White matter integrity correlates with depressive symptomatology in temporal lobe epilepsy

Neurobehavioral and Clinical Comorbidities in Epilepsy: The Role of White Matter Network Disruption

Epilepsy is a common neurological disorder associated with alterations in cortical and subcortical brain networks. Despite a historical focus on gray matter regions involved in seizure generation and propagation, the role of white matter (WM) network disruption in epilepsy and its comorbidities has sparked recent attention. In this review, we describe patterns of WM alterations observed in focal and generalized epilepsy syndromes and highlight studies linking WM disruption to cognitive and psychiatric comorbidities, drug resistance, and poor surgical outcomes. Both tract-based and connectome-based approaches implicate the importance of extratemporal and temporo-limbic WM disconnection across a range of comorbidities, and an evolving literature reveals the utility of WM patterns for predicting outcomes following epilepsy surgery. We encourage new research employing advanced analytic techniques (e.g., machine learning) that will further shape our understanding of epilepsy as a network disorder and guide individualized treatment decisions. We also address the need for research that examines how neuromodulation and other treatments (e.g., laser ablation) affect WM networks, as well as research that leverages larger and more diverse samples, longitudinal designs, and improved magnetic resonance imaging acquisitions. These steps will be critical to ensuring generalizability of current research and determining the extent to which neuroplasticity within WM networks can influence patient outcomes.

Felt Stigma and Its Underlying Contributors in Epilepsy Patients

Objective

To explore the correlated clinical and psychological factors of stigmatization and investigate the relationship between stigma and white matter abnormalities in epilepsy patients.

Methods

Stigmatization was obtained by a three-item stigma scale in 256 epilepsy patients with genetic or unknown etiology. Personality and quality of life (QOL) were assessed by Eysenck Personality Questionnaire (EPQ) and QOL-31 questionnaire respectively. One hundred and fourteen of them were performed Hamilton Depression Scale-17 (HAMD) and scanned with diffusion tensor imaging in 3T MRI. Fractional anisotropy (FA) values of frontotemporal contact fibers were calculated.

Results

There were about 39.8% patients felt stigma, with the highest score (Score 3) in 8.2% (21/256). Stigma scores were significantly negatively correlated with education (P < 0.01), age of onset (P < 0.05), extraversion score of EPQ (P < 0.01), total and all the subscale QOL scores (P < 0.001), and positively correlated with duration (P < 0.01), HAMD score (P < 0.001), neuroticism score of EPQ (P < 0.001). We found negative correlation between stigma scores and FA values of right superior longitudinal fasciculus and left cingulum (P < 0.05). Logistic regression results showed that FA value of left cingulum (P = 0.011; OR = 0.000), social function (P = 0.000; OR = 0.935) of QOL, and neuroticism score of EPQ (P = 0.033; OR = 1.123) independently correlated to felt stigma.

Conclusion

Felt stigma in epilepsy patients was found to be correlated with neuroticism, depression, and deficient social function of QOL, which might be predisposed by the impairment of the left cingulum. Our results provide preliminary evidence for the underlying neural circuits in stigmatization.

Psychiatric comorbidities in adult patients with epilepsy (A systematic review)

The co-occurrence of epilepsy and psychiatric disorders is long known. The scope of this systematic review was to describe the prevalence of specific interictal psychiatric disorders in patients with epilepsy and to assess possible associations between psychiatric disorders and other sociodemographic or clinical characteristics of epilepsy patients. MEDLINE and ScienceDirect were searched for original articles published between January 2015 and February 2021 describing studies that involved epilepsy patients with psychiatric comorbidities. We identified 13 studies with heterogenous methodology and reporting. Prevalence of any psychiatric disorder observed was up to 51% in idiopathic generalized epilepsy (IGE), up to 43.1% in temporal lobe epilepsy (TLE) and up to 43.3% in a general population of patients with epilepsy. The most frequent psychiatric comorbidities associated with epilepsy included mood/affective disorders (up to 40% for lifetime occurrence and up to 23% for current occurrence), anxiety disorders (up to 30.8% for lifetime occurrence and up to 15.6% for current occurrence), personality disorders [up to 11% in juvenile myoclonic epilepsy (JME)] and psychotic disorders (up to 4% of epilepsy patients). In focal epilepsy, depressive disorders might be associated with specific brain imaging findings and with cognitive impairment. Anxiety disorders are associated with a higher frequency of generalized tonico-clonic seizure (GTCS) and with worse social functioning. Psychotic disorders were found to be associated with longer duration of epilepsy. Childhood maltreatment experiences were found to be a powerful predictor for the occurrence of psychiatric comorbidities in epilepsy patients, while data regarding association of other epilepsy characteristics with the presence of psychiatric disorders is conflicting.

