017), Salpekar and Mula (Epilepsy Behav 98:293-297, 2019)). Psychiatric comorbidities negatively impact the quality of life of patients (Johnson et al., Epilepsia 45:544-550, 2004; Cramer et al., Epilepsy Behav 4:515-521, 2003) and present a significant challenge to treating patients with epilepsy (Hitiris et al., Epilepsy Res 75:192-196, 2007; Petrovski et al., Neurology 75:1015-1021, 2010; Fazel et al., Lancet 382:1646-1654, 2013) (for review see Kanner (Seizure 49:79-82, 2017)). It has long been acknowledged that there is an association between psychiatric illnesses and epilepsy. Hippocrates, in the fourth-fifth century B.C., considered epilepsy and melancholia to be closely related in which he writes that "melancholics ordinarily become epileptics, and epileptics, melancholics" (Lewis, J Ment Sci 80:1-42, 1934). The Babylonians also recognized the frequency of psychosis in patients with epilepsy (Reynolds and Kinnier Wilson, Epilepsia 49:1488-1490, 2008). Despite the fact that the relationship between psychiatric comorbidities and epilepsy has been recognized for thousands of years, psychiatric illnesses in people with epilepsy still commonly go undiagnosed and untreated (Hermann et al., Epilepsia 41(Suppl 2):S31-S41, 2000) and systematic research in this area is still lacking (Devinsky, Epilepsy Behav 4(Suppl 4):S2-S10, 2003). Thus, although it is clear that these are not new issues, there is a need for improvements in the screening and management of patients with psychiatric comorbidities in epilepsy (Lopez et al., Epilepsy Behav 98:302-305, 2019) and progress is needed to understand the underlying neurobiology contributing to these comorbid conditions. To that end, this chapter will raise awareness regarding the scope of the problem as it relates to comorbid psychiatric illnesses and epilepsy and review our current understanding of the potential mechanisms contributing to these comorbidities, focusing on both basic science and clinical research findings.

Emotional asymmetries in refractory medial temporal and frontal lobe epilepsy: Their impact on predicting lateralization and localization of seizures

BACKGROUND

Emotional disturbances have been reported in patients with epilepsy. Although conflicting results emanate from relevant studies, depressive symptoms are seen more often in temporal lobe epilepsy (TLE) whereas, hypomanic/manic symptoms usually accompany frontal lobe epilepsy (FLE); the above psychiatric symptoms are especially seen in refractory epilepsy. However, neocortical TLE and medial TLE are considered as distinct epileptic syndromes, and there is limited literature on comparison of affective traits in medial TLE (MTLE) and FLE.

AIM

In the present study, we sought to investigate affective traits among epilepsy surgery candidates suffering refractory left medial TLE (LMTLE), right medial TLE (RMTLE), left FLE (LFLE), and right FLE (RFLE).

RESULTS

Our results revealed that patients with MTLE scored significantly higher than the ones with FLE in depression, anxiety, asthenia, and melancholia as measured by the Symptoms Rating Scale for Depression and Anxiety (SRSDA), while patients with FLE scored significantly higher in mania than those with MTLE. Moreover, patients with MTLE scored significantly higher than their FLE counterparts on the anxiety scale of the State Trait Personality Inventory (STPI)-trait version. When laterality of the seizure focus was taken into account, no differences were found among both patients with MTLE and patients with FLE, with exception for the Trail Making Test part B (TMT-B) in which patients with RMTLE performed significantly worse than patients with LMTLE. Seizure frequency was higher for FLE.

CONCLUSIONS

We provide evidence for an anterior-frontal versus a posterior-medial temporal cerebral functional asymmetry with regard to the manifestation of manic and depressive emotional traits in FLE and MTLE, respectively. Our results are mainly discussed within the frame of their contribution in localizing and to a lesser extent in lateralizing seizures foci in epilepsy surgery candidates. We suggest that this is of great importance in the context of preoperative monitoring of epilepsy surgery, especially when neuropsychologists are called upon to provide anatomical information in defining the functional deficit zone.

Role of inflammation in epilepsy and neurobehavioral comorbidities: Implication for therapy

Epilepsy is a devastating condition affecting around 70 million people worldwide. Moreover, the quality of life of people with epilepsy (PWE) is worsened by a series of comorbidities. The neurobehavioral comorbidities discussed herein share a reciprocal and complex relationship with epilepsy, which ultimately complicates the treatment process in PWE. Understanding the mechanistic pathway by which these comorbidities are associated with epilepsy might be instrumental in developing therapeutic interventions. Inflammatory cytokine signaling in the brain regulates important brain functions including neurotransmitter metabolism, neuroendocrine function, synaptic plasticity, dopaminergic transmission, the kynurenine pathway, and affects neurogenesis as well as the neural circuitry of moods. In this review, we hypothesize that the complex relationship between epilepsy and its related comorbidities (cognitive impairment, depression, anxiety, autism, and schizophrenia) can be unraveled through the inflammatory mechanism that plays a prominent role in all these individual conditions. An ample amount of evidence is available reporting the role of inflammation in epilepsy and all individual comorbid condition but their complex relationship with epilepsy has not yet been explored through the prospective of inflammatory pathway. Our review suggests that epilepsy and its neurobehavioral comorbidities are associated with elevated levels of several key inflammatory markers. This review also sheds light on the mechanistic association between epilepsy and its neurobehavioral comorbidities. Moreover, we analyzed several anti-inflammatory therapies available for epilepsy and its neurobehavioral comorbidities. We suggest, these anti-inflammatory therapies might be a possible intervention and could be a promising strategy for preventing epileptogenesis and its related neurobehavioral comorbidities.

