Depression and partial epilepsy: relevance of laterality of the epileptic focus

Detrended fluctuation analysis of resting EEG in depressed outpatients and healthy controls

OBJECTIVE

Recent findings have demonstrated that the EEG possesses long-range temporal (auto-) correlations (LRTC) in the dynamics of broad band oscillations. The analysis of LRTC provides a quantitative index of statistical dependencies in oscillations on different time scales. We analyzed LRTC in resting EEG signals in depressed outpatients and healthy controls.

METHODS

The participants in this study were 11 non-depressed, age-matched controls, and 11 unmedicated unipolar depressed patients. EEG data were obtained from each participant during 5-min resting baseline periods with eyes closed and then analyzed with detrended fluctuation analysis (DFA), a scaling analysis method that quantifies a simple parameter to represent the correlation properties of a time series. The scaling exponent, the result of DFA, provides a quantitative measure of LRTC from the EEG.

RESULTS

The present study demonstrates that all the scaling exponents in depressed patients and healthy controls were greater than 0.5 and less than 1.0, regardless of condition. Furthermore, the scaling exponents of depressed patients have relatively higher values in whole brain regions compared to healthy controls, with significant differences at F3, C3, T3, T4 and O1 channels (p<0.05). Finally, a significant linear correlation was observed between the severity of depression and the scaling exponent over most of the channels, except O2.

CONCLUSIONS

These results suggest that the brain affected by a major depressive disorder shows slower decay of the LRTC, and that the persistence of the LRTC of EEG in depressed patients was associated with the severity of depression over most of the cortical areas.

SIGNIFICANCE

The DFA method may broaden our understanding of the psychophysiological basis of depression.

Interictal Depression, Anxiety, Personality Traits, and Psychological Dissociation in Patients with Temporal Lobe Epilepsy (TLE) and Extra-TLE

PURPOSE

This study was performed to investigate the relation between symptoms of interictal depression, anxiety, personality traits, and psychological dissociation with the localization and lateralization of the epileptogenic zone in patients with partial epilepsy.

METHODS

All patients were diagnosed according to the localization-related concept of the 1989 International League Against Epilepsy (ILAE) Classification of Epilepsies and Epileptic Syndromes, and the localization and lateralization of the epileptogenic zone was established by using the clinical criteria for noninvasive presurgical evaluation. This resulted in 67 patients with temporal lobe epilepsy (TLE) and 64 patients with extra-TLE. All patients were assessed on the various aspects of psychopathology by using a comprehensive battery of standardized diagnostic instruments.

RESULTS

We did not find the hypothesized excess of psychiatric symptoms in patients with (mesial) TLE in comparison with patients with extra-TLE. We also found no differences between patients with the lateralization of epilepsy in the left versus the right hemisphere.

CONCLUSIONS

TLE per se cannot be considered a risk factor in developing more or more severe symptoms of psychopathology in patients with partial epilepsy. Concomitant factors, such as the duration of epilepsy, seizure frequency, and frontal lobe dysfunction may play an additional role. Our findings support the hypothesis of a multifactorial explanation for the psychiatric symptoms in patients with epilepsy.

Is major depression a neurologic disorder with psychiatric symptoms?

In the last decade, multiple investigator groups have identified structural changes of various neuroanatomic structures in patients with idiopathic major depression and bipolar disorders. Using high-resolution MRI of the brain and functional neuroimaging studies (i.e., PET, SPECT), researchers have described decreases in the volume of hippocampal formation, amygdala, entorhinal cortex, various frontal lobe structures, and basal ganglia, in addition to abnormal cerebral blood flow and metabolic activity in these structures as well as in thalamic nuclei. Similar structural and functional changes have been identified in patients with depression associated with a variety of neurologic disorders (i.e., stroke, Parkinson's disease, epilepsy, Alzheimer's dementia). In addition, recent data have shown that depression is a risk factor for the development of several neurologic disorders, including epilepsy, stroke, and Parkinson's disease and bears a negative impact on the course and outcome of most neurologic disorders. This article reviews these data and provides evidence that major depressive and bipolar disorders may in fact be neurologic disorders with psychiatric symptoms.

Depression and anxiety before and after temporal lobe epilepsy surgery

PURPOSE

To examine the course of depression and anxiety in patients with temporal lobe epilepsy (TLE) treated with epilepsy surgery (and anticonvulsant drugs) or medical means alone.

METHODS

Of 94 TLE patients evaluated for epilepsy surgery, 76 underwent a resective procedure, 18 continued on medical treatment alone. Depression (Beck Depression Inventory (BDI)) and anxiety scores (Self-Rating Anxiety Scale (SRAS)) were examined during presurgical evaluation (T1) and after a mean of 16 months (T2), or 12 months after surgery. Depression and anxiety scores were related to type of intervention, underlying epileptogenic lesion, change of seizure control and anticonvulsant therapy.

RESULTS

At T1, depression and anxiety scores were higher in patients with TLE than scores in published normal populations. At T2, depression but not anxiety scores were significantly lower than at T1. Change of depression scores interacted with improvements of seizure control.

CONCLUSIONS

Evidence of depression and anxiety is commonly found in patients with TLE. Depression improves not because of epilepsy surgery per se, but because of improved seizure control. This is more commonly achieved by surgery than medical treatment. The results are consistent with the hypothesis that depression in TLE is caused by pathological epileptic activity rather than a fixed structural defect.

The complex epilepsy patient: intricacies of assessment and treatment

The aim of treatment of all patients with epilepsy is the same: a complete remission of seizures with minimal or no adverse events. However, the means to reach that common goal may differ among patients, not only because of differences in their epileptic syndrome or type of seizures within the same syndrome, but also because of a variety of comorbid pathologic entities that are commonly identified in patients with epilepsy. In this article, we discuss some of the complexities inherent in the planning of therapeutic regimens for epilepsy patients. Comorbid conditions, whether intrinsic or extrinsic to the epileptic disorder, must play a paramount role in the choice of the therapeutic regimen for seizure control. We review the impact of psychiatric comorbidities on the quality of life of patients with epilepsy, with special attention to the tight relationship between depression and epilepsy. Yet, despite this close relationship, comorbid depression is more often than not underrecognized and undertreated. Next, we review the impact of antiepileptic drugs (AEDs) on comorbid medical disorders and give clear examples of the potentially deleterious impact of several AEDs on the therapeutic effects of concomitant medications used for their treatment. Clearly, treating epilepsy is not only about controlling seizures.

Depression in epilepsy: a common but often unrecognized comorbid malady

Depressive disorders (DDs) represent the most frequent psychiatric comorbidity in epilepsy (1-5). Despite their relatively high prevalence, DDs remain unrecognized and untreated in many patients with epilepsy. The purpose of this review is to examine the reasons behind the failure to recognize and treat DDs in epilepsy. We highlight the essential epidemiologic, etiopathogenic, and clinical aspects that need to be considered in the evaluation of every epileptic patient and dedicate the last section of this paper to the review of the most relevant treatment issues. If we are successful in our goals, the reader will be impressed by the significant impact of DDs on the quality of life of these patients, and by the need to investigate treatment modalities with the same scientific rigor used in the assessment of efficacy of antiepileptic drugs in the control of seizures.