A systematic review of neuroimaging studies of depression in adults with epilepsy

OBJECTIVE

Depression is a relatively common comorbidity in people with epilepsy with a lifetime history identified in 1 in 4 individuals. In this paper, we aimed to provide a systematic review of structural and functional brain region-specific group differences of adults with epilepsy and depression and to discuss existing evidence as compared to that in people with depression.

METHODS

We undertook a systematic review of neuroimaging studies of depression in adults with epilepsy through MEDLINE/PubMed, Embase and PsycInfo searches until June 2020.

RESULTS

A total of 44 studies were included in the qualitative synthesis: 21 on structural neuroimaging, 9 on functional, and 14 on pharmaco/metabolic neuroimaging. Almost all studies focused on temporal lobe epilepsy (TLE). Patterns of changes in the hippocampi and subcortical structures seem to be different from those reported in depression outside epilepsy. Cortical changes are grossly similar as well as the lack of any laterality effect. Serotonin dysfunction seems to be due to different mechanisms with reduced synaptic availability for depression in epilepsy as compared to reduced 5HT1 receptor density outside epilepsy. Depressive symptoms seem to correlate with a dysfunction in temporolimbic structures contralateral to the epileptogenic zone especially in patients with de novo postsurgical depression.

CONCLUSIONS

Depression, at least in TLE, seems to be associated with a different pattern of brain changes as compared to major depression, potentially supporting the notion of phenomenological peculiarities of depression in epilepsy.

Demyelination contributes to depression comorbidity in a rat model of chronic epilepsy via dysregulation of Olig2/LINGO-1 and disturbance of calcium homeostasis

Depression is the most common comorbidity among patients with epilepsy. Despite prior assumptions that antiepileptic drugs are to blame, more and more pathological studies have shown that latent neurological alterations associated with white matter injury and demyelination may underlie this link. However, whether disturbances in cerebral myelination contribute to the initiation of depression in epilepsy remains unclear. In the present study, we investigated the connection between demyelination disorders and the development of depression comorbidity in epilepsy. We first induced spontaneous recurrent epilepticus seizure (SRS) in young rats with pilocarpine. We then established depressive behaviors by recurrent forced swimming test and evaluate the depression state by sucrose preference test. The ratio of depression comorbidity in SRS rats was then calculated. Next, myelination in SRS-Depressed (SRS-D) rats was explored via PCR, western blotting, and immunohistochemistry for the key myelin promotion factor, Olig2 and inhibition factor, LINGO-1. Finally, in situ RNA hybridization of NCX3, one of the dominant Ca²⁺ extrusion proteins in oligodendrocytes (OLs) was performed to explore whether Ca²⁺ homeostasis of OLs was disturbed in epilepsy-induced hypoxic conditions and involved in the epilepsy-depression comorbidity. Our results revealed that one-quarter of the SRS rats displayed typical depressive behaviors, which were defined as SRS-D rats. In SRS-D rats, severe demyelination was also observed, accompanied with reduced expression of MBP, Olig2, and NCX3 and increased expression of LINGO-1 in the cingulate gyrus. In SRS-Non depressed rats, no significant changes were found from the control animals. This work provides new insights into the demyelination in epilepsy-depression comorbidity, which involves dysregulation of Olig2/LINGO-1 and disturbance of Ca²⁺ homeostasis.