Functional disruption of stress modulatory circuits in a model of temporal lobe epilepsy

Clinical data suggest that the neuroendocrine stress response is chronically dysregulated in a subset of patients with temporal lobe epilepsy (TLE), potentially contributing to both disease progression and the development of psychiatric comorbidities such as anxiety and depression. Whether neuroendocrine dysregulation and psychiatric comorbidities reflect direct effects of epilepsy-related pathologies, or secondary effects of disease burden particular to humans with epilepsy (i.e. social estrangement, employment changes) is not clear. Animal models provide an opportunity to dissociate these factors. Therefore, we queried whether epileptic mice would reproduce neuroendocrine and behavioral changes associated with human epilepsy. Male FVB mice were exposed to pilocarpine to induce status epilepticus (SE) and the subsequent development of spontaneous recurrent seizures. Morning baseline corticosterone levels were elevated in pilocarpine treated mice at 1, 7 and 10 weeks post-SE relative to controls. Similarly, epileptic mice had increased adrenal weight when compared to control mice. Exposure to acute restraint stress resulted in hypersecretion of corticosterone 30 min after the onset of the challenge. Anatomical analyses revealed reduced Fos expression in infralimbic and prelimbic prefrontal cortex, ventral subiculum and basal amygdala following restraint. No differences in Fos immunoreactivity were found in the paraventricular nucleus of the hypothalamus, hippocampal subfields or central amygdala. In order to assess emotional behavior, a second cohort of mice underwent a battery of behavioral tests, including sucrose preference, open field, elevated plus maze, 24h home-cage monitoring and forced swim. Epileptic mice showed increased anhedonic behavior, hyperactivity and anxiety-like behaviors. Together these data demonstrate that epileptic mice develop HPA axis hyperactivity and exhibit behavioral dysfunction. Endocrine and behavioral changes are associated with impaired recruitment of forebrain circuits regulating stress inhibition and emotional reactivity. Loss of forebrain control may underlie pronounced endocrine dysfunction and comorbid psychopathologies seen in temporal lobe epilepsy.

Chronic agomelatine treatment prevents comorbid depression in the post-status epilepticus model of acquired epilepsy through suppression of inflammatory signaling

Inflammatory signal molecules are suggested to be involved in the mechanism underlying comorbid depression in epilepsy. In the present study, we tested the hypothesis that the novel antidepressant agomelatine, a potent melatonin MT₁ and MT₂ receptor agonist and serotonin 5HT_2C receptor antagonist, can prevent depressive symptoms developed during the chronic epileptic phase by suppressing an inflammatory response. Chronic treatment with agomelatine (40 mg/kg, i.p.) was initiated an hour after the kainate acid (KA)-induced status epilepticus (SE) and maintained for a period of 10 weeks in Wistar rats. Registration of spontaneous motor seizures was performed through a video (24 h/day) and EEG monitoring. Antidepressant activity of agomelatine was explored in the splash test, sucrose preference test (SPT) and forced swimming test (FST) while anxiolytic effect was observed through the novelty suppression-feeding test (NSFT) during chronic phase in epileptic rats. The frequency of motor seizures detected by video and EEG recording did not differ between vehicle and Ago group. Rats with registered spontaneous motor seizures showed symptoms typical for depressive behavior that included decreased grooming, anhedonia during the dark period and hopeless-like behavior. Epileptic rats exhibited also anxiety with novelty-induced hypophagia. This behavioral deficit correlated with increased signal markers of inflammation (plasma levels of interleukin (IL)-1β and activated glia in brain), while plasma corticosterone levels were not changed. Agomelatine treatment during epileptogenesis exerted a clear antidepressant effect by suppressing all behavioral hallmarks, reducing plasma IL-1β levels and preventing microgliosis and astrogliosis in specific limbic regions. The present results suggest that agomelatine treatment starting after SE can provide an effective therapy of comorbid depression in chronic epileptic condition through suppression of inflammatory signaling.

