Patterns of brain activity in patients with epilepsy and depression

Left Hemisphere Lateralization of Epileptic Focus Can Be More Frequent in Temporal Lobe Epilepsy Surgical Patients with No Consensus Associated with Depression Lateralization

Temporal lobe epilepsy (TLE) is considered to be the most common form of epilepsy, and it has been seen that most patients are refractory to antiepileptic drugs. A strong association of this ailment has been established with psychiatric comorbidities, primarily mood and anxiety disorders. The side of epileptogenic may contribute to depressive and anxiety symptoms; thus, in this study, we performed a systematic review to evaluate the prevalence of depression in TLE in surgical patients. The literature search was performed using PubMed/Medline, Web of Science, and PsycNet to gather data from inception until January 2019. The search strategy was related to TLE, depressive disorder, and anxiety. After reading full texts, 14 articles meeting the inclusion criteria were screened. The main method utilized for psychiatric diagnosis was Diagnostic and Statistical Manual of Mental Disorders/Structured Clinical Interview for DSM. However, most studies failed to perform the neuropsychological evaluation. For those with lateralization of epilepsy, focus mostly occurred in the left hemisphere. For individual depressive diagnosis, 9 studies were evaluated, and 5 for anxiety. Therefore, from the data analyzed in both situations, no diagnosis was representative in preoperative and postoperative cases. In order to estimate the efficacy of surgery in the psychiatry episodes and its relation to seizure control, the risk of depression and anxiety symptoms in epileptic patients need to be determined before surgical procedures. Rigorous preoperative and postoperative evaluation is essential for psychiatry conditions in patients with refractory epilepsy candidates for surgery.

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.

Epilepsy, depression, and growth hormone

Depression affects a large proportion of patients with epilepsy, and is likely due in part to biological mechanism. Hormonal dysregulation due to the disruptive effects of seizures and interictal epileptiform discharges on the hypothalamic-pituitary-adrenal axis likely contributes to high rates of depression in epilepsy. This paper reviews the largely unexplored role of neuroendocrine factors in epilepsy-related depression, focusing on Growth Hormone (GH). While GH deficiency is traditionally considered a childhood disorder manifested by impaired skeletal growth, GH deficiency in adulthood is now recognized as a serious disorder characterized by impairments in multiple domains including mood and quality of life. Could high rates of depression in patients with epilepsy relate to subtle GH deficiency? Because GH replacement therapy has been shown to improve mood and quality of life in patients with GH deficiency, this emerging area may hold promise for patients suffering from epilepsy-related depression.

Comorbidity between temporal lobe epilepsy and depression: a [18F]MPPF PET study

Brain and brainstem changes of serotoninergic 5-hydroxytryptophan (5-HT)(1A) receptor density have been reported in patients with major depressive disorder as well as in patients with temporal lobe epilepsy (TLE), using PET and the selective antagonist radiotracers [(11)C]WAY-100635 or [(18)F]FC-WAY. We used a distinct 5-HT(1A) antagonist, [(18)F]MPPF, whose binding potential depends on both receptor density and extracellular serotonin concentration, in 24 patients with drug-resistant TLE and MRI evidence of hippocampal sclerosis but without prior antidepressant exposure. Their Beck Depression Inventory (BDI-2) score ranged from 0 to 34, with nine patients having a score >11. We used a simplified reference tissue model, statistical parametric mapping and anatomical regions of interest (ROIs) to correlate parametric images of [(18)F]MPPF BP with the total BDI score and its four subclasses. The total BDI score, as well as symptoms of psychomotor anhedonia and negative cognition, correlated positively with [(18)F]MPPF BP in the raphe nuclei and in the insula contralateral to seizure onset, whereas somatic symptoms correlated positively with [(18)F]MPPF binding potential in the hippocampal/parahippocampal region ipsilateral to seizure onset, the left mid-cingulate gyrus and the inferior dorsolateral frontal cortex, bilaterally. We confirm an association of depressive symptoms in TLE patients with changes of the central serotoninergic pathways, in particular within the raphe nuclei, insula, cingulate gyrus and epileptogenic hippocampus. These changes are likely to reflect lower extracellular serotonin concentration in more depressed patients, with an upregulation of receptors a less likely alternative.

Major depression in temporal lobe epilepsy with hippocampal sclerosis: clinical and imaging correlates

PURPOSE

Refractory temporal lobe epilepsy (TLE) is often associated with hippocampal sclerosis (HS). Patients with major depression (MD) may also show structural abnormalities in the limbic system. Co-occurrence of TLE with HS and MD is not uncommon. We have investigated the clinical and morphological characteristics of TLE patients in relation to MD.

METHODS

34 TLE patients with HS were assessed at a Comprehensive Epilepsy Programme. All relevant clinical data were obtained, including the history of antecedent events to epilepsy. MD was diagnosed based on detailed psychiatric investigation. MRI was used to measure the volume and tissue signal (T2 relaxometry) of the hippocampus and amygdala. The imaging data were expressed as a percentage of the values obtained in a series of 55 controls.

RESULTS

A history of MD was present in 15 (44%) of 34 patients. Patients with MD had a longer duration of their epilepsy (p<0.05) and a lower frequency of antecedent events (13% with MD, 58% without MD, p<0.05). Both groups had a similar degree of ipsilateral HS (small hippocampal volume, increased hippocampal T2 relaxation time) and demonstrated bilateral amygdaloid atrophy. However, the contralateral amygdala showed lower signal in the presence of MD (97 (9) ms; no MD 103 (8) ms; ANCOVA, p = 0.02).

CONCLUSION

The integrity of the amygdala may influence mood disturbances in TLE patients with HS, as depression was associated with a relative preservation of the contralateral amygdala. In contrast, hippocampal abnormalities were not related to the presence of depression.

Epilepsy and depression: imaging potential common factors

Patients with seizure disorders have an increased incidence of depression. This may be due in part to psychosocial factors; or side effects of antiepileptic drugs. However, there may be underlying physiologic mechanisms for the relationship. Neuroimaging studies, including structural magnetic resonance imaging, positron emission tomography measurements of cerebral glucose metabolism, and, more recently, imaging of serotonin 1A receptors, may provide additional data to explain overlapping clinical manifestations of epilepsy and depression.

Hemispheric specialization in emotion: attention, arousal, and EEG activation in unilateral temporal lobe epilepsy

To investigate the neural processing of emotion in right and left temporal lobe epilepsy (TLE), we monitored EEG during neutral and emotionally positive and negative auditory stimulation. Left TLE patients displayed increased right lateralization and a negative emotional stimulus rating bias, while right TLE patients did not. This EEG arousal and negative affect may reflect deactivated inhibition of the right hemisphere, symptomatically expressed as arousal and anxiety. Failure to increase lateralization to emotional stimuli in right TLE may reflect compromised emotional attention/arousal centers in the right hemisphere. Results support a two-dimensional theory of the neural processing of emotion.