Depressive disorders in patients with pharmaco-resistant mesial temporal lobe epilepsy

Objectives To assess depressive disorders in patients with mesial temporal lobe epilepsy (MTLE) refractory to medical treatment. Methods Adult patients with refractory MTLE completed two questionnaires (Mini International Neuropsychiatric Interview (MINI) and the Beck Depression Inventory (BDI) had a semi-structured psychiatric interview and a high resolution MRI scan. For complete neuropsychiatric diagnosis, as per International Classification of Diseases (ICD-10), the results were combined with clinical history and additional information from the patients' family. Results Of the 40 patients identified for this case series study which took place from 2008-2012, 31 (77.5%) had a depressive disorder: 14 had dysthymia, 11 had recurrent depressive disorder and 6 had bipolar disorder. Of the nine patients without a firm diagnosis of mood disorder, seven had isolated symptoms of depression or anxiety and two presented with mixed depression/anxiety symptoms. Only 8/31 (25.8%) patients were receiving antidepressant treatment. There was no association between BDI scores and seizure frequency. No significant difference was found between patients with and without depression and the presence or laterality of HA. Conclusions Depressive disorders are common, underdiagnosed and undertreated in patients with refractory MTLE.

Epilepsy coexisting with depression

Depression episodes in epilepsy is the most common commorbidity, affecting between 11% and 62% of patients with epilepsy. Although researchers have documented a strong association between epilepsy and psychiatric comorbidities, the nature of this relationship is poorly understood. The manifestation of depression in epilepsy is a complex issue having many interacting neurobiological and psychosocial determinants, including clinical features of epilepsy (seizure frequency, type, foci, or lateralization of foci) and neurochemical or iatrogenic mechanisms. Other risk factors are a family history of psychiatric illness, particularly depression, a lack of control over the seizures and iatrogenic causes (pharmacologic and surgical). In addition, treatment with antiepileptic drugs (AEDs) as well as social coping and adaptation skills have also been recognised as risk factors of depression associated with epilepsy. Epilepsy may foster the development of depression through being exposed to chronic stress. The uncertainty and unpredictability of seizures may instigate sadness, loneliness, despair, low self-esteem, and self-reproach in patients with epilepsy and lead to social isolation, stigmatization, or disability. Often, depression is viewed as a reaction to epilepsy's stigma and the associated poor quality of life. Moreover, patients with epilepsy display a 4-5 higher rate of depression and suicide compared with healthy population.

Managing epilepsy-associated depression: Serotonin enhancers or serotonin producers?

Depression is one of the major psychiatric comorbidities having a major impact on the quality of life in people with epilepsy (PWE). Selective serotonin reuptake inhibitors (SSRIs) are considered as safest therapy for the treatment of depression in PWE. Although administration of SSRIs increases the synaptic serotonin levels, it decreases the overall serotonin synthesis in the brain. Long-term therapy with SSRIs has been reported to decrease serotonin synthesis, which may be the possible reason for lessening of their antidepressant effect over time as well as elevated seizure outcomes observed in PWE. Thus the present scenario warrants streamlined studies to explore the safety and efficacy of SSRIs as well as approaches beyond SSRIs for treatment of depression in epilepsy. In this review, we outline the approaches which may restore serotonin levels rather than a pseudo enhancement of serotonin with SSRIs. The potential of various anti-inflammatory approaches such as selective cyclooxygenase-2 inhibitors, inflammatory cytokine inhibitors, and indoleamine 2,3-dioxygenase inhibitors pertaining to their serotonin restoring effects is discussed as possible therapy for treatment of depression in epilepsy.

Diagnosing and treating depression in epilepsy

At least one third of patients with active epilepsy suffer from significant impairment of their emotional well-being. A targeted examination for possible depression (irrespective of any social, financial or personal burdens) can identify patients who may benefit from medical attention and therapeutic support. Reliable screening instruments such as the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) are suitable for the timely identification of patients needing help. Neurologists should be capable of managing mild to moderate comorbid depression but referral to mental health specialists is mandatory in severe and difficult-to-treat depression, or if the patient is acutely suicidal. In terms of the therapeutic approach, it is essential first to optimize seizure control and minimize unwanted antiepileptic drug-related side effects. Psychotherapy for depression in epilepsy (including online self-treatment programs) is underutilized although it has proven effective in ten well-controlled trials. In contrast, the effectiveness of antidepressant drugs for depression in epilepsy is unknown. However, if modern antidepressants are used (e.g. SSRI, SNRI, NaSSA), concerns about an aggravation of seizures and or problematic interactions with antiepileptic drugs seem unwarranted. Epilepsy-related stress ("burden of epilepsy") explains depression in many patients but acute and temporary seizure-related states of depression or suicidality have also been reported. Limbic encephalitits may cause isolated mood alteration without any recognizable psychoetiological background indicating a possible role of neuroinflammation. This review will argue that, overall, a bio-psycho-social model best captures the currently available evidence relating to the etiology and treatment of depression as a comorbidity of epilepsy.

Depression and anxiety in children with benign childhood epilepsy with centrotemporal spikes (BCECTS)

Background

Elevated rates of affective disturbance in children with benign childhood epilepsy with centrotemporal spikes (BCECTS) have been reported. However, it remains unclear how anxiety and depression are related to epilepsy, and it is unknown whether these mood disorders are influenced by the use of antiepileptic drugs. In the present report, we performed a prospective study designed to evaluate affective disorders (anxiety and depression) without the bias of antiepileptic drug treatment in 89 children with BCECTS, based on self-reporting. Furthermore, we sought to determine whether clinical factors, such as age, disease course, seizure frequency, and spike wave index (SWI), were related to the psychological profiles.

Methods

Patients with BCECTS (n = 89) and healthy matched controls (n = 75) were included in this study. The Depression Self-Rating Scale for Children (DSRSC) and the Screen for Child Anxiety-Related Emotional Disorders (SCARED) were completed by the children.

Results

None of the children met criteria for clinically significant anxiety or depression. However, the children with BCECTS had significantly higher depression and anxiety scores compared with children in the control group. We found no significant differences in depression or anxiety between the left, right, and bilateral lobe groups. The DSRSC scores were similar between the children with partial seizures and those with secondarily generalized seizures. Similarly, there were no significant differences in the SCARED scores between these two groups. However, the DSRSC and SCARED scores were positively correlated with age, seizure frequency, SWI, and disease course.

Conclusions

The children with BCECTS had an increased likelihood of depression and anxiety, and these higher rates were unrelated to seizure type or epileptic focus, but were positively correlated with age, seizure frequency, SWI, and disease course.

Effect of endurance training on seizure susceptibility, behavioral changes and neuronal damage after kainate-induced status epilepticus in spontaneously hypertensive rats

The therapeutic efficacy of regular physical exercises in an animal model of epilepsy and depression comorbidity has been confirmed previously. In the present study, we examined the effects of endurance training on susceptibility to kainate (KA)-induced status epilepticus (SE), behavioral changes and neuronal damage in spontaneously hypertensive rats (SHRs). Male SHRs were randomly divided into two groups. One group was exercised on a treadmill with submaximal loading for four weeks and the other group was sedentary. Immediately after the training period, SE was evoked in half of the sedentary and trained rats by KA, while the other half of the two groups received saline. Basal systolic (SP), diastolic (DP) and mean arterial pressure (MAP) of all rats were measured at the beginning and at the end of the training period. Anxiety, memory and depression-like behaviour were evaluated a month after SE. The release of 5-HT in the hippocampus was measured using a liquid scintillation method and neuronal damage was analyzed by hematoxylin and eosin staining. SP and MAP of exercised SHRs decreased in comparison with the initial values. The increased resistance of SHRs to KA-induced SE was accompanied by an elongated latent seizure-free period, improved object recognition memory and antidepressant effect after the training program. While the anticonvulsant and positive behavioral effects of endurance training were accompanied by an increase of 5-HT release in the hippocampus, it did not exert neuroprotective activity. Our results indicate that prior exercise is an effective means to attenuate KA-induced seizures and comorbid behavioral changes in a model of hypertension and epilepsy suggesting a potential influence of hippocampal 5-HT on a comorbid depression. However, this beneficial impact does not prevent the development of epilepsy and concomitant brain damage.

Botanicals for mood disorders with a focus on epilepsy

Mood disorders are among the major health problems that exist worldwide. They are highly prevalent in the general population and cause significant disturbance of life quality and social functioning of the affected persons. The two major classes of mood disorders are bipolar disorders and depression. The latter is assumed to be the most frequent psychiatric comorbidity in epilepsy. Studies published during the second half of the 20th century recognized that certain patients with epilepsy present a depressed mood. Synthesized pharmaceuticals have been in use for decades to treat both mood disorders and epilepsy, but despite their efficiency, their use is limited by numerous side effects. On the other hand, animal models have been developed to deeply study potential botanicals which have an effect on mood disorders. Studies to investigate the potential effects of medicinal plants acting on the nervous system and used to treat seizures and anxiety are increasingly growing. However, these studies discuss the two conditions separately without association. In this review, we present animal models of depression and investigative models (methods of assessing depression) of depression and anxiety in animals. Other classical test models for prediction of clinical antidepressant activity are presented. Finally, this review also highlights antidepressant activities of herbals focusing specially on depression-like behaviors associated with epilepsy. The pharmacological properties and active principles of cited medicinal plants are emphasized. This review, therefore, provides an overview of the work done on botanicals for mood disorders, potential mechanisms of action of botanicals, and the major compounds. This article is part of a Special Issue entitled "Botanicals for Epilepsy".

Religious convictions in patients with epilepsy-associated affective disorders: a controlled study from a psychiatric acute department

Patients with epilepsy often have different mood symptoms and behavioral trait characteristics compared to the non-epileptic population. In the present prospective study, we aimed to assess differences in behavioral trait characteristics between acutely admitted, psychiatric in-patients with epilepsy-associated depressive symptoms and gender/age-matched patients with major depression. Patients with epilepsy-associated depression had significantly higher scores for "religious convictions," "philosophical and intellectual interests" and "sense of personal destiny." These behavioral trait characteristics at admission or in clinical history should alert the psychiatrist and lead to closer examination for a possible convulsive disorder.

Event-related potentials reveal preserved attention allocation but impaired emotion regulation in patients with epilepsy and comorbid negative affect

Patients with epilepsy have a high prevalence of comorbid mood disorders. This study aims to evaluate whether negative affect in epilepsy is associated with dysfunction of emotion regulation. Event-related potentials (ERPs) are used in order to unravel the exact electrophysiological time course and investigate whether a possible dysfunction arises during early (attention) and/or late (regulation) stages of emotion control. Fifty epileptic patients with (n = 25) versus without (n = 25) comorbid negative affect plus twenty-five matched controls were recruited. ERPs were recorded while subjects performed a face- or house-matching task in which fearful, sad or neutral faces were presented either at attended or unattended spatial locations. Two ERP components were analyzed: the early vertex positive potential (VPP) which is normally enhanced for faces, and the late positive potential (LPP) that is typically larger for emotional stimuli. All participants had larger amplitude of the early face-sensitive VPP for attended faces compared to houses, regardless of their emotional content. By contrast, in patients with negative affect only, the amplitude of the LPP was significantly increased for unattended negative emotional expressions. These VPP results indicate that epilepsy with or without negative affect does not interfere with the early structural encoding and attention selection of faces. However, the LPP results suggest abnormal regulation processes during the processing of unattended emotional faces in patients with epilepsy and comorbid negative affect. In conclusion, this ERP study reveals that early object-based attention processes are not compromised by epilepsy, but instead, when combined with negative affect, this neurological disease is associated with dysfunction during the later stages of emotion regulation. As such, these new neurophysiological findings shed light on the complex interplay of epilepsy with negative affect during the processing of emotional visual stimuli and in turn might help to better understand the etiology and maintenance of mood disorders in epilepsy.

GABAergic alterations in neocortex of patients with pharmacoresistant temporal lobe epilepsy can explain the comorbidity of anxiety and depression: the potential impact of clinical factors

Temporal lobe epilepsy (TLE) is a chronic neurodegenerative disease with a high prevalence of psychiatric disorders. Temporal neocortex contributes to either seizure propagation or generation in TLE, a situation that has been associated with alterations of the γ-amino-butyric acid (GABA) system. On the other hand, an impaired neurotransmission mediated by GABA in temporal neocortex has also been involved with the pathophysiology of psychiatric disorders. In spite of these situations, the role of the necortical GABA system in the comorbidity of TLE and mood disorders has not been investigated. The present study was designed to identify alterations in the GABA system such as binding to GABA_A and GABA_B receptors and benzodiazepine site, the tissue content of GABA and the expression of the mRNA encoding the α1–6, β1–3, and γ GABA_A subunits, in the temporal neocortex of surgically treated patients with TLE with and without anxiety, and/or depression. Neocortex of patients with TLE and comorbid anxiety and/or depression showed increased expression of the mRNA encoding the γ2-subunit, reduced GABA_B-induced G-protein activation in spite of elevated GABA_B binding, and lower tissue content of GABA when compared to autopsy controls. Some of these changes significantly correlated with seizure frequency and duration of epilepsy. The results obtained suggest a dysfunction of the GABAergic neurotransmission in temporal neocortex of patients with TLE and comorbid anxiety and/or depression that could be also influenced by clinical factors such as seizure frequency and duration of illness.

GABAergic alterations in neocortex of patients with pharmacoresistant temporal lobe epilepsy can explain the comorbidity of anxiety and depression: the potential impact of clinical factors

Temporal lobe epilepsy (TLE) is a chronic neurodegenerative disease with a high prevalence of psychiatric disorders. Temporal neocortex contributes to either seizure propagation or generation in TLE, a situation that has been associated with alterations of the γ-amino-butyric acid (GABA) system. On the other hand, an impaired neurotransmission mediated by GABA in temporal neocortex has also been involved with the pathophysiology of psychiatric disorders. In spite of these situations, the role of the necortical GABA system in the comorbidity of TLE and mood disorders has not been investigated. The present study was designed to identify alterations in the GABA system such as binding to GABAA and GABAB receptors and benzodiazepine site, the tissue content of GABA and the expression of the mRNA encoding the α1-6, β1-3, and γ GABAA subunits, in the temporal neocortex of surgically treated patients with TLE with and without anxiety, and/or depression. Neocortex of patients with TLE and comorbid anxiety and/or depression showed increased expression of the mRNA encoding the γ2-subunit, reduced GABAB-induced G-protein activation in spite of elevated GABAB binding, and lower tissue content of GABA when compared to autopsy controls. Some of these changes significantly correlated with seizure frequency and duration of epilepsy. The results obtained suggest a dysfunction of the GABAergic neurotransmission in temporal neocortex of patients with TLE and comorbid anxiety and/or depression that could be also influenced by clinical factors such as seizure frequency and duration of illness.

Atorvastatin prevents development of kindling by modulating hippocampal levels of dopamine, glutamate, and GABA in mice

PURPOSE

Atorvastatin (ATV) is widely used for the treatment of dyslipidemias. Recent evidence has shown that ATV has protection effects against seizures. However, the effect of ATV on certain neurotransmitter and oxidative stress markers associated with seizures had not been reported. Therefore, the present study aimed to evaluate the effects of ATV on oxidative stress markers on whole brain and GABA, glutamate, and dopamine levels in the hippocampus of PTZ-kindled mice. Additionally, effects of ATV on animal models of seizures, anxiety, and depression were also assessed.

MATERIALS AND METHODS

Swiss albino mice were given ATV (20, 40, and 80mg/kg/p.o.) in an acute study. On the seventh day, animals were subjected to various neurological and neurobehavioral tests, viz, increasing current electroshock (ICES) test, pentylenetetrazole (PTZ)-induced seizures, Elevated Plus Maze (EPM), and Forced Swim Test (FST). For the development of kindling, a subconvulsant dose of PTZ, i.e., 25mg/kg, i.p., was administered every other day, and ATV in all the three doses was administered daily. Seizure score was continuously monitored until the development of kindling. Thiobarbituric acid reacting species (TBARS), glutathione, dopamine, GABA, and glutamate levels were also assessed in the brain tissues of mice.

RESULTS

The results showed that in the ICES test, ATV 80mg/kg increased the seizure threshold to hind limb extension (HLE), and a complete protection against HLE was observed when ATV 80mg/kg was combined with a subanticonvulsant dose of phenytoin. Atorvastatin in all the tested doses suppressed the development of kindling, reduced lipid peroxidation, and increased glutathione levels. All doses of ATV maintained the normal levels of glutamate, GABA, and dopamine in kindled mice.

CONCLUSION

Atorvastatin possesses anticonvulsant activity against electroconvulsions. It was found to suppress the development of PTZ kindling, presumably altering the redox status and hippocampal levels of dopamine, glutamate, and GABA.

Is interictal EEG activity a biomarker for mood disorders in temporal lobe epilepsy?

OBJECTIVE

Psychiatric comorbidities are frequent in temporal lobe epilepsy (TLE), and symptoms of these comorbidities may be related to epilepsy activity. Here we evaluated interictal EEG activity in TLE patients with or without psychiatric comorbidities.

METHODS

A cohort study of 78 patients with TLE, with evaluation of wake/sleep interictal scalp EEG. All subjects were submitted to a psychiatric structured clinical interview (SCID) for the diagnosis of lifetime psychiatric comorbidities. Three major diagnostic categories were studied: mood disorders, anxiety disorders, and psychosis. We then evaluated differences in interictal EEG activity between patients with and without these psychiatric comorbidities.

RESULTS

Infrequent EEG interictal spikes, defined as less than one event per minute, were significantly associated with mood disorders in TLE (p=0.02).

CONCLUSIONS

Low intensity seizure disorder has been associated with a decrease in interictal EEG discharges and with an increase in psychiatric symptoms in TLE, a phenomenon known as forced normalization. In our study, we observed a low interictal spike frequency on EEG in TLE patients with mood disorders.

SIGNIFICANCE

A low spike index might be a neurophysiological marker for depression in temporal lobe epilepsy.

Behavioral impairments in rats with chronic epilepsy suggest comorbidity between epilepsy and attention deficit/hyperactivity disorder

Attention deficit/hyperactivity disorder (ADHD) is encountered among patients with epilepsy at a significantly higher rate than in the general population. Mechanisms of epilepsy-ADHD comorbidity remain largely unknown. We investigated whether a model of chronic epilepsy in rats produces signs of ADHD, and thus, whether it can be used for studying mechanisms of this comorbidity. Epilepsy was induced in male Wistar rats via pilocarpine status epilepticus. Half of the animals exhibited chronic ADHD-like abnormalities, particularly increased impulsivity and diminished attention in the lateralized reaction-time task. These impairments correlated with the suppressed noradrenergic transmission in locus coeruleus outputs. The other half of animals exhibited depressive behavior in the forced swimming test congruently with the diminished serotonergic transmission in raphe nucleus outputs. Attention deficit/hyperactivity disorder and depressive behavior appeared mutually exclusive. Therefore, the pilocarpine model of epilepsy affords a system for reproducing and studying mechanisms of comorbidity between epilepsy and both ADHD and/or depression.

Epilepsy comorbidities: how can animal models help?

An epilepsy comorbidity is a condition or disorder that occurs at a frequency greater than chance in a person with epilepsy. Examples of common epilepsy comorbidities are depression, anxiety, and intellectual disability. Epilepsy comorbidities can be quite disabling, sometimes affecting a patient's quality of life to a greater extent than seizures. Animal models offer the opportunity to explore shared pathophysiological mechanisms, therapeutic options, and consequences of both the epilepsy syndrome and a given comorbidity. In this chapter, depression is used as an example of how animal models can inform translational questions about epilepsy comorbidities.

Antidepressant-like effects of the aqueous macerate of the bulb of Gladiolus dalenii Van Geel (Iridaceae) in a rat model of epilepsy-associated depression

BACKGROUND

In Cameroonian traditional medicine various extracts of Gladiolus dalenii Van Geel (Iridaceae) have been used as a cure for various ailments that include headaches, digestive problems, muscle and joint aches, and some central nervous system disorders such as epilepsy, schizophrenia and mood disorders. Owning to this background, the aim of the study was to investigate whether an aqueous macerate of the bulb of Gladiolus dalenii has any antidepressant activity focusing specifically on depression-like behaviours associated with epilepsy.

METHOD

We used the combined administration of atropine and pilocarpine to rats as our animal model of epilepsy. The forced swim test and spontaneous locomotor activity in the open field test were the two tools used to assess the presence of depression-like behaviour in epileptic and control animals. The following depression-related parameters were determined: plasma ACTH, plasma corticosterone, adrenal gland weight and hippocampal levels of brain-derived neurotrophic factor (BDNF). The effects of Gladiolus dalenii were compared to that of fluoxetine.

RESULTS

Our results showed that we had a valid animal model of epilepsy-induced depression as all 3 measures of construct, predictive and face validity were satisfied. The data indicated that Gladiolus dalenii significantly reduced the immobility times in the forced swim test and the locomotor activity as assessed in the open field. A similar pattern was observed when the HPA axis parameters were analysed. Gladiolus dalenii significantly reduced the levels of ACTH, corticosterone, but not the adrenal gland weight. Gladiolus dalenii significantly increased the level of BDNF in the hippocampus. In all parameters measured the effects of Gladiolus dalenii were significantly greater than those of fluoxetine.

CONCLUSION

The results show that Gladiolus dalenii has antidepressant-like properties similar to those of fluoxetine in epilepsy-associated depressive states. The antidepressant activity of Gladiolus dalenii is likely to be mediated by restoring the activity of the HPA axis and increasing the levels of BDNF in the hippocampus.

Functional connectivity abnormalities vary by amygdala subdivision and are associated with psychiatric symptoms in unilateral temporal epilepsy

The amygdala has been described as a structure affected by mesial temporal lobe epilepsy (MTLE). Indeed, it is suggested that amygdala abnormalities are related to the co-morbid depression and anxiety reported in MTLE. In this context, we investigated the relation between functional connectivity (FC) emerging from this structure in fMRI and depression and anxiety levels reported in MTLE patients. We focused on resting-state BOLD activity and evaluated whether FC differences emerge from each of three amygdala subdivisions (laterobasal, centromedial and superficial) in left and right MTLE groups, compared with healthy controls. Results revealed significant differences between patient groups and controls. Specifically, the left MTLE group showed abnormal FC for the left-sided seeds only. Furthermore, regardless of the seed, we observed more reliable differences between the right MTLE group and controls. Further analysis of these results revealed correlations between these impaired connectivities and psychiatric symptoms in both MTLE groups. Opposite relations, however, were highlighted: the more depressed or anxious the right MTLE patients, the closer their FC values approached controls; whereas the less anxious the left MTLE patients, the closer their FC values were normative. These results highlight how MTLE alter FC emerging from the limbic system. Overall, our data demonstrate that right TLE has a more maladaptive impact on emotion-related networks, in ways specific to the amygdala region, and the emotion symptom involved, than left TLE.

Pathophysiology of mood disorders in temporal lobe epilepsy

OBJECTIVE

There is accumulating evidence that the limbic system is pathologically involved in cases of psychiatric comorbidities in temporal lobe epilepsy (TLE) patients. Our objective was to develop a conceptual framework describing how neuropathological, neurochemical and electrophysiological aspects might contribute to the development of psychiatric symptoms in TLE and the putative neurobiological mechanisms that cause mood disorders in this patient subgroup.

METHODS

In this review, clinical, experimental and neuropathological findings, as well as neurochemical features of the limbic system were examined together to enhance our understanding of the association between TLE and psychiatric comorbidities. Finally, the value of animal models in epilepsy and mood disorders was discussed.

CONCLUSIONS

TLE and psychiatric symptoms coexist more frequently than chance would predict. Alterations and neurotransmission disturbance among critical anatomical networks, and impaired or aberrant plastic changes might predispose patients with TLE to mood disorders. Clinical and experimental studies of the effects of seizures on behavior and electrophysiological patterns may offer a model of how limbic seizures increase the vulnerability of TLE patients to precipitants of psychiatric symptoms.

Prophylactic treatment with melatonin after status epilepticus: effects on epileptogenesis, neuronal damage, and behavioral changes in a kainate model of temporal lobe epilepsy

Melatonin is a potent antioxidant which showed anticonvulsant activities both in experimental and clinical studies. In the present study, we examined the effect of melatonin treatment (10mg/kg/day, diluted in drinking water, 8 weeks) during epileptogenesis on the consequences of a kainate (KA)-induced status epilepticus (SE) in rats. Melatonin increased the latency in the appearance of spontaneous recurrent seizures (SRSs) and decreased their frequency only during the treatment period. The behavioral alterations associated with hyperactivity, depression-like behavior during the light phase, and deficits in hippocampus-dependent working memory were positively affected by melatonin treatment in rats with epilepsy. Melatonin reduced the neuronal damage in the CA1 area of the hippocampus and piriform cortex and recovered the decrease of hippocampal serotonin (5-HT) level in rats with epilepsy. Taken together, long-term melatonin treatment after SE was unable to suppress the development of epileptogenesis. However, it showed a potential in reducing some of the deleterious alterations that develop during the chronic epileptic state in a diurnal phase-dependent mode.

Seizure susceptibility and epileptogenesis in a rat model of epilepsy and depression co-morbidity

Although a strong co-morbidity exists clinically between epilepsy and depression, the cause of this co-morbidity remains unknown, and a valid animal model is crucial for the identification of underlying mechanisms and the development of a screening tool for novel therapies. Although some rodent models of epilepsy have been reported to display behaviors relevant to affective disorders, the seizure susceptibility of animals prone to depression-like behavior has not been characterized. Toward this end, we assessed several forms of seizure sensitivity and epileptogenesis in rats selectively bred for vulnerability (Swim Lo-Active; SwLo) or resilience (Swim High-Active; SwHi) to depression-like phenotypes. The SwLo rats exhibit decreased motor activity in a swim test and other depression-like phenotypes, whereas the SwHi rats display increased motor activity in a swim test. SwLo rats exhibited a decreased latency to limbic motor seizures following acute pilocarpine administration in the absence of differences in pilocarpine pharmacokinetics, and also had a decreased threshold to tonic seizures induced by electroshock. Approximately half of the SwLo rats, but none of the SwHi rats, had spontaneous limbic motor seizures 5 weeks following pilocarpine-induced status epilepticus. While the number of stimulations required to achieve full amygdala and hippocampal electrical kindling were similar in the two rat lines, SwLo rats had a lower final hippocampal kindling threshold and more wet dog shakes during both amygdala and hippocampal kindling. Combined, these results indicate that SwLo rats are a model of epilepsy and depression co-morbidity that can be used for investigating underlying neurobiological and genetic mechanisms and screening novel therapeutics.

Different emotional disturbances in two experimental models of temporal lobe epilepsy in rats

Affective symptoms such as anxiety and depression are frequently observed in patients with epilepsy. The mechanisms of comorbidity of epilepsy and affective disorders, however, remain unclear. Diverse models are traditionally used in epilepsy research, including the status epilepticus (SE) model in rats, which are aimed at generating chronic epileptic animals; however, the implications of different SE models and rat strains in emotional behaviors has not been reported. To address this issue, we examined the emotional sequelae of two SE models of temporal lobe epilepsy (TLE)--the lithium-pilocarpine (LIP) model and the kainic acid (KA) model--in two different rat strains (Wistar and Sprague-Dawley), which differ significantly in the pattern and extent of TLE-associated brain lesions. We found differences between LIP- and KA-treated animals in tests for depression-like and anxiety-like behaviors, as well as differences in plasma corticosterone levels. Whereas only LIP-treated rats displayed increased motivation to consume saccharin, both SE models led to reduced motivation for social contact, with LIP-treated animals being particularly affected. Evaluation of behavior in the open field test indicated very low levels of anxiety in LIP-treated rats and a mild decrease in KA-treated rats compared to controls. After exposure to a battery of behavioral tests, plasma corticosterone levels were increased only in LIP-treated animals. This hyperactivity in the hypothalamus-pituitary-adrenocortical (HPA) axis was highly correlated with performance in the open field test and the social interaction test, suggesting that comorbidity of epilepsy and emotional behaviors might also be related to other factors such as HPA axis function. Our results indicate that altered emotional behaviors are not inherent to the epileptic condition in experimental TLE; instead, they likely reflect alterations in anxiety levels related to model-dependent dysregulation of the HPA axis.

Interleukin-1β causes fluoxetine resistance in an animal model of epilepsy-associated depression

Depression represents a common comorbidity of epilepsy and is frequently resistant to selective serotonin reuptake inhibitors (SSRI). We tested the hypothesis that the SSRI resistance in epilepsy associated depression may be a result of a pathologically enhanced interleukin-1β (IL1-β) signaling, and consequently that the blockade of IL1-β may restore the effectiveness of SSRI. Epilepsy and concurrent depression-like impairments were induced in Wistar rats by pilocarpine status epilepticus (SE). The effects of the 2-week long treatment with fluoxetine, interleukin-1 receptor antagonist (IL-1ra), and their combination were examined using behavioral, biochemical, neuroendocrine, and autoradiographic assays. In post-SE rats, depression-like impairments included behavioral deficits indicative of hopelessness and anhedonia; the hyperactivity of the hypothalamo-pituitary-adrenocortical axis; the diminished serotonin output from raphe nucleus; and the upregulation of presynaptic serotonin 1-A (5-HT1A) receptors. Fluoxetine monotherapy exerted no antidepressant effects, whereas the treatment with IL-1ra led to the complete reversal of anhedonia and to a partial improvement of all other depressive impairments. Combined administration of fluoxetine and IL-1ra completely abolished all hallmarks of epilepsy-associated depressive abnormalities, with the exception of the hyperactivity of the hypothalamo-pituitary-adrenocortical axis, the latter remaining only partially improved. We propose that in certain forms of depression, including but not limited to depression associated with epilepsy, the resistance to SSRI may be driven by the pathologically enhanced interleukin-1β signaling and by the subsequent upregulation of presynaptic 5-HT1A receptors. In such forms of depression, the use of interleukin-1β blockers in conjunction with SSRI may represent an effective therapeutic